Double outlet right ventricle with subpulmonary ventricular septal defect (Taussig-Bing anomaly) and other complex congenital cardiac malformations in an American Quarter Horse foal

A 4-week-old American Quarter Horse colt presented with a recent history of diarrhea and decreased activity level. On initial physical examination, the animal was bright and alert and major findings were limited to a loud systolic heart murmur radiating widely over both sides of the thorax. While in the hospital, the clinical condition of the foal warranted further imaging to determine the cause and extent of cardiac disease. A variety of congenital cardiac malformations were identified during echocardiographic examination and autopsy, including a double outlet right ventricle and a subpulmonary interventricular septal defect (Taussig-Bing anomaly), ventricular inversion with atrioventricular discordance, tricuspid valve atresia, a septum primum interatrial septal defect, mitral valve dysplasia with a cleft in the septal mitral valve cusp, aortic, and subaortic stenosis, tubular hypoplasia of the ascending aorta and the aortic arch, a patent ductus arteriosus, an aberrant circumflex coronary artery, and aberrant left and right subclavian arteries. Echocardiographic and postmortem findings of the cardiac defects in this foal are presented and discussed.