Predictors of exercise capacity in patients with hypertrophic obstructive cardiomyopathy

Hypertrophic obstructive cardiomyopathy (HOCM) patients exhibit compromised peak exercise capacity (VO₂ peak). Importantly, severely reduced VO₂ peak is directly related to increased morbidity and mortality in these patients. Therefore, we sought to determine clinical predictors of VO₂ peak in HOCM patients. HOCM patients who performed symptom-limited cardiopulmonary exercise testing between 1995 and 2016 were included for analysis. Peak VO₂ was reported as absolute peak VO₂, indexed to body weight and analyzed as quartiles, with quartile 1 representing the lowest VO₂ peak. Step-wise regression models using demographic features and clinical and physiologic characteristics were created to determine predictors of HOCM patients with the lowest VO₂ peak. We included 1177 HOCM patients (age: 53 ± 14 years; BMI: 24 ± 12 kg/m² ) with a VO₂ peak of 18.0 ± 5.6 mL/kg/min. Significant univariate predictors of the lowest VO₂ peak included age, female sex, New York Health Association (NYHA) class, BMI, left atrial volume index, E/e’, E/A, hemoglobin, N-terminal pro b-type natriuretic peptide (NT-proBNP), and a history of diabetes, hypertension, stroke, atrial fibrillation, or coronary artery disease. Independent predictors of the lowest VO₂ peak included age (OR, CI: 1.03, 1.02–1.06; p < 0.0001), women (4.66, 2.94–7.47; p = 0.001), a history of diabetes (2.05, 1.17–3.60; p = 0.01), BMI (0.94, 0.92–0.96; p < 0.0001), left atrial volume index (1.07, 1.05–1.21; p = 0.04), E/e’ (1.05, 1.01–1.08; p = 0.004), hemoglobin (0.76, 0.65–0.88; p = 0.0004), and NT-proBNP (1.72, 1.42–2.11; p < 0.0001). These findings demonstrate that demographic factors (i.e., age and sex), comorbidities (e.g., diabetes and obesity), echocardiography indices, and biomarkers (e.g., hemoglobin and NT-proBNP) are predictive of severely compromised VO₂ peak in HOCM patients.