Poor performance on an exercise treadmill can mean double risk for heart attack

Among men without heart disease but who have significant cardiac risk factors, a poor performance on an exercise treadmill test is associated with more than doubling of the risk for a heart attack or other coronary heart disease event, according to a report in Circulation: Journal of the American Heart Association.

Exercise treadmill testing is not generally recommended as routine screening for people with no history or symptoms of heart disease. This is the first study to evaluate exercise testing among asymptomatic people relative to their predicted coronary heart disease (CHD) risk using the Framingham risk score.

The Framingham Risk Score assigns point values to risk factors such as high blood pressure, total cholesterol, HDL cholesterol, age, diabetes and smoking history to predict the risk of an event such as chest pain, heart attack or coronary death over a 10-year period. A risk score of 9 percent or less is considered low risk, 10 percent to 19 percent is considered intermediate risk, while a score of more than 20 percent, meaning that the person has a one in five chance of an event in 10 years, is classified as high risk.

"Our results suggest that exercise testing may be of benefit in asymptomatic men with intermediate to high risk," said Gary J. Balady, M.D., a professor of medicine at Boston University School of Medicine and an investigator with the Framingham Heart Study.

He and colleagues found that a change in electrocardiogram (ECG) tracing called ST-segment depression or failure to reach target heart rate during exercise testing more than doubled the 10-year risk of coronary event in men with high Framingham risk, compared to those who did not have these findings on the stress test.

But increased exercise capacity predicted lower CHD risk in the high-risk men.

"Greater exercise tolerance as measured in metabolic equivalents (METS) had a lower 10 year event rate," he said. Each MET increase, which is a multiple of the resting metabolic rate, was associated with a 13 percent decrease in risk of coronary event.

The study did not provide evidence to support exercise testing for asymptomatic women because the event rate in women was too low to suggest any significant correlations between the exercise results and future events, he said.

All study participants were asymptomatic at baseline. The study included 1,431 male and 1,612 female Framingham Heart Study participants. Their average age at baseline was 45 and the participants were followed for more than 18 years.

During follow-up, 224 men (15.7 percent) developed a coronary event such as chest pain, heart attack or died from CHD.

Balady said that high-risk men who have ST-segment depression or fail to achieve target heart rate on the exercise treadmill test "should get maximum risk reduction. That means aggressive blood pressure and lipid control, and of course, we want everyone to stop smoking." Also, among these patients it would be prudent to consider additional diagnostic tests to determine the extent of disease, which may include imaging stress tests or invasive procedures such as angiography to assess the condition of arteries and locate any blocked or narrowed vessels.

However, he said it is important to note that this study did not find that exercise testing provided additional prognostic information in those with 10-year-CHD risk less than 10 percent. The authors conclude that clinicians should consider the global cardiac risk, using the Framingham Risk Score, prior to ordering an exercise tolerance test in asymptomatic men without known heart disease.