Cardiovascular System

Pathophysiologic manifestations
	Aneurysm
	Cardiac shunts
	Embolus
	Release of cardiac enzymes and proteins
	Stenosis
	Thrombus
	Valve incompetence
Disorders
	Atrial septal defect
	Cardiac arrhythmias
	Cardiac tamponade
	Cardiomyopathy
	Coarctation of the aorta
	Coronary artery disease
	Heart failure
	Hypertension
	Myocardial infarction
	Myocarditis
	Patent ductus arteriosus
	Pericarditis
	Raynaud's disease
	Rheumatic fever and rheumatic heart disease
	Shock
	Tetralogy of Fallot
	Transposition of the great arteries
	Valvular heart disease
	Varicose veins
	Ventricular septal defect

T he cardiovascular system begins its activity when the fetus is barely 4 weeks old and is the last system to cease activity at the end of life. This body system is so vital that its activity helps define the presence of life.

The heart, arteries, veins, and lymphatics form the cardiovascular network that serves the body's transport system. This system brings life-supporting oxygen and nutrients to cells, removes metabolic waste products, and carries hormones from one part of the body to another.

The cardiovascular system, often called the circulatory system, may be divided into two branches: pulmonary and systemic circulations. In pulmonary circulation , blood picks up oxygen and liberates the waste product carbon dioxide. In systemic circulation (which includes coronary circulation), blood carries oxygen and nutrients to all active cells and transports waste products to the kidneys, liver, and skin for excretion.

Circulation requires normal heart function, which propels blood through the system by continuous rhythmic contractions. Blood circulates through three types of vessels: arteries, veins, and capillaries. The sturdy, pliable walls of the arteries adjust to the volume of blood leaving the heart. The aorta is the major artery arching out of the left ventricle; its segments and sub-branches ultimately divide into minute, thin-walled (one cell thick) capillaries. Capillaries pass the blood to the veins, which return it to the heart. In the veins, valves prevent blood backflow.

PATHOPHYSIOLOGIC MANIFESTATIONS

Pathophysiologic manifestations of cardiovascular disease may stem from aneurysm, cardiac shunts, embolus, release of cardiac enzymes, stenosis, thrombus, and valve incompetence.

Aneurysm

An aneurysm is a localized outpouching or dilation of a weakened arterial wall. This weakness can be the result of either atherosclerotic plaque formation that erodes the vessel wall, or the loss of elastin and collagen in the vessel wall. Congenital abnormalities in the media of the arterial wall, trauma, and infections such as syphilis may lead to aneurysm formation. A ruptured aneurysm may cause massive hemorrhage and death.

Several types of aneurysms can occur:

• A saccular aneurysm occurs when increased pressure in the artery pushes out a pouch on one side of the artery, creating a bulge. (See Types of aortic aneurysms .)
• A fusiform aneurysm develops when the arterial wall weakens around its circumference, creating a spindle-shaped aneurysm.
• A dissecting aneurysm occurs when blood is forced between the layers of the arterial wall, causing them to separate and creating a false lumen.
• A false aneurysm develops when there is a break in all layers of the arterial wall and blood leaks out but is contained by surrounding structures, creating a pulsatile hematoma.

TYPES OF AORTIC ANEURYSMS <center></center>

Cardiac shunts

A cardiac shunt provides communication between the pulmonary and systemic circulations. Before birth, shunts between the right and left sides of the heart and between the aorta and pulmonary artery are a normal part of fetal circulation. Following birth, however, the mixing of pulmonary and systemic blood or the movement of blood between the left and right sides of the heart is abnormal. Blood flows through a shunt from an area of high pressure to an area of low pressure or from an area of high resistance to an area of low resistance.

Left-to-right shunts

In a left-to-right shunt, blood flows from the left side of the heart to the right side through an atrial or ventricular defect, or from the aorta to the pulmonary circulation through a patent ductus arteriosus. Because the blood in the left side of the heart is rich in oxygen, a left-to-right shunt delivers oxygenated blood back to the right side of the heart or to the lungs. Consequently, a left-to-right shunt that occurs as a result of a congenital heart defect is called an acyanotic defect .

In a left-to-right shunt, pulmonary blood flow increases as blood is continually recirculated to the lungs, leading to hypertrophy of the pulmonary vessels. The increased amounts of blood circulated from the left side of the heart to the right side can result in right-sided heart failure. Eventually, left-sided heart failure may also occur.

Right-to-left shunts

A right-to-left shunt occurs when blood flows from the right side of the heart to the left side such as occurs in tetralogy of Fallot, or from the pulmonary artery directly into the systemic circulation through a patent ductus arteriosus. Because blood returning to the right side of the heart and the pulmonary artery is low in oxygen, a right-to-left shunt adds deoxygenated blood to the systemic circulation, causing hypoxia and cyanosis. Congenital defects that involve right-to-left shunts are therefore called cyanotic defects . Common manifestations of a right-to-left shunt related to poor tissue and organ perfusion include fatigue, increased respiratory rate, and clubbing of the fingers.

Embolus

An embolus is a substance that circulates from one location in the body to another, through the bloodstream. Although most emboli are blood clots from a thrombus, they may also consist of pieces of tissue, an air bubble, amniotic fluid, fat, bacteria, tumor cells, or a foreign substance.

Emboli that originate in the venous circulation, such as from deep vein thrombosis, travel to the right side of the heart to the pulmonary circulation and eventually lodge in a capillary, causing pulmonary infarction and even death. Most emboli in the arterial system originate from the left side of the heart from conditions such as arrhythmias, valvular heart disease, myocardial infarction, heart failure, or endocarditis. Arterial emboli may lodge in organs, such as the brain, kidneys, or extremities, causing ischemia or infarction.

Release of cardiac enzymes and proteins

When the heart muscle is damaged, the integrity of the cell membrane is impaired, and intracellular contents ― including cardiac enzymes and proteins ― are released and can be measured in the bloodstream. The release follows a characteristic rising and falling of values. The released enzymes include creatine kinase, lactate dehydrogenase, and aspartate aminotransferase; the proteins released include troponin T, troponin I, and myoglobin. (See Release of cardiac enzymes and proteins .)

Stenosis

Stenosis is the narrowing of any tubular structure such as a blood vessel or heart valve. When an artery is stenosed, the tissues and organs perfused by that blood vessel may become ischemic, function abnormally, or die. An occluded vein may result in venous congestion and chronic venous insufficiency.

When a heart valve is stenosed, blood flow through that valve is reduced, causing blood to accumulate in the chamber behind the valve. Pressure in that chamber rises in order to pump against the resistance of the stenosed valve. Consequently, the heart has to work harder, resulting in hypertrophy. Hypertrophy and an increase in workload raise the oxygen demands of the heart. A heart with diseased coronary arteries may not be able to sufficiently increase oxygen supply to meet the increased demand.

When stenosis occurs in a valve on the left side of the heart, the increased pressure leads to greater pulmonary venous pressure and pulmonary congestion. As pulmonary vascular resistance rises, right-sided heart failure may occur. Stenosis in a valve on the right side of the heart causes an increase in pressures on the right side of the heart, leading to systemic venous congestion.

Thrombus

A thrombus is a blood clot, consisting of platelets, fibrin, and red and white blood cells, that forms anywhere within the vascular system, such as the arteries, veins, heart chambers, or heart valves.

Three conditions, known as Virchow's triad, promote thrombus formation: endothelial injury, sluggish blood flow, and increased coagulability. When a blood vessel wall is injured, the endothelial lining attracts platelets and other inflammatory mediators, which may stimulate clot formation. Sluggish or abnormal blood flow also promotes thrombus formation by allowing platelets and clotting factors to accumulate and adhere to the blood vessel walls. Conditions that increase the coagulability of blood also promote clot formation.

RELEASE OF CARDIAC ENZYMES AND PROTEINS Because they're released by damaged tissue, serum enzymes and isoenzymes ― catalytic proteins that vary in concentration in specific organs ― can help identify the compromised organ and assess the extent of damage. After acute myocardial infarction (MI), cardiac enzymes and proteins rise and fall in a characteristic pattern, as shown in the graph below. <center></center>

The consequences of thrombus formation include occlusion of the blood vessel or the formation of an embolus (if a portion of a thrombus breaks loose and travels through the circulatory system until it lodges in a smaller vessel).

Valve incompetence

Valve incompetence, also called insufficiency or regurgitation, occurs when valve leaflets do not completely close. Incompetence may affect valves of the veins or the heart.

In the veins, valves keep the blood flowing in one direction, toward the heart. When valve leaflets close improperly, blood flows backward and pools above, causing that valve to weaken and become incompetent. Eventually, the veins become distended, which may result in varicose veins, chronic venous insufficiency, and venous ulcers. Blood clots may form as blood flow becomes sluggish.

In the heart, incompetent valves allow blood to flow in both directions through the valve, increasing the volume of blood that must be pumped (as well as the heart's workload) and resulting in hypertrophy. As blood volume in the heart increases, the involved heart chambers dilate to accommodate the increased volume. Although incompetence may occur in any of the valves of the heart, it's more common in the mitral and aortic valves.

DISORDERS

Atrial septal defect

In this acyanotic congenital heart defect, an opening between the left and right atria allows the blood to flow from left to right, resulting in ineffective pumping of the heart, thus increasing the risk of heart failure.

The three types of atrial septal defects (ASDs) are:

• an ostium secundum defect , the most common type, which occurs in the region of the fossa ovalis and, occasionally, extends inferiorly, close to the vena cava
• a sinus venosus defect that occurs in the superior-posterior portion of the atrial septum, sometimes extending into the vena cava, and is almost always associated with abnormal drainage of pulmonary veins into the right atrium
• an ostium primum defect that occurs in the inferior portion of the septum primum and is usually associated with atrioventricular valve abnormalities (cleft mitral valve) and conduction defects.

ASD accounts for about 10% of congenital heart defects and appears almost twice as often in females as in males, with a strong familial tendency. Although an ASD is usually a benign defect during infancy and childhood, delayed development of symptoms and complications makes it one of the most common congenital heart defects diagnosed in adults.

The prognosis is excellent in asymptomatic patients and in those with uncomplicated surgical repair, but poor in patients with cyanosis caused by large, untreated defects.

Causes

The cause of an ASD is unknown. Ostium primum defects commonly occur in patients with Down syndrome.

Pathophysiology

In an ASD, blood shunts from the left atrium to the right atrium because the left atrial pressure is normally slightly higher than the right atrial pressure. This shunt results in right heart volume overload, affecting the right atrium, right ventricle, and pulmonary arteries. Eventually, the right atrium enlarges, and the right ventricle dilates to accommodate the increased blood volume. If pulmonary artery hypertension develops, increased pulmonary vascular resistance and right ventricular hypertrophy follow. In some adults, irreversible pulmonary artery hypertension causes reversal of the shunt direction, which results in unoxygenated blood entering the systemic circulation, causing cyanosis.

Signs and symptoms

The following are signs and symptoms of an ASD:

• fatigue after exertion due to decreased cardiac output from the left ventricle
• early to midsystolic murmur at the second or third left intercostal space, caused by extra blood passing through the pulmonic valve
• low-pitched diastolic murmur at the lower left sternal border, more pronounced on inspiration, resulting from increased tricuspid valve flow in patients with large shunts
• fixed, widely split S ₂ due to delayed closure of the pulmonic valve, resulting from an increased volume of blood
• systolic click or late systolic murmur at the apex, resulting from mitral valve prolapse in older children with ASD
• clubbing and cyanosis, if right-to-left shunt develops.

AGE ALERT An infant may be cyanotic because he has a cardiac or pulmonary disorder. Cyanosis that worsens with crying is most likely associated with cardiac causes because crying increases pulmonary resistance to blood flow, resulting in an increased right-to-left shunt. Cyanosis that improves with crying is most likely due to pulmonary causes as deep breathing improves tidal volume.

Complications

Complications of an ASD may include:

• physical underdevelopment
• respiratory infections
• heart failure
• atrial arrhythmias
• mitral valve prolapse.

Diagnosis

The following tests help diagnose atrial septal defect:

• Chest X-rays show an enlarged right atrium and right ventricle, a prominent pulmonary artery, and increased pulmonary vascular markings.
• Electrocardiography results may be normal but often show right axis deviation, prolonged PR interval, varying degrees of right bundle branch block, right ventricular hypertrophy, atrial fibrillation (particularly in severe cases after age 30) and, in ostium primum defect, left axis deviation.
• Echocardiography measures right ventricular enlargement, may locate the defect, and shows volume overload in the right side of the heart. It may reveal right ventricular and pulmonary artery dilation.
• Cardiac catheterization may confirm an ASD. Right atrial blood is more oxygenated than superior vena caval blood, indicating a left-to-right shunt, and determines the degree of shunting and pulmonary vascular disease. Dye injection shows the defect's size and location, the location of pulmonary venous drainage, and the competence of the atrioventricular valves.

Treatment

Correcting an ASD typically involves:

• surgery to repair the defect by age 3 to 6, using a patch of pericardium or prosthetic material. A small defect may be sutured closed. Monitor for arrhythmias postoperatively because edema of the atria may interfere with sinoatrial node function.
• valve repair if heart valves are involved
• antibiotic prophylaxis to prevent infective endocarditis
• antiarrhythmic medication to treat arrhythmias.

Cardiac arrhythmias

In arrhythmias, abnormal electrical conduction or automaticity changes heart rate and rhythm. Arrhythmias vary in severity, from those that are mild, asymptomatic, and require no treatment (such as sinus arrhythmia, in which heart rate increases and decreases with respiration) to catastrophic ventricular fibrillation, which requires immediate resuscitation. Arrhythmias are generally classified according to their origin (ventricular or supraventricular). Their effect on cardiac output and blood pressure, partially influenced by the site of origin, determines their clinical significance.

Causes

Common causes of arrhythmias include:

• congenital defects
• myocardial ischemia or infarction
• organic heart disease
• drug toxicity
• degeneration of the conductive tissue
• connective tissue disorders
• electrolyte imbalances
• cellular hypoxia
• hypertrophy of the heart muscle
• acid-base imbalances
• emotional stress.

However, each arrhythmia may have its own specific causes. (See Types of cardiac arrhythmias .)

Pathophysiology

Arrhythmias may result from enhanced automaticity, reentry, escape beats, or abnormal electrical conduction. (See Comparing normal and abnormal conduction .)

Signs and symptoms

Signs and symptoms of arrhythmias result from reduced cardiac output and altered perfusion to the organs, and may include:

• dyspnea
• hypotension
• dizziness, syncope, and weakness
• chest pain
• cool, clammy skin
• altered level of consciousness
• reduced urinary output.

Complications

Possible complications of arrhythmias include:

• sudden cardiac death
• myocardial infarction
• heart failure
• thromboembolism.

Diagnosis

• Electrocardiography detects arrhythmias as well as ischemia and infarction that may result in arrhythmias.
• Laboratory testing may reveal electrolyte abnormalities, acid-base abnormalities, or drug toxicities that may cause arrhythmias.
• Holter monitoring detects arrhythmias and effectiveness of drug therapy during a patient's daily activities.
• Exercise testing may detect exercise-induced arrhythmias.
• Electrophysiologic testing identifies the mechanism of an arrhythmia and the location of accessory pathways; it also assesses the effectiveness of antiarrhythmic drugs.

Treatment

Follow the specific treatment guidelines for each arrhythmia. (See Types of cardiac arrhythmias .)

Cardiac tamponade

Cardiac tamponade is a rapid, unchecked rise in pressure in the pericardial sac that compresses the heart, impairs diastolic filling, and reduces cardiac output. The rise in pressure usually results from blood or fluid accumulation in the pericardial sac. Even a small amount of fluid (50 to 100 ml) can cause a serious tamponade if it accumulates rapidly.

Prognosis depends on the rate of fluid accumulation. If fluid accumulates rapidly, cardiac tamponade requires emergency lifesaving measures to prevent death. A slow accumulation and rise in pressure may not produce immediate symptoms because the fibrous wall of the pericardial sac can gradually stretch to accommodate as much as 1 to 2 L of fluid.

Causes

Cause of cardiac tamponade may include:

• idiopathic causes (e.g., Dressler's syndrome)
• effusion (from cancer, bacterial infections, tuberculosis and, rarely, acute rheumatic fever)
• hemorrhage from trauma (such as gunshot or stab wounds of the chest)
• hemorrhage from nontraumatic causes (such as anticoagulant therapy in patients with pericarditis or rupture of the heart or great vessels)
• viral or postirradiation pericarditis
• chronic renal failure requiring dialysis
• drug reaction from procainamide, hydralazine, minoxidil, isoniazid, penicillin, methysergide maleate, or daunorubicin
• connective tissue disorders (such as rheumatoid arthritis, systemic lupus erythematosus, rheumatic fever, vasculitis, and scleroderma)
• acute myocardial infarction.

