The ventilatory efficiency parameters outperform peak oxygen consumption in monitoring the therapy effects on the right ventricular load in patients with hypertrophic cardiomyopathy

Abstract Aim We sought the cardiopulmonary exercise testing (CPET) parameter that is the most reflective of right ventricular (RV) load and its coupling with pulmonary artery (PA) in patients diagnosed with hypertrophic cardiomyopathy (HCM) undergoing medical therapy. Methods CPET on recumbent bike was performed in adult patients with symptomatic non-obstructive HCM with NYHA class I–III, during phase II, randomised, open-label multicentre study, before and after diverse medical treatment for 16 weeks. Endpoints were the changes in: 1) peak oxygen consumption (peak VO2); 2) minute ventilation (VE)/carbon-dioxide (CO2) production slope during the whole CPET; 3) VE/VCO2 slope before anaerobic threshold (AT); 4) VE/VCO2 slope after AT; 5) VE/VCO2 nadir; 6) VE/VCO2 at AT; and 7) VE/VCO2 intercept. Standard ehocardiography at rest was performed concomitantly with CPET to assess tricuspid annular plane systolic excursion (TAPSE), pulmonary artery systolic pressure (PASP), severity of mitral regurgitation (MR) and TAPSE/PASP ratio as a measure of RV-PA coupling. Results Of 115 screened patients, 61 (mean age 52 years [SD 14], 43% women) met the study inclusion criteria and underwent CPET. On regression analysis, among all CPET end-point variables, the best independent predictor of the change in PASP, TAPSE and MR severity after 16 weeks of medical treatment was VE/VCO2 below AT (B=-0.28, -0.01,-0.11; SE=0.10, 0.05, 0.01; CI=-0.48 to -0.08, -0.22 to -0.01; -0.02 to 0.01; p=0.007, 0.035, 0.004, respectively), whereas the best predictor of TAPSE/PASP ratio was intercept of the VE/VCO2 curve (B=0.014, CI=0.01to 0.03, p=0.005). Conclusion The changes in VE/VCO2 slope below anaerobic threshold, and intercept of the VE/VCO2 curve outperform peak VO2 in the monitoring of therapy effects on the right heart load and RV-PV coupling in patients with hypertrophic cardiomyopathy.