Is the Verification Phase a Suitable Criterion for the Determination of Maximum Oxygen Uptake in Patients with Heart Failure and Reduced Ejection Fraction? A Validation Study

The verification phase (VP) has been proposed as an alternative to the traditional criteria used for the determination of the maximum oxygen uptake (VO(2) max) in several populations. Nonetheless, its validity in patients with heart failure with reduced ejection fraction (HFrEF) remains unclear. Therefore, the aim of this study was to analyse whether the VP is a safe and suitable method to determine the VO(2) max in patients with HFrEF. Adult male and female patients with HFrEF performed a ramp-incremental phase (IP), followed by a submaximal constant VP (i.e., 95% of the maximal workload during the IP) on a cycle ergometer. A 5-min active recovery period (i.e., 10 W) was performed between the two exercise phases. Group (i.e., median values) and individual comparisons were performed. VO(2) max was confirmed when there was a difference of ≤ 3% in peak oxygen uptake (VO(2) peak) values between the two exercise phases. Twenty-one patients (13 males) were finally included. There were no adverse events during the VP. Group comparisons showed no differences in the absolute and relative VO(2) peak values between both exercise phases (p = 0.557 and p = 0.400, respectively). The results did not change when only male or female patients were included. In contrast, individual comparisons showed that the VO(2) max was confirmed in 11 patients (52.4%) and not confirmed in 10 (47.6%). The submaximal VP is a safe and suitable method for the determination of the VO(2) max in patients with HFrEF. In addition, an individual approach should be used because group comparisons could mask individual differences.