TYPES OF CARDIAC ARRHYTHMIAS This chart reviews many common cardiac arrhythmias and outlines their features, causes, and treatments. Use a normal electrocardiogram strip, if available, to compare normal cardiac rhythm configurations with the rhythm strips below. Characteristics of normal sinus rhythm include: ventricular and atrial rates of 60 to 100 beats/minute regular and uniform QRS complexes and P waves PR interval of 0.12 to 0.20 second QRS duration < 0.12 second identical atrial and ventricular rates, with constant PR intervals. ARRHYTHMIA AND FEATURES   CAUSES TREATMENT Sinus tachycardia <center></center> Atrial and ventricular rates regular Rate > 100 beats/minute; rarely, > 160 beats/minute Normal P wave preceding each QRS complex Normal physiologic response to fever, exercise, anxiety, pain, dehydration; may also accompany shock, left ventricular failure, cardiac tamponade, hyperthyroidism, anemia, hypovolemia, pulmonary embolism, and anterior wall myocardial infarction (MI) May also occur with atropine, epinephrine, isoproterenol, quinidine, caffeine, alcohol, and nicotine use Correction of underlying cause Propranolol for symptomatic patients Sinus bradycardia <center></center> Regular atrial and ventricular rates Rate < 60 beats/minute Normal P waves preceding each QRS complex Normal, in well-conditioned heart, as in an athlete Increased intracranial pressure; increased vagal tone due to straining during defecation, vomiting, intubation, or mechanical ventilation; sick sinus syndrome; hypothyroidism; and inferior wall MI May also occur with anticholinesterase, beta blocker, digoxin, and morphine use For low cardiac output, dizziness, weakness, altered level of consciousness, or low blood pressure; advanced cardiac life support (ACLS) protocol for administration of atropine Temporary pacemaker or isoproterenol if atropine fails; may need permanent pacemaker Paroxysmal supraventricular tachycardia (PSVT) <center></center> Atrial and ventricular rates regular Heart rate > 160 beats/minute; rarely exceeds 250 beats/minute P waves regular but aberrant; difficult to differentiate from preceding T wave P wave preceding each QRS complex Sudden onset and termination of arrhythmia Intrinsic abnormality of atrioventricular (AV) conduction system Physical or psychological stress, hypoxia, hypokalemia, cardiomyopathy, congenital heart disease, MI, valvular disease, Wolff-Parkinson-White syndrome, cor pulmonale, hyperthyroidism, and systemic hypertension Digoxin toxicity; use of caffeine, marijuana, or central nervous system stimulants If patient is unstable, prepare for immediate cardioversion If patient is stable, apply vagal stimulation, Valsalva's maneuver, carotid sinus massage Adenosine by rapid intravenous (I.V.) bolus injection to rapidly convert arrhythmia If patient is stable, determine QRS complex width. For wide complex width, follow ACLS protocol for lidocaine and procainamide. For narrow complex width and normal or elevated blood pressure, follow ACLS protocol for verapamil and consider digoxin, beta blockers, and diltiazem. For narrow complex width with low or unstable blood pressure (and for ineffective drug response for others), use synchronized cardioversion. ARRHYTHMIA AND FEATURES   CAUSES TREATMENT Atrial flutter <center></center> Atrial rhythm at regular rate; 250 to 400 beats/minute Ventricular rate variable, depending on degree of atrioventricular (AV) block (usually 60 to 100 beats/minute) Sawtooth P-wave configuration possible (F waves) QRS complexes uniform in shape, but often irregular in rate Heart failure, tricuspid or mitral valve disease, pulmonary embolism, cor pulmonale, inferior wall MI, and pericarditis Digoxin toxicity If patient is unstable with a ventricular rate > 150 beats/minute, prepare for immediate cardioversion If patient is stable, drug therapy may include diltiazem, beta blockers, verapamil, digoxin, procainamide, or quinidine Atrial fibrillation <center></center> Atrial rhythm grossly irregular; rate > 400 beats/minute Ventricular rate grossly irregular QRS complexes of uniform configuration and duration PR interval indiscernible No P waves, or P waves that appear as erratic, irregular, baseline fibrillatory waves Heart failure, chronic obstructive pulmonary disease, thyrotoxicosis, constrictive pericarditis, ischemic heart disease, sepsis, pulmonary embolus, rheumatic heart disease, hypertension, mitral stenosis, atrial irritation, or complication of coronary bypass or valve replacement surgery Nifedipine and digoxin use If patient is unstable with a ventricular rate > 150 beats/minute, prepare for immediate cardioversion If patient is stable, drug therapy may include diltiazem, beta blockers, verapamil, digoxin, procainamide, or ibutilide, given I.V. Junctional rhythm <center></center> Atrial and ventricular rates regular; atrial rate 40 to 60 beats/minute; ventricular rate usually 40 to 60 beats/minute (60 to 100 beats/minute is accelerated junctional rhythm) P waves preceding, hidden within (absent), or after QRS complex; inverted if visible PR interval (when present) < 0.12 second QRS complex configuration and duration normal, except in aberrant conduction Inferior wall MI or ischemia, hypoxia, vagal stimulation, and sick sinus syndrome Acute rheumatic fever Valve surgery Digoxin toxicity Atropine for symptomatic slow rate Pacemaker insertion if patient doesn't respond to drugs Discontinuation of digoxin if appropriate First-degree AV block <center></center> Atrial and ventricular rates regular PR interval > 0.20 second P wave precedes QRS complex QRS complex normal May be seen in healthy persons Inferior wall MI or ischemia, hypothyroidism, hypokalemia, and hyperkalemia Digoxin toxicity; use of quinidine, procainamide, or propranolol Cautious use of digoxin Correction of underlying cause Possibly atropine if PR interval > 0.26 second or bradycardia develops Second-degree AV block Mobitz I (Wenckebach) <center></center> Atrial rhythm regular Ventricular rhythm irregular Atrial rate exceeds ventricular rate PR interval progressively, but only slightly, longer with each cycle until QRS complex disappears (dropped beat); PR interval shorter after dropped beat Inferior wall MI, cardiac surgery, acute rheumatic fever, and vagal stimulation Digoxin toxicity; use of propranolol, quinidine, or procainamide Treatment of underlying cause Atropine or temporary pacemaker for symptomatic bradycardia Discontinuation of digoxin if appropriate ARRHYTHMIA AND FEATURES   CAUSES TREATMENT Second-degree AV block Mobitz II <center></center> Atrial rate regular Ventricular rhythm regular or irregular, with varying degree of block P-P interval constant QRS complexes periodically absent Severe coronary artery disease, anterior wall MI, and acute myocarditis Digoxin toxicity Atropine or isoproterenol for symptomatic bradycardia Temporary or permanent pacemaker Discontinuation of digoxin if appropriate Third-degree AV block (complete heart block) <center></center> Atrial rate regular Ventricular rate slow and regular No relation between P waves and QRS complexes No constant PR interval QRS interval normal (nodal pacemaker) or wide and bizarre (ventricular pacemaker) Inferior or anterior wall MI, congenital abnormality, rheumatic fever, hypoxia, postoperative complication of mitral valve replacement, Lev's disease (fibrosis and calcification that spreads from cardiac structures to the conductive tissue), and Lenègre's disease (conductive tissue fibrosis) Digoxin toxicity Atropine or isoproterenol for symptomatic bradycardia Temporary or permanent pacemaker Premature ventricular contraction (PVC) <center></center> Atrial rate regular Ventricular rate irregular QRS complex premature, usually followed by a compensatory pause QRS complex wide and distorted, usually > 0.14 second Premature QRS complexes occurring singly, in pairs, or in threes, alternating with normal beats; focus from one or more sites Ominous when clustered, multifocal, with R wave on T pattern Heart failure; old or acute MI, ischemia, or contusion; myocardial irritation by ventricular catheter or a pacemaker; hypercapnia; hypokalemia; and hypocalcemia Drug toxicity (digoxin, aminophylline, tricyclic antidepressants, beta-blockers, isoproterenol, or dopamine) Caffeine, tobacco, or alcohol use Psychological stress, anxiety, pain, or exercise If warranted, lidocaine, procainamide, or bretylium I.V. Treatment of underlying cause Discontinuation of drug causing toxicity Potassium chloride I.V. if PVC induced by hypokalemia Ventricular tachycardia <center></center> Ventricular rate 140 to 220 beats/minute, regular or irregular QRS complexes wide, bizarre, and independent of P waves P waves not discernible May start and stop suddenly Myocardial ischemia, MI, or aneurysm; coronary artery disease; rheumatic heart disease; mitral valve prolapse; heart failure; cardiomyopathy; ventricular catheters; hypokalemia; hypercalcemia; and pulmonary embolism Digoxin, procainamide, epinephrine, or quinidine toxicity Anxiety With pulse: If hemodynamically stable with ventricular rate < 150 beats/minute, follow ACLS protocol for administration of lidocaine, procainamide, or bretylium; if drugs are ineffective, initiate synchronized cardioversion If ventricular rate > 150 beats/minute, follow ACLS protocol for immediate synchronized cardioversion, followed by antiarrhythmic agents Pulseless: Initiate cardiopulmonary resuscitation (CPR); follow ACLS protocol for defibrillation, endotracheal (ET) intubation, and administration of epinephrine, lidocaine, bretylium, magnesium sulfate, or procainamide ARRHYTHMIA AND FEATURES   CAUSES TREATMENT Ventricular fibrillation <center></center> Ventricular rhythm rapid and chaotic QRS complexes wide and irregular; no visible P waves Myocardial ischemia, MI, untreated ventricular tachycardia, R-on-T phenomenon, hypokalemia, hyperkalemia, hypercalcemia, alkalosis, electric shock, and hypothermia Digoxin, epinephrine, or quinidine toxicity Initiate CPR; follow ACLS protocol for defibrillation, ET intubation, and administration of epinephrine, lidocaine, bretylium, magnesium sulfate, or procainamide Asystole <center></center> No atrial or ventricular rate or rhythm No discernible P waves, QRS complexes, or T waves Myocardial ischemia, MI, aortic valve disease, heart failure, hypoxia, hypokalemia, severe acidosis, electric shock, ventricular arrhythmia, AV block, pulmonary embolism, heart rupture, cardiac tamponade, hyperkalemia, and electromechanical dissociation Cocaine overdose Continue CPR, follow ACLS protocol for ET intubation, administration of epinephrine and atropine, and possible transcutaneous pacing

Pathophysiology

In cardiac tamponade, the progressive accumulation of fluid in the pericardial sac causes compression of the heart chambers. This compression obstructs blood flow into the ventricles and reduces the amount of blood that can be pumped out of the heart with each contraction. (See Understanding cardiac tamponade .)

Each time the ventricles contract, more fluid accumulates in the pericardial sac. This further limits the amount of blood that can fill the ventricular chambers, especially the left ventricle, during the next cardiac cycle.

The amount of fluid necessary to cause cardiac tamponade varies greatly; it may be as little as 200 ml when the fluid accumulates rapidly or more than 2,000 ml if the fluid accumulates slowly and the pericardium stretches to adapt.

Signs and symptoms

The following signs and symptoms may occur:

• elevated central venous pressure (CVP) with neck vein distention due to increased jugular venous pressure
• muffled heart sounds caused by fluid in the pericardial sac
• pulsus paradoxus (an inspiratory drop in systemic blood pressure greater than 15 mm Hg) due to impaired diastolic filling
• diaphoresis and cool clammy skin caused by a drop in cardiac output
• anxiety, restlessness, and syncope due to a drop in cardiac output
• cyanosis due to reduced oxygenation of the tissues
• weak, rapid pulse in response to a drop in cardiac output
• cough, dyspnea, orthopnea, and tachypnea because the lungs are compressed by an expanding pericardial sac.

Complications

Reduced cardiac output may be fatal without prompt treatment.

Diagnosis

• Chest X-rays show slightly widened mediastinum and possible cardiomegaly. The cardiac silhouette may have a goblet-shaped appearance.
• Electrocardiography (ECG) may show low-amplitude QRS complex and electrical alternans, an alternating beat-to-beat change in amplitude of the P wave, QRS complex, and T wave. Generalized ST-segment elevation is noted in all leads. An ECG is used to rule out other cardiac disorders; it may reveal changes produced by acute pericarditis.
• Pulmonary artery catheterization detects increased right atrial pressure, right ventricular diastolic pressure, and CVP.
• Echocardiography may reveal pericardial effusion with signs of right ventricular and atrial compression.

Treatment

Correcting cardiac tamponade typically involves:

• supplemental oxygen to improve oxygenation
• continuous ECG and hemodynamic monitoring in an intensive care unit to detect complications and monitor effects of therapy
• pericardiocentesis (needle aspiration of the pericardial cavity) to reduce fluid in the pericardial sac and improve systemic arterial pressure and cardiac output. A catheter may be left in the pericardial space attached to a drainage bag to allow for continuous drainage of fluid
• pericardectomy ― the surgical creation of an opening to remove accumulated fluid from the pericardial sac
• resection of a portion or all of the pericardium to allow full communication with the pleura, if repeated pericardiocentesis fails to prevent recurrence
• trial volume loading with crystalloids such as intravenous 0.9% normal saline to maintain systolic blood pressure
• inotropic drugs, such as isoproterenol or dopamine, to improve myocardial contractility until fluid in the pericardial sac can be removed
• in traumatic injury, a blood transfusion or a thoracotomy to drain reaccumulating fluid or to repair bleeding sites may be necessary
• heparin-induced tamponade requires administration of heparin antagonist protamine sulfate to stop bleeding
• warfarin-induced tamponade may necessitate use of vitamin K to stop bleeding.

COMPARING NORMAL AND ABNORMAL CONDUCTION NORMAL CARDIAC CONDUCTION The conduction system of the heart, shown below, begins at the heart's pacemaker, the sinoatrial (SA) node. When an impulse leaves the SA node, it travels through the atria along Bachmann's bundle and the internodal pathways to the atrioventricular (AV) node and then down the bundle of His, along the bundle branches and, finally, down the Purkinje fibers to the ventricles. <center></center> ABNORMAL CARDIAC CONDUCTION Altered automaticity, reentry, or conduction disturbances may cause cardiac arrhythmias. Altered automaticity Enhanced automaticity is the result of partial depolarization, which may increase the intrinsic rate of the SA node or latent pacemakers, or may induce ectopic pacemakers to reach threshold and depolarize. Automaticity may be enhanced by drugs such as epinephrine, atropine, and digoxin and conditions such as acidosis, alkalosis, hypoxia, myocardial infarction, hypokalemia, and hypocalcemia. Examples of arrhythmias caused by enhanced automaticity include atrial fibrillation and flutter; supraventricular tachycardia; premature atrial, junctional, and ventricular complexes; ventricular tachycardia and fibrillation; and accelerated idioventricular and junctional rhythms. Reentry Ischemia or deformation causes an abnormal circuit to develop within conductive fibers. Although current flow is blocked in one direction within the circuit, the descending impulse can travel in the other direction. By the time the impulse completes the circuit, the previously depolarized tissue within the circuit is no longer refractory to stimulation. Conditions that increase the likelihood of reentry include hyperkalemia, myocardial ischemia, and the use of certain antiarrhythmic drugs. Reentry may be responsible for dysrhythmias such as paroxysmal supraventricular tachycardia; premature atrial, junctional, and ventricular complexes; and ventricular tachycardia. An alternative reentry mechanism depends on the presence of a congenital accessory pathway linking the atria and the ventricles outside the AV junction, for example, Wolff-Parkinson-White syndrome. Conduction disturbances Conduction disturbances occur when impulses are conducted too quickly or too slowly. Possible causes include trauma, drug toxicity, myocardial ischemia, myocardial infarction, and electrolyte abnormalities. The atrioventricular blocks occur as a result of conduction disturbances.

Cardiomyopathy

Cardiomyopathy generally applies to disease of the heart muscle fibers, and it occurs in three main forms: dilated, hypertrophic, and restrictive (extremely rare). Cardiomyopathy is the second most common direct cause of sudden death; coronary artery disease is first. Approximately 5 to 8 per 100,000 Americans have dilated congestive cardiomyopathy , the most common type. At greatest risk of cardiomyopathy are males and blacks; other risk factors include hypertension, pregnancy, viral infections, and alcohol use. Because dilated cardiomyopathy is usually not diagnosed until its advanced stages, the prognosis is generally poor. The course of hypertrophic cardiomyopathy is variable. Some patients progressively deteriorate, whereas others remain stable for years. It is estimated that almost 50% of all sudden deaths in competitive athletes age 35 or younger are due to hypertrophic cardiomyopathy. If severe, restrictive cardiomyopathy is irreversible.

Causes

Most patients with cardiomyopathy have idiopathic, or primary, disease, but some are secondary to identifiable causes. (See Comparing the cardiomyopathies .) Hypertrophic cardiomyopathy is almost always inherited as a non�sex-linked autosomal dominant trait.

Pathophysiology

Dilated cardiomyopathy results from extensively damaged myocardial muscle fibers. Consequently, there is reduced contractility in the left ventricle. As systolic function declines, stroke volume, ejection fraction, and cardiac output fall. As end-diastolic volumes rise, pulmonary congestion may occur. The elevated end-diastolic volume is a compensatory response to preserve stroke volume despite a reduced ejection fraction. The sympathetic nervous system is also stimulated to increase heart rate and contractility. The kidneys are stimulated to retain sodium and water to maintain cardiac output, and vasoconstriction also occurs as the renin-angiotensin system is stimulated. When these compensatory mechanisms can no longer maintain cardiac output, the heart begins to fail. Left ventricular dilation occurs as venous return and systemic vascular resistance rise. Eventually, the atria also dilate as more work is required to pump blood into the full ventricles. Cardiomegaly occurs as a consequence of dilation of the atria and ventricles. Blood pooling in the ventricles increases the risk of emboli.

UNDERSTANDING CARDIAC TAMPONADE <center> <br /> </center> The pericardial sac, which surrounds and protects the heart, is composed of several layers. The fibrous pericardium is the tough outermost membrane; the inner membrane, called the serous membrane, consists of the visceral and parietal layers. The visceral layer clings to the heart and is also known as the epicardial layer of the heart. The parietal layer lies between the visceral layer and the fibrous pericardium. The pericardial space ― between the visceral and parietal layers ― contains 10 to 30 ml of pericardial fluid. This fluid lubricates the layers and minimizes friction when the heart contracts. <center></center> In cardiac tamponade, blood or fluid fills the pericardial space, compressing the heart chambers, increasing intracardiac pressure, and obstructing venous return. As blood flow into the ventricles falls, so does cardiac output. Without prompt treatment, low cardiac output can be fatal.

AGE ALERT Barth syndrome is a rare genetic disorder that can cause dilated cardiomyopathy in boys. This syndrome may be associated with skeletal muscle changes, short stature, neutropenia, and increased susceptibility to bacterial infections. Evidence of dilated cardiomyopathy may appear as early as the first few days or months of life.

Unlike dilated cardiomyopathy, which affects systolic function, hypertrophic cardiomyopathy primarily affects diastolic function. The features of hypertrophic cardiomyopathy include asymmetrical left ventricular hypertrophy; hypertrophy of the intraventricular septum; rapid, forceful contractions of the left ventricle; impaired relaxation; and obstruction to left ventricular outflow. The hypertrophied ventricle becomes stiff, noncompliant, and unable to relax during ventricular filling. Consequently, ventricular filling is reduced and left ventricular filling pressure rises, causing a rise in left atrial and pulmonary venous pressures and leading to venous congestion and dyspnea. Ventricular filling time is further reduced as a compensatory response to tachycardia. Reduced ventricular filling during diastole and obstruction to ventricular outflow lead to low cardiac output. If papillary muscles become hypertrophied and do not close completely during contraction, mitral regurgitation occurs. Moreover, intramural coronary arteries are abnormally small and may not be sufficient to supply the hypertrophied muscle with enough blood and oxygen to meet the increased needs of the hyperdynamic muscle.

Restrictive cardiomyopathy is characterized by stiffness of the ventricle caused by left ventricular hypertrophy and endocardial fibrosis and thickening, thus reducing the ability of the ventricle to relax and fill during diastole. Moreover, the rigid myocardium fails to contract completely during systole. As a result, cardiac output falls.

Signs and symptoms

Clinical manifestations of dilated cardiomyopathy may include:

• shortness of breath, orthopnea, dyspnea on exertion, paroxysmal nocturnal dyspnea, fatigue, and a dry cough at night due to left-sided heart failure
• peripheral edema, hepatomegaly, jugular venous distention, and weight gain caused by right-sided heart failure
• peripheral cyanosis associated with a low cardiac output
• tachycardia as a compensatory response to low cardiac output
• pansystolic murmur associated with mitral and tricuspid insufficiency secondary to cardiomegaly and weak papillary muscles
• S ₃ and S ₄ gallop rhythms associated with heart failure
• irregular pulse if atrial fibrillation exists.

Clinical manifestations of hypertrophic cardiomyopathy may include:

• angina caused by the inability of the intramural coronary arteries to supply enough blood to meet the increased oxygen demands of the hypertrophied heart
• syncope resulting from arrhythmias or reduced ventricular filling leading to a reduced cardiac output
• dyspnea due to elevated left ventricular filling pressure
• fatigue associated with a reduced cardiac output
• systolic ejection murmur along the left sternal border and at the apex caused by mitral regurgitation
• peripheral pulse with a characteristic double impulse (pulsus biferiens) caused by powerful left ventricular contractions and rapid ejection of blood during systole
• abrupt arterial pulse secondary to vigorous left ventricular contractions
• irregular pulse if an enlarged atrium causes atrial fibrillation.

