Functional assessment based on cardiopulmonary exercise testing in mild heart failure: A multicentre study

AIMS: In this multicentre study, we compared cardio‐pulmonary exercise test (CPET) parameters between heart failure (HF) patients classified as New York Heart Association (NYHA) class I and II to assess NYHA performance and prognostic role in mild HF. METHODS AND RESULTS: We included consecutive HF patients in NYHA class I or II who underwent CPET in three Brazilian centres. We analysed the overlap between kernel density estimations for the per cent‐predicted peak oxygen consumption (VO(2)), minute ventilation/carbon dioxide production (VE/VCO(2)) slope, and oxygen uptake efficiency slope (OUES) by NYHA class. Area under the receiver‐operating characteristic curve (AUC) was used to assess the capacity of per cent‐predicted peak VO(2) to discriminate between NYHA class I and II. For prognostication, time to all‐cause death was used to produce Kaplan–Meier estimates. Of 688 patients included in this study, 42% were classified as NYHA I and 58% as NYHA II, 55% were men, and mean age was 56 years. Median global per cent‐predicted peak VO(2) was 66.8% (IQR 56–80), VE/VCO(2) slope was 36.9 (31.6–43.3), and mean OUES was 1.51 (±0.59). Kernel density overlap between NYHA class I and II was 86% for per cent‐predicted peak VO(2), 89% for VE/VCO(2) slope, and 84% for OUES. Receiving‐operating curve analysis showed a significant, albeit limited performance of per cent‐predicted peak VO(2) alone to discriminate between NYHA class I vs. II (AUC 0.55, 95% CI 0.51–0.59, P = 0.005). Model accuracy for probability of being classified as NYHA class I (vs. NYHA class II) across the spectrum of the per cent‐predicted peak VO(2) was limited, with an absolute probability increment of 13% when per cent‐predicted peak VO(2) increased from 50% to 100%. Overall mortality in NYHA class I and II was not significantly different (P = 0.41), whereas NYHA class III patients displayed a distinctively higher death rate (P < 0.001). CONCLUSIONS: Patients with chronic HF classified as NYHA I overlapped substantially with those classified as NYHA II in objective physiological measures and prognosis. NYHA classification may represent a poor discriminator of cardiopulmonary capacity in patients with mild HF.