Can the Six-Minute Walk Test Predict Peak Oxygen Uptake in Men With Heart Transplant?

Abstract 

Doutreleau S, Di Marco P, Talha S, Charloux A, Piquard F, Geny B. Can the six-minute walk test predict peak oxygen uptake in men with heart transplant?

Objective

To determine whether the six-minute walk test (6MWT) might predict peak oxygen consumption (Vo₂peak) after heart transplantation.

Design

Case-control prospective study.

Setting

Public hospital.

Participants

Patients with heart transplant (n=22) and age-matched sedentary male subjects (n=13).

Interventions

Not applicable.

Main Outcome Measures

Exercise performance using a maximal exercise test, distance walked using the 6MWT, heart rate, and Vo₂peak.

Results

Compared with controls, exercise performance was decreased in patients with heart transplant with less distance ambulated (516±13m vs 592±13m; P<.001) and a decrease in mean Vo₂peak (23.3±1.3 vs 29.6±1mL·min⁻¹·kg⁻¹; P<.001). Patients with heart transplant showed an increased resting heart rate, a response delayed both at the onset of exercise and during recovery. However, the patient's heart rate at the end of the 6MWT was similar to that obtained at the ventilatory threshold. The formula did not predict measured V̇o₂, with a weak correlation observed between the six-minute walk distance and both Vo₂peak (r=.53; P<.01) and ventilatory threshold (r=.53; P<.01) after heart transplantation. Interestingly, when body weight was considered, correlations coefficient increased to .74 and .77, respectively (P<.001).

Conclusions

In heart transplant recipients, the 6MWT is a safe, practical, and submaximal functional test. The distance-weight product can be used as an alternative method for assessing the functional capacity after heart transplantation but cannot totally replace maximal V̇o₂ determination.

Key Words: Exercise, Functional residual capacity, Rehabilitation, Transplantation

List of Abbreviations: 6MWD, six-minute walk distance, 6MWT, six-minute walk test, SEM, standard error of the mean, V̇o₂, oxygen uptake, Vo₂peak, peak oxygen uptake, VT, ventilatory threshold