Pathologic alterations in congestive cardiomyopathy of dogs.

Eleven large-breed dogs with congestive cardiomyopathy were studied at necropsy. Seven of 11 dogs were Great Dane and 9 of 11 were male. The most common clinical signs in affected dogs were dyspnea, abdominal distention by ascites, and weight loss. Three dogs had severe congestive cardiac failure. At necropsy, gross alterations in the hearts were cardiomegaly, dilation of all chambers, opacity of the endocardium, atrial thrombosis, and disseminated foci of myocardial necrosis. Extracardiac changes included hepatic congestion, pulmonary congestion and edema, ascites, and infarction of kidney, liver, lung, and spleen. Microscopically, the affected hearts had disseminated foci of subendocardial myocardial necrosis, scattered areas of myocardial fibrosis, and medial hyperplasia of intramyocardial arteries. Ultrastructurally, degenerated cardiac muscle cells had myocytolysis, proliferated elements of sarcoplasmic reticulum, numerous myelin figures and autophagic vacuoles, large numbers of lipofuscin granules, and mitochondrial alterations. These ultrastructural alterations are similar to those described for cardiomyopathy in persons and cats.