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 x min(-1) x 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 VO2, 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 VO2 determination.