A 45-year-old man presents with progressive dyspnea, exertional chest pain, and multiple syncopal episodes. On examination, there is a harsh systolic murmur at the left lower sternal border that increases with Valsalva maneuver and decreases with squatting. Echo shows asymmetric septal hypertrophy with septal-to-posterior wall ratio of 1.8 and dynamic LVOT obstruction with resting gradient 70 mmHg. What is the first-line pharmacological treatment?
- A Amlodipine (dihydropyridine calcium channel blocker)
- B Isosorbide dinitrate
- C Metoprolol succinate or verapamil ✓
- D Digoxin to improve contractility
Correct answer: C. Metoprolol succinate or verapamil
Explanation
Hypertrophic cardiomyopathy (HCM) with LVOT obstruction is treated with negative inotropic agents to reduce contractility, slow heart rate, and prolong diastolic filling. Beta-blockers (metoprolol, atenolol) are first-line; non-dihydropyridine calcium channel blockers (verapamil, diltiazem) are used when beta-blockers are not tolerated. Dihydropyridine CCBs and vasodilators (nitrates) are contraindicated as they reduce preload and afterload, worsening the dynamic obstruction. Digoxin increases contractility and is also contraindicated.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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