Simple walk test predicts heart events

RESEARCHERS have found that a 6-minute walk test can provide prognostic information at low cost in patients with stable coronary heart disease.

The research, involving 556 patients with stable coronary heart disease (CHD) followed over 8 years, was published in the Archives of Internal Medicine. (1)

The researchers found that a shorter distance on the 6-minute walk test (6MWT) was associated with higher rates of heart failure, myocardial infarction and death, independent of traditional cardiovascular disease risk factors and markers of cardiac disease severity.

Study participants were instructed to walk continuously for 6 minutes on a 44 m hospital corridor, covering as much ground as they could. Encouragement was given every minute and total distance walked was recorded.

The researchers found those who walked the lowest quartile distance (87‒419 m) had four times the rate of cardiovascular events as those in the highest quartile (544–837 m). Each 104 m decrease in distance was associated with a 55% higher rate of cardiovascular events.

The researchers concluded that it offered improved risk prediction when added to traditional risk factors and was as effective as treadmill exercise testing in predicting cardiovascular events. The 6MWT was simple and easy to perform which made it cheaper and more convenient than a treadmill test.

An additional benefit was that the test could help doctors get their patients started on regular exercise, the researchers wrote.

“The ability of the 6MWT, a simple office-based test of functional exercise capacity, to predict outcomes in patients with stable CHD is especially relevant because the 6MWT addresses physical activity, a modifiable risk factor for secondary prevention of CHD”, the researchers said.

A commentary published in the same issue of the Archives of Internal Medicine said the 6MWT offered a “convenient assessment of the patient’s cardiovascular disease risk factors and can help guide personalized risk factor reduction based on lifestyle measures”. (2)

In addition, due to the self-paced nature of the test, adverse events of chest pain, dyspnoea, or musculoskeletal pain were usually mild.

However, the authors also noted that the study had several limitations, including the possibility of selection bias.

Associate Professor John Atherton, director of cardiology at the Royal Brisbane and Women’s Hospital, said a further limitation was whether they accounted for all covariates, especially comorbidity and frailty.

“There were also trends for less statins and aspirin in the lowest quartile for 6MWT, which weren’t statistically significant and were therefore not accounted for in the adjusted analysis”, he said.

Professor Atherton agreed with the study’s main conclusion that the 6MWT was an independent predictor of cardiovascular events, but said questions remained over how to manage those patients deemed to be at higher risk.

“For example, in patients with either reduced or deteriorating 6MWT, should we intensify medical therapy, intensify lifestyle measures, enrol the patient in a secondary prevention or heart health program, perform a stress imaging study and consider revascularisation or perform an echocardiogram to assess LV function?”

Professor Atherton said clinicians who use treadmill exercise testing to monitor stable asymptomatic coronary artery disease patients could use a 6MWT as an initial screening investigation.

“In my view, this was a nice study that demonstrated that 6MWT was an independent predictor of subsequent cardiovascular events. This will inform future intervention studies and clinical trialists should consider including this measure to inform subgroup analyses to determine whether 6MWT can be used to guide management to improve health outcomes” he said.

– Amanda Bryan

1. Arch Intern Med 2012; Online 18 June
2. Arch Intern Med 2012; Online 18 June

Posted 25 June 2012