Mechanisms of closure of VSDs are-

1. Muscular VSDs may close by growth or hypertrophy of muscle surrounding the edges of the defect.

2. Perimembranous VSDs may close by formation of an aneurysm. Although this is called aneurysm of the ventricular septum, it is actually formed from the septal leaflet of the tricuspid valve.

3. Outlet VSDs may close by prolapsing aortic cusp tissue. Fibrosis may also contribute.

4. Infective endocarditis- vegetations block the VSD.