A Review of Current Thoughts*

Ventricular septal defect, alone or in combination with other cardiac malformations, is the commonest form of congenital heart disease in man. Morphogenically, the ventricular septum is composed of three parts: (a) the conal septum, (b) the septum of the endocardial cushions, and (c) the muscular septum proper. Consequently, most cono-truncal abnormalities (transposition of the great arteries, tetralogy of Fallot, common truncus arteriosus) include a defect of the ventricular septum and, similarly, most endocardial cushion defects (and all complete AV canals) have a ventricular component. Isolated ventricular septal defects may occur in any of the three parts. The majority of the complex intracardiac malformations are associated with a ventricular septal defect. The purpose of this clinical review, however, is to discuss problems relating to patients whose principal, even exclusive, problem is a defect of the ventricular septum. We will, therefore, exclude from consideration patients with tetralogy of Fallot, truncus arteriosus, transposition of the great arteries, as well as endocardial cushion defect. Furthermore, because of its invariable association with other serious malformations of the endocardial cushion as well as cono-truncal regions, we will exclude from this discussion patients with single ventricle who in our view do not simply represent very large ventricular defects but a more profound developmental abnormality (Van Praagh, Ongley, and Swan, 1964). Patients with dextrocardia will not be considered either, partly because the occurrence of a solitary ventricular defect in this setting is rare and partly because they represent unique diagnostic and surgical problems. Finally, and rather arbitrarily, we will exclude from consideration patients with ventricular septal defect