Six-minute walking performance in patients with moderate-to-severe heart failure: Is it a useful indicator in clinical practice?

Aims: The 6-min walk test has been incorporated into studies on the efficacy of new therapies and into prognostic stratification for chronic heart failure patients. Firm conclusions on the usefulness of the test in clinical practice are still lacking. The aim of this study was to investigate (1) the correlation between walk test performance and standard indices of cardiac function and exercise capacity, and (2) the prognostic value of the walk test with respect to peak V̇O₂ and NYHA class. Methods and Results: Three hundred and fifteen chronic heart failure patients (age: 53 ± 9 years, NYHA class: II (182), III (133)) underwent a functional evaluation and a 6-min walk test. Of these, 270 were followed-up for a minimum of 6 months (mean 3874 ± 177 days). Walked distance was 396 ± 92 m. There was no significant correlation between distance walked and central haemodynamic data. Functional capacity, as measured by ergometry, correlated moderately with distance walked (duration: r=0.48, peak V̇O₂: r=0.59, anaerobic threshold: r=0.54; all P2 measurements or after categorization of (a) quartile segmentation, (b) cut-off points from the literature and (c) thresholds from receiver operating characteristic curves. At univariate survival analysis (Cox regression), the association of the walk test with survival was of significance (P=0.03, continuous variable), or borderline significance (0.05≤P≤0.1, after categorization). Peak V̇O₂ was always significant, indepedent of the scale used (0.005≤P≤0.03). The strongest association was found for NYHA class (P2, it lost any significant association with survival (P>0.76 in all models with NYHA class and P>0.27 in all models with peak V̇O₂). Conclusion: In moderate-to-severe chronic heart failure patients, the 6-min walk test is not related to cardiac function and only moderately related to exercise capacity. Walking performance does not provide prognostic information which can complement or substitute for that provided by peak V̇O₂ or NYHA class. Hence the test is of limited usefulness as a decisional indicator in clinical practice.