CARDIOMYOPATHY



Cardiomyopathy, a disease involving the heart muscle itself, is classified into three basic cate­gories (Table 9-1). This classification is not rigid, and some cardiomyopathies may demonstrate characteristics that overlap among the three groups.

Dilated Cardiomyopathy
In dilated cardiomyopathy, ventricular enlarge­ment occurs and systolic dysfunction results in symptoms of congestive heart failure. The cause of dilated cardiomyopathy is often not apparent but appears to be the end result of myocardial damage produced by a variety of toxic, metabolic, and infectious agents (Table 9-2). Clinical symp­toms usually develop slowly, and patients may have ventricular dysfunction for some time before symptoms, usually of both left and right ventric­ular failure, appear. Q waves may be present on ECG without infarction when extensive left ven­tricular fibrosis has occurred. Echocardiography is important to exclude other causes of congestive heart failure. A pericardial effusion is sometimes present. Ventriculography shows enlargement of the left ventricle with diffuse wall motion reduc­tion and sometimes left ventricular thrombi. Functional mitral regurgitation may be present, and occasionally it is difficult to distinguish from primary mitral regurgitation. The coronary arter­ies are normal or incidentally involved. Endo­myocardial biopsy may sometimes be useful in di­agnosing patients with cardiomyopathy.

Peripartum cardiomyopathy refers to conges­tive cardiomyopathy occurring in the last month of pregnancy or within five months of delivery in the absence of pre-existing heart disease. It occurs most frequently in multiparous blacks and is more common in older women and those with poor nu­trition, poor prenatal care, or toxemia. Doxorub­icin (Adriamycin) is an effective antitumor drug that commonly produces congestive cardiomy­opathy. The risk of toxicity appears to be related to the cumulative dose, increasing as the dose in­creases but with a relatively abrupt increase in risk after approximately 450 to 550 mg/sq m. The prognosis after development of symptoms is ex­tremely poor.