Hypertrophic cardiomyopathy with dynamic LVOTO shows which specific echocardiographic finding related to mitral valve systolic anterior motion (SAM)?

• A Anterior motion of the anterior mitral leaflet in systole contacting the interventricular septum (Venturi effect) ✓
• B Mitral valve prolapse with posterior leaflet billowing in systole
• C Restricted opening of the posterior mitral leaflet in diastole
• D Incomplete closure of the anterior leaflet causing mitral regurgitation jet directed anteriorly

Explanation

In HCM with dynamic LVOTO, the combination of a hypertrophied septum, anterior displacement of mitral apparatus, and high-velocity systolic flow creates a Venturi effect and drag force that draws the anterior mitral leaflet (and occasionally the posterior leaflet) anteriorly into the outflow tract during systole — SAM (systolic anterior motion). Contact of the mitral leaflet with the septum causes LVOTO and a posteriorly directed mitral regurgitation jet. SAM severity correlates with LVOTO gradient. Treatment includes disopyramide, beta-blockers, and surgical myectomy or alcohol septal ablation for severe cases.

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

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