COMPARING THE CARDIOMYOPATHIES Cardiomyopathies include a variety of structural or functional abnormalities of the ventricles. They are grouped into three main pathophysiologic types ― dilated, hypertrophic, and restrictive. These conditions may lead to heart failure by impairing myocardial structure and function. NORMAL HEART DILATED CARDIOMYOPATHY HYPERTROPHIC CARDIOMYOPATHY RESTRICTIVE CARDIOMYOPATHY Ventricles greatly increased chamber size thinning of left ventricular muscle normal or decreased chamber size left ventricular hypertrophy thickened interventricular septum decreased ventricular chamber size left ventricular hypertrophy Atrial chamber size increased increased increased Myocardial mass increased increased normal Ventricular inflow resistance normal increased increased Contractility decreased increased or decreased normal or decreased Possible causes viral or bacterial infection hypertension peripartum syndrome related to toxemia ischemic heart disease valvular disease drug hypersensitivity chemotherapy cardiotoxic effects of drugs or alcohol autosomal dominant trait hypertension obstructive valvular disease thyroid disease amyloidosis sarcoidosis hemochromatosis infiltrative neoplastic disease

COMPARING DIAGNOSTIC TESTS IN CARDIOMYOPATHY TEST DILATED CARDIOMYOPATHY HYPERTROPHIC CARDIOMYOPATHY RESTRICTIVE CARDIOMYOPATHY Electrocardiography Biventricular hypertrophy, sinus tachycardia, atrial enlargement, atrial and ventricular arrhythmias, bundle branch block, and ST-segment and T-wave abnormalities Left ventricular hypertrophy, ST-segment and T-wave abnormalities, left anterior hemiblock, Q waves in precordial and inferior leads, ventricular arrhythmias and, possibly, atrial fibrillation Low voltage, hypertrophy, atrioventricular conduction defects, and arrhythmias Echocardiography Left ventricular thrombi, global hypokinesia, enlarged atria, left ventricular dilation and, possibly, valvular abnormalities Asymmetrical thickening of the left ventricular wall, increased thickness of the intraventricular septum and abnormal motion of the anterior mitral leaflet during systole, and occluding left ventricular outflow in obstructive disease Increased left ventricular muscle mass, normal or reduced left ventricular cavity size, and normal systolic function; rules out constrictive pericarditis Chest X-ray Cardiomegaly, pulmonary congestion, pulmonary venous hypertension, and pleural or pericardial effusions Cardiomegaly Cardiomegaly, pericardial effusion, and pulmonary congestion Increased left ventricular end-diastolic pressure; rules out constrictive pericarditis Cardiac catheterization Elevated left atrial and left ventricular end-diastolic pressures, left ventricular enlargement, and mitral and tricuspid incompetence; may identify coronary artery disease as a cause Elevated ventricular end-diastolic pressure and, possibly, mitral insufficiency, hyperdynamic systolic function, left ventricular outflow obstruction Normal or reduced systolic function and myocardial infiltration Radionuclide studies Left ventricular dilation and hypokinesis, reduced ejection fraction Reduced left ventricular volume, increased muscle mass, and ischemia Left ventricular hypertrophy with restricted ventricular filling

Clinical manifestations of restrictive cardiomyopathy may include:

• fatigue, dyspnea, orthopnea, chest pain, edema, liver engorgement, peripheral cyanosis, pallor, and S ₃ or S ₄ gallop rhythms due to heart failure
• systolic murmurs caused by mitral and tricuspid insufficiency.

Complications

Possible complications of cardiomyopathy include:

• heart failure
• arrhythmias
• systemic or pulmonary embolization
• sudden death.

Diagnosis

The following tests help diagnose cardiomyopathy:

• Echocardiography confirms dilated cardiomyopathy.
• Chest X-ray may reveal cardiomegaly associated with any of the cardiomyopathies.
• Cardiac catheterization with possible heart biopsy can be definitive with hypertrophic cardiomyopathy.
• Diagnosis requires elimination of other possible causes of heart failure and arrhythmias. (See Comparing diagnostic tests in cardiomyopathy .)

Treatment

Correction of dilated cardiomyopathy may involve:

• treatment of the underlying cause, if identifiable
• angiotensin-converting enzyme (ACE) inhibitors, as first-line therapy, to reduce afterload through vasodilation
• diuretics, taken with ACE inhibitors, to reduce fluid retention
• digoxin, for patients not responding to ACE inhibitor and diuretic therapy, to improve myocardial contractility
• hydralazine and isosorbide dinitrate, in combination, to produce vasodilation
• beta-adrenergic blockers for patients with New York Heart Association class II or III heart failure. (See Classifying heart failure .)
• antiarrythmics such as amiodarone, used cautiously, to control arrhythmias
• cardioversion to convert atrial fibrillation to sinus rhythm
• pacemaker insertion to correct arrhythmias
• anticoagulants (controversial) to reduce the risk of emboli
• revascularization, such as coronary artery bypass graft surgery, if dilated cardiomyopathy is due to ischemia
• valvular repair or replacement, if dilated cardiomyopathy is due to valve dysfunction
• heart transplantation in patients refractory to medical therapy
• lifestyle modifications, such as smoking cessation; low-fat, low-sodium diet; physical activity; and abstinence from alcohol.

CLASSIFYING HEART FAILURE The New York Heart Association (NYHA) classification is a universal gauge of heart failure severity based on physical limitations. CLASS I: MINIMAL No limitations Ordinary physical activity doesn't cause undue fatigue, dyspnea, palpitations, or angina CLASS II: MILD Slightly limited physical activity Comfortable at rest Ordinary physical activity results in fatigue, palpitations, dyspnea, or angina CLASS III: MODERATE Markedly limited physical activity Comfortable at rest Less than ordinary activity produces symptoms CLASS IV: SEVERE Patient unable to perform any physical activity without discomfort Angina or symptoms of cardiac inefficiency may develop at rest

Correction of hypertrophic cardiomyopathy may involve:

• beta-adrenergic blockers to slow the heart rate, reduce myocardial oxygen demands, and increase ventricular filling by relaxing the obstructing muscle, thereby increasing cardiac output
• antiarrhythmic drugs, such as amiodarone, to reduce arrhythmias
• cardioversion to treat atrial fibrillation
• anticoagulation to reduce risk of systemic embolism with atrial fibrillation
• verapamil and diltiazem to reduce ventricular stiffness and elevated diastolic pressures
• ablation of the atrioventricular node and implantation of a dual-chamber pacemaker (controversial), in patients with obstructive hypertrophic cardiomyopathy and ventricular tachycardias, to reduce the outflow gradient by altering the pattern of ventricular contraction
• implantable cardioverter-defibrillator to treat ventricular arrhythmias
• ventricular myotomy or myectomy (resection of the hypertrophied septum) to ease outflow tract obstruction and relieve symptoms
• mitral valve replacement to treat mitral regurgitation
• cardiac transplantation for intractable symptoms.

Correction of restrictive cardiomyopathy may involve:

• treatment of the underlying cause, such as administering deferoxamine to bind iron in restrictive cardiomyopathy due to hemochromatosis
• although no therapy exists for restricted ventricular filling, digoxin, diuretics, and a restricted sodium diet may ease the symptoms of heart failure
• oral vasodilators may control intractable heart failure.

Coarctation of the aorta

Coarctation is a narrowing of the aorta, usually just below the left subclavian artery, near the site where the ligamentum arteriosum (the remnant of the ductus arteriosus, a fetal blood vessel) joins the pulmonary artery to the aorta. Coarctation may occur with aortic valve stenosis (usually of a bicuspid aortic valve) and with severe cases of hypoplasia of the aortic arch, patent ductus arteriosus (PDA), and ventricular septal defect (VSD). The obstruction to blood flow results in ineffective pumping of the heart and increases the risk for heart failure.

This acyanotic condition accounts for about 7% of all congenital heart defects in children and is twice as common in males as in females. When coarctation of the aorta occurs in females, it's often associated with Turner's syndrome, a chromosomal disorder that causes ovarian dysgenesis.

The prognosis depends on the severity of associated cardiac anomalies. If corrective surgery is performed before isolated coarctation induces severe systemic hypertension or degenerative changes in the aorta, the prognosis is good.

Causes

Although the cause of this defect is unknown, it may be associated with Turner's syndrome.

Pathophysiology

Coarctation of the aorta may develop as a result of spasm and constriction of the smooth muscle in the ductus arteriosus as it closes. Possibly, this contractile tissue extends into the aortic wall, causing narrowing. The obstructive process causes hypertension in the aortic branches above the constriction (arteries that supply the arms, neck, and head) and diminished pressure in the vessel below the constriction.

Restricted blood flow through the narrowed aorta increases the pressure load on the left ventricle and causes dilation of the proximal aorta and ventricular hypertrophy.

As oxygenated blood leaves the left ventricle, a portion travels through the arteries that branch off the aorta proximal to the coarctation. If PDA is present, the rest of the blood travels through the coarctation, mixes with deoxygenated blood from the PDA, and travels to the legs. If the PDA is closed, the legs and lower portion of the body must rely solely on the blood that gets through the coarctation.

Untreated, this condition may lead to left-sided heart failure and, rarely, to cerebral hemorrhage and aortic rupture. If VSD accompanies coarctation, blood shunts from left to right, straining the right side of the heart. This leads to pulmonary hypertension and, eventually, right-sided heart hypertrophy and failure.

If coarctation is asymptomatic in infancy, it usually remains so throughout adolescence as collateral circulation develops to bypass the narrowed segment.

Signs and symptoms

The following signs and symptoms may occur:

• during the first year of life, an infant may display tachypnea, dyspnea, pulmonary edema, pallor, tachycardia, failure to thrive, cardiomegaly, and hepatomegaly due to heart failure
• claudication due to reduced blood flow to the legs
• hypertension in the upper body due to increased pressure in the arteries proximal to the coarctation
• headache, vertigo, and epistaxis secondary to hypertension
• upper extremity blood pressure greater than lower extremity blood pressure because blood flow through the coarctation is greater to the upper body than to the lower body
• pink upper extremities and cyanotic lower extremities due to reduced oxygenated blood reaching the legs
• absent or diminished femoral pulses due to restricted blood flow to the lower extremities through the constricted aorta
• continuous midsystolic murmur due to left-to-right shunting of the blood; the murmur is best heard at the base of the heart
• chest and arms may be more developed than the legs because circulation to legs is restricted.

Complications

Possible complications of this defect include:

• heart failure
• severe hypertension
• cerebral aneurysms and hemorrhage
• rupture of the aorta
• aortic aneurysm
• infective endocarditis.

Diagnosis

The following tests help diagnose coarctation of the aorta:

• Physical examination reveals the cardinal signs ― resting systolic hypertension in the upper body, absent or diminished femoral pulses, and a wide pulse pressure.
• Chest X-rays may demonstrate left ventricular hypertrophy, heart failure, a wide ascending and descending aorta, and notching of the undersurfaces of the ribs due to erosion by collateral circulation.
• Electrocardiography may reveal left ventricular hypertrophy.
• Echocardiography may show increased left ventricular muscle thickness, coexisting aortic valve abnormalities, and the coarctation site.
• Cardiac catheterization evaluates collateral circulation and measures pressure in the right and left ventricles and in the ascending and descending aortas (on both sides of the obstruction). Aortography locates the site and extent of coarctation.

Treatment

Correction of coarctation of the aorta may involve:

• digoxin, diuretics, oxygen, and sedatives in infants with heart failure
• prostaglandin infusion to keep the ductus open
• antibiotic prophylaxis against infective endocarditis before and after surgery
• antihypertensive therapy for children with previous undetected coarctation until surgery is performed
• preparation of the infant with heart failure or hypertension for early surgery, or else surgery is delayed until the preschool years. A flap of the left subclavian artery may be used to reconstruct the aorta. Balloon angioplasty or resection with end-to-end anastomosis or use of a tubular graft may also be performed.

Coronary artery disease

Coronary artery disease (CAD) results from the narrowing of the coronary arteries over time due to atherosclerosis. The primary effect of CAD is the loss of oxygen and nutrients to myocardial tissue because of diminished coronary blood flow. As the population ages, the prevalence of CAD is rising. Approximately 11 million Americans have CAD, and it occurs more often in males, whites, and in the middle-aged and elderly. With proper care, the prognosis for CAD is favorable.

Causes

CAD is commonly caused by atherosclerosis. Less common causes of reduced coronary artery blood flow include:

• dissecting aneurysm
• infectious vasculitis
• syphilis
• congenital defects.

Pathophysiology

Fatty, fibrous plaques progressively narrow the coronary artery lumina, reducing the volume of blood that can flow through them and leading to myocardial ischemia. (See Atherosclerotic plaque development .)

ATHEROSCLEROTIC PLAQUE DEVELOPMENT The coronary arteries are made of three layers: intima (the innermost layer, media (the middle layer), and adventitia (the outermost layer). Damaged by risk factors, a fatty streak begins to build up on the intimal layer. Fibrous plaque and lipids progressively narrow the lumen and impede blood flow to the myocardium. The plaque continues to grow and, in advanced stages, may become a complicated calcified lesion that may rupture.

As atherosclerosis progresses, luminal narrowing is accompanied by vascular changes that impair the ability of the diseased vessel to dilate. This causes a precarious balance between myocardial oxygen supply and demand, threatening the myocardium beyond the lesion. When oxygen demand exceeds what the diseased vessel can supply, localized myocardial ischemia results.

Myocardial cells become ischemic within 10 seconds of a coronary artery occlusion. Transient ischemia causes reversible changes at the cellular and tissue levels, depressing myocardial function. Untreated, this can lead to tissue injury or necrosis. Within several minutes, oxygen deprivation forces the myocardium to shift from aerobic to anaerobic metabolism, leading to accumulation of lactic acid and reduction of cellular pH.

The combination of hypoxia, reduced energy availability, and acidosis rapidly impairs left ventricular function. The strength of contractions in the affected myocardial region is reduced as the fibers shorten inadequately, resulting in less force and velocity. Moreover, wall motion is abnormal in the ischemic area, resulting in less blood being ejected from the heart with each contraction. Restoring blood flow through the coronary arteries restores aerobic metabolism and contractility. However, if blood flow is not restored, myocardial infarction results.

Signs and symptoms

The following signs and symptoms may occur:

• angina, the classic sign of CAD, results from a reduced supply of oxygen to the myocardium. It may be described as burning, squeezing, or tightness in the chest that may radiate to the left arm, neck, jaw, or shoulder blade (See Types of angina .)
• nausea and vomiting as a result of reflex stimulation of the vomiting centers by pain
• cool extremities and pallor caused by sympathetic stimulation
• diaphoresis due to sympathetic stimulation
• xanthelasma (fat deposits on the eyelids) occurs secondary to hyperlipidemia and atherosclerosis.

TYPES OF ANGINA There are four types of angina: Stable angina: pain is predictable in frequency and duration and is relieved by rest and nitroglycerin. Unstable angina: pain increases in frequency and duration and is more easily induced; it indicates a worsening of coronary artery disease that may progress to myocardial infarction. Prinzmetal's or variant angina: pain is caused by spasm of the coronary arteries; it may occur spontaneously and may not be related to physical exercise or emotional stress. Microvascular angina: impairment of vasodilator reserve causes angina-like chest pain in a person with normal coronary arteries.

AGE ALERT CAD may be asymptomatic in the older adult because of a decrease in sympathetic response. Dyspnea and fatigue are two key signals of ischemia in an active, older adult.

Complications

Complications of CAD include:

• arrhythmias
• myocardial infarction.

Diagnosis

The following tests help diagnose coronary artery disease:

• Electrocardiography may be normal between anginal episodes. During angina, it may show ischemic changes, such as T-wave inversion, ST-segment depression and, possibly, arrhythmias. ST-segment elevation suggests Prinzmetal's angina.
• Exercise testing may be performed to detect ST-segment changes during exercise, indicating ischemia, and to determine a safe exercise prescription.
• Coronary angiography reveals location and degree of coronary artery stenosis or obstruction, collateral circulation, and the condition of the artery beyond the narrowing.
• Myocardial perfusion imaging with thallium-201 may be performed during treadmill exercise to detect ischemic areas of the myocardium; they appear as “cold spots.”
• Stress echocardiography may show abnormal wall motion.

Treatment

Treatment of CAD may involve:

• nitrates, such as nitroglycerin (given sublingually, orally, transdermally, or topically in ointment form) or isosorbide dinitrate (given sublingually or orally) to reduce myocardial oxygen consumption
• beta-adrenergic blockers to reduce the workload and oxygen demands of the heart by reducing heart rate and peripheral resistance to blood flow
• calcium channel blockers to prevent coronary artery spasm
• antiplatelet drugs to minimize platelet aggregation and the risk of coronary occlusion
• antilipemic drugs to reduce serum cholesterol or triglyceride levels
• antihypertensive drugs to control hypertension
• estrogen replacement therapy to reduce the risk for CAD in postmenopausal women
• coronary artery bypass graft (CABG) surgery to restore blood flow by bypassing an occluded artery using another vessel
• “key hole” or minimally invasive surgery, an alternative to traditional CABG using fiber-optic cameras inserted through small cuts in the chest, to correct blockages in one or two accessible arteries
• angioplasty, to relieve occlusion in patients without calcification and partial occlusion
• laser angioplasty to correct occlusion by vaporizing fatty deposits
• rotational atherectomy to remove arterial plaque with a high-speed burr
• stent placement in a reopened artery to hold the artery open
• lifestyle modifications to reduce further progression of CAD; these include smoking cessation, regular exercise, maintaining an ideal body weight, and following a low-fat, low-sodium diet.

Heart failure

A syndrome rather than a disease, heart failure occurs when the heart can't pump enough blood to meet the metabolic needs of the body. Heart failure results in intravascular and interstitial volume overload and poor tissue perfusion. An individual with heart failure experiences reduced exercise tolerance, a reduced quality of life, and a shortened life span.

Although the most common cause of heart failure is coronary artery disease, it also occurs in infants, children, and adults with congenital and acquired heart defects. The incidence of heart failure rises with age. Approximately 1% of people older than age 50 experience heart failure; it occurs in 10% of people older than age 80. About 700,000 Americans die of heart failure each year. Mortality from heart failure is greater for males, blacks, and the elderly.

Although advances in diagnostic and therapeutic techniques have greatly improved the outlook for patients with heart failure, the prognosis still depends on the underlying cause and its response to treatment.

Causes

Causes of heart failure may be divided into four general categories. (See Causes of heart failure .)

Pathophysiology

Heart failure may be classified according to the side of the heart affected (left- or right-sided heart failure) or by the cardiac cycle involved (systolic or diastolic dysfunction).

Left-sided heart failure. This type of heart failure occurs as a result of ineffective left ventricular contractile function. As the pumping ability of the left ventricle fails, cardiac output falls. Blood is no longer effectively pumped out into the body; it backs up into the left atrium and then into the lungs, causing pulmonary congestion, dyspnea, and activity intolerance. If the condition persists, pulmonary edema and right-sided heart failure may result. Common causes include left ventricular infarction, hypertension, and aortic and mitral valve stenosis.

