Abnormal cardiac septum morphology Atrioventricular canal defect true Hole in center of heart UMLS:C0344783 Hole in centre of heart UMLS:C1389016 UMLS:C0014116 SNOMEDCT_US:15459006 A defect of the atrioventricular septum of the heart. HP:0005139 HP:0006695 HP:0010439 HP:0005298 DOID:50651 Endocardial cushion defect Fyler:0606 During atrioventricular valvuloseptal morphogenesis, the endocardial cushions expand as they are infiltrated by extracellular matrix secreted from the surrounding myocardium. The cushions then fuse and are remodeled to form the atrioventricular valves and septa. Failure of this process results in AVSD, with the degree of severity dependent on the stage at which the developmental failure occurs. AVSD are a spectrum of cardiac malformations that result in a persistent common atrioventricular canal. Fyler:606 Fyler:1100 Atrioventricular septal defect