Cardiomyopathy of English cocker spaniels.

In an English Cocker Spaniel kennel in which the adult population varied between 20 and 30, 11 dogs had evidence of cardiomyopathy over a 5-year period. Three of the affected dogs were found dead, with cardiac enlargement and pulmonary edema found at necropsy. In the other affected dogs, dyspnea and other signs of congestive heart failure developed; 5 of these died. Necropsies were performed on 4 dogs, all of which had cardiac enlargement and pulmonary edema. In 3 dogs, the dyspnea abated with treatment. Four of the 11 affected dogs were less than 5 years old. Chronic valvular disease was discounted because some dogs had no murmurs and, at necropsy, valve leaflets were only slightly thickened. Heart weight ranged from 1.21%-1.56% of body weight.