The 6-minute walk test in outpatient cardiac rehabilitation: validity, reliability and responsiveness--a systematic review

Background: The 6-minute walk test (6MWT) is a common outcome measurement in cardiac rehabilitation. However, a search of the literature found no established guidelines for use of the 6MWT in cardiac rehabilitation.

Objectives: Systematic review of the validity, reliability and responsiveness of the 6MWT in cardiac rehabilitation.

Data sources: OvidMEDLINE, SPORTdiscus, EMBASE, CINAHL, Cochrane Reviews and Cochrane Clinical Trials between January 1948 and April 2011.

Eligibility criteria: Studies using 6MWTs in subjects with coronary artery disease undergoing cardiac rehabilitation on an outpatient basis, published in English, were included. STUDY APPRAISAL AND METHODS: Quantitative and qualitative analyses were conducted, including quality assessment of methodology, meta-analysis and assessment against level of evidence criteria.

Results: Fifteen articles met the inclusion criteria. One high-quality study was identified for reliability, six high-quality studies were identified for validity and 11 high-quality studies were identified for responsiveness. The meta-analysis found strong evidence that the 6MWT was responsive to change in clinical status following cardiac rehabilitation, with an estimated mean difference in 6-minute walk distance of 60.43m (95% confidence interval 54.57 to 66.30m; P<0.001). Qualitative analysis indicated moderate evidence for repeatability of the 6MWT in patients undergoing cardiac rehabilitation, for a 2% to 8% learning effect between repeated 6MWTs, for a relationship between peak heart rate during the 6MWT and during cycle exercise at the ventilatory threshold, and for moderate-to-high correlation between the 6-minute walk distance and maximum metabolic equivalents achieved on symptom-limited exercise tests.

Limitations: Few studies assessed similar aspects of validity for the 6MWT.

Conclusion: Strong evidence suggests that the 6MWT is responsive to clinical change following cardiac rehabilitation. Intra- and intertester reliability of the 6MWT and its validity in patients undergoing cardiac rehabilitation requires further research.