Reliability, construct validity and determinants of 6-minute walk test performance in patients with chronic heart failure

Background: In-depth analyses of the measurement properties of the 6-minute walk test (6MWT) in patients with chronic heart failure (CHF) are lacking. We investigated the reliability, construct validity, and determinants of the distance covered in the 6MWT (6MWD) in CHF patients.

Methods: 337 patients were studied (median age 65 years, 70% male, ejection fraction 35%). Participants performed two 6MWTs on subsequent days. Demographics, anthropometrics, clinical data, ejection fraction, maximal exercise capacity, body composition, lung function, and symptoms of anxiety and depression were also assessed. Construct validity was assessed in terms of convergent, discriminant and known-groups validity. Step-wise linear regression was used.

Results: 6MWT was reliable (ICC = 0.90, P <0.0001). The learning effect was 31 m (95%CI 27, 35 m). Older age (>= 65 years), lower lung diffusing capacity (>= 80% predicted) and higher NYHA class (NYHA III) were associated with a lower likelihood of a meaningful increase in the second test (OR 0.45-0.56, P <0.05 for all). The best 6MWD had moderate-to-good correlations with peak exercise capacity (r(s)= 0.54-0.69) and no-to-fair correlations with body composition, lung function, ejection fraction, and symptoms of anxiety and depression (r(s) = 0.04-0.49). Patients with higher NYHA classes had lower 6MWD. 6MWD was independently associated with maximal power output during maximal exercise, estimated glomerular filtration rate and age (51.7% of the variability).

Conclusion: 6MWT was found to be reliable and valid in patients with mild-to-moderate CHF. Maximal exercise capacity, renal function and age were significant determinants of the best 6MWD. These findings strengthen the clinical utility of the 6MWT in CHF. (C) 2017 Elsevier B. V. All rights reserved.