Shuttle versus six-minute walk test in the prediction of outcome in chronic heart failure

We prospectively analysed the potential usefulness of a symptom-limited walk test, the shuttle walk test (SWT), in the prediction of major cardiac events in 46 consecutive patients with chronic heart failure (NYHA class II-IV, ejection fraction <0.40) and compared it with that of a time-limited walk test, the six-minute walk test (6-MT). After a mean follow-up of 17 months (range, 8-28 months), 15 of 46 patients (33%) experienced a major cardiac event, defined as a cardiac death, urgent transplantation, or hospital admission for continuous inotropic or mechanical support. Distance walked in the SWT was shown to be a predictor of outcome at one year of follow-up (P=0.03), but distance ambulated in the 6-MT was not (P=0.07). In multivariate analysis, percentage of age-gender predicted peak oxygen uptake was the best predictor of major cardiac events. When patients were divided into tertiles according to performance in both walk tests, there was an overall difference in event-free survival at 12 months among SWT tertiles (P=0.004), but not among 6-MT tertiles (P=0.09). A low performance in the SWT (distance ambulated <450 m) allowed identification of a subgroup of patients with a high risk for major cardiac events at short-term. We conclude that, in patients with chronic heart failure, distance ambulated in the SWT predicts event-free survival at one year better than that in the 6-MT.