Right-sided heart failure. Right-sided heart failure results from ineffective right ventricular contractile function. Consequently, blood is not pumped effectively through the right ventricle to the lungs, causing blood to back up into the right atrium and into the peripheral circulation. The patient gains weight and develops peripheral edema and engorgement of the kidney and other organs. It may be due to an acute right ventricular infarction or a pulmonary embolus. However, the most common cause is profound backward flow due to left-sided heart failure.

CAUSES OF HEART FAILURE CAUSE EXAMPLES Abnormal cardiac muscle function Myocardial infarction Cardiomyopathy Abnormal left ventricular volume Valvular insufficiency High-output states: chronic anemia arteriovenous fistula thyrotoxicosis pregnancy septicemia beriberi infusion of large volume of intravenous fluids in a short time period Abnormal left ventricular pressure Hypertension Pulmonary hypertension Chronic obstructive pulmonary disease Aortic or pulmonic valve stenosis Abnormal left ventricular filling Mitral valve stenosis Tricuspid valve stenosis Atrial myxoma Constrictive pericarditis Atrial fibrillation Impaired ventricular relaxation: hypertension myocardial hibernation myocardial stunning

Systolic dysfunction. Systolic dysfunction occurs when the left ventricle can't pump enough blood out to the systemic circulation during systole and the ejection fraction falls. Consequently, blood backs up into the pulmonary circulation and pressure rises in the pulmonary venous system. Cardiac output falls; weakness, fatigue, and shortness of breath may occur. Causes of systolic dysfunction include myocardial infarction and dilated cardiomyopathy.

Diastolic dysfunction. Diastolic dysfunction occurs when the ability of the left ventricle to relax and fill during diastole is reduced and the stroke volume falls. Therefore, higher volumes are needed in the ventricles to maintain cardiac output. Consequently, pulmonary congestion and peripheral edema develop. Diastolic dysfunction may occur as a result of left ventricular hypertrophy, hypertension, or restrictive cardiomyopathy. This type of heart failure is less common than systolic dysfunction, and its treatment is not as clear.

All causes of heart failure eventually lead to reduced cardiac output, which triggers compensatory mechanisms such as increased sympathetic activity, activation of the renin-angiotensin-aldosterone system, ventricular dilation, and hypertrophy. These mechanisms improve cardiac output at the expense of increased ventricular work.

Increased sympathetic activity ― a response to decreased cardiac output and blood pressure ― enhances peripheral vascular resistance, contractility, heart rate, and venous return. Signs of increased sympathetic activity, such as cool extremities and clamminess, may indicate impending heart failure.

Increased sympathetic activity also restricts blood flow to the kidneys, causing them to secrete renin which, in turn, converts angiotensinogen to angiotensin I, which then becomes angiotensin II ― a potent vasoconstrictor. Angiotensin causes the adrenal cortex to release aldosterone, leading to sodium and water retention and an increase in circulating blood volume. This renal mechanism is helpful; however, if it persists unchecked, it can aggravate heart failure as the heart struggles to pump against the increased volume.

In ventricular dilation, an increase in end-diastolic ventricular volume (preload) causes increased stroke work and stroke volume during contraction, stretching cardiac muscle fibers so that the ventricle can accept the increased intravascular volume. Eventually, the muscle becomes stretched beyond optimum limits and contractility declines.

In ventricular hypertrophy, an increase in ventricular muscle mass allows the heart to pump against increased resistance to the outflow of blood, improving cardiac output. However, this increased muscle mass also increases the myocardial oxygen requirements. An increase in the ventricular diastolic pressure necessary to fill the enlarged ventricle may compromise diastolic coronary blood flow, limiting the oxygen supply to the ventricle, and causing ischemia and impaired muscle contractility.

In heart failure, counterregulatory substances ― prostaglandins and atrial natriuretic factor ― are produced in an attempt to reduce the negative effects of volume overload and vasoconstriction caused by the compensatory mechanisms.

The kidneys release the prostaglandins, prostacyclin and prostaglandin E ₂ , which are potent vasodilators. These vasodilators also act to reduce volume overload produced by the renin-angiotensin-aldosterone system by inhibiting sodium and water reabsorption by the kidneys.

Atrial natriuretic factor is a hormone that is secreted mainly by the atria in response to stimulation of the stretch receptors in the atria caused by excess fluid volume. Atrial natriuretic factor works to counteract the negative effects of sympathetic nervous system stimulation and the renin-angiotensin-aldosterone system by producing vasodilation and diuresis.

Signs and symptoms

Early clinical manifestations of left-sided heart failure include:

• dyspnea caused by pulmonary congestion
• orthopnea as blood is redistributed from the legs to the central circulation when the patient lies down at night
• paroxysmal nocturnal dyspnea due to the reabsorption of interstitial fluid when lying down and reduced sympathetic stimulation while sleeping
• fatigue associated with reduced oxygenation and a lack of activity
• nonproductive cough associated with pulmonary congestion.

Later clinical manifestations of left-sided heart failure may include:

• crackles due to pulmonary congestion
• hemoptysis resulting from bleeding veins in the bronchial system caused by venous distention
• point of maximal impulse displaced toward the left anterior axillary line caused by left ventricular hypertrophy
• tachycardia due to sympathetic stimulation
• S ₃ heart sound caused by rapid ventricular filling
• S ₄ heart sound resulting from atrial contraction against a noncompliant ventricle
• cool, pale skin resulting from peripheral vasoconstriction
• restlessness and confusion due to reduced cardiac output.

Clinical manifestations of right-sided heart failure include:

• elevated jugular venous distention due to venous congestion
• positive hepatojugular reflux and hepatomegaly secondary to venous congestion
• right upper quadrant pain caused by liver engorgement
• anorexia, fullness, and nausea may be caused by congestion of the liver and intestines
• nocturia as fluid is redistributed at night and reabsorbed
• weight gain due to the retention of sodium and water
• edema associated with fluid volume excess
• ascites or anasarca caused by fluid retention.

CULTURAL DIVERSITY In the Chinese culture, disagreement or discomfort isn't typically displayed openly. Direct questioning and vigilant assessment skills are necessary to ensure that a patient's quiet nature doesn't mask signs and symptoms that may be life-threatening.

Complications

Acute complications of heart failure include:

• pulmonary edema
• acute renal failure
• arrhythmias.

Chronic complications include:

• activity intolerance
• renal impairment
• cardiac cachexia
• metabolic impairment
• thromboembolism.

Diagnosis

The following tests help diagnose heart failure:

• Chest X-rays show increased pulmonary vascular markings, interstitial edema, or pleural effusion and cardiomegaly.
• Electrocardiography may indicate hypertrophy, ischemic changes, or infarction, and may also reveal tachycardia and extrasystoles.
• Laboratory testing may reveal abnormal liver function tests and elevated blood urea nitrogen and creatinine levels.
• Echocardiography may reveal left ventricular hypertrophy, dilation, and abnormal contractility.
• Pulmonary artery monitoring typically demonstrates elevated pulmonary artery and pulmonary artery wedge pressures, left ventricular end-diastolic pressure in left-sided heart failure, and elevated right atrial pressure or central venous pressure in right-sided heart failure.
• Radionuclide ventriculography may reveal an ejection fraction less than 40%; in diastolic dysfunction, the ejection fraction may be normal.

Treatment

Correction of heart failure may involve:

• treatment of the underlying cause, if known
• angiotensin-converting enzyme (ACE) inhibitors to patients with left ventricle dysfunction to reduce production of angiotensin II, resulting in preload and afterload reduction

AGE ALERT Older adults may require lower doses of ACE inhibitors because of impaired renal clearance. Monitor for severe hypotension, signifying a toxic effect.

• digoxin for patients with heart failure due to left ventricular systolic dysfunction to increase myocardial contractility, improve cardiac output, reduce the volume of the ventricle, and decrease ventricular stretch
• diuretics to reduce fluid volume overload and venous return
• beta-adrenergic blockers in patients with New York Heart Association class II or class III heart failure caused by left ventricular systolic dysfunction to prevent remodeling (See Classifying heart failure .)
• diuretics, nitrates, morphine, and oxygen to treat pulmonary edema
• lifestyle modifications (to reduce symptoms of heart failure) such as weight loss (if obese); limited sodium (to 3 g/day) and alcohol intake; reduced fat intake; smoking cessation; reduced stress; and development of an exercise program. Heart failure is no longer a contraindication to exercise and cardiac rehabilitation.

CULTURAL DIVERSITY Asian Americans consume large amounts of sodium. Encourage an Asian patient to substitute fresh vegetables, herbs, and spices for canned foods, monosodium glutamate, and soy sauce.

• coronary artery bypass surgery or angioplasty for heart failure due to coronary artery disease
• cardiac transplantation in patients receiving aggressive medical treatment but still experiencing limitations or repeated hospitalizations
• other surgery or invasive procedures may be recommended in patients with severe limitations or repeated hospitalizations, despite maximal medical therapy. Some are controversial and may include cardiomyoplasty, insertion of an intra-aortic balloon pump, partial left ventriculectomy, use of a mechanical ventricular assist device, and implanting an internal cardioverter-defibrillator.

AGE ALERT Heart failure in children occurs mainly as a result of congenital heart defects. Therefore, treatment guidelines are directed toward the specific cause.

Hypertension

Hypertension, an elevation in diastolic or systolic blood pressure, occurs as two major types: essential (primary) hypertension, the most common, and secondary hypertension, which results from renal disease or another identifiable cause. Malignant hypertension is a severe, fulminant form of hypertension common to both types. Hypertension is a major cause of cerebrovascular accident, cardiac disease, and renal failure.

Hypertension affects 15% to 20% of adults in the United States. The risk of hypertension increases with age and is higher for blacks than whites and in those with less education and lower income. Men have a higher incidence of hypertension in young and early middle adulthood; thereafter, women have a higher incidence.

Essential hypertension usually begins insidiously as a benign disease, slowly progressing to a malignant state. If untreated, even mild cases can cause major complications and death. Carefully managed treatment, which may include lifestyle modifications and drug therapy, improves prognosis. Untreated, it carries a high mortality rate. Severely elevated blood pressure (hypertensive crisis) may be fatal.

Causes

Risk factors for primary hypertension include:

• family history
• advancing age

AGE ALERT Older adults may have isolated systolic hypertension (ISH), in which just the systolic blood pressure is elevated, as atherosclerosis causes a loss of elasticity in large arteries. Previously, it was believed that ISH was a normal part of the aging process and should not be treated. Results of the Systolic Hypertension in the Elderly Program (SHEP), however, found that treating ISH with antihypertensive drugs lowered the incidence of stroke, coronary artery disease (CAD), and left ventricular heart failure.

• race (most common in blacks)

CULTURAL DIVERSITY Blacks are at increased risk for primary hypertension when predisposition to low plasma renin levels diminishes ability to excrete excess sodium. Hypertension develops at an earlier age and, at any age, it is more severe than in whites.

• obesity
• tobacco use
• high intake of sodium
• high intake of saturated fat
• excessive alcohol consumption
• sedentary lifestyle
• stress
• excess renin
• mineral deficiencies (calcium, potassium, and magnesium)
• diabetes mellitus.

Causes of secondary hypertension include:

• coarctation of the aorta
• renal artery stenosis and parenchymal disease
• brain tumor, quadriplegia, and head injury
• pheochromocytoma, Cushing's syndrome, hyperaldosteronism, and thyroid, pituitary, or parathyroid dysfunction
• oral contraceptives, cocaine, epoetin alfa, sympathetic stimulants, monoamine oxidase inhibitors taken with tyramine, estrogen replacement therapy, and nonsteroidal anti-inflammatory drugs
• pregnancy-induced hypertension
• excessive alcohol consumption.

Pathophysiology

Arterial blood pressure is a product of total peripheral resistance and cardiac output. Cardiac output is increased by conditions that increase heart rate or stroke volume, or both. Peripheral resistance is increased by factors that increase blood viscosity or reduce the lumen size of vessels, especially the arterioles.

Several theories help to explain the development of hypertension, including:

• changes in the arteriolar bed causing increased peripheral vascular resistance
• abnormally increased tone in the sympathetic nervous system that originates in the vasomotor system centers, causing increased peripheral vascular resistance
• increased blood volume resulting from renal or hormonal dysfunction
• an increase in arteriolar thickening caused by genetic factors, leading to increased peripheral vascular resistance
• abnormal renin release, resulting in the formation of angiotensin II, which constricts the arteriole and increases blood volume. (See Understanding blood pressure regulation .)

Prolonged hypertension increases the workload of the heart as resistance to left ventricular ejection increases. To increase contractile force, the left ventricle hypertrophies, raising the oxygen demands and workload of the heart. Cardiac dilation and failure may occur when hypertrophy can no longer maintain sufficient cardiac output. Because hypertension promotes coronary atherosclerosis, the heart may be further compromised by reduced blood flow to the myocardium, resulting in angina or myocardial infarction (MI). Hypertension also causes vascular damage, leading to accelerated atherosclerosis and target organ damage, such as retinal injury, renal failure, stroke, and aortic aneurysm and dissection.

The pathophysiology of secondary hypertension is related to the underlying disease. For example:

• The most common cause of secondary hypertension is chronic renal disease. Insult to the kidney from chronic glomerulonephritis or renal artery stenosis interferes with sodium excretion, the renin-angiotensin-aldosterone system, or renal perfusion, causing blood pressure to rise.
• In Cushing's syndrome, increased cortisol levels raise blood pressure by increasing renal sodium retention, angiotensin II levels, and vascular response to norepinephrine.
• In primary aldosteronism, increased intravascular volume, altered sodium concentrations in vessel walls, or very high aldosterone levels cause vasoconstriction and increased resistance.
• Pheochromocytoma is a chromaffin cell tumor of the adrenal medulla that secretes epinephrine and norepinephrine. Epinephrine increases cardiac contractility and rate, whereas norepinephrine increases peripheral vascular resistance.

UNDERSTANDING BLOOD PRESSURE REGULATION Hypertension may result from a disturbance in one of the following intrinsic mechanisms. RENIN-ANGIOTENSIN SYSTEM The renin-angiotensin system acts to increase blood pressure through the following mechanisms: sodium depletion, reduced blood pressure, and dehydration stimulate renin release renin reacts with angiotensin, a liver enzyme, and converts it to angiotensin I, which increases preload and afterload angiotensin I converts to angiotensin II in the lungs; angiotensin II is a potent vasoconstrictor that targets the arterioles circulating angiotensin II works to increase preload and afterload by stimulating the adrenal cortex to secrete aldosterone; this increases blood volume by conserving sodium and water. AUTOREGULATION Several intrinsic mechanisms work to change an artery's diameter to maintain tissue and organ perfusion despite fluctuations in systemic blood pressure. These mechanisms include stress relaxation and capillary fluid shifts: in stress relaxation, blood vessels gradually dilate when blood pressure rises to reduce peripheral resistance in capillary fluid shift, plasma moves between vessels and extravascular spaces to maintain intravascular volume. SYMPATHETIC NERVOUS SYSTEM When blood pressure drops, baroreceptors in the aortic arch and carotid sinuses decrease their inhibition of the medulla's vasomotor center. The consequent increases in sympathetic stimulation of the heart by norepinephrine increases cardiac output by strengthening the contractile force, raising the heart rate, and augmenting peripheral resistance by vasoconstriction. Stress can also stimulate the sympathetic nervous system to increase cardiac output and peripheral vascular resistance. ANTIDIURETIC HORMONE The release of antidiuretic hormone can regulate hypotension by increasing reabsorption of water by the kidney. With reabsorption, blood plasma volume increases, thus raising blood pressure.

Signs and symptoms

Although hypertension is frequently asymptomatic, the following signs and symptoms may occur:

• elevated blood pressure readings on at least two consecutive occasions after initial screening

WHAT HAPPENS IN HYPERTENSIVE CRISIS Hypertensive crisis is a severe rise in arterial blood pressure caused by a disturbance in one or more of the regulating mechanisms. If untreated, hypertensive crisis may result in renal, cardiac, or cerebral complications and, possibly, death. <center></center>

AGE ALERT Because many older adults have a wide auscultatory gap ― the hiatus between the first Korotkoff sound and the next sound ― failure to pump the blood pressure cuff up high enough can lead to missing the first beat and underestimating the systolic blood pressure. To avoid missing the first Korotkoff sound, palpate the radial artery and inflate the cuff to a point approximately 20 mm beyond which the pulse beat disappears.

• occipital headache (may worsen on rising in the morning as a result of increased intracranial pressure); nausea and vomiting may also occur
• epistaxis possibly due to vascular involvement
• bruits (which may be heard over the abdominal aorta or carotid, renal, and femoral arteries) caused by stenosis or aneurysm
• dizziness, confusion, and fatigue caused by decreased tissue perfusion due to vasoconstriction of blood vessels
• blurry vision as a result of damage to the retina
• nocturia caused by an increase in blood flow to the kidneys and an increase in glomerular filtration
• edema caused by increased capillary pressure.

If secondary hypertension exists, other signs and symptoms may be related to the cause. For example, Cushing's syndrome may cause truncal obesity and purple striae, whereas patients with pheochromocytoma may develop headache, nausea, vomiting, palpitations, pallor, and profuse perspiration.

Complications

Complications of hypertension include:

• hypertensive crisis, peripheral arterial disease, dissecting aortic aneurysm, CAD, angina, MI, heart failure, arrhythmias, and sudden death (See What happens in hypertensive crisis .)
• transient ischemic attacks, cerebrovascular accident, retinopathy, and hypertensive encephalopathy
• renal failure.

Diagnosis

The following tests help diagnose hypertension:

• Serial blood pressure measurements may be useful.
• Urinalysis may show protein, casts, red blood cells, or white blood cells, suggesting renal disease; presence of catecholamines associated with pheochromocytoma; or glucose, suggesting diabetes.
• Laboratory testing may reveal elevated blood urea nitrogen and serum creatinine levels suggestive of renal disease, or hypokalemia indicating adrenal dysfunction (primary hyperaldosteronism).
• Complete blood count may reveal other causes of hypertension, such as polycythemia or anemia.
• Excretory urography may reveal renal atrophy, indicating chronic renal disease. One kidney smaller than the other suggests unilateral renal disease.
• Electrocardiography may show left ventricular hypertrophy or ischemia.
• Chest X-rays may show cardiomegaly.
• Echocardiography may reveal left ventricular hypertrophy.

Treatment

Hypertension may be treated by following the 1997 revised guidelines of the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure to determine the approach to treatment according to the patient's blood pressure, risk factors, and target organ damage. (See Risk stratification and treatment .)

• diuretics (thiazide diuretics such as hydrochlorothiazide, loop diuretics such as furosemide, and combination diuretics such as hydrochlorothiazide-spironolactone) to reduce excess fluid volume

RISK STRATIFICATION AND TREATMENT BLOOD PRESSURE STAGES RISK GROUP A (No major risk factors No TOD/CCD ~undefined ) RISK GROUP B (At least 1 risk factor, not including diabetes; no TOD/CCD) RISK GROUP C (TOD/CCD and/or diabetes, with or without other risk factors) High normal (130�139/85�89) Lifestyle modification Lifestyle modification Drug therapy for those with heart failure, renal insufficiency, or diabetes Lifestyle modification Stage 1 (140�159/90�99) Lifestyle modification (up to 12 months) Lifestyle modification ? (up to 6 months) Drug therapy Lifestyle modification Stages 2 and 3 (>160/>100) Drug therapy Drug therapy Drug therapy Lifestyle modification Notes: ~undefined TOD/CCD indicates target organ disease/clinical cardiovascular disease. ? For patients with multiple risk factors, clinicians should consider drugs as initial therapy plus lifestyle modifications.

