Clinical Utility of the Cardiorespiratory Optimal Point in Patients with Heart Failure

INTRODUCTION: We assessed the cardiorespiratory optimal point (COP)-the minimal V̇E /V̇O 2 in a given minute of an incremental cardiopulmonary exercise test-in patients with heart failure (HF) and aimed to determine 1) its association with patient and disease characteristics, 2) changes after an exercise-based cardiac rehabilitation program (CR), and 3) the association with clinical outcomes. METHODS: We studied 277 HF patients (67 (58-74) yr, 30% female, 72% HF with restricted ejection fraction) between 2009 and 2018. Patients participated in a 12- to 24-wk CR program, and COP was assessed pre- and post-CR. Patient and disease characteristics and clinical outcomes (mortality and cardiovascular-related hospitalization) were extracted from patient files. The incidence of clinical outcomes was compared across COP tertiles (low, <26.0; moderate, 26.0-30.7; high, >30.7). RESULTS: Median COP was 28.2 (24.9-32.1) and was reached at 51% ± 15% of V̇O 2peak . Lower age, female sex, higher body mass index, the absence of a pacemaker or the absence of chronic obstructive pulmonary disease, and lower N-terminal prohormone brain natriuretic peptide concentrations were associated with a lower COP. Participation in CR reduced COP (-0.8; 95% confidence interval, -1.3 to -0.3). Low COP had a reduced risk (adjusted hazard ratio, 0.53; 95% confidence interval, 0.33-0.84) for adverse clinical outcomes as compared with high COP. CONCLUSIONS: Classic cardiovascular risk factors are associated with a higher, more unfavorable, COP. CR-based exercise training reduces COP, whereas a lower COP is associated with a better clinical prognosis. As COP can be established during a submaximal exercise test, this may offer novel risk stratification possibilities for HF care programs.