Multicentre study of the determination of peak oxygen uptake and ventilatory threshold during bicycle exercise in chronic heart failure. Comparison of graphical methods, interobserver variability and influence of the exercise protocol. The VO2 French Study Group.

Assessment of the ventilatory threshold (VT) has been proposed to assess exercise tolerance more objectively, particularly in clinical trials, but reproducibility, interobserver variability and feasibility of the graphical methods for determination of VT have not been properly studied in patients with chronic heart failure (CHF). Fifty-one patients with mild to moderate CHF (mean peak oxygen uptake (VO2): 20.5 ml.min-1.kg-1) were assessed during two consecutive bicycle exercise tests within 8 days. Two graded exercise protocols were compared with stages of 30 W every 3 min (22 patients) or 10 W/min (29 patients). VT was determined separately by five trained physicians using five different graphical methods. The 'crossing method' (first crossing of the VCO2 and VO2 curves) yielded the highest rate of determination (88%) but tended to overestimate the mean VT. The VE method (disproportionate increase of ventilation relative to VO2) produced the best interobserver agreement (coefficient of variation = 78%). Peak VO2 was very highly reproducible in both exercise protocols (relative difference 2-test 1/test 1 = -0.32% for the 30 W 3 min protocol; +2.18% for the 10 W.min-1 protocol). The reproducibility of VT was slightly lower regardless of the graphical method used to determine it (relative differences varied from -3.3% to +7.3%). Therefore, peak VO2 appears more suitable than VT for assessment of exercise tolerance in CHF.