AIM: Will the six-minute walk test ever replace treadmill testing?
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The six-minute walk test may soon give treadmill exercise testing a run for its money, at least in terms of helping to predict subsequent cardiovascular events in coronary heart disease patients, a study published online June 18 in the Archives of Internal Medicine found. The walk test could be a welcome addition to tools available to measure functionality and exercise capacity in these patients.

“Exercise treadmill testing provides information regarding prognosis in patients with stable CHD [coronary heart disease], but testing can be costly and time consuming, especially if testing is bundled with imaging studies that may be unnecessary in stable patients,” Alexis L. Beatty, MD, of the University of California, San Francisco, and colleagues wrote. However, the value of the six-minute walk test in patients with stable CHD remains understudied, the authors wrote.

Beatty et al evaluated the value of the test to predict heart failure, MI and death in 556 patients with CHD who were enrolled in the Heart and Soul Study between Sept. 11, 2000, and Dec. 20, 2002. The researchers followed the patients for a median of eight years.

The authors reported CV events in 218 of the 556 patients. The median six-minute walk test distance during the study was 481 meters. Those in the highest quartile walked between 544 and 837 meters while those in the lowest quartile walked a distance of 87 to 419 meters. It was reported that those in the lowest quartile had four times the rate of CV events as those in the highest quartile.

Beatty et al noted that every decrease in six-minute walk test distance was linked with an 86 percent higher rate of heart failure, 47 percent higher rate of MI and a 54 percent higher rate of death. A decreased six-minute walk test distance was also associated with a 55 percent higher rate of any CV event.

“After adjusting for baseline characteristics and markers of cardiac disease severity, 6MWT [six-minute walk test] distance remained independently associated with cardiovascular events,” the authors noted. “The 6MWT [six-minute walk test] distance and treadmill exercise capacity had similar discrimination for predicting cardiovascular events, integrated discrimination improvement and category-free net reclassification improvement.”

The authors suggested that the study’s findings showed that the six-minute walk test may be a useful marker for identifying patients with CHD and who are at a high risk of CV events. In fact, the walk test was useful in a broader population of patients with stable CHD.

Beatty et al concluded that the walk test could be a good alternative to treadmill exercise testing that could help assess patients with stable CAD; however, the authors said that treadmill testing will remain the preferred method for evaluating patients with ischemia.

But in terms of costs, the six-minute walk test was less expensive. According to the 2012 Medicare Physician Fee schedule, payments for six-minute walk tests were $59.91 compared with cardiovascular stress testing at $88.50.

While six-minute walk tests proved beneficial in terms of predicting CV events in stable CHD patients, the authors said that using the test to improve prognosis will need additional study.

“The six-minute walk test may be a useful tool for measuring functional exercise capacity in patients with stable CHD to help target secondary prevention goals for physical activity,” the authors wrote.

In an accompanying editorial, David T. Nash, MD, of the State University of New York Upstate Medical Center in Syracuse, N.Y., wrote: “Given the greater ease and lesser cost of the six-minute walk test compared with cardiovascular stress testing, I would recommend that physicians interested in improving their patients' level of fitness use the six-minute walk test as a means of getting the patient started on regular exercise.”

Once the patient becomes comfortable with the test it can be used more frequently, added Nash, and could even help lengthen the walk.

“The six-minute walk test allows convenient assessment of the patient's cardiovascular disease risk factors and can help guide personalized risk factor reduction based on lifestyle measures—diet, physical activity, and control of blood pressure and lipid levels,” Nash summed.