The Threshold for a Clinically Meaningful Improvement in Cardiopulmonary Exercise Testing Measures for Patients With Symptomatic Obstructive Hypertrophic Cardiomyopathy

ABSTRACT BACKGROUND Peak oxygen uptake (pVO 2 ) is a strong, independent predictor of adverse cardiovascular outcomes, supporting cardiopulmonary exercise testing as a primary end point assessing efficacy of novel drug therapies in obstructive hypertrophic cardiomyopathy (oHCM) clinical trials. However, characterizing changes in pVO 2 that patients perceive as beneficial or meaningful (ie, minimal important difference [MID]) has not been determined. METHODS Data from patients with symptomatic oHCM enrolled in SEQUOIA-HCM and MAPLE-HCM were pooled. A total of 282 patients were randomized 1:1 to aficamten (5–20 mg daily) or matching placebo in SEQUOIA-HCM, and 175 patients were randomized 1:1 to aficamten (5-20mg daily) or to metoprolol (50–200 mg) in MAPLE-HCM; follow-up in both trials was 24 weeks. Primary outcome was change from baseline to week 24 (Δ) in pVO 2 using Patient Global Impression of Change with anchor-based analysis to define MID. RESULTS At week 24, ΔpVO 2 (mL/kg/min) that corresponded to no change, one-category improvement, and one-category worsening were –0.05 (95% CI, –0.58 to 0.48), +0.35 (95% CI, –0.22 to 0.91), and –0.61 (95% CI, –1.36 to 0.13), respectively. Similarly, minute ventilation to carbon dioxide production ratio (VE/VCO 2 ) slope that corresponded to no change, one-category improvement, and one-category worsening were 0.16 (95% CI, –0.59 to 0.90), –1.15 (95% CI, – 1.89 to –0.42), and 0.88 (95% CI, –0.42 to 2.19), respectively. In a responder analysis using this new threshold for pVO 2 , 60% of patients receiving aficamten achieved a ΔpVO 2 ≥0.35 versus 31% of patients on placebo or metoprolol (odds ratio, 3.4 [95% CI, 2.3–4.9], P