Ventricular septal defect in interruption of aortic arch.

A necroscopy study of 34 patients with interruption of the aortic arch was carried out to characterize more fully the ventricular septal defect and the anatomic basis of subaortic obstruction. In 21 patients (61.8 percent) the site of interruption was between the left common carotid artery and the left subclavian artery; in 13 (38.2 percent) it was distal to the left subclavian artery; no case of interruption just distal to the innominate artery was found. A ventricular septal defect was present in all but two patients, both with large aortopulmonary fenestrations. All patients had visceroatrial situs solitus and D-ventricular loop. The great arteries were normally related in 33 patients and D-transposition was found in one patient. Twenty-one patients had a ventricular septal defect involving the conal septum. Conoventricular malalignment resulted in a typical subpulmonary ventricular defect. The malignant was characteristically in a leftward direction allowing for potential muscular narrowing of the left ventricular outflow tract. In some patients, the conal ventricular septal defect was characterized by a deficiency of a the conal septum without malalignment. In 4 of 21 patients with a ventricular septal defect involving the conal septum, the defect was immediately adjacent to the pulmonary.value. Typical infracristal membranous ventricular defects five patients), cushion defects (3 patients) and muscular defects (3 patients), were also found. The potential for subaortic narrowing was present in some of these patients as well. No relation between position of ventricular septal defect and type of arch interruption could be discerned. The presence or absence of subaortic obstruction was not predictive of a specific type of interruption. Similarly, although deformity of the aortic valve was not uncommon in this series, it was not associated with any specific type of interruption.