Atlas of pathophysiology, 2 Edition

Part II - Disorders

Cardiovascular disorders

Valvular Heart Disease

In valvular heart disease, three types of mechanical disruptions can occur: stenosis, or narrowing, of the valve opening; incomplete closure of the valve; or prolapse of the valve.

Causes

The causes of valvular heart disease are varied and differ for each type of valve disorder.

Mitral stenosis

·   Rheumatic fever

·   Congenital anomalies

Mitral insufficiency

·   Rheumatic fever

·   Mitral valve prolapse

·   Myocardial infarction

·   Severe left ventricular failure

·   Ruptured chordae tendinae

·   Marfan syndrome

Aortic insufficiency

·   Rheumatic fever

·   Syphilis

·   Hypertension

·   Endocarditis

·   Marfan syndrome

Aortic stenosis

·   Congenital

·   Bicuspid aortic valve

·   Rheumatic fever

·   Atherosclerosis

Pulmonic stenosis

·   Congenital

·   Rheumatic fever (rare)

Pathophysiology

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

Mitral stenosis: Structural abnormality, fibrosis, or calcification obstructs blood flow from the left atrium to the left ventricle. 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. Inadequate filling of the left ventricle causes low cardiac output.

Mitral insufficiency: An 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, and the atrium enlarges to accommodate the backflow. 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 raise pulmonary artery pressure, eventually leading to left-sided and right-sided heart failure.

Aortic insufficiency: 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 result.

Aortic stenosis: Over time, left ventricular pressure rises 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, resulting in right-sided heart failure.

Signs and symptoms

The clinical manifestations vary according to valvular defects and the severity of the defect. The patient may be asymptomatic.

Common to all valvular disorders

·   Dyspnea, weakness, fatigue

Mitral stenosis

·   Orthopnea

·   Palpitations, right-sided heart failure, crackles, jugular vein distention

·   Atrial fibrillation

·   Diastolic thrill, loud S1, opening snap-diastolic murmur

Mitral insufficiency

·   Palpitations, angina, tachycardia

·   Left-sided heart failure, pulmonary edema, crackles

·   Split S2; S3; holosystolic murmur at apex

·   Apical thrill

Aortic insufficiency

·   Palpitations, angina, syncope

·   Cough

·   Pulmonary congestion, left-sided heart failure

·   Quincke's sign

·   Pulsus biferiens, visible apical pulse

·   S3 and blowing diastolic murmur at left sternal border

Aortic stenosis

·   Palpitations, angina, arrhythmias

·   Syncope

·   Pulmonary congestion, left-sided heart failure

·   Diminished carotid pulses, systolic thrill (carotid)

·   Decreased cardiac output

·   Systolic ejection murmur that radiates to neck, S4

Pulmonic stenosis

·   Commonly produces no symptoms

·   Syncope, chest pain, right-sided heart failure

·   Systolic murmur at left sternal border, S2 split

Diagnostic test results

Diagnostic test results vary with the type of valvular disease that's present. Cardiac catheterization, chest X-ray, echocardiography, and electrocardiography are the standard diagnostic tools used to detect valvular heart disease.

Mitral stenosis

·   Cardiac catheterization reveals diastolic pressure gradient across the valve; elevated left atrial and pulmonary artery wedge pressures (PAWP) with severe pulmonary hypertension; elevated right-sided heart pressure with decreased cardiac output; and abnormal contraction of the left ventricle.

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·   Chest X-ray shows left atrial and ventricular enlargement, enlarged pulmonary arteries, and mitral valve calcification.

·   Echocardiography reveals left atrial and ventricular enlargement, enlarged pulmonary arteries, and mitral valve calcification.

·   Electrocardiography (ECG) detects left atrial hypertrophy, atrial fibrillation, right ventricular hypertrophy, and right axis deviation.

Mitral insufficiency

·   Cardiac catheterization reveals mitral regurgitation with increased left ventricular end-diastolic volume and pressure, increased atrial pressure and PAWP, and decreased cardiac output.

·   Chest X-ray shows left atrial and ventricular enlargement and pulmonary venous congestion.

·   Echocardiography shows abnormal valve leaflet motion and left atrial enlargement.

·   ECG may show left atrial and ventricular hypertrophy, sinus tachycardia, and atrial fibrillation.

Aortic insufficiency

·   Cardiac catheterization reveals reduction in arterial diastolic pressure, aortic regurgitation, other valvular abnormalities, and increased left ventricular end-diastolic pressure.

·   Chest X-ray shows left ventricular enlargement and pulmonary vein congestion.

·   Echocardiography shows left ventricular enlargement, alteration in mitral valve movement, and mitral valve thickening.

·   ECG shows sinus tachycardia, left ventricular hypertrophy, and left atrial hypertrophy in severe disease.

Aortic stenosis

·   Cardiac catheterization reveals pressure gradient across valve and increased left ventricular end-diastolic pressures.

·   Chest X-ray shows valvular calcification, left ventricular enlargement, and pulmonary vein congestion.

·   Echocardiography shows thickened aortic valve and left ventricular wall, possibly coexisting with mitral valve stenosis.

·   ECG shows left ventricular hypertrophy.

Pulmonic stenosis

·   Cardiac catheterization reveals increased right ventricular pressure, decreased pulmonary artery pressure, and abnormal valve orifice.

·   ECG shows right ventricular hypertrophy, right axis deviation, right atrial hypertrophy, and atrial fibrillation.

Treatment

·   Digoxin, anticoagulants, nitroglycerin, beta-adrenergic blockers, diuretics, vasodilators, angiotensin-converting enzyme inhibitors

·   Low-sodium diet

·   Oxygen

·   Prophylactic antibiotics for invasive procedures, such as dental cleanings, endoscopies, and other procedures where the risk of introducing bacteria into the bloodstream is present

·   Cardioversion

·   Open or closed commissurotomy

·   Annuloplasty or valvuloplasty

·   Prosthetic valve for mitral or aortic valve disease

HEART VALVES

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