Morphology of the ventricular septal defect in two types of interrupted aortic arch.

Whether coarctation or interruption (IAA) of the aorta, ostensibly similar in morphology (and management), result from the same or different developmental errors can be inferred by examining the pattern of associated anomalies. Among the most common associated lesions, especially in IAA, is ventricular septal defect (VSD). Although muscular and perimembranous VSDs are the most common in aortic coarctation, the prevalence of various VSD morphologies in IAA has not been examined in as much detail. As part of the recent prospective multiinstitutional study of IAA conducted by the Congenital Heart Surgeons Society, 53 echocardiographic studies were reviewed; 42 of 45 patients with type B IAA had VSDs involving maldevelopment of the outflow region. In type A IAA, a significantly lower percentage (4/8) had this kind of VSD. Therefore the mechanism of development of type B IAA is likely to be different from that of type A IAA.