Correlation Between the 6-Min Walk Test and Exercise Tolerance Test in Cardiac Rehabilitation After Coronary Artery Bypass Grafting: A Cross-sectional Study

Introduction: Exercise capacity and quality of life are the main outcomes in cardiac rehabilitation (CR). Exercise capacity is one of the important prognostic and diagnostic measures acquired by the exercise tolerance test (ETT). The 6-min walk test (6MWT), as a functional walking test, is another tool for assessing exercise capacity.

Methods: Eighty postoperative coronary artery bypass grafting (CABG) participants admitted to three CR units were recruited for this cross-sectional and multicenter study, based on convenient non-probability sampling. All participants performed an ETT and two repeated 6MWTs. Maximum heart rate (HR), maximum blood pressure (BP), maximal oxygen uptake (VO2_max), and peak metabolic equivalents of tasks (MET) during the tests and also the 6-min walk distance (6MWD) were the outcome measures.

Results: The mean age of all participants was 62.13 (7.12) years and 80% were male. Pearson correlation showed that maximum HR (r(78) = 0.67, P < 0.001) and maximum systolic BP (r(78) = 0.57, P < 0.001) during the 6MWT correlated moderately with those achieved during ETT. Maximum HR in the 6MWT corresponded to 86% of that achieved during ETT. The 6MWD showed a strong positive correlation with peak MET estimated during ETT as a measure of exercise capacity (r = 0.77, P < 0.001).

Conclusions: The results from this study suggest that the 6MWT is a valid tool for assessing functional capacity for prescribing exercise in a group of postoperative CABG participants admitted to CR units. This finding is helpful for healthcare professionals and for patients, as the test is easy to administer and also well tolerated by patients.

Trial registration number: PHT-9923.