Figure 8

As shown in these specimens, it is crucial to identify the borders of ventricular septal defects, since this provides information regarding the location of the atrioventricular conduction axis. As shown in Figure 8A, the axis (red dots) will run along the postero-inferior aspect of perimembranous ventricular septal defects, in other words to the right hand of the surgeon approaching through the tricuspid valve. In contrast, when a muscular defect opens to the inlet of the right ventricle, as shown in Figure 8B, the conduction axis is located to the left hand of the surgeon approaching through the tricuspid valve. The red star shows the location of the atrioventricular node at the apex of the triangle of Koch (yellow lines).