CULTURAL DIVERSITY According to the treatment guidelines issued by the National Institutes of Health in 1997, drug therapy for blacks should consist of calcium channel blockers and diuretics.

• beta blockers (such as metoprolol) to reduce heart rate and contractility, and to dilate the blood vessels

CULTURAL DIVERSITY Asians are twice as sensitive as whites to propranolol and are able to metabolize and clear this drug more rapidly. Hypertensive whites are more responsive to beta blockers than are hypertensive blacks.

• calcium channel blockers such as diltiazem to reduce heart rate and contractility; these agents are also effective against vasospasm
• angiotensin-converting enzyme (ACE) inhibitors such as captopril or angiotensin II receptor blockers such as valsartan to produce vasodilation
• alpha-receptor blockers such as doxazosin to produce vasodilation
• alpha-receptor agonists such as clonidine to lower peripheral vascular resistance

AGE ALERT Older adults are at an increased risk for adverse effects of antihypertensives, especially orthostatic hypotension. Lower doses may be needed.

• treatment of underlying cause of secondary hypertension and controlling hypertensive effects
• treatment of hypertensive emergencies with a parenteral vasodilator such as nitroprusside or an adrenergic inhibitor, or oral administration of a selected drug, such as nifedipine, captopril, clonidine, or labetalol, to rapidly reduce blood pressure
• lifestyle modifications, including weight control; limited alcohol, saturated fat, and sodium (2.4 g/day) intake; regular exercise; and smoking cessation
• inclusion of adequate amounts of calcium, magnesium, and potassium in the diet.

Myocardial infarction

In myocardial infarction (MI) ― also known as a heart attack ― reduced blood flow through one of the coronary arteries results in myocardial ischemia and necrosis. In cardiovascular disease, the leading cause of death in the United States and Western Europe, death usually results from cardiac damage or complications of MI. Each year, approximately 900,000 people in the United States experience MI. Mortality is high when treatment is delayed, and almost half of sudden deaths due to MI occur before hospitalization, within 1 hour of the onset of symptoms. The prognosis improves if vigorous treatment begins immediately.

Causes

Predisposing risk factors include:

• positive family history
• gender (men and postmenopausal women are more susceptible to MI than premenopausal women, although the incidence is rising among women, especially those who smoke and take oral contraceptives)
• hypertension
• smoking
• elevated serum triglyceride, total cholesterol, and low-density lipoprotein levels
• obesity
• excessive intake of saturated fats
• sedentary lifestyle
• aging
• stress or type A personality
• drug use, especially cocaine and amphetamines.

Pathophysiology

MI results from occlusion of one or more of the coronary arteries. Occlusion can stem from atherosclerosis, thrombosis, platelet aggregation, or coronary artery stenosis or spasm. If coronary occlusion causes prolonged ischemia, lasting longer than 30 to 45 minutes, irreversible myocardial cell damage and muscle death occur. All MIs have a central area of necrosis or infarction surrounded by an area of potentially viable hypoxic injury. This zone may be salvaged if circulation is restored, or it may progress to necrosis. The zone of injury, in turn, is surrounded by an area of viable ischemic tissue. (See Zones of myocardial infarction .) Although ischemia begins immediately, the size of the infarct can be limited if circulation is restored within 6 hours.

Several changes occur after MI. Cardiac enzymes and proteins are released by the infarcted myocardial cells, which are used in the diagnosis of an MI. (See Release of cardiac enzymes and proteins .) Within 24 hours, the infarcted muscle becomes edematous and cyanotic. During the next several days, leukocytes infiltrate the necrotic area and begin to remove necrotic cells, thinning the ventricular wall. Scar formation begins by the third week after MI, and by the sixth week, scar tissue is well established.

ZONES OF MYOCARDIAL INFARCTION Myocardial infarction has a central area of necrosis surrounded by a zone of injury that may recover if revascularization occurs. This zone of injury is surrounded by an outer ring of reversible ischemia. Characteristic electrocardiographic changes are associated with each zone. <center></center>

The scar tissue that forms on the necrotic area inhibits contractility. When this occurs, the compensatory mechanisms (vascular constriction, increased heart rate, and renal retention of sodium and water) try to maintain cardiac output. Ventricular dilation may also occur in a process called remodeling. Functionally, an MI may cause reduced contractility with abnormal wall motion, altered left ventricular compliance, reduced stroke volume, reduced ejection fraction, and elevated left ventricular end-diastolic pressure.

Signs and symptoms

The following signs and symptoms may occur:

• persistent, crushing substernal chest pain that may radiate to the left arm, jaw, neck, or shoulder blades caused by reduced oxygen supply to the myocardial cells; it may be described as heavy, squeezing, or crushing

AGE ALERT Many older adults do not have chest pain with MI, but experience atypical symptoms such as fatigue, dyspnea, falls, tingling of the extremities, nausea, vomiting, weakness, syncope, and confusion.

• cool extremities, perspiration, anxiety, and restlessness due to the release of catecholamines
• blood pressure and pulse initially elevated as a result of sympathetic nervous system activation. If cardiac output is reduced, blood pressure may fall. Bradycardia may be associated with conduction disturbances
• fatigue and weakness caused by reduced perfusion to skeletal muscles
• nausea and vomiting as a result of reflex stimulation of vomiting centers by pain fibers or from vasovagal reflexes
• shortness of breath and crackles reflecting heart failure
• low-grade temperature in the days following acute MI due to the inflammatory response
• jugular venous distention reflecting right ventricular dysfunction and pulmonary congestion
• S ₃ and S ₄ heart sounds reflecting ventricular dysfunction
• loud holosystolic murmur in apex possibly caused by papillary muscle rupture
• reduced urine output secondary to reduced renal perfusion and increased aldosterone and antidiuretic hormone.

PINPOINTING MYOCARDIAL INFARCTION Depending on location, ischemia or infarction causes changes in the following electrocardiographic leads. TYPE OF MYOCARDIAL INFARCTION LEADS Inferior II, III, aV F Anterior V 3 , V 4 Septal V 1 , V 2 Lateral I, aV L , V 5 , V 6 Anterolateral I, aV L , V 3 -V 6 Posterior V 1 or V 2 Right ventricular II, III, aV F , V 1R � V 4R

Complications

Complications of MI include:

• arrhythmias
• cardiogenic shock
• heart failure causing pulmonary edema
• pericarditis
• rupture of the atrial or ventricular septum, ventricular wall, or valves
• mural thrombi causing cerebral or pulmonary emboli
• ventricular aneurysms
• myocardial rupture
• extensions of the original infarction.

Diagnosis

The following tests help diagnose MI:

• Serial 12-lead electrocardiography (ECG) may reveal characteristic changes, such as serial ST-segment depression in non�Q-wave MI (subendocardial MI that affects the innermost myocardial layer) and ST-segment elevation in Q-wave MI (transmural MI with damage extending through all myocardial layers). An ECG can also identify the location of MI, arrhythmias, hypertrophy, and pericarditis. (See Pinpointing myocardial infarction .)
• Serial cardiac enzymes and proteins may show a characteristic rise and fall of cardiac enzymes, specifically CK-MB, and the proteins troponin T and I, and myoglobin to confirm the diagnosis of MI. (See Release of cardiac enzymes and proteins .)
• Laboratory testing may reveal elevated white blood cell count and erythrocyte sedimentation rate due to inflammation, and increased glucose levels following the release of catecholamines.
• Echocardiography may show ventricular wall motion abnormalities and may detect septal or papillary muscle rupture.
• Chest X-rays may show left-sided heart failure or cardiomegaly.
• Nuclear imaging scanning using thallium-201 and technetium 99m can be used to identify areas of infarction and areas of viable muscle cells.
• Cardiac catheterization may be used to identify the involved coronary artery as well as to provide information on ventricular function and pressures and volumes within the heart.

Treatment

Treatment of an MI typically involves following the treatment guidelines recommended by the American College of Cardiology/American Heart Association (ACC/AHA) Task Force on Practice Guidelines. These include:

• assessment of patients with chest pain in the Emergency Department within 10 minutes of an MI because at least 50% of deaths take place within 1 hour of the onset of symptoms. Moreover, thrombolytic therapy is most effective when started within the first 6 hours after the onset of symptoms
• oxygen by nasal cannula for 2 to 3 hours to increase oxygenation of the blood (See Blocking myocardial infarction .)
• nitroglycerin sublingually to relieve chest pain, unless systolic blood pressure is less than 90 mm Hg or heart rate is less than 50 or greater than 100 beats per minute
• morphine or meperidine (Demerol) for analgesia because pain stimulates the sympathetic nervous system, leading to an increase in heart rate and vasoconstriction
• aspirin 160 to 325 mg/day indefinitely, to inhibit platelet aggregation
• continuous cardiac monitoring to detect arrhythmias and ischemia
• intravenous thrombolytic therapy to patients with chest pain of at least 30 minutes' duration who reach the hospital within 12 hours of the onset of symptoms (unless contraindications exist) and whose ECG shows new left bundle branch block or ST-segment elevation of at least 1 to 2 mm in two or more ECG leads. The greatest benefit of reperfusion therapy, however, occurs when reperfusion takes place within 6 hours of the onset of chest pain
• intravenous heparin for patients who have received tissue plasminogen activator (tPA) to increase the chances of patency in the affected coronary artery. Limited evidence exists that intravenous or subcutaneous heparin is beneficial in patients with acute MI treated with nonspecific thrombolytic drugs, such as streptokinase or anistreplase
• percutaneous transluminal coronary angioplasty (PTCA) may be an alternative to thrombolytic therapy if it can be performed in a timely manner in an institution with personnel skilled in the procedure
• limitation of physical activity for the first 12 hours to reduce cardiac workload, thereby limiting the area of necrosis
• keeping atropine, lidocaine, transcutaneous pacing patches or a transvenous pacemaker, a defibrillator, and epinephrine readily available to treat arrhythmias. The ACC/AHA doesn't recommend the prophylactic use of antiarrhythmic drugs during the first 24 hours
• intravenous nitroglycerin for 24 to 48 hours in patients without hypotension, bradycardia, or excessive tachycardia to reduce afterload and preload and relieve chest pain
• early intravenous beta blockers to patients with an evolving acute MI followed by oral therapy, as long as there are no contraindications, to reduce heart rate and myocardial contractile force, thereby reducing myocardial oxygen requirements
• angiotensin-converting enzyme inhibitors in patients with an evolving MI with ST-segment elevation or left bundle branch block, but without hypotension or other contraindications, to reduce afterload and preload and prevent remodeling
• if needed, magnesium sulfate for 24 hours to correct hypomagnesemia
• angiography and possible percutaneous or surgical revascularization for patients with spontaneous or provoked myocardial ischemia following an acute MI
• exercise testing before discharge to determine adequacy of medical therapy and to obtain baseline information for an appropriate exercise prescription; it can also determine functional capacity and stratify the patient's risk of a subsequent cardiac event
• cardiac risk modification program of weight control; a low-fat, low-cholesterol diet; smoking cessation; and regular exercise to reduce cardiac risk.

Myocarditis

Myocarditis is focal or diffuse inflammation of the cardiac muscle (myocardium). It may be acute or chronic and can occur at any age. In many cases, myocarditis fails to produce specific cardiovascular symptoms or electrocardiogram (ECG) abnormalities, and recovery is usually spontaneous without residual defects. Occasionally, myocarditis is complicated by heart failure; in rare cases, it leads to cardiomyopathy.

Causes

Common causes of myocarditis include:

• viral infections (most common cause in the United States and western Europe), such as Coxsackie virus A and B strains and, possibly, poliomyelitis, influenza, Epstein-Barr virus, human immunodeficiency virus, cytomegalovirus, measles, mumps, rubeola, rubella, and adenoviruses and echoviruses
• bacterial infections, such as diphtheria, tuberculosis, typhoid fever, tetanus, and staphylococcal, pneumococcal, and gonococcal infections
• hypersensitive immune reactions, including acute rheumatic fever and post-cardiotomy syndrome
• radiation therapy ― large doses of radiation to the chest in treating lung or breast cancer
• toxins such as lead, chemicals, cocaine, and chronic alcoholism
• parasitic infections, especially South American trypanosomiasis (Chagas' disease) in infants and immunosuppressed adults; also, toxoplasmosis
• fungal infections, including candidiasis and aspergillosis
• helminthic infections such as trichinosis.

Pathophysiology

Damage to the myocardium occurs when an infectious organism triggers an autoimmune, cellular, and humoral reaction. The resulting inflammation may lead to hypertrophy, fibrosis, and inflammatory changes of the myocardium and conduction system. The heart muscle weakens and contractility is reduced. The heart muscle becomes flabby and dilated and pinpoint hemorrhages may develop.

Signs and symptoms

The following signs and symptoms may occur:

• nonspecific symptoms such as fatigue, dyspnea, palpitations, and fever caused by systemic infection
• mild, continuous pressure or soreness in the chest (occasionally) related to inflammation
• tachycardia due to a compensatory sympathetic response
• S ₃ and S ₄ gallops as a result of heart failure
• murmur of mitral insufficiency may be heard, if papillary muscles involved
• pericardial friction rub, if pericarditis exists
• if myofibril degeneration occurs, it may lead to right-sided and left-sided heart failure, with cardiomegaly, neck vein distention, dyspnea, edema, pulmonary congestion, persistent fever with resting or exertional tachycardia disproportionate to the degree of fever, and supraventricular and ventricular arrhythmias.

Complications

Complications of myocarditis include:

• recurrence of myocarditis
• chronic valvulitis (when it results from rheumatic fever)
• dilated cardiomyopathy
• arrhythmias and sudden death
• heart failure
• pericarditis
• ruptured myocardial aneurysm
• thromboembolism.

BLOCKING MYOCARDIAL INFARCTION This chart shows how treatments can be applied to myocardial infarction at various stages of its development. <center></center>

Diagnosis

• History reveals recent febrile upper respiratory infection.
• Laboratory testing may reveal elevated levels of creatine kinase (CK), CK-MB, aspartate aminotransferase, and lactate dehydrogenase. Also, inflammation and infection can cause elevated white blood cell count and erythrocyte sedimentation rate.
• Antibody titers may be elevated, such as antistreptolysin-O titer in rheumatic fever.
• Electrocardiography may reveal diffuse ST-segment and T-wave abnormalities, conduction defects (prolonged PR interval, bundle branch block, or complete heart block), supraventricular arrhythmias, and ventricular extrasystoles.
• Chest X-rays may show an enlarged heart and pulmonary vascular congestion.
• Echocardiography may demonstrate some degree of left ventricular dysfunction.
• Radionuclide scanning may identify inflammatory and necrotic changes characteristic of myocarditis.
• Laboratory cultures of stool, throat, and other body fluids may identify bacterial or viral causes of infection.
• Endomyocardial biopsy may confirm diagnosis. A negative biopsy does not exclude the diagnosis.

Treatment

Correction of myocarditis may involve:

• antibiotics to treat bacterial infections
• antipyretics to reduce fever and decrease stress on the heart
• bed rest to reduce oxygen demands and the workload on the heart
• restricted activity to minimize myocardial oxygen consumption; supplemental oxygen therapy; sodium restriction and diuretics to decrease fluid retention; angiotensin-converting enzyme inhibitors; and digoxin to increase myocardial contractility for patients with heart failure. Administer digoxin cautiously because some patients may show a paradoxical sensitivity even to small doses
• antiarrhythmic drugs, such as quinidine or procainamide, to treat arrhythmias; use cautiously because these drugs may depress myocardial contractility. A temporary pacemaker may be inserted if complete atrioventricular block occurs
• anticoagulation to prevent thromboembolism
• corticosteroids and immunosuppressants, although controversial, may be used to combat life-threatening complications such as intractable heart failure
• nonsteroidal anti-inflammatory drugs are contraindicated during the acute phase (first 2 weeks) because they increase myocardial damage
• cardiac assist devices or transplantation as a last resort in severe cases resistant to treatment.

Patent ductus arteriosus

The ductus arteriosus is a fetal blood vessel that connects the pulmonary artery to the descending aorta, just distal to the left subclavian artery. Normally, the ductus closes within days to weeks after birth. In patent ductus arteriosus (PDA), the lumen of the ductus remains open after birth. This creates a left-to-right shunt of blood from the aorta to the pulmonary artery and results in recirculation of arterial blood through the lungs. Initially, PDA may produce no clinical effects, but over time it can precipitate pulmonary vascular disease, causing symptoms to appear by age 40. PDA affects twice as many females as males and is the most common acyanotic congenital heart defect found in adults.

The prognosis is good if the shunt is small or surgical repair is effective. Otherwise, PDA may advance to intractable heart failure, which may be fatal.

Causes

PDA is associated with:

• premature birth, probably as a result of abnormalities in oxygenation or the relaxant action of prostaglandin E, which prevents ductal spasm and contracture necessary for closure
• rubella syndrome
• coarctation of the aorta
• ventricular septal defect
• pulmonary and aortic stenosis
• living at high altitudes.

Pathophysiology

The ductus arteriosus normally closes as prostaglandin levels from the placenta fall and oxygen levels rise. This process should begin as soon as the newborn takes its first breath, but may take as long as 3 months in some children.

In PDA, relative resistances in pulmonary and systemic vasculature and the size of the ductus determine the quantity of blood that is shunted from left to right. Because of increased aortic pressure, oxygenated blood is shunted from the aorta through the ductus arteriosus to the pulmonary artery. The blood returns to the left side of the heart and is pumped out to the aorta once more.

The left atrium and left ventricle must accommodate the increased pulmonary venous return, in turn increasing filling pressure and workload on the left side of the heart and causing left ventricular hypertrophy and possibly heart failure. In the final stages of untreated PDA, the left-to-right shunt leads to chronic pulmonary artery hypertension that becomes fixed and unreactive. This causes the shunt to reverse so that unoxygenated blood enters systemic circulation, causing cyanosis.

Signs and symptoms

The following signs and symptoms may occur:

• respiratory distress with signs of heart failure in infants, especially those who are premature, due to the tremendous volume of blood shunted to the lungs through a patent ductus and the increased workload on the left side of the heart
• classic machinery murmur (Gibson murmur), a continuous murmur heard throughout systole and diastole in older children and adults due to shunting of blood from the aorta to the pulmonary artery throughout systole and diastole. It is best heard at the base of the heart, at the second left intercostal space under the left clavicle. The murmur may obscure S ₂ . However, in a right-to-left shunt, this murmur may be absent
• thrill palpated at the left sternal border caused by the shunting of blood from the aorta to the pulmonary artery
• prominent left ventricular impulse due to left ventricular hypertrophy
• bounding peripheral pulses (Corrigan's pulse) due to the high-flow state
• widened pulse pressure because of an elevated systolic blood pressure and, primarily, a drop in diastolic blood pressure as blood is shunted through the PDA, thus reducing peripheral resistance
• slow motor development caused by heart failure
• failure to thrive as a result of heart failure
• fatigue and dyspnea on exertion may develop in adults with undetected PDA.

