What does hypertrophic obstructive cardiomyopathy (HOCM) murmur sound like?

• A. Holosystolic murmur
• B. Opening snap
• C. Mid-systolic crescendo-decrescendo murmur similar to AS
• D. Diastolic rumble

Answer: (C)

Hypertrophic obstructive cardiomyopathy causes a dynamic obstruction of the left ventricular outflow tract, so the murmur reflects that process. The sound is a midsystolic, harsh, crescendo-decrescendo murmur, similar in timing and overall feel to aortic stenosis, because both peak in midsystole and arise from flow across a narrowed outflow tract. It’s typically best heard at the left lower sternal border.

A key feature is its dynamic nature: it gets louder when preload is reduced (standing up, Valsalva) and softer with increased preload or afterload (squatting, handgrip), since these maneuvers alter the degree of obstruction from systolic anterior motion of the mitral valve and septal hypertrophy. This distinguishes it from fixed murmurs like those from aortic stenosis, which don’t intensify with decreased preload in the same way.