Diagnosis and surgical treatment for complete atrioventricular septal defect with intact atrial septum

A six-month-old boy with Down syndrome, complete atrioventricular septal defect with intact atrial septum, and moderate left-sided atrioventricular valve regurgitation underwent surgery. The presence of a common atrioventricular junction could not be diagnosed preoperatively. Postoperative left-sided atrioventricular valve regurgitation remained mild by complete cleft closure, direct closure of incised atrial septum, and patch augmentation of the underside of septum primum.