Figure 22b. VSD. CT scans reformatted along the interventricular septum provide en face views. (a) Normal interventricular septum. (b-e) Various types of VSDs (*). (b) Large perimembranous defect (arrowheads), which typically abuts the fibrous continuity between the tricuspid and mitral valves and the aortic valve ("central fibrous body"). (c) Perimembranous defect with inlet extension (arrowheads). (d) Doubly committed juxtaarterial defect (arrowheads) immediately below the aortic and pulmonary valves. (e) Restrictive defect ("bulboventricular foramen") (arrowheads) in the double inlet ventricle.