Abstract
Atrioventricular septal defects were observed in 5 of 687 (0.73%) bovine hearts with congenital cardiovascular anomalies. All of these 5 hearts had no connecting tongue of valve tissue joining together the anterior and posterior bridging cusps and showed the complete form of the atrioventricular septal defects with a common atrioventricular orifice. In each of these hearts the anterior bridging cusp extended from the left ventricle across the interventricular septum to the right ventricle. Each anterior bridging cusp was not attached to the interventricular septum and was free floating over the septum, moreover the right ventricular portion of this cusp inserted to the great papillary muscle of the right ventricle by the chordae tendineae (Rastelli, type C).
