Figure 6

In this heart (A) with a doubly committed and juxta-arterial ventricular septal defect there is fibrous continuity between the leaflets of the arterial valves (black dots) at the roof of the defect, with a muscular bar (yellow dots) separating the leaflets of the tricuspid and aortic valves. The muscular bar is formed by fusion of the caudal limb of the septal band (red Y) with the inner heart curvature, the latter also known as the ventriculo-infundibular fold. As shown in Figure 6B, defects with fibrous continuity between the leaflets of the arterial valves (black dots), due to failure of muscularisation of the subpulmonary infundibulum, can also extend to become perimembranous. The leaflets of the tricuspid and aortic valves in this specimen are in fibrous continuity (yellow dots), with the defect again positioned within the Y of the septal band.