A 48-year-old with hypertrophic obstructive cardiomyopathy (HOCM) has dynamic LV outflow tract obstruction. Maneuvers that worsen the obstruction include:

• A Squatting and leg raising (both worsen obstruction by increasing preload)
• B Valsalva maneuver (strain phase) and standing from squat (both reduce preload, decreasing LV cavity size and worsening dynamic obstruction) ✓
• C Passive leg raising and hand-grip exercise (both worsen obstruction)
• D Amyl nitrite inhalation worsens obstruction; phenylephrine improves it; standing worsens it — all three in the same direction

Explanation

In HOCM, the gradient across the LVOT is dynamic and worsens when the LV cavity becomes smaller (reduced preload or afterload): (1) Valsalva maneuver strain phase: increased intrathoracic pressure reduces venous return → smaller LV cavity → worsened obstruction + increased murmur. (2) Standing from squatting: venous pooling in legs reduces preload → smaller LV → worsened obstruction. Conversely, squatting increases preload (enlarges LV) and afterload (reduces obstruction). Passive leg raising increases venous return (reduces obstruction). Amyl nitrite reduces afterload and preload, worsening obstruction. Phenylephrine (alpha-1 agonist) increases afterload without tachycardia, enlarging LV and reducing obstruction. Option D is internally inconsistent since amyl nitrite and phenylephrine have opposite effects.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.