The heart has a remarkable capacity to work unceasingly throughout the entire human lifespan. It is a small, two-sided muscular pump with the two vascular circuits placed in series.

When an increased workload is imposed for a long period (as occurs in patients with systemic hypertension), the left ventricle undergoes hypertrophy. When this compensatory mechanism ultimately fails, patients develop complications of congestive heart failure.

Damage to the myocardium, caused mostly by ischemic heart disease, also limits the capacity of the left ventricle to pump blood and similarly results in heart failure. If the initial impairment is severe, cardiac output is not maintained, and the result is cardiogenic shock. Valvular heart disase also causes hemodynamic disorders of perfusion, which may give rise to pulmonary congestion and heart failure.

By far the most common type of heart disease responsible for cardiac failure is ischemic heart disease. Virtually all of the organs of the body suffer from the effects of heart failure.

Here are the Key Points:

1. Left-sided heart failure is the more common type of heart failure. As a compensatory response to left ventricular failure, left atrial pressure and pulmonary venous pressure both increase, resulting in pulmonary congestion. Capillaries in the alveolar septae fill with blood. The alveoli contain edema and hemosiderin-laden macrophages (heart failure cells).

2. Ischemic heart disease is typically the consequence of atherosclerosis of the coronary arteries. Ischemic heart disease is by far the most common type of heart disease in the United States, where it remains the leading cause of death.

3. The major elements that predispose a person to coronary heart disease are elevated blood cholesterol level, hypertension, and cigarette smoking.

4. Infarcts may involve predominantly the subendocardial portion of the myocardium, or they may be transmural.

5. Polymorphonuclear leukocytes are attracted to the necrotic myocytes and reach their maximum concentration in infarcts after 2 days. The process of repair is initiated at about 5 days, with sprouting of capillaries and the onset of collagen deposition.

6. Complications of myocardial infarction include arrhythmias, cardiogenic shock, rupture, and aneurysms.

7. Cor pulmonale is defined as right ventricular hypertrophy and dilatation secondary to pulmonary hypertension. It may be caused by a variety of lung diseases, including chronic bronchitis and emphysema.

8. Bacterial endocarditis refers to colonization of the heart valves by bacteria. Before the antibiotic era, bacterial endocarditis was almost invariable fatal. Mitral valve prolapse and congenital heart disease are today the most frequent basis for bacterial endocarditis in adults. Transient bacteremia from any procedure may lead to infective endocarditis.

9. Nonbacterial thrombotic (marantic) endocarditis refers to the presence of sterile vegetations on apparently normal cardiac valves, almost always in association with cancer or some other wasting disease.

10. Calcific aortic stenosis refers to a narrowing of the aortic valve lumen as a result of the deposition of calcium in the cusps and valve ring.

The following images illustrate Key Morphological Concepts:

1. This is an example of MYOCARDIAL INFARCTION. Note the rupture of the papillary muscle.

2. This is an example of a large MURAL THROMBUS in the heart. Mural thrombi typically form at sites of an acute myocardial infarct. The major complication of mural thrombosis is arterial embolization and gangrene of the extremities.

3. This is an example of CALCIFIC AORTIC STENOSIS. This congenital bicuspid aortic valve has undergone dystrophic calcification. Large calcium deposits lead to impeded blood flow (aortic stenosis) and arotic insufficiency.

4. This is an example of BACTERIAL ENDOCARDITIS. The mitral valve shows destructive vegetations composed of bacteria and fibrin-rich debris. The most serious complication of bacterial endocarditis is congestive heart failure.

5. This is an example of GANGRENE of the extremity caused by embolization. Possible causes of arterial embolization include mural thrombosis and bacterial endocarditits.