Morphology of ventricular septal defect in complete transposition of the great arteries.

The morphologic characteristics of ventricular septal defect (VSD) was studied in 50 hearts with complete transposition of the great arteries. Except for 1 membranous and 1 subarterial defect, all VSDs could be classified into 1 of 4 categories. Group A included 14 specimens with a perimembranous defect extending into inlet and trabecular septum with rightward malalignment of the outlet septum; in this group aortic arch anomalies (6 hearts) and tricuspid valve abnormalities (7 hearts) were frequently present. Group B comprised 13 hearts with perimembranous defects extending into the inlet septum; 11 hearts in this group also had an anomalous mitral valve. Group C included 13 hearts with muscular inlet defects, with signs of spontaneous closure by marginal fibrosis in 10 cases. Group D included 8 hearts with muscular infundibular defects; in 6 of these hearts the outlet septum was malaligned to the left, causing different degrees of subpulmonary stenosis. A small second VSD was present in 5 hearts. Thus, the spectrum of VSD in transposition of the great arteries is different from that of isolated VSD.