A 38-year-old man presents with exertional syncope and a 4th heart sound. His father died suddenly at age 42. Echocardiogram shows asymmetric septal hypertrophy (IVS 22 mm), systolic anterior motion of the mitral valve, and a LVOT gradient of 48 mmHg at rest increasing to 90 mmHg with Valsalva. He is in sinus rhythm. Which medication is CONTRAINDICATED in symptomatic hypertrophic obstructive cardiomyopathy (HOCM)?
- A Nifedipine (dihydropyridine calcium channel blocker) ✓
- B Metoprolol succinate
- C Disopyramide
- D Verapamil
Explanation
In HOCM, dihydropyridine calcium channel blockers (e.g., nifedipine, amlodipine) are contraindicated because they cause vasodilation and reflex tachycardia, both of which worsen LVOT obstruction. Vasodilation reduces afterload (worsening obstruction as per the dynamic nature of HOCM gradient) and tachycardia reduces diastolic filling time, increasing gradient. Beta-blockers (metoprolol) are first-line by reducing heart rate and contractility. Disopyramide (negative inotrope) is used as add-on to beta-blockers. Non-dihydropyridine CCBs (verapamil) are alternatives when beta-blockers are not tolerated, but should be used cautiously with severe obstruction.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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