Perimembranous and muscular ventricular septal defects--morphology revisited in the era of device closure.

Transcatheter closure of ventricular septal defects has advanced rapidly with improvements in device designs. We review the morphology of ventricular septal defects in heart specimens for a closer look at the shapes, sizes, and proximity to important structures. The three main types of defects, perimembranous, muscular, doubly committed and juxta-arterial, all have variable morphologies within each group. Oval rather than round shapes are more common. The shapes of muscular defects, in particular, can change from one side of the septum to the other. Perimembranous defects are close to the aortic and tricuspid valves and adjacent to the atrioventricular conduction bundle. Ventricular septal defects are three-dimensional and require careful assessment of proximity to important structures in their vicinity when assessing suitability for interventional closure.