The pattern of myocardial degeneration in nonischemic congestive cardiomyopathy

The histopathologic features of nonischemic congestive cardiomyopathy (CCM) include diffuse and focal fibrosis, vacuolar degeneration, and myofiber hypertrophy. Eleven patients with CCM and five controls were studied. Fibrosis and degree of vacuolization were quantified by means of stereologic techniques; myocardial cell diameter was measured with an ocular micrometer. Five levels of the left ventricular free wall were examined. Area I was immediately subepicardial, and area 5 was immediately subendocardial. In all areas, fibrosis, vacuolization, and fiber diameter were significantly greater in the experimental group than in the control group (P less than 0.05). In addition, fibrosis and vacuolization had an umbrella distribution, which peaked in area 4, the area adjacent to the subendocardium (P less than 0.01). The distributions of fibrosis and vacuolar degeneration suggest compromised blood flow to the inner myocardial layers, with relative sparing of the immediate subendocardial region owing to its proximity to the left ventricular cavity.