How well a woman does on a treadmill stress test can reveal a lot about her heart attack risk, according to a longitudinal study of nearly 3,000 women.
Results show that two fitness measures – stamina and recovery time – clearly identified women at risk for death from heart disease or any cause. Specifically, peak exercise capacity (obtained from the length of time women could exercise during a standard treadmill test) and heart rate recovery or HRR (peak heart rate minus heart rate two minutes after exercise) predicted their risk of death from heart disease or other causes. Not achieving target heart rate was also associated with increased death rate.
Study Specifics
At the start of the study, participants underwent treadmill exercise tests. They were then followed for an average of 20 years with mailed questionnaires, phone calls, or home visits.
Overall, after accounting for many risk factors, scientists found that women who performed below average in peak exercise capacity and recovery rate were 3.5 times more likely to die of heart disease than women who were above average. Among women who were seemingly low risk for heart disease based on traditional criteria, but who scored below average on these measures, were nearly 13 times more likely to die of heart disease than those who performed better on the tests. Death risk increased gradually with each level of poorer performance. Researchers noted the difference as early as one year after the treadmill test.
A woman's fitness level and the time it takes for her heart to return to normal after exercise are more accurate predictors of female heart disease risk than electrical recordings of the heart (an electrocardiogram test). Although an electrocardiogram is typically used to diagnose hidden heart disease in men, results of this study demonstrated that electrocardiogram readings did not accurately identify women with hidden heart disease.
What It Means
How well a woman performs during a treadmill stress test – how long she can exercise at peak capacity and how long it takes her to recover – is a good predictor of physical fitness. The results of this study and others suggest that physical fitness is a stronger predictor of heart attack risk than blood pressure, smoking, cholesterol, and weight.
Researchers concluded that regular exercise is the best way women can combat heart disease.
"Our study suggests that women might benefit from higher fitness levels, independent of changes in weight, blood pressure, or cholesterol levels," said Samia Mora, MD, MHS, from Harvard Medical School. "Exercise capacity might be improved by 15 to 30 percent with moderate, regular physical activity."
If you are over age 40, are sedentary, or have multiple risk factors, check with your healthcare team before starting a vigorous exercise program.
Caution
A treadmill stress test can sometimes show false heart abnormalities, leading to unnecessary and expensive follow-up testing. Researchers do not recommend routine treadmill exercise tests for women without symptoms or risk factors.
Senior study author, Roger S. Blumenthal, MD, said, "There is great public health interest in cost-effective and readily available tests that can predict cardiovascular risk in asymptomatic women, since nearly two-thirds of women who die suddenly have no previous symptoms." The results, he emphasized, support the potential role of exercise treadmill testing for further risk analysis in women with low or intermediate risk scores on the Framingham scale, a method that uses factors such as age, cholesterol level, and smoking status to tally a person's risk for heart disease within a 10-year time period. |
