Histopathological study on myocardial hypertrophy associated with ischemic heart disease.

The mode and causes of myocardial hypertrophy occurring in association with ischemic heart disease were studied. The investigation involved autopsied hearts (15 cases of subendocardial infarction, 27 of transmural infarction, 20 of non-infarcted three vessel disease and 17 controls) and biopsied materials obtained during coronary-aorta bypass graft surgery (23 patients with angina pectoris and 46 with myocardial infarction). The subendocardial infarction group showed most marked myocardial hypertrophy that reflected extensive infarction and fibrosis, dilatation of the left ventricular cavity and the loss of myocytes. Despite a marked decrease in the number of myocyte layers, the residual myocardium of the left ventricle was uniformly hypertrophic, accompanied by an increase in the heart weight. The larger the area of fibrosis, the more marked was myocardial hypertrophy irrespective of the luminal diameter of the responsible coronary artery. These findings indicate that myocardial hypertrophy associated with ischemic heart disease is enhanced by the compensatory mechanisms for a decrease in the contractile myocardium due to fibrosis.