Partial atrioventricular septal defects (pAVSD) accounted for 80% of atrioventricular septal defects (AVSD). These defects have also been called Partial atrioventricular canal, Ostium primum atrial septal defect, of Endocardial cushion defect. Main anatomic lesions included: primum defect of the atrial septum, two separate atrioventricular valve. The left valve (mitral valve) may have a cleft that causes valve regurgitation.