Randomized Trial of Metoprolol in Patients with Obstructive Hypertrophic Cardiomyopathy

<p><strong>Background: </strong>The use of β-adrenergic receptor blocking agents in symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM) rests on clinical experience and observational cohort studies.</p> <p><strong>Objectives: </strong>This study aimed to investigate the effects of metoprolol on left ventricular outflow tract (LVOT) obstruction, symptoms, and exercise capacity in patients with obstructive hypertrophic cardiomyopathy.</p> <p><strong>In this</strong> double-blind, placebo-controlled, randomized crossover trial 29 patients with obstructive HCM and New York Heart Association (NYHA) functional class II or higher symptoms from May 2018 to September 2020 were enrolled.</p> <p>Patients received metoprolol or placebo for 2 consecutive 2-week periods in random order. The effect parameters were LVOT gradients, NYHA functional class, Canadian Cardiovascular Society (CCS) angina class, Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS), and cardiopulmonary exercise testing.</p> <p><strong>Results: </strong>Compared with placebo, the LVOT gradient during metoprolol was lower at rest (25 mm Hg vs 72 mm Hg [P = 0.007),</p> <p>at peak exercise it was 28 mm Hg vs 62 mm Hg [P &lt; 0.001),</p> <p>and postexercise (45 mm Hg vs 115 mm Hg [P &lt; 0.0001).</p> <p>During metoprolol treatment, 14% of patients were in NYHA functional class III or higher compared with 38% of patients receiving placebo (P &lt; 0.01). Similarly, no patients were in Canadian Cardiovascular Society (CCS) angina class III or higher during metoprolol treatment compared with 10% during placebo treatment (P &lt; 0.01). These findings were confirmed by higher Kansas City Cardiomyopathy Questionnaire Overall Summary Score during metoprolol treatment (P = 0.039). Measures of exercise capacity, peak oxygen consumption, and N-terminal pro-B-type natriuretic peptide did not differ between the study arms.</p> <p><strong>Conclusions: </strong>Compared with placebo, metoprolol reduced LVOT obstruction at rest and du