A 28-year-old athlete collapses during a race. Resuscitated from ventricular fibrillation. Echocardiography shows asymmetric septal hypertrophy (IVS 22 mm), SAM (systolic anterior motion of MV), dynamic LVOT gradient of 65 mmHg. What is the first-line pharmacological treatment for symptomatic obstructive HCM?
- A Non-vasodilating beta-blocker (metoprolol or propranolol) ✓
- B Mavacamten — cardiac myosin inhibitor
- C Verapamil (calcium channel blocker) as monotherapy
- D Disopyramide added to beta-blocker for LVOT obstruction
Explanation
Non-vasodilating beta-blockers (metoprolol, propranolol, atenolol) are first-line pharmacological therapy for symptomatic obstructive HCM. They reduce heart rate, prolong diastolic filling time, decrease contractility, and reduce the LVOT gradient during exercise. Verapamil is second-line if beta-blockers are not tolerated. Disopyramide (a Na+ channel blocker with negative inotropic effect) is added as third-line or in combination with beta-blockers for persistent obstruction. Mavacamten, a cardiac myosin inhibitor (approved by FDA in 2022 based on EXPLORER-HCM and VALOR-HCM trials), significantly reduces LVOT gradient and symptoms but is currently positioned as second-line after beta-blockers fail.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.