Fig. 3

AVSD with normal orientation of the atrial septum (a). Atrioventricular malalignment with leftward deviation of the atrial septum results in double outlet right atrium (b). Extreme atrioventricular malalignment and fusion of the septum primum with the lateral atrioventricular junction results in UBC (c). (Redrawn according to [6, 7])