Authors

1. Chirico, Daniele PhD
2. Davidson, Travis W. PhD, MD
3. Terada, Tasuku PhD
4. Scott, Kyle MSc
5. Keast, Marja-Leena DipPT
6. Reid, Robert D. PhD, MBA
7. Pipe, Andrew L. MD, CM
8. Reed, Jennifer L. PhD, RKin

Abstract

Purpose: We examined the agreement between peak oxygen uptake (V[spacing dot above]o₂peak), estimated using prediction equations from the 6-min Walk Test (6MWT), and V[spacing dot above]o₂peak measured using a cardiopulmonary exercise test (CPX) to estimate change in V[spacing dot above]o₂peak in patients with heart failure (HF) enrolled in cardiac rehabilitation (CR).

Methods: This was secondary analysis of 54 (including 9 women) patients with HF who completed a clinical CR program. Four previously published equations using 6MWT distance were used to estimate V[spacing dot above]o₂peak and were compared with a CPX at baseline, follow-up, and change using the standard and modified Bland-Altman method. Analyses were repeated for quartiles of cardiorespiratory fitness (CRF) based on measured V[spacing dot above]o₂peak from the CPX.

Results: Bland-Altman plots revealed proportional bias between all prediction equations and the measured V[spacing dot above]o₂peak. The difference between methods varied by the level of CRF, with overestimation of prediction equations at greater levels of CRF and underestimation at lower levels of CRF. This poor agreement remained when comparisons were made between the estimated and measured V[spacing dot above]o₂peak values at quartiles of CRF, indicating prediction equations have limited ability to predict V[spacing dot above]o₂peak at any level of CRF.

Conclusion: Estimated V[spacing dot above]o₂peak using 6MWT distance demonstrated poor agreement with measured V[spacing dot above]o₂peak from a CPX. While distance ambulated on the 6MWT remains an important measure of physical performance in patients with HF, prediction equations using 6MWT distance are not appropriate to monitor changes in V[spacing dot above]o₂peak following CR in patients with HF.