Abstract
Atresia of the atrioventricular (AV) orifice was observed in 9 (1.3%) of 694 bovine hearts showing congenital cardiac anomalies. All of the 9 hearts were detected in Japanese Black cattle. The atrial situs of these hearts was situs solitus. Among the 9 cases with the AV orificial atresia, 8 showed the left, while remaining 1 showed the right AV orifices. In 6 of the 8 hearts with the left AV oricicial atresia the right atrium was connected to a morphologically right ventricle and their ventriculoarterial (VA) connections were double outlet right ventricle in 4, concordant connection in 1 and aortic atresia in remaining 1, respectively. In other 2 of 8 the right atrium was connected to a morphologically left ventricle and their VA connection was concordant connection. In a case with the right AV orificial atresia the left atrium was connected to a morphologically left ventricle and its VA connection was concordant connection.
