Midsystolic murmur that decreases with squatting and increases with Valsalva is most consistent with which condition?

Midsystolic murmur that decreases with squatting and increases with Valsalva is most consistent with which condition?

• A. Aortic Stenosis
• B. Mitral Valve Prolapse
• C. Hypertrophic Cardiomyopathy
• D. Pulmonic Stenosis

Answer: (C)

Dynamic obstruction of the left ventricular outflow tract drives this pattern. In hypertrophic cardiomyopathy, the thickened septum and the systolic anterior motion of the mitral valve narrow the LV outflow during the middle of systole, so a midsystolic murmur develops there. Changing preload and afterload alters how open that outflow tract is. Reducing preload/afterload (as with Valsalva or standing) makes the LV cavity smaller and the obstruction worse, so the murmur becomes louder. Increasing preload/afterload (as with squatting) enlarges the LV cavity and reduces the obstruction, so the murmur diminishes. This combination—midsystolic murmur that grows with Valsalva and shrinks with squatting—is classic for hypertrophic cardiomyopathy. Other conditions involve fixed obstructions or different timing/behavior with these maneuvers, so they don’t fit this pattern as well.

Dynamic obstruction of the left ventricular outflow tract drives this pattern. In hypertrophic cardiomyopathy, the thickened septum and the systolic anterior motion of the mitral valve narrow the LV outflow during the middle of systole, so a midsystolic murmur develops there.

Changing preload and afterload alters how open that outflow tract is. Reducing preload/afterload (as with Valsalva or standing) makes the LV cavity smaller and the obstruction worse, so the murmur becomes louder. Increasing preload/afterload (as with squatting) enlarges the LV cavity and reduces the obstruction, so the murmur diminishes.

This combination—midsystolic murmur that grows with Valsalva and shrinks with squatting—is classic for hypertrophic cardiomyopathy. Other conditions involve fixed obstructions or different timing/behavior with these maneuvers, so they don’t fit this pattern as well.