Complications

Possible complications of PDA may include:

• infective endocarditis
• heart failure
• recurrent pneumonia.

Diagnosis

The following tests help diagnose patent ductus arteriosus:

• Chest X-rays may show increased pulmonary vascular markings, prominent pulmonary arteries, and enlargement of the left ventricle and aorta.
• Electrocardiography may be normal or may indicate left atrial or ventricular hypertrophy and, in pulmonary vascular disease, biventricular hypertrophy.
• Echocardiography detects and estimates the size of a PDA. It also reveals an enlarged left atrium and left ventricle, or right ventricular hypertrophy from pulmonary vascular disease.
• Cardiac catheterization shows higher pulmonary arterial oxygen content than right ventricular content because of the influx of aortic blood. Increased pulmonary artery pressure indicates a large shunt or, if it exceeds systemic arterial pressure, severe pulmonary vascular disease. Cardiac catheterization allows for the calculation of blood volume crossing the ductus, and can rule out associated cardiac defects. Injection of contrast agent can conclusively demonstrate PDA.

Treatment

Correction of PDA may involve the following:

• surgery to ligate the ductus if medical management can't control heart failure. Asymptomatic infants with PDA don't require immediate treatment. If symptoms are mild, surgical ligation of the PDA is usually delayed until age 1
• indomethacin (a prostaglandin inhibitor) to induce ductus spasm and closure in premature infants
• prophylactic antibiotics to protect against infective endocarditis
• treatment of heart failure with fluid restriction, diuretics, and digoxin
• other therapy, including cardiac catheterization, to deposit a plug or umbrella in the ductus to stop shunting.

Pericarditis

Pericarditis is an inflammation of the pericardium ― the fibroserous sac that envelops, supports, and protects the heart. It occurs in both acute and chronic forms. Acute pericarditis can be fibrinous or effusive, with purulent, serous, or hemorrhagic exudate. Chronic constrictive pericarditis is characterized by dense fibrous pericardial thickening. The prognosis depends on the underlying cause but is generally good in acute pericarditis, unless constriction occurs.

Causes

Common causes of pericarditis include:

• bacterial, fungal, or viral infection (infectious pericarditis)
• neoplasms (primary, or metastases from lungs, breasts, or other organs)
• high-dose radiation to the chest
• uremia
• hypersensitivity or autoimmune disease, such as acute rheumatic fever (most common cause of pericarditis in children), systemic lupus erythematosus, and rheumatoid arthritis
• previous cardiac injury, such as myocardial infarction (Dressler's syndrome), trauma, or surgery (post-cardiotomy syndrome), that leaves the pericardium intact but causes blood to leak into the pericardial cavity
• drugs such as hydralazine or procainamide
• idiopathic factors (most common in acute pericarditis)
• aortic aneurysm with pericardial leakage (less common)
• myxedema with cholesterol deposits in the pericardium (less common).

Pathophysiology

Pericardial tissue damaged by bacteria or other substances results in the release of chemical mediators of inflammation (prostaglandins, histamines, bradykinins, and serotonin) into the surrounding tissue, thereby initiating the inflammatory process. Friction occurs as the inflamed pericardial layers rub against each other. Histamines and other chemical mediators dilate vessels and increase vessel permeability. Vessel walls then leak fluids and protein (including fibrinogen) into tissues, causing extracellular edema. Macrophages already present in the tissue begin to phagocytize the invading bacteria and are joined by neutrophils and monocytes. After several days, the area fills with an exudate composed of necrotic tissue and dead and dying bacteria, neutrophils, and macrophages. Eventually, the contents of the cavity autolyze and are gradually reabsorbed into healthy tissue.

A pericardial effusion develops if fluid accumulates in the pericardial cavity. Cardiac tamponade results when there is a rapid accumulation of fluid in the pericardial space, compressing the heart and preventing it from filling during diastole, and resulting in a drop in cardiac output. (See “ Cardiac tamponade .”)

Chronic constrictive pericarditis develops if the pericardium becomes thick and stiff from chronic or recurrent pericarditis, encasing the heart in a stiff shell and preventing the heart from properly filling during diastole. This causes an increase in both left- and right-sided filling pressures, leading to a drop in stroke volume and cardiac output.

Signs and symptoms

The following signs and symptoms of pericarditis may occur:

• pericardial friction rub caused by the roughened pericardial membranes rubbing against one another; although rub may be heard intermittently, it's best heard when the patient leans forward and exhales
• sharp and often sudden pain, usually starting over the sternum and radiating to the neck (especially the left trapezius ridge), shoulders, back, and arms due to inflammation and irritation of the pericardial membranes. The pain is often pleuritic, increasing with deep inspiration and decreasing when the patient sits up and leans forward, pulling the heart away from the diaphragmatic pleurae of the lungs.
• shallow, rapid respirations to reduce pleuritic pain
• mild fever caused by the inflammatory process
• dyspnea, orthopnea, and tachycardia as well as other signs of heart failure may occur as fluid builds up in the pericardial space causing pericardial effusion, a major complication of acute pericarditis
• muffled and distant heart sounds due to the buildup of fluid
• pallor, clammy skin, hypotension, pulsus paradoxus, neck vein distention and, eventually, cardiovascular collapse may occur with the rapid fluid accumulation of cardiac tamponade
• fluid retention, ascites, hepatomegaly, jugular venous distention, and other signs of chronic right-sided heart failure may occur with chronic constrictive pericarditis as the systemic venous pressure gradually rises
• pericardial knock in early diastole along the left sternal border produced by restricted ventricular filling
• Kussmaul's sign, increased jugular venous distention on inspiration, occurs due to restricted right-sided filling.

Diagnosis

The following tests help diagnose pericarditis:

• Electrocardiography may reveal diffuse ST-segment elevation in the limb leads and most precordial leads that reflects the inflammatory process. Upright T waves are present in most leads. QRS segments may be diminished when pericardial effusion exists. Arrhythmias, such as atrial fibrillation and sinus arrhythmias, may occur. In chronic constrictive pericarditis, there may be low-voltage QRS complexes, T-wave inversion or flattening, and P mitrale (wide P waves) in leads I, II, and V ₆ .
• Laboratory testing may reveal an elevated erythrocyte sedimentation rate as a result of the inflammatory process or a normal or elevated white blood cell count, especially in infectious pericarditis; blood urea nitrogen may detect uremia as a cause of pericarditis.
• Blood cultures may identify an infectious cause.
• Antistreptolysin-O titers may be positive if pericarditis is due to rheumatic fever.
• Purified protein derivative skin test may be positive if pericarditis is due to tuberculosis.
• Echocardiography may show an echo-free space between the ventricular wall and the pericardium, and reduced pumping action of the heart.
• Chest X-rays may be normal with acute pericarditis. The cardiac silhouette may be enlarged with a water bottle shape caused by fluid accumulation, if pleural effusion is present.

Treatment

Correcting pericarditis typically involves:

• bed rest as long as fever and pain persist, to reduce metabolic needs
• treatment of the underlying cause, if it can be identified
• nonsteroidal anti-inflammatory drugs, such as aspirin and indomethacin, to relieve pain and reduce inflammation
• corticosteroids if nonsteroidal anti-inflammatory drugs are ineffective and no infection exists; corticosteroids must be administered cautiously because episodes may recur when therapy is discontinued
• antibacterial, antifungal, or antiviral therapy if an infectious cause is suspected
• partial pericardectomy, for recurrent pericarditis, to create a window that allows fluid to drain into the pleural space
• total pericardectomy may be necessary in constrictive pericarditis to permit adequate filling and contraction of the heart
• pericardiocentesis to remove excess fluid from the pericardial space
• idiopathic pericarditis may be benign and self-limiting.

Raynaud's disease

Raynaud's disease is one of several primary arteriospastic disorders characterized by episodic vasospasm in the small peripheral arteries and arterioles, precipitated by exposure to cold or stress. This condition occurs bilaterally and usually affects the hands or, less often, the feet. Raynaud's disease is most prevalent in females, particularly between puberty and age 40. It is a benign condition, requiring no specific treatment and causing no serious sequelae.

Raynaud's phenomenon , however, a condition often associated with several connective disorders ― such as scleroderma, systemic lupus erythematosus, or polymyositis ― has a progressive course, leading to ischemia, gangrene, and amputation. Distinguishing between the two disorders is difficult because some patients who experience mild symptoms of Raynaud's disease for several years may later develop overt connective tissue disease, especially scleroderma.

Causes

Although family history is a risk factor, the cause of this disorder is unknown.

Raynaud's phenomenon may develop secondary to:

• connective tissue disorders, such as scleroderma, rheumatoid arthritis, systemic lupus erythematosus, or polymyositis
• pulmonary hypertension
• thoracic outlet syndrome
• arterioocclusive disease
• myxedema
• trauma
• serum sickness
• exposure to heavy metals
• previous damage from cold exposure
• long-term exposure to cold, vibrating machinery (such as operating a jackhammer), or pressure to the fingertips (such as occurs in typists and pianists).

Pathophysiology

Although the cause is unknown, several theories account for the reduced digital blood flow, including:

• intrinsic vascular wall hyperactivity to cold
• increased vasomotor tone due to sympathetic stimulation
• antigen-antibody immune response (the most likely theory because abnormal immunologic test results accompany Raynaud's phenomenon).

Signs and symptoms

The following signs and symptoms may occur:

• blanching of the fingers bilaterally after exposure to cold or stress as vasoconstriction or vasospasm reduces blood flow. This is followed by cyanosis due to increased oxygen extraction resulting from sluggish blood flow. As the spasm resolves, the fingers turn red as blood rushes back into the arterioles
• cold and numbness may occur during the vasoconstrictive phase due to ischemia
• throbbing, aching pain, swelling, and tingling may occur during the hyperemic phase
• trophic changes, such as sclerodactyly, ulcerations, or chronic paronychia may occur as a result of ischemia in longstanding disease.

Complications

Cutaneous gangrene may occur as a result of prolonged ischemia, necessitating amputation of one or more digits (although extremely rare).

Diagnosis

The following tests help diagnose Raynaud's disease:

• Clinical criteria include skin color changes induced by cold or stress; bilateral involvement; absence of gangrene or, if present, minimal cutaneous gangrene; normal arterial pulses; and patient history of symptoms for at least 2 years.
• Antinuclear antibody (ANA) titer to identify autoimmune disease as an underlying cause of Raynaud's phenomenon; further tests must be performed if ANA titer is positive.
• Arteriography to rule out arterial occlusive disease.
• Doppler ultrasonography may show reduced blood flow if symptoms result from arterial occlusive disease.

Treatment

Treatment of this disorder typically involves:

• teaching the patient to avoid triggers such as cold, mechanical, or chemical injury
• encouraging the patient to cease smoking and avoid decongestants and caffeine to reduce vasoconstriction
• keeping fingers and toes warm to reduce vasoconstriction
• calcium channel blockers, such as nifedipine, diltiazem, and nicardipine, to produce vasodilation and prevent vasospasm
• adrenergic blockers, such as phenoxybenzamine or reserpine, which may improve blood flow to fingers or toes
• biofeedback and relaxation exercises to reduce stress and improve circulation
• sympathectomy to prevent ischemic ulcers by promoting vasodilation (necessary in less than 25% of patients)
• amputation if ischemia causes ulceration and gangrene.

Rheumatic fever and rheumatic heart disease

A systemic inflammatory disease of childhood, acute rheumatic fever develops after infection of the upper respiratory tract with group A beta-hemolytic streptococci. It mainly involves the heart, joints, central nervous system, skin, and subcutaneous tissues, and often recurs. Rheumatic heart disease refers to the cardiac manifestations of rheumatic fever and includes pancarditis (myocarditis, pericarditis, and endocarditis) during the early acute phase and chronic valvular disease later. Cardiac involvement develops in up to 50% of patients.

Worldwide, 15 to 20 million new cases of rheumatic fever are reported each year. The disease strikes most often during cool, damp weather in the winter and early spring. In the United States, it is most common in the North.

Rheumatic fever tends to run in families, lending support to the existence of genetic predisposition. Environmental factors also seem to be significant in the development of the disorder. For example, in lower socioeconomic groups, the incidence is highest in children between ages 5 and 15, probably due to malnutrition and crowded living conditions.

Patients without carditis or with mild carditis have a good long-term prognosis. Severe pancarditis occasionally produces fatal heart failure during the acute phase. Of patients who survive this complication, about 20% die within 10 years. Antibiotic therapy has greatly reduced the mortality of rheumatic heart disease. In 1950, approximately 15,000 people in the United States died of the disease compared with an estimated 5,000 deaths in 1996.

Causes

Rheumatic fever is caused by group A beta-hemolytic streptococcal pharyngitis.

Pathophysiology

Rheumatic fever appears to be a hypersensitivity reaction to a group A beta-hemolytic streptococcal infection. Because very few persons (3%) with streptococcal infections contract rheumatic fever, altered host resistance must be involved in its development or recurrence. The antigens of group A streptococci bind to receptors in the heart, muscle, brain, and synovial joints, causing an autoimmune response. Because of a similarity between the antigens of the streptococcus bacteria and the antigens of the body's own cells, antibodies may attack healthy body cells by mistake.

Carditis may affect the endocardium, myocardium, or pericardium during the early acute phase. Later, the heart valves may be damaged, causing chronic valvular disease.

Pericarditis produces a serofibrinous effusion. Myocarditis produces characteristic lesions called Aschoff's bodies (fibrin deposits surrounded by necrosis) in the interstitial tissue of the heart, as well as cellular swelling and fragmentation of interstitial collagen. These lesions lead to formation of progressively fibrotic nodules and interstitial scars.

Endocarditis causes valve leaflet swelling, erosion along the lines of leaflet closure, and blood, platelet, and fibrin deposits, which form bead-like vegetation. Eventually, the valve leaflets become scarred, lose their elasticity, and begin to adhere to each other. Endocarditis strikes the mitral valve most often in females and the aortic valve in males. In both sexes, it occasionally affects the tricuspid valve and, rarely, the pulmonic valve.

Signs and symptoms

The classic symptoms of rheumatic fever and rheumatic heart disease include:

• polyarthritis or migratory joint pain, caused by inflammation, occurs in most patients. Swelling, redness, and signs of effusion usually accompany such pain, which most often affects the knees, ankles, elbows, and hips
• erythema marginatum, a nonpruritic, macular, transient rash on the trunk or inner aspects of the upper arms or thighs, that gives rise to red lesions with blanched centers
• subcutaneous nodules ― firm, movable, and nontender, about 3 mm to 2 cm in diameter, usually near tendons or bony prominences of joints, especially the elbows, knuckles, wrists, and knees. They often accompany carditis and may last a few days to several weeks
• chorea ― rapid jerky movements ― may develop up to 6 months after the original streptococcal infection. Mild chorea may produce hyperirritability, a deterioration in handwriting, or inability to concentrate. Severe chorea causes purposeless, nonrepetitive, involuntary muscle spasms; poor muscle coordination; and weakness.

Other signs and symptoms include:

• report of a streptococcal infection a few days to 6 weeks earlier; it occurs in 95% of those with rheumatic fever
• temperature of at least 100.4° F (38° C) due to infection and inflammation
• a new mitral or aortic heart murmur or a worsening murmur in a person with a preexisting murmur
• pericardial friction rub caused by inflamed pericardial membranes rubbing against one another, if pericarditis exists
• chest pain, often pleuritic, due to inflammation and irritation of the pericardial membranes. Pain may increase with deep inspiration and decrease when the patient sits up and leans forward, pulling the heart away from the diaphragmatic pleurae of the lungs
• dyspnea, tachypnea, nonproductive cough, bibasilar crackles, and edema due to heart failure in severe rheumatic carditis.

JONES CRITERIA FOR DIAGNOSING RHEUMATIC FEVER The Jones criteria are used to standardize the diagnosis of rheumatic fever. Diagnosis requires that the patient have either two major criteria, or one major criterion and two minor criteria, plus evidence of a previous streptococcal infection. MAJOR CRITERIA MINOR CRITERIA Carditis Migratory polyarthritis Sydenham's chorea Subcutaneous nodules Erythema marginatum Fever Arthralgia Elevated acute phase reactants Prolonged PR interval

Complications

Possible complications of rheumatic fever and rheumatic heart disease include:

• destruction of the mitral and aortic valves
• pancarditis (pericarditis, myocarditis, and endocarditis)
• heart failure.

Diagnosis

The following tests help diagnose rheumatic fever:

• Jones criteria revealing either two major criteria, or one major criterion and two minor criteria, plus evidence of a previous group A streptococcal infection, are necessary for diagnosis. (See Jones Criteria for diagnosing rheumatic fever .)
• Laboratory testing may reveal an elevated white blood cell count and erythrocyte sedimentation rate during the acute phase.
• Hemoglobin and hematocrit may show slight anemia due to suppressed erythropoiesis during inflammation.
• C-reactive protein may be positive, especially during the acute phase.
• Cardiac enzyme levels may be increased in severe carditis.
• Antistreptolysin-O titer may be elevated in 95% of patients within 2 months of onset.
• Throat cultures may continue to show the presence of group A beta-hemolytic streptococci; however, they usually occur in small numbers.
• Electrocardiography may show changes that are not diagnostic, but PR interval is prolonged in 20% of patients.
• Chest X-rays may show normal heart size or cardiomegaly, pericardial effusion, or heart failure.
• Echocardiography can detect valvular damage and pericardial effusion, and can measure chamber size and provide information on ventricular function.
• Cardiac catheterization provides information on valvular damage and left ventricular function.

Treatment

Typically, treatment of these disorders involves:

• prompt treatment of all group A beta-hemolytic streptococcal pharyngitis with oral penicillin V or intramuscular benzathine penicillin G; erythromycin is given for patients with penicillin hypersensitivity
• salicylates to relieve fever and pain and minimize joint swelling
• corticosteroids if the patient has carditis or if salicylates fail to relieve pain and inflammation
• strict bed rest for about 5 weeks for the patient with active carditis to reduce cardiac demands
• bed rest, sodium restriction, angiotensin-converting enzyme inhibitors, digoxin, and diuretics to treat heart failure
• corrective surgery, such as commissurotomy (separation of adherent, thickened valve leaflets of the mitral valve), valvuloplasty (inflation of a balloon within a valve), or valve replacement (with a prosthetic valve) for severe mitral or aortic valvular dysfunction that causes persistent heart failure
• secondary prevention of rheumatic fever, which begins after the acute phase subsides with monthly intramuscular injections of penicillin G benzathine or daily doses of oral penicillin V or sulfadiazine; treatment usually continues for at least 5 years or until age 21, whichever is longer
• prophylactic antibiotics for dental work and other invasive or surgical procedures to prevent endocarditis.

Shock

Shock is not a disease but rather a clinical syndrome leading to reduced perfusion of tissues and organs and, eventually, organ dysfunction and failure. Shock can be classified into three major categories based on the precipitating factors: distributive (neurogenic, septic, and anaphylactic); cardiogenic; and hypovolemic shock. Even with treatment, shock has a high mortality rate once the body's compensatory mechanisms fail. (See Types of shock .)

