Figure 23. Atrioventricular septal defect. CT scan shows an atrioventricular septal defect (*) and a free-floating common atrioventricular valve with a bridging leaflet (arrowheads) that involves the adjacent atrial and ventricular septa as well as the atrioventricular septum. Dextrocardia and a right descending aorta are also noted.