Reproducibility of peak oxygen uptake and other cardiopulmonary exercise testing parameters in patients with heart failure (from the Heart Failure and A Controlled Trial Investigating Outcomes of exercise traiNing)

Peak oxygen uptake (pVo(2)) is an important parameter in assessing the functional capacity and prognosis of patients with heart failure. In heart failure trials, change in pVo(2) was often used to assess the effectiveness of an intervention. However, the within-subject variability of pVo(2) on serial testing may limit its usefulness. This study was designed to evaluate the within-subject variability of pVo(2) over 2 baseline cardiopulmonary exercise tests. As a substudy of the HF-ACTION trial, 398 subjects (73% men, 27% women; mean age 59 years) with heart failure and left ventricular ejection fraction <= 35% underwent 2 baseline cardiopulmonary exercise tests within 14 days. Mean pVo(2) was unchanged from test 1 to test 2 (15.16 +/- 4.97 vs 15.18 +/- 4.97 ml/kg/min; p = 0.78). However, mean within-subject absolute change was 1.3 ml/kg/min (10th, 90th percentiles 0.1, 3.0), with 46% of subjects increasing and 48% decreasing on the second test. Other parameters, including the ventilation-to-carbon-dioxide production slope and Vo(2) at ventilatory threshold, also showed significant within-subject variation with minimal mean differences between tests. In conclusion, pVo(2) showed substantial within-subject variability in patients with heart failure and should be taken into account in clinical applications. However, on repeated baseline cardiopulmonary exercise tests, there appears to be no familiarization effect for Vo(2) in patients with HF. Therefore, in multicenter trials, there is no need to perform >1 baseline cardiopulmonary exercise test. (C) 2008 Elsevier Inc. All rights reserved.