Causes

Causes of neurogenic shock may include:

• spinal cord injury
• spinal anesthesia
• vasomotor center depression
• severe pain
• medications
• hypoglycemia.

Causes of septic shock may include:

• gram-negative bacteria (most common cause)
• gram-positive bacteria
• viruses, fungi, Rickettsiae , parasites, yeast, protozoa, or mycobacteria.

AGE ALERT The immature immune system of newborns and infants and the weakened immune system of older adults, often accompanied by chronic illness, make these populations more susceptible to septic shock.

Causes of anaphylactic shock may include:

• medications
• vaccines
• venom
• foods
• contrast media
• ABO-incompatible blood.

Causes of cardiogenic shock may include:

• myocardial infarction (most common cause)
• heart failure
• cardiomyopathy
• arrhythmias
• obstruction
• pericardial tamponade
• tension pneumothorax
• pulmonary embolism.

Causes of hypovolemic shock may include:

• blood loss (most common cause)
• gastrointestinal fluid loss
• burns
• renal loss (diabetic ketoacidosis, diabetes insipidus, adrenal insufficiency)
• fluid shifts
• ascites
• peritonitis
• hemothorax.

TYPES OF SHOCK DISTRIBUTIVE SHOCK In this type of shock, vasodilation causes a state of hypovolemia. Neurogenic shock . A loss of sympathetic vasoconstrictor tone in the vascular smooth muscle and reduced autonomic function lead to widespread arterial and venous vasodilation. Venous return is reduced as blood pools in the venous system, leading to a drop in cardiac output and hypotension. Septic shock . An immune response is triggered when bacteria release endotoxins. In response, macrophages secrete tumor necrosis factor (TNF) and interleukins. These mediators, in turn, are responsible for increase release of platelet-activating factor (PAF), prostaglandins, leukotrienes, thromboxane A 2 , kinins, and complement. The consequences are vasodilation and vasoconstriction, increased capillary permeability, reduced systemic vascular resistance, microemboli, and an elevated cardiac output. Endotoxins also stimulate the release of histamine, further increasing capillary permeability. Moreover, myocardial depressant factor, TNF, PAF, and other factors depress myocardial function. Cardiac output falls, resulting in multisystem organ failure. Anaphylactic shock . Triggered by an allergic reaction, anaphylactic shock occurs when a person is exposed to an antigen to which he has already been sensitized. Exposure results in the production of specific immunoglobulin E (IgE) antibodies by plasma cells that bind to membrane receptors on mast cells and basophils. On reexposure, the antigen binds to IgE antibodies or cross-linked IgE receptors, triggering the release of powerful chemical mediators from mast cells. IgG or IgM enters into the reaction and activates the release of complement factors. At the same time, the chemical mediators bradykinin and leukotrienes induce vascular collapse by stimulating contraction of certain groups of smooth muscles and by increasing vascular permeability, leading to decreased peripheral resistance and plasma leakage into the extravascular tissues, thereby reducing blood volume and causing hypotension, hypovolemic shock, and cardiac dysfunction. Bronchospasm and laryngeal edema also occur. CARDIOGENIC SHOCK In cardiogenic shock, the left ventricle can't maintain an adequate cardiac output. Compensatory mechanisms increase heart rate, strengthen myocardial contractions, promote sodium and water retention, and cause selective vasoconstriction. However, these mechanisms increase myocardial workload and oxygen consumption, which reduces the heart's ability to pump blood, especially if the patient has myocardial ischemia. Consequently, blood backs up, resulting in pulmonary edema. Eventually, cardiac output falls and multisystem organ failure develops as the compensatory mechanisms fail to maintain perfusion. HYPOVOLEMIC SHOCK When fluid is lost from the intravascular space through external losses or the shift of fluid from the vessels to the interstitial or intracellular spaces, venous return to the heart is reduced. This reduction in preload decreases ventricular filling, leading to a drop in stroke volume. Then, cardiac output falls, causing reduced perfusion of the tissues and organs.

Pathophysiology

There are three basic stages common to each type of shock: the compensatory, progressive, and irreversible or refractory stages.

Compensatory stage. When arterial pressure and tissue perfusion are reduced, compensatory mechanisms are activated to maintain perfusion to the heart and brain. As the baroreceptors in the carotid sinus and aortic arch sense a drop in blood pressure, epinephrine and norepinephrine are secreted to increase peripheral resistance, blood pressure, and myocardial contractility. Reduced blood flow to the kidney activates the renin-angiotensin-aldosterone system, causing vasoconstriction and sodium and water retention, leading to increased blood volume and venous return. As a result of these compensatory mechanisms, cardiac output and tissue perfusion are maintained.

Progressive stage. This stage of shock begins as compensatory mechanisms fail to maintain cardiac output. Tissues become hypoxic because of poor perfusion. As cells switch to anaerobic metabolism, lactic acid builds up, producing metabolic acidosis. This acidotic state depresses myocardial function. Tissue hypoxia also promotes the release of endothelial mediators, which produce vasodilation and endothelial abnormalities, leading to venous pooling and increased capillary permeability. Sluggish blood flow increases the risk of disseminated intravascular coagulation.

Irreversible (refractory) stage. As the shock syndrome progresses, permanent organ damage occurs as compensatory mechanisms can no longer maintain cardiac output. Reduced perfusion damages cell membranes, lysosomal enzymes are released, and energy stores are depleted, possibly leading to cell death. As cells use anaerobic metabolism, lactic acid accumulates, increasing capillary permeability and the movement of fluid out of the vascular space. This loss of intravascular fluid further contributes to hypotension. Perfusion to the coronary arteries is reduced, causing myocardial depression and a further reduction in cardiac output. Eventually, circulatory and respiratory failure occur. Death is inevitable.

Signs and symptoms

In the compensatory stage of shock, signs and symptoms may include:

• tachycardia and bounding pulse due to sympathetic stimulation
• restlessness and irritability related to cerebral hypoxia
• tachypnea to compensate for hypoxia
• reduced urinary output secondary to vasoconstriction
• cool, pale skin associated with vasoconstriction; warm, dry skin in septic shock due to vasodilation.

In the progressive stage of shock, signs and symptoms may include:

• hypotension as compensatory mechanisms begin to fail
• narrowed pulse pressure associated with reduced stroke volume
• weak, rapid, thready pulse caused by decreased cardiac output
• shallow respirations as the patient weakens
• reduced urinary output as poor renal perfusion continues
• cold, clammy skin caused by vasoconstriction
• cyanosis related to hypoxia.

AGE ALERT Hypotension, altered level of consciousness, and hyperventilation may be the only signs of septic shock in infants and the elderly.

In the irreversible stage , clinical findings may include:

• unconsciousness and absent reflexes caused by reduced cerebral perfusion, acid-base imbalance, or electrolyte abnormalities
• rapidly falling blood pressure as decompensation occurs
• weak pulse caused by reduced cardiac output
• slow, shallow or Cheyne-Stokes respirations secondary to respiratory center depression
• anuria related to renal failure.

Complications

Possible complications of shock include:

• acute respiratory distress syndrome
• acute tubular necrosis
• disseminated intravascular coagulation (DIC)
• cerebral hypoxia
• death.

Diagnosis

The following tests help diagnose shock:

• Hematocrit may be reduced in hemorrhage or elevated in other types of shock due to hypovolemia.
• Blood, urine, and sputum cultures may identify the organism responsible for septic shock.
• Coagulation studies may detect coagulopathy from DIC.
• Laboratory testing may reveal increased white blood cell count and erythrocyte sedimentation rate due to injury and inflammation; elevated blood urea nitrogen and creatinine levels due to reduced renal perfusion; serum lactate may be increased secondary to anaerobic metabolism; and serum glucose may be elevated in early stages of shock as liver releases glycogen stores in response to sympathetic stimulation.
• Cardiac enzymes and proteins may be elevated, indicating myocardial infarction as a cause of cardiogenic shock.
• Arterial blood gas analysis may reveal respiratory alkalosis in early shock associated with tachypnea, respiratory acidosis in later stages associated with respiratory depression, and metabolic acidosis in later stages secondary to anaerobic metabolism.
• Urine specific gravity may be high in response to effects of antidiuretic hormone.
• Chest X-rays may be normal in early stages; pulmonary congestion may be seen in later stages.
• Hemodynamic monitoring may reveal characteristic patterns of intracardiac pressures and cardiac output, which are used to guide fluid and drug management. (See Putting hemodynamic monitoring to use .)
• Electrocardiography determines the heart rate and detects arrhythmias, ischemic changes, and myocardial infarction.
• Echocardiography determines left ventricular function and reveals valvular abnormalities.

Treatment

Correction of shock typically involves the following measures:

• identification and treatment of the underlying cause, if possible
• maintaining a patent airway; preparing for intubation and mechanical ventilation if the patient develops respiratory distress
• supplemental oxygen to increase oxygenation
• continuous cardiac monitoring to detect changes in heart rate and rhythm; administration of antiarrhythmics, as necessary
• initiating and maintaining at least two intravenous lines with large-gauge needles for fluid and drug administration
• intravenous fluids, crystalloids, colloids, or blood products, as necessary, to maintain intravascular volume.

Additional therapy for hypovolemic shock may include:

• pneumatic antishock garment, although controversial, which may be applied to control both internal and external hemorrhage by direct pressure
• fluids such as normal saline or lactated Ringer's solution, initially, to restore filling pressures
• packed red blood cells in hemorrhagic shock to restore blood loss and improve oxygen-carrying capacity of the blood.

PUTTING HEMODYNAMIC MONITORING TO USE Hemodynamic monitoring provides information on intracardiac pressures and cardiac output. To understand intracardiac pressures, picture the cardiovascular system as a continuous loop with constantly changing pressure gradients that keep the blood moving. RIGHT ATRIAL PRESSURE (RAP), OR CENTRAL VENOUS PRESSURE (CVP) The RAP reflects right atrial, or right heart, function and end-diastolic pressure. Normal: 1 to 6 mm Hg (1.34 to 8 cm H 2 O). (To convert mm Hg to cm H 2 0, multiply mm Hg by 1.34) Elevated value suggests: right ventricular (RV) failure, volume overload, tricuspid valve stenosis or regurgitation, constrictive pericarditis, pulmonary hypertension, cardiac tamponade, or RV infarction. Low value suggests: reduced circulating blood volume. RIGHT VENTRICULAR PRESSURE (RVP) RV systolic pressure normally equals pulmonary artery systolic pressure; RV end-diastolic pressure, which equals right atrial pressure, reflects RV function. Normal : systolic, 15 to 25 mm Hg; diastolic, 0 to 8 mm Hg. Elevated value suggests: mitral stenosis or insufficiency, pulmonary disease, hypoxemia, constrictive pericarditis, chronic heart failure, atrial and ventricular septal defects, and patent ductus arteriosus. PULMONARY ARTERY PRESSURE Pulmonary artery systolic pressure reflects right ventricular function and pulmonary circulation pressures. Pulmonary artery diastolic pressure (PADP) reflects left ventricular (LV) pressures, specifically left ventricular end-diastolic pressure. Normal: Systolic, 15 to 25 mm Hg; diastolic, 8 to 15 mm Hg; mean, 10 to 20 mm Hg. Elevated value suggests: LV failure, increased pulmonary blood flow (left or right shunting, as in atrial or ventricular septal defects), and in any condition causing increased pulmonary arteriolar resistance. PULMONARY CAPILLARY WEDGE PRESSURE (PCWP) PCWP reflects left atrial and LV pressures unless the patient has mitral stenosis. Changes in PCWP reflect changes in LV filling pressure. The heart momentarily relaxes during diastole as it fills with blood from the pulmonary veins; this permits the pulmonary vasculature, left atrium, and left ventricle to act as a single chamber. Normal : mean pressure, 6 to 12 mm Hg. Elevated value suggests: LV failure, mitral stenosis or insufficiency, and pericardial tamponade. Low value suggests: hypovolemia. LEFT ATRIAL PRESSURE This value reflects left ventricular end-diastolic pressure in patients without mitral valve disease. Normal: 6 to 12 mm Hg. CARDIAC OUTPUT Cardiac output is the amount of blood ejected by the heart each minute. Normal: 4 to 8 liters; varies with a patient's weight, height, and body surface area. Adjusting the cardiac output to the patient's size yields a measurement called the cardiac index.

Additional measures for cardiogenic shock may include:

• inotropic drugs such as dopamine, dobutamine, amrinone, and epinephrine, to increase contractility of the heart and increase cardiac output
• vasodilators, such as nitroglycerin or nitroprusside, given with a vasopressor to reduce the workload of the left ventricle
• diuretics to reduce preload, if patient has fluid volume overload
• intra-aortic balloon pump therapy to reduce the work of the left ventricle by decreasing systemic vascular resistance. Diastolic pressure is increased, resulting in improved coronary artery perfusion
• thrombolytic therapy or coronary artery revascularization to restore coronary artery blood flow, if cardiogenic shock is due to acute myocardial infarction
• emergency surgery to repair papillary muscle rupture or ventricular septal defect, if either is the cause of cardiogenic shock
• ventricular assist device to assist the pumping action of the heart when intra-aortic balloon pump and drug therapy fail
• cardiac transplantation, which may be considered when other medical and surgical therapeutic measures fail.

Correction of septic shock may also include:

• antibiotic therapy to eradicate the causative organism
• inotropic and vasopressor drugs, such as dopamine, dobutamine, and norepinephrine, to improve perfusion and maintain blood pressure
• although still investigational, monoclonal antibodies to tumor necrosis factor, endotoxin, and interleukin-1, to counteract mediators of septic shock.

Additional therapy for neurogenic shock may include:

• vasopressor drugs to raise blood pressure by vasoconstriction
• fluid replacement to maintain blood pressure and cardiac output.

Tetralogy of Fallot

Tetralogy of Fallot is a combination of four cardiac defects: ventricular septal defect (VSD), right ventricular outflow tract obstruction (pulmonary stenosis), right ventricular hypertrophy, and dextroposition of the aorta, with overriding of the VSD. Blood shunts from right to left through the VSD, allowing unoxygenated blood to mix with oxygenated blood and resulting in cyanosis. This cyanotic heart defect sometimes coexists with other congenital acyanotic heart defects, such as patent ductus arteriosus or atrial septal defect. It accounts for about 10% of all congenital defects and occurs equally in males and females. Before surgical advances made correction possible, about one-third of these children died in infancy.

Causes

The cause of tetralogy of Fallot is unknown. It may be associated with:

• fetal alcohol syndrome
• thalidomide use during pregnancy.

Pathophysiology

In tetralogy of Fallot, unoxygenated venous blood returning to the right side of the heart may pass through the VSD to the left ventricle, bypassing the lungs, or it may enter the pulmonary artery, depending on the extent of the pulmonic stenosis. Rather than originating from the left ventricle, the aorta overrides both ventricles.

The VSD usually lies in the outflow tract of the right ventricle and is generally large enough to permit equalization of right and left ventricular pressures. However, the ratio of systemic vascular resistance to pulmonary stenosis affects the direction and magnitude of shunt flow across the VSD. Severe obstruction of right ventricular outflow produces a right-to-left shunt, causing decreased systemic arterial oxygen saturation, cyanosis, reduced pulmonary blood flow, and hypoplasia of the entire pulmonary vasculature. Right ventricular hypertrophy develops in response to the extra force needed to push blood into the stenotic pulmonary artery. Milder forms of pulmonary stenosis result in a left-to-right shunt or no shunt at all.

Signs and symptoms

The following signs and symptoms may occur:

• cyanosis, the hallmark of tetralogy of Fallot, is caused by a right-to-left shunt
• cyanotic or “blue” spells (Tet spells), characterized by dyspnea; deep, sighing respirations; bradycardia; fainting; seizures; and loss of consciousness following exercise, crying, straining, infection, or fever. It may result from reduced oxygen to the brain because of increased right-to-left shunting, possibly caused by spasm of the right ventricular outflow tract, increased systemic venous return, or decreased systemic arterial resistance
• clubbing, diminished exercise tolerance, increasing dyspnea on exertion, growth retardation, and eating difficulties in older children due to poor oxygenation
• squatting with shortness of breath to reduce venous return of unoxygenated blood from the legs and to increase systemic arterial resistance
• loud systolic murmur best heard along the left sternal border, which may diminish or obscure the pulmonic component of S ₂
• continuous murmur of the ductus in a patient with a large patent ductus, which may obscure systolic murmur
• thrill at the left sternal border caused by abnormal blood flow through the heart
• obvious right ventricular impulse and prominent inferior sternum associated with right ventricular hypertrophy.

Complications

Possible complications of tetralogy of Fallot include:

• pulmonary thrombosis
• venous thrombosis
• cerebral embolism
• infective endocarditis
• risk of spontaneous abortion, premature birth, and low-birth-weight infants born to women with tetralogy of Fallot.

Diagnosis

The following tests help diagnose tetralogy of Fallot:

• Chest X-rays may demonstrate decreased pulmonary vascular marking (depending on the severity of the pulmonary obstruction), an enlarged right ventricle, and a boot-shaped cardiac silhouette.
• Electrocardiography shows right ventricular hypertrophy, right axis deviation and, possibly, right atrial hypertrophy.
• Echocardiography identifies septal overriding of the aorta, the VSD, and pulmonary stenosis, and detects the hypertrophied walls of the right ventricle.
• Laboratory testing reveals diminished oxygen saturation and polycythemia (hematocrit may be more than 60%) if the cyanosis is severe and longstanding, predisposing the patient to thrombosis.
• Cardiac catheterization confirms the diagnosis by providing visualization of pulmonary stenosis, the VSD, and the overriding aorta and ruling out other cyanotic heart defects. This test also measures the degree of oxygen saturation in aortic blood.

Treatment

Tetralogy of Fallot may be managed by:

• a knee-chest position, and administration of oxygen and morphine to improve oxygenation
• palliative surgery with a Blalock-Taussig procedure, which joins the subclavian artery to the pulmonary artery to enhance blood flow to the lungs to reduce hypoxia
• prophylactic antibiotics to prevent infective endocarditis or cerebral abscesses
• phlebotomy to reduce polycythemia
• corrective surgery to relieve pulmonary stenosis and close the VSD, directing left ventricular outflow to the aorta.

Transposition of the great arteries

In this cyanotic congenital heart defect, the great arteries are reversed such that the aorta arises from the right ventricle and the pulmonary artery from the left ventricle, producing two noncommunicating circulatory systems (pulmonic and systemic). The right-to-left shunting of blood leads to an increased risk of heart failure and anoxia. Transposition accounts for about 5% of all congenital heart defects and often coexists with other congenital heart defects, such as ventricular septal defect (VSD), VSD with pulmonary stenosis, atrial septal defect (ASD), and patent ductus arteriosus (PDA). It affects two to three times more males than females.

Causes

The cause of this disorder is unknown.

Pathophysiology

Transposition of the great arteries results from faulty embryonic development. Oxygenated blood returning to the left side of the heart is carried back to the lungs by a transposed pulmonary artery. Unoxygenated blood returning to the right side of the heart is carried to the systemic circulation by a transposed aorta.

Communication between the pulmonary and systemic circulations is necessary for survival. In infants with isolated transposition, blood mixes only at the patent foramen ovale and at the patent ductus arteriosus, resulting in slight mixing of unoxygenated systemic blood and oxygenated pulmonary blood. In infants with concurrent cardiac defects, greater mixing of blood occurs.

