Pathologic anatomy of the cardiomyopathies. Idiopathic dilated and hypertrophic types, infiltrative types, and endomyocardial disease with and without eosinophilia.
This presentation summarizes necropsy observations in patients with three types of cardiomyopathy: idiopathic, infiltrative, and endomyocardial disease. The idiopathic variety is subdivided into two types depending on the size of the ventricular cavity. In the dilated ventricular type the left ventricular wall is frequently less than 1.5 cm. thick, intracardiac thrombi are common, the atrioventricular valve rings usually are mildly dilated, and focal myocardial and endocardial scars are common. In the nondilated type (hypertrophic cardiomyopathy), the ventricular septum is usually thicker than the left ventricular free wall, which also is thick (greater than 1.5 cm.). When the septum is similar in thickness to the left ventricular free wall (symmetric), left ventricular outflow obstruction does not occur. When the septum is thicker than the left ventricular free wall (asymmetric), left or right ventricular outflow obstruction may or may not be present. The orientation of myocardial fibers one to another in the ventricular septum in the nondilated (hypertrophic) type is abnormal, whereas it is normal in the dilated ventricular type. Intracardiac thrombi are rare and atrioventricular valve rings are never dilated in the nondilated type of idiopathic cardiomegaly. The infiltrative types of cardiomyopathies include iron, calcium, lipids, mucopolysaccharides, granulomas, amyloid, and neoplasms. The first four usually are located within myocardial cells and the latter three, between myocardial cells. It is probable that all these myocardial infiltrates are capable of producing cardiac dysfunction, primarily on a restrictive basis. Endomyocardial disease may or may not be associated with eosinophilia. When the latter occurs, the eosinophils are structurally normal. Death is related to congestive cardiac failure. This category is actuality also in idiopathic.