Tricuspid atresia in a foal.

An Arabian crossbred foal was examined because of a suspected congenital cardiac anomaly. There was a grade V/V crescendo-decresendo holosystolic murmur and thrill in the left 4th intercostal space. The foal was slightly cyanotic and polycythemic. Electrocardiography suggested left ventricular hypertrophy. Angiography and cardiac and vascular pressure recordings led to a diagnosis of pulmonic stenosis. The foal died after cardiac bypass and corrective surgery. Postmortem examination revealed an enlarged right atrium, atresia of the tricuspid orifice, a large, fenestrated patent foramen ovale, eccentric left ventricular hypertrophy, and a large interventricular septal defect. The right ventricle had a small lumen and a relatively thick wall. There was valvular and supravalvular pulmonic stenosis, with poststenotic dilatation of the pulmonary artery. A single coronary artery originated from the anterior sinus of the aorta.