A rare, congenital cardiac anomaly characterized by a common atrioventricular junction with a common AV valve, an interatrial communication just above the common AV valve (ostium primum defect), a posterior interventricular communication (inlet VSD), that results in shunting at both the atrial and ventricular level. Morphologically, the common atrioventricular valve has 4 or 5 leaflets including superior and inferior bridging leaflets with a single annulus.