5 In early era, it was considered that left AV valve is a trifoliate valve different from mitral valve morphologically, so it was not needed to join superior and inferior bridging leaflets.
Partial Atrioventricular septal defect is a congenital malformation of atrioventricular canal with crescent shaped atrial septal defect above the AV valve but no ventricular septal defect below this valve and have two separate right and left AV valves with cleft in left AV valve.
Multiple 1-2-mm opaque nodules were present along the 12-15-mm-wide free margin of the right AV valve
Incomplete endocardial cushion formation leads to variations of primum atrial septal defect, AV valve
malformations, and/or membranous ventricular septal defect (Van Mierop & Kutsche, 1990).
The left atrioventricular (AV) valve is thin, bicuspid, and membranous, whereas the right AV valve
is a simple muscular flap devoid of chordae tendinae.
In 2005, we validated quantitative echocardiographic measurements that helped in diagnosing of AVSD with no primum ASD: the measurements of the left ventricle inlet to outlet distance ratio and the percentage of the left AV valve
guarded by the mural leaflet (3).
The right and left components of the common AV valves
were at the same place with evidence of regurgitation through both the components of the valve.