Pulmonary atresia with dextroposition of the aorta and ventricular septal defect in three Arabian foals

Three Arabian males foals were presented with cyanosis, heart murmur, and exercise intolerance, Results of clinical evaluation suggested a tentative diagnosis of ventricular septal defect in conjunction with malformations of the great arteries. Each foal had a poor prognosis and was killed at the owners' requests. At necropsy, the malformed hearts of the three foals were virtually identical. Each heart had a large defect in the upper interventricular septum. The aorta originated from the hypertrophied right ventricle and partially overrode the ventricular septal defect. The aortic ostium was guarded by three semilunar valvules. The position of the valvules and the ostia of the coronary arteries was abnormal. The pulmonary arteries arose from the persistent ductus arteriosus. The pulmonary trunk was reduced to a thin, fibrous cord extending from a short and narrow persistent ductus arteriosus to the level of the semilunar valve, where it fused with the wall of the aorta. No communication of the atretic pulmonary trunk with the cavity of the right ventricle was seen.