Cardiomyopathy in the dog

Medical records of 12 dogs determined at necropsy as having had cardiomyopathy and of 5 live dogs with clinical, electrocardiographic and radiographic evidence of the disease were reviewed. Congestive cardiomyopathy was the most common form of the disease, affecting 15 of the 17 dogs. The dogs were primarily of large breeds and ranged in age from 2 to 8 years. Clinical findings included right and left congestive heart failure presenting as pulmonary congestion and edema, pleural effusion, hepatomegaly, and ascites. Thoracic radiographs showed moderate severe enlargement of all cardiac chambers and evidence of congestive heart failure. Atrial fibrillation was the predominant rhythmn; ventricular premature contractions and left ventricular hypertrophy were sometimes noted. At necropsy, biventricular dilation including dilation of the atrioventricular annular rings and accompanying massive atrial dilation was observed. Myocardial contractility was poor and had resulted in dilation of the heart chambers with minimal hypertrophic responses. The atrioventricular valve leaflets and chordae tendinae were usually near normal. Medical treatment included rest, digoxin, and diuretics, Medical or electrical cardioversion of atrial fibrillation to normal sinus rhythm was also attempted. Prognosis for congestive cardiomyopathy is very poor. The average survival time after onset of signs is 6-12 months; 1 dog in our study survived for 20 months. In contrast to congestive cardiomyopathy, the hypertrophic form is rare in the dog. Only two of the dogs studied had hypertrophic cardiomyopathy; one case was diagnosed at necropsy and one by angiocardiography. Both had features of idiopathic hypertrophic subaortic stenosis (IHSS) as reported in man.