Atrioventricular septal defect with double-outlet right atrium.

A rare type of primum atrial septal defect is described in which the atrial septum deviated to the left, resulting in a double-outlet right atrium. The obstruction at the site of the small atrial septum defect led to an elevation of the left atrial mean pressure and to pulmonary arterial hypertension. The presence of mixed blood in the right atrium caused systemic arterial desaturation. A cleft in the septal leaflet of the left atrioventricular (AV) valve caused a left ventricular-right atrial shunt, which-added to the left-to-right atrial shunt--totaled 60% of the pulmonary circulating volume. Preoperative knowledge of the anatomic features facilitated surgical repair, which consisted in resection of the abnormal septum, construction of a new septum with a Dacron patch, and closure of the septal commissure of the left-sided AV valve.