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 (VO₂); 2) VO₂ at anaerobic threshold (AT); 3) oxygen pulse; 4) minute ventilation (VE)/carbon-dioxide (CO₂) production slope; 5) VE/VCO₂ at AT (VE/VCO₂_AT); 6) VE/VCO₂ nadir; 7) VE/VCO₂ intercept; and 8) partial end-tidal pressure of carbon-dioxide (P_ETCO₂) 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/VCO₂ intercept and P_ETCO₂ change, whereas the differences between medical regimens were detected by differences in VE/VCO₂ nadir and VE/VCO₂_AT changes after the treatment. The best predictors of the change in well-being were left ventricular outflow tract maximal gradient and VE/VCO₂ 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/VCO₂ nadir.

Conclusion: Ventilatory efficiency parameters outperform peak VO₂ in gauging therapy effects in patients with HCM.