The electrocardiogram in cardiomyopathy.

Cardiomyopathy has been defined as "a subacute or chronic disorder of heart muscle of unknown or obscure etiology, often with associated endocardial, and sometimes with pericardial, involvement, but not atherosclerotic in origin". Using this definition a differentiation of chronic cardiomyopathies into three types has been made on clinical grounds (Goodwin et al., 1961). Obstructive Cardiomyopathy. We have given this term to a group of disorders that are characterized by diffuse obstruction to outflow from the left ventricle below the aortic valve (Goodwin et al., 1960). We believe the commonest cause to be asymmetrical hypertrophy of the heart mainly involving the ventricular septum (Teare, 1958). In some patients, the major obstruction involves the inflow tract of the left ventricle, or both outflow and inflow tracts of the right ventricle, when there is evidence of obstruction at more than one site. But the commonest presentation is that of left ventricular outflow tract obstruction. The clinical features are a normal orjerky arterial pulse; an ejection murmur oflate onset maximal at the left sternal edge (and often a thrill); and absence of aortic valvular calcification or dilatation of the ascending aorta (Goodwin et al., 1960). Commonly, a family history of heart disease or of sudden death is present, and the condition mimics aortic valvular or sub-valvular stenosis. Obstruction involving the left ventricular or right ventricular inflow tracts may present signs of mitral and tricuspid stenosis respectively, while muscular obstruction to right ventricular outflow simulates pulmonary stenosis. Congestive Cardiomyopathy. This, the commonest form of cardiomyopathy, is characterized by cardiomegaly, gallop rhythm, and often pan-systolic murmurs due to mitral or tricuspid valvular insufficiency. It frequently simulates ischlemic heart disease. Constrictive Cardiomyopathy. This, the least common of the three clinical forms of cardiomyopathy, generally shows no remarkable cardiac enlargement, murmurs are trivial or absent, but a third heart sound is common, the jugular venous pressure is raised, and there are steep "x" and "y" descents. The venous pressure may rise in inspiration. This type must be distinguished from constrictive pericarditis. The object of this paper is to present an analysis of the cardiographic appearances in the three types of cardiomyopathy, and to compare these appearances with those of cardiograms of patients with disorders that clinically resemble the cardiomyopathies.