Three cases of bovine extreme tetralogy of Fallot.

Three female Holstein calves having cyanosis of the visible mucous membrane, exercise intolerance and systolic murmur were examined. Extreme Tetralogy of Fallot with ventricular septal defect was confirmed at autopsy. All of the intrapericardial pulmonary arteries were completely absent in two cases. In the other case, the atretic pulmonary trunk, with a bicuspid valve, rose from a very small chamber which was located on the blind-ending muscular infundibulum. There was no connection between the atretic pulmonary trunk and the right ventricle.