Signs and symptoms

The following signs and symptoms may occur:

• cyanosis and tachypnea that worsens with crying within the first few hours after birth, when no other heart defects exist that allow mixing of systemic and pulmonary blood. Cyanosis may be minimized with associated defects such as ASD, VSD, or PDA
• gallop rhythm, tachycardia, dyspnea, hepatomegaly, and cardiomegaly within days to weeks due to heart failure
• loud S ₂ because the anteriorly transposed aorta is directly behind the sternum
• murmurs of ASD, VSD, or PDA
• diminished exercise tolerance, fatigability, and clubbing due to reduced oxygenation.

Complications

Transposition of the great arteries may be complicated by:

• heart failure
• infective endocarditis.

Diagnosis

The following tests help diagnose transposition of the great arteries:

• Chest X-rays are normal in the first days after birth. Within days to weeks, right atrial and right ventricular enlargement characteristically cause the heart to appear oblong. X-ray may also show increased pulmonary vascular markings, except when pulmonary stenosis exists.
• Electrocardiography typically reveals right axis deviation and right ventricular hypertrophy but may be normal in a neonate.
• Echocardiography demonstrates the reversed position of the aorta and pulmonary artery, and records echoes from both semilunar valves simultaneously, due to aortic valve displacement. It also detects other cardiac defects.
• Cardiac catheterization reveals decreased oxygen saturation in left ventricular blood and aortic blood; increased right atrial, right ventricular, and pulmonary artery oxygen saturation; and right ventricular systolic pressure equal to systemic pressure. Dye injection reveals the transposed vessels and the presence of any other cardiac defects.
• Arterial blood gas analysis indicates hypoxia and secondary metabolic acidosis.

Treatment

Treatment of this disorder may involve:

• prostaglandin infusion to keep the ductus arteriosus patent until surgical correction
• atrial balloon septostomy (Rashkind procedure) during cardiac catheterization if needed as a palliative measure until surgery can be performed; enlarges the patent foramen ovale and thereby improves oxygenation and alleviates hypoxia by allowing greater mixing of blood from the pulmonary and systemic circulations
• digoxin and diuretics after atrial balloon septostomy to lessen heart failure until the infant is ready to withstand corrective surgery (usually between birth and age 1)
• surgery to correct transposition, although the procedure depends on the physiology of the defect.

Valvular heart disease

In valvular heart disease, three types of mechanical disruption can occur: stenosis, or narrowing, of the valve opening; incomplete closure of the valve; or prolapse of the valve. Valvular disorders in children and adolescents most commonly occur as a result of congenital heart defects, whereas in adults, rheumatic heart disease is a common cause.

Causes

The causes of valvular heart disease are varied and are different for each type of valve disorder. (See Types of valvular heart disease .)

Pathophysiology

Pathophysiology of valvular heart disease varies according to the valve and the disorder.

Mitral regurgitation. Any abnormality of the mitral leaflets, mitral annulus, chordae tendineae, papillary muscles, left atrium, or left ventricle can lead to mitral regurgitation. Blood from the left ventricle flows back into the left atrium during systole, causing the atrium to enlarge to accommodate the backflow. As a result, the left ventricle also dilates to accommodate the increased volume of blood from the atrium and to compensate for diminishing cardiac output. Ventricular hypertrophy and increased end-diastolic pressure result in increased pulmonary artery pressure, eventually leading to left-sided and right-sided heart failure.

Mitral stenosis. Narrowing of the valve by valvular abnormalities, fibrosis, or calcification obstructs blood flow from the left atrium to the left ventricle. Consequently, left atrial volume and pressure rise and the chamber dilates. Greater resistance to blood flow causes pulmonary hypertension, right ventricular hypertrophy, and right-sided heart failure. Also, inadequate filling of the left ventricle produces low cardiac output.

Aortic regurgitation. Blood flows back into the left ventricle during diastole, causing fluid overload in the ventricle, which dilates and hypertrophies. The excess volume causes fluid overload in the left atrium and, finally, the pulmonary system. Left-sided heart failure and pulmonary edema eventually result.

Aortic stenosis. Increased left ventricular pressure tries to overcome the resistance of the narrowed valvular opening. The added workload increases the demand for oxygen, and diminished cardiac output causes poor coronary artery perfusion, ischemia of the left ventricle, and left-sided heart failure.

Pulmonic stenosis. Obstructed right ventricular outflow causes right ventricular hypertrophy, eventually resulting in right-sided heart failure.

Signs and symptoms

The clinical manifestations vary according to the type of valvular defects. (See Types of valvular heart disease , for specific clinical features of each valve disorder.)

Complications

Possible complications of valvular heart disease include:

• heart failure
• pulmonary edema
• thromboembolism
• endocarditis.

Diagnosis

The diagnosis of valvular heart disease can be made through cardiac catheterization, chest X-rays, echocardiography, or electrocardiography. (See Types of valvular heart disease .)

Treatment

Correcting this disorder typically involves:

• digoxin, a low-sodium diet, diuretics, vasodilators, and especially angiotensin-converting enzyme inhibitors to treat left ventricular failure
• oxygen in acute situations, to increase oxygenation
• anticoagulants to prevent thrombus formation around diseased or replaced valves
• prophylactic antibiotics before and after surgery or dental care to prevent endocarditis
• nitroglycerin to relieve angina in conditions such as aortic stenosis
• beta-adrenergic blockers or digoxin to slow the ventricular rate in atrial fibrillation or atrial flutter
• cardioversion to convert atrial fibrillation to sinus rhythm
• open or closed commissurotomy to separate thick or adherent mitral valve leaflets
• balloon valvuloplasty to enlarge the orifice of a stenotic mitral, aortic, or pulmonic valve
• annuloplasty or valvuloplasty to reconstruct or repair the valve in mitral regurgitation
• valve replacement with a prosthetic valve for mitral and aortic valve disease.

Varicose veins

Varicose veins are dilated, tortuous veins, engorged with blood and resulting from improper venous valve function. They can be primary, originating in the superficial veins, or secondary, occurring in the deep veins.

Primary varicose veins tend to be familial and to affect both legs; they are twice as common in females as in males. They account for approximately 90% of varicose veins; about 10% to 20% of Americans have primary varicose veins. Usually, secondary varicose veins occur in one leg. Both types are more common in middle adulthood.

Without treatment, varicose veins continue to enlarge. Although there is no cure, certain measures such as walking and use of compression stockings can reduce symptoms. Surgery may remove varicose veins but the condition can occur in other veins.

Causes

Primary varicose veins can result from:

• congenital weakness of the valves or venous wall
• conditions that produce prolonged venous stasis or increased intra-abdominal pressure such as pregnancy, obesity, constipation, or wearing tight clothes
• occupations that necessitate standing for an extended period of time
• family history of varicose veins.

Secondary varicose veins can result from:

• deep vein thrombosis
• venous malformation
• arteriovenous fistulas
• trauma to the venous system
• occlusion.

Pathophysiology

Veins are thin-walled, distensible vessels with valves that keep blood flowing in one direction. Any condition that weakens, destroys, or distends these valves allows the backflow of blood to the previous valve. If a valve cannot hold the pooling blood, it can become incompetent, allowing even more blood to flow backward. As the volume of venous blood builds, pressure in the vein increases and the vein becomes distended. As the veins are stretched, their walls weaken and they lose their elasticity. As the veins enlarge, they become lumpy and tortuous. As hydrostatic pressure increases, plasma is forced out of the veins and into the surrounding tissues, resulting in edema.

TYPES OF VALVULAR HEART DISEASE CAUSES AND INCIDENCE CLINICAL FEATURES DIAGNOSTIC MEASURES Mitral stenosis Results from rheumatic fever (most common cause) Most common in females May be associated with other congenital anomalies Dyspnea on exertion, paroxysmal nocturnal dyspnea, orthopnea, weakness, fatigue, and palpitations Peripheral edema, jugular vein distention, ascites, and hepatomegaly (right ventricular failure) Crackles, atrial fibrillation, and signs of systemic emboli Auscultation reveals a loud S 1 or opening snap and a diastolic murmur at the apex Cardiac catheterization: diastolic pressure gradient across valve; elevated left atrial and pulmonary capillary wedge pressures (PCWP) > 15 mm Hg with severe pulmonary hypertension; elevated right-sided heart pressure with decreased cardiac output (CO); and abnormal contraction of the left ventricle Chest X-rays: left atrial and ventricular enlargement, enlarged pulmonary arteries, and mitral valve calcification Echocardiography: thickened mitral valve leaflets and left atrial enlargement Electrocardiography: left atrial hypertrophy, atrial fibrillation, right ventricular hypertrophy, and right axis deviation Mitral insufficiency Results from rheumatic fever, hypertrophic cardiomyopathy, mitral valve prolapse, myocardial infarction, severe left ventricular failure, or ruptured chordae tendineae Associated with other congenital anomalies such as transposition of the great arteries Rare in children without other congenital anomalies Orthopnea, dyspnea, fatigue, angina, and palpitations Peripheral edema, jugular vein distention, and hepatomegaly (right ventricular failure) Tachycardia, crackles, and pulmonary edema Auscultation reveals a holosystolic murmur at apex, a possible split S 2 , and an S 3 Cardiac catheterization: mitral regurgitation with increased left ventricular end-diastolic volume and pressure, increased atrial pressure and PCWP, and decreased CO Chest X-rays: left atrial and ventricular enlargement and pulmonary venous congestion Echocardiography: abnormal valve leaflet motion, and left atrial enlargement Electrocardiography: may show left atrial and ventricular hypertrophy, sinus tachycardia, and atrial fibrillation Aortic insufficiency Results from rheumatic fever, syphilis, hypertension, or endocarditis, or may be idiopathic Associated with Marfan syndrome Most common in males Associated with ventricular septal defect, even after surgical closure Dyspnea, cough, fatigue, palpitations, angina, and syncope Pulmonary congestion, left ventricular failure, and “pulsating” nail beds (Quincke's sign) Rapidly rising and collapsing pulses (pulsus biferiens), cardiac arrhythmias, and widened pulse pressure Auscultation reveals an S 3 and a diastolic blowing murmur at left sternal border Palpation and visualization of apical impulse in chronic disease Cardiac catheterization: reduction in arterial diastolic pressures, aortic regurgitation, other valvular abnormalities, and increased left ventricular end-diastolic pressure Chest X-rays: left ventricular enlargement and pulmonary venous congestion Echocardiography: left ventricular enlargement, alterations in mitral valve movement (indirect indication of aortic valve disease), and mitral thickening Electrocardiography: sinus tachycardia, left ventricular hypertrophy, and left atrial hypertrophy in severe disease Aortic stenosis Results from congenital aortic bicuspid valve (associated with coarctation of the aorta), congenital stenosis of valve cusps, rheumatic fever, or atherosclerosis in the elderly Most common in males Dyspnea on exertion, paroxysmal nocturnal dyspnea, fatigue, syncope, angina, and palpitations Pulmonary congestion, and left ventricular failure Diminished carotid pulses, decreased cardiac output, and cardiac arrhythmias; may have pulsus alternans Auscuitation reveaIs systolic murmur heard at base or in carotids and, possibly, an S 4 Cardiac catheterization: pressure gradient across valve (indicating obstruction), and increased left ventricular end-diastolic pressures Chest X-rays: valvular calcification, left ventricular enlargement, and pulmonary vein congestion Echocardiography: thickened aortic valve and left ventricular wall, possibly coexistent with mitral valve stenosis Electrocardiography: left ventricular hypertrophy Pulmonic stenosis Results from congenital stenosis of valve cusp or rheumatic heart disease (infrequent) Associated with tetralogy of Fallot Asymptomatic or symptomatic with dyspnea on exertion, fatigue, chest pain, and syncope May cause jugular distention/right ventricular failure Auscultation reveals a systolic murmur at the left sternal border and a split S 2 with a delayed or absent pulmonic component Cardiac catheterization: increased right ventricular pressure, decreased pulmonary artery pressure, and abnormal valve orifice Electrocardiography: may show right ventricular hypertrophy, right axis deviation, right atrial hypertrophy, and atrial fibrillation

People who stand for prolonged periods of time may also develop venous pooling because there is no muscular contraction in the legs forcing blood back up to the heart. If the valves in the veins are too weak to hold the pooling blood, they begin to leak, allowing blood to flow backward.

Signs and symptoms

The following signs and symptoms may occur:

• dilated, tortuous, purplish, ropelike veins, particularly in the calves, due to venous pooling
• edema of the calves and ankles due to deep vein incompetence
• leg heaviness that worsens in the evening and in warm weather; caused by venous pooling
• dull aching in the legs after prolonged standing or walking, which may be due to tissue breakdown
• aching during menses as a result of increased fluid retention.

Complications

Possible complications of varicose veins include:

• blood clots secondary to venous stasis
• venous stasis ulcers
• chronic venous insufficiency.

AGE ALERT As a person ages, veins dilate and stretch, increasing susceptibility to varicose veins and chronic venous insufficiency. Because the skin is very friable and can easily break down, ulcers in the elderly caused by chronic venous insufficiency may take longer to heal.

Diagnosis

The following tests help diagnose varicose veins:

• Manual compression test detects a palpable impulse when the vein is firmly occluded at least 8” above the point of palpation, indicating incompetent valves in the vein.
• Trendelenburg's test (retrograde filling test) detects incompetent deep and superficial vein valves.
• Photoplethysmography characterizes venous blood flow by noting changes in the skin's circulation.
• Doppler ultrasonography detects the presence or absence of venous backflow in deep or superficial veins.
• Venous outflow and reflux plethysmography detects deep venous occlusion; this test is invasive and not routinely used.
• Ascending and descending venography demonstrates venous occlusion and patterns of collateral flow.

Treatment

Correction of this disorder typically involves:

• if possible, treatment of the underlying cause, such as an abdominal tumor or obesity
• antiembolism stockings or elastic bandages to counteract swelling by supporting the veins and improving circulation
• a regular exercise program to promote muscular contraction to force blood through the veins and reduce venous pooling
• injection of a sclerosing agent into small to medium-sized varicosities
• surgical stripping and ligation of severe varicose veins
• phlebectomy, removing the varicose vein through small incisions in the skin, may be performed in an outpatient setting.

Additional treatment measures include the following:

• Discourage the patient from wearing constrictive clothing that interferes with venous return.
• Encourage the obese patient to lose weight, to reduce increased intra-abdominal pressure.
• Elevate the legs above the heart whenever possible to promote venous return.
• Instruct the patient to avoid prolonged standing or sitting because these actions enhance venous pooling.

Ventricular septal defect

In a ventricular septal defect (VSD), the most common acyanotic congenital heart disorder, an opening in the septum between the ventricles allows blood to shunt between the left and right ventricles. This results in ineffective pumping of the heart and increases the risk for heart failure.

VSDs account for up to 30% of all congenital heart defects. The prognosis is good for defects that close spontaneously or are correctable surgically, but poor for untreated defects, which are sometimes fatal in children by age 1, usually from secondary complications.

Causes

A VSD may be associated with the following conditions:

• fetal alcohol syndrome
• Down syndrome and other autosomal trisomies
• renal anomalies
• patent ductus arteriosus and coarctation of the aorta
• prematurity.

Pathophysiology

In infants with VSD, the ventricular septum fails to close completely by the eighth week of gestation. VSDs are located in the membranous or muscular portion of the ventricular septum and vary in size. Some defects close spontaneously; in other defects, the septum is entirely absent, creating a single ventricle. Small VSDs are likely to close spontaneously. Large VSDs should be surgically repaired before pulmonary vascular disease occurs or while it is still reversible.

VSD isn't readily apparent at birth because right and left pressures are approximately equal and pulmonary artery resistance is elevated. Alveoli are not yet completely opened, so blood doesn't shunt through the defect. As the pulmonary vasculature gradually relaxes, between 4 and 8 weeks after birth, right ventricular pressure decreases, allowing blood to shunt from the left to the right ventricle. Initially, large VSD shunts cause left atrial and left ventricular hypertrophy. Later, an uncorrected VSD causes right ventricular hypertrophy due to increasing pulmonary resistance. Eventually, biventricular heart failure and cyanosis (from reversal of the shunt direction) occur. Fixed pulmonary hypertension may occur much later in life with right-to-left shunting (Eisenmenger's syndrome), causing cyanosis and clubbing of the nail beds.

Signs and symptoms

Signs and symptoms of a VSD may include:

• thin, small infants who gain weight slowly when a large VSD is present secondary to heart failure
• loud, harsh systolic murmur heard best along the left sternal border at the third or fourth intercostal space, caused by abnormal blood flow through the VSD; murmur is widely transmitted
• palpable thrill caused by turbulent blood flow between the ventricles through a small VSD
• loud, widely split pulmonic component of S ₂ caused by increased pressure gradient across the VSD
• displacement of point of maximal impulse to the left due to hypertrophy of the heart

AGE ALERT Typically, in infants the apical impulse is palpated over the fourth intercostal space, just to the left of the midclavicular line. In children older than age 7, it's palpated over the fifth intercostal space. When the heart is enlarged, the apical beat is displaced to the left or downward.

• prominent anterior chest secondary to cardiac hypertrophy
• liver, heart, and spleen enlargement because of systemic congestion
• feeding difficulties associated with heart failure
• diaphoresis, tachycardia, and rapid, grunting respirations secondary to heart failure
• cyanosis and clubbing if right-to-left shunting occurs later in life secondary to pulmonary hypertension.

Complications

Complications of a VSD may include:

• pulmonary hypertension
• infective endocarditis
• pneumonia
• heart failure
• Eisenmenger's syndrome
• aortic regurgitation (if the aortic valve is involved).

Diagnosis

The following tests help diagnose ventricular septal defect:

• Chest X-rays appear normal in small defects. In large VSDs, the X-ray may show cardiomegaly, left atrial and left ventricular enlargement, and prominent vascular markings.
• Electrocardiography may be normal with small VSDs, whereas in large VSDs it may show left and right ventricular hypertrophy, suggestive of pulmonary hypertension.
• Echocardiography can detect VSD in the septum, estimate the size of the left-to-right shunt, suggest pulmonary hypertension, and identify associated lesions and complications.
• Cardiac catheterization determines the size and exact location of the VSD and the extent of pulmonary hypertension; it also detects associated defects. It calculates the degree of shunting by comparing the blood oxygen saturation in each ventricle. The oxygen saturation of the right ventricle is greater than normal because oxygenated blood is shunted from the left ventricle to the right.

Treatment

Typically, correction of a VSD may involve:

• early surgical correction for a large VSD, usually performed using a patch graft, before heart failure and irreversible pulmonary vascular disease develop
• placement of a permanent pacemaker, which may be necessary after VSD repair if complete heart block develops from interference with the bundle of His during surgery
• surgical closure of small defects using sutures. They may not be surgically repaired if the patient has normal pulmonary artery pressure and a small shunt
• pulmonary artery banding to normalize pressures and flow distal to the band and to prevent pulmonary vascular disease if the child has other defects and will benefit from delaying surgery
• digoxin, sodium restriction, and diuretics before surgery to prevent heart failure
• prophylactic antibiotics before and after surgery to prevent infective endocarditis.