Atrioventricular canal defect

Atrioventricular canal malformation, formerly known as endocardial cushion defect, ostium primum defect, common atrioventricular canal, or primum atrial septal defect, is a series of congenital cardiac malformations caused by hypoplasia of the septum primum and endocardial cushions. The main pathological feature is partial absence of atrial and ventricular septal tissue above and below the atrioventricular ring, which may be accompanied by varying degrees of atrioventricular valve malformation. Atrioventricular canal malformation is uncommon, accounting for only 5% of all atrial septal defect cases.