Ventricular septal defect

A ventricular septal defect is a hole in the ventricular septum, the muscular and membranous wall that divides the heart's left and right ventricles. It is one of the most common congenital heart conditions, though small restrictive muscular openings often close on their own rather than requiring treatment as a true pathological defect. Defects of this kind are common in newborns, ranging in size from a pinpoint opening to, in rare cases, complete absence of the septum resulting in a single ventricle. The septum itself is made up of a lower muscular portion and an upper membranous portion that is closely connected to the heart's electrical conduction system. In older children and adults in the United States, the membranous portion, positioned near the atrioventricular node, is the site most frequently affected and more than eighty percent of these cases go on to require surgical repair. More recent research indicates that muscular ventricular septal defects are actually more common than membranous ones and represent the single most common congenital heart anomaly, with the Copenhagen Baby Heart Study finding that roughly three to five percent of newborns have a small muscular defect.