Dissecting functional impairment in hypertrophic cardiomyopathy by dynamic assessment of diastolic reserve and outflow obstruction: A combined cardiopulmonary-echocardiographic study

Exercise limitation in hypertrophic cardiomyopathy (HCM) patients is often attributed to left ventricular outflow tract (LVOT) obstruction and diastolic impairment. However, these features assessed at rest fail to predict performance. To evaluate their variations and interplay during effort in HCM, we performed echocardiographic assessment of diastolic function and outflow obstruction during cardiopulmonary test (CPX). Methods We included 197 HCM patients (mean age 45 ± 15 years, 129 males), undergoing CPX. Diastolic dysfunction (DD) grade was measured at baseline and at peak exercise. Oxygen consumption (VO2 max) values < 75% of maximum predicted were considered abnormal. Results One hundred-seven patients (54%) had DD grade II-III at rest (Rest DD), 40 (20%) showed preserved diastolic function (grade 0/I) both at rest and on effort (No DD). The remaining 50 patients (25%) had a grade 0/I pattern at rest but exhibited impaired diastolic reserve on exercise (Latent DD). Latent DD was associated with higher prevalence of patients with VO2 < 75% in both the non-obstructive and the latent-obstructive group: at multivariate regression analysis, left atrium volume index, LV obstruction at rest and rest or latent DD were significantly associated with lower peak VO2. Excluding rest-obstructive patients from the analysis, rest- or latent DD were the only determinants of exercise impairment (latent-obstructive, OR 8.9; 95% CI 1.5–18.8; p = 0.012; non-obstructive, OR 2.2; 95% CI 1.0–5.8; p = 0.03). Conclusion Latent DD is a major determinant of exercise intolerance in HCM. Comprehensive assessment of outflow obstruction and diastolic reserve during cardiopulmonary test represents an important adjunct to clinical management.