Spontaneous cor pulmonale in laboratory beagles.

Right heart failure associated with postmortem evidence of pulmonary hypertension (cor pulmonale) was observed in nearly 1% of the young beagles of a large research colony. During the past 18 years, 176 dogs with cor pulmonale were observed. Most cases occurred between September and April of each year. Nearly equal numbers of males and females were involved, and some siblings were affected. Ninety-six percent of known affected dogs died, and 85% of the deaths occurred by 5 weeks of age. Clinically, most dogs were stunted and exhibited ascites, subcutaneous edema, hypothermia, dyspnea, cyanosis, and systolic murmur. Radiography revealed cardiomegaly, and electrocardiography revealed right axis deviation and an enlarged right atrium. Postmortem evidence of cor pulmonale included subcutaneous edema, ascites, hydrothorax, mediastinal and mesenteric edema, splenomegaly, centrolobular hepatic congestion and necrosis, right ventricular hypertrophy, interstitial pneumonia, and medial hypertrophy of pulmonary arteries and arterioles. The specific cause of the disease was not determined.