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

Aim: We sought the cardiopulmonary exercise testing (CPET) parameter that most accurately reflected therapeutic efficacy in patients with hypertrophic cardiomyopathy (HCM). Methods: Well-being questionnaire, N-terminal brain natriuretic peptide measurements, echocardiography, and CPET were performed in patients with symptomatic non-obstructive HCM during phase II, randomized, open-label multicentre study, before and after 16 weeks of traditional or sacubitril/valsartan treatment. Patients were followed 36 months after the initial CPET. Primary endpoints were changes in: 1) peak oxygen consumption (VO ₂); 2) VO ₂ at anaerobic threshold (AT); 3) oxygen pulse; 4) minute ventilation (VE)/carbon-dioxide (CO ₂) production slope; 5) VE/VCO ₂ at AT (VE/VCO ₂_AT); 6) VE/VCO ₂ nadir; 7) VE/VCO ₂ intercept; and 8) partial end-tidal pressure of carbon-dioxide (P _ETCO ₂) change during CPET. Results: Of 115 screened patients, 61 (52 ± 14 years, 43 % women) were included. Within subject therapy effects were detected only by the VE/VCO ₂ intercept and P _ETCO ₂ change, whereas the differences between medical regimens were detected by differences in VE/VCO ₂ nadir and VE/VCO ₂_AT changes after the treatment. The best predictors of the change in well-being were left ventricular outflow tract maximal gradient and VE/VCO ₂ intercept (B = 0.41,0.36; SE = 0.16,0.30; CI = 0.14–0.79, 0.15–1.14; p = 0.006,0.016, respectively). Adverse cardiac events were best predicted by the initial VE/VCO ₂ nadir. Conclusion: Ventilatory efficiency parameters outperform peak VO ₂ in gauging therapy effects in patients with HCM.