Ventricular septal defect: a review.

Henri Roger, in 1879, was the first to accurately describe the clinical manifestations of ventricular septal defect, and the term “maladie de Roger” is often used in connection with these malformations. The lesion and the problems associated with it have attracted a great deal of attention in recent years, particularly with the advent of open heart surgery and a means for affecting a cure. Embryology of The Ventricular SeptumThe septum develops between the fourth and seventh weeks of gestational life.1 At the end of the fourth week a median partition begins to project inward from the base of the common ventricle. This septum is brought into existence by the enlargement of the future halves of the ventricle on either side of it, and increases in height proportionately as the ventricular sacs become deeper. The anterior part of the septum is derived from a union of the ventral atrioventricular cushion, a local endocardial thickening, with this muscular septum below, and the right and left conus ridges from above. The posterior septum arises from the posterior atrioventricular cushion and the portion of the muscular septum that arises from the apical and dorsal walls of the embryo.2 The central points of fusion of these regions occurs at the pars membranacea. The anlagen of this part of the septum are a matter of dispute. Classification of Ventricular Septal DefectsDefects of the septum may involve regions of the septum related to either the outflow or inflow tracts.3The outflow portion of the right ventricle lies between the pulmonary valve above and the nearest part of the tricuspid valve below. Defects in this region are all spoken of as high defects. The inflow tract lies posterior and caudal to the outflow tract. The outflow tract of the right side of the ventricular septum is divided into superior and inferior regions by the crista supraventricularis. This muscular ridge lies on the floor of the right ventricle between the papillary muscle of the conus below and posteriorly, and the pulmonary valve above and anteriorly. The lesions inferior to the crista represent the most common site for ventricular septal defects, and anatomically lie just below the aortic valve cusps. This is generally spoken of as a membranous ventricular septal defect, but in most cases Becu et a13 found that the defect involved little or none of the membranous septum, but that the size of the defect was mainly related to the muscular part of the septum that was malformed. The lesions superior to the crista are closely related to the pulmonary valve whose tissue forms their upper border. The membranous septum is generally intact. Also known as high defects are those lesions in the upper or basal portion of the septum that are in close relation to the mitral and tricuspid valves.