Exercise capacity in patients with hypertrophic cardiomyopathy: non-invasive hemodynamic responses to exercise and association with clinical and imaging variables

Background and aim: Hypertrophic cardiomyopathy (HCM) could be characterized by reduced exercise capacity. The intrinsic mechanisms affecting a reduced functional tolerance are not completely understood. The aim of the study was to determine the association between cardiopulmonary exercise test (CPET), non-invasively-determined hemodynamic variables, and clinical and echocardiographic variables and outcomes in patients with HCM. Methods: The study sample included 156 patients consecutively enrolled from 2007 to 2012 with a complete clinical assessment, including exercise echocardiography and CPX with impedence cardiography. Patients were followed for the composite outcome of cardiac-related death, heart transplant and functional deterioration leading to septal reduction (myectomy or alcholization). A Cox proportional hazard model was used to quantify determinants of the composite outcome. Results: Abnormalities in CPET parameters were commonly observed, with 39% (n=61) of our patients showing a reduced exercise tolerance (VO2 max 34). The variables that were independently associated with peak VO2 (R2=0.65) were age (r=-0.32, p 34 (HR: 3.14 CI 1.26 to 7.87, p=0.014) and LAVi > 40 ml/m2 (HR: 3.32 CI 1.08 to 10.16, p=0.036). Conclusions: In HCM peak CI is the main determinant of exercise capacity, but is not significantly related to ventilatory efficiency. Peak VO2, ventilatory efficiency and LAVi are major independent predictors of short/medium-term outcomes in HCM and could be helpful in the prognostic stratification of these patients.