Shapes and Length

1. Where is the usual VSD situated?

ANS: In the membranous septum, i.e., in a small translucent area, extending about 1 or 2 cm below the aortic valve.

Note: The attachment of the septal leaflet of the tricuspid valve bisects the membranous septum, so that the usual VSD is below the attachment, but if the VSD is above this attachment it may shunt blood directly into the right atrium.

Defects in the membranous septum below the tricuspid valve are the most common.

Membranous septum crossed by tricuspid valve

Supracristal VSD

Crista supraventriculars

Membranous VSD below tricuspid valve (usual type of VSD)

Muscular VSD

Supracristal VSD

Crista supraventriculars

Membranous VSD below tricuspid valve (usual type of VSD)

Muscular VSD

2. What are the various shapes of VSD murmurs? ANS:

Unlike some MR murmurs, VSD murmurs probably always begin with the M1.

Unlike some MR murmurs, VSD murmurs probably always begin with the M1.

3. When is the VSD murmur mostly decrescendo?

ANS: If it is of the muscular type, i.e., in the muscular part of the septum. Muscular contraction of the septum can close the VSD off toward the end of systole.

Small muscular VSD murmur in a 16-year-old girl. Her physiological S3 is loud enough to be heard at the left lower sternal border (LLSB), probably because she has a long chest with a slightly medially placed apex beat.

4. How can you make the short decrescendo of a muscular VSD obviously pansystolic?

ANS: By increasing peripheral resistance either by squatting, handgrip, or by using a vasopressor agent.

5. Why may a very large VSD produce a short ejection murmur or no murmur at all?

ANS: It may create, in effect, a single ventricle, with the same systolic pressure in both RV and LV so that the shunt murmur may be soft or may even disappear. Thus, the systolic murmur that you hear may be only an ejection murmur due to flow into a slightly dilated pulmonary artery.

Note: The syndrome of a VSD with pulmonary hypertension severe enough to cause a right-to-left shunt may be called Eisenmenger's complex, because this is what Eisenmenger originally described. If the right-to-left shunt is at PDA or ASD levels, it is called Eisenmenger syndrome.

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