Abstract
The partial form of atrioventricular septal defect without persistent ostium primum was observed in a 28-day-old female Holstein calf. The heart had a large defect in inlet ventricular septum, and the septum showed a characteristic ‘scooped-out’ appearance. In the atrial septum, the septum primum at the base connected to the limbus fosae ovalis of septum secundum joining the fibrous ring, consequently, the septum primum was not present. The septal leaflet of the left atrioventricular valve was completely divided into discrete anterior and posterior components. While, the septal leaflet of the right atrioventricular valve exhibited an incomplete cleft and produced separate left and right atrioventricular orifices. Anterior halves of both septal leaflets fused to produce a bridging cusp. The posterior component of the left septal leaflet committed to the left ventricle and the right one committed to the right ventricle. Associated cardiovascular anomalies such as double outlet right ventricle, ostium secundum defect, double cranial vena cava, and aberrant origin of left subclavian artery were demonstrated in this heart.
