Atrioventricular Septal Defect (Atrioventricular Canal Defect; Endocardial Cushion Defect) By Lee B Beerman, MD, Children's Hospital of Pittsburgh of the University of Pittsburgh School of Medicine Reviewed / Revised Apr 2023 View Patient Education Symptoms and Signs Diagnosis Treatment Key Points More Information Topic Resources Atrioventricular septal defect... Atrioventricular (AV) septal defect consists of an ostium primum type atrial septal defect and a common AV valve, with or without an associated inlet (AV septal type) ventricular septal defect (VSD).