Question

Which of the following is a known complication of subpulmonic VSD

• A. RV outflow tract obstruction
• B. LV outflow tract obstruction
• C. Aortic Regurgitation
• D. Pulmonary Hypertension is the earliest finding

Hint:

Supracristal/Subpulmonic VSD = High risk of Right Coronary Cusp prolapse $\rightarrow$ Aortic Regurgitation (due to the Venturi effect). Surgical closure is indicated even for small defects if AR or prolapse begins.

Answer 1

The Correct Option is C

Concept:
Subpulmonic (also called doubly committed subarterial, supracristal, or infundibular) VSD is a defect located immediately beneath both the aortic and pulmonary semilunar valve rings.
This defect is particularly prevalent in Asian populations (accounting for up to $30\%$ of all VSDs in these groups) and carries a well-known risk of progressive valve distortion.
Explanation:
• In subpulmonic VSD, there is a lack of superior muscular and fibrous support beneath the right coronary cusp (and occasionally the non-coronary cusp) of the aortic valve.

• During systole, high-velocity jet flow through the defect creates a localized low-pressure field (the Venturi effect) that sucks the unsupported right coronary aortic cusp down into the defect.

• This repetitive mechanical pulling leads to progressive cusp elongation, cusp prolapse, and progressive aortic regurgitation (AR).

• Once aortic regurgitation develops, it tends to progress rapidly and rarely resolves spontaneously; therefore, early surgical closure is indicated whenever cusp prolapse or AR is detected, regardless of shunt magnitude.
Final Answer:
Aortic regurgitation resulting from aortic valve cusp prolapse via the Venturi effect is a well-established classic complication of subpulmonic (supracristal) VSD.