Hypertrophic obstructive cardiomyopathy (HOCM) causes dynamic LVOT obstruction. Which bedside manoeuvre INCREASES the LVOT gradient and therefore WORSENS the murmur intensity?

• A Squatting from standing
• B Leg elevation in supine position
• C Handgrip exercise
• D Valsalva manoeuvre (straining phase) ✓

Explanation

HOCM murmur is dynamic: it increases with manoeuvres that decrease preload or afterload (thereby decreasing LV cavity size, worsening obstruction). The Valsalva straining phase reduces venous return, decreasing LV size and increasing LVOT obstruction — the murmur increases. Standing from squatting also decreases preload. Squatting from standing, leg elevation, and handgrip all increase preload or afterload, increasing LV filling, reducing obstruction, and decreasing murmur intensity. HOCM is one of only two murmurs that increase with Valsalva (the other being MVP click moving earlier).

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.