“It’s only been in the last decade that we have really begun to study exercise stress testing in women,” says Dr. Martha Gulati, section director for preventive cardiology and women’s cardiovascular health at The Ohio State University Medical Center, and co-author of a review article in Circulation, The Journal of the American Heart Association. “By going ‘back to the basics’ and using all the important information that comes with an exercise stress test, we can improve its value and better determine risks for women, which will help us provide customized approaches to diagnosing and treating coronary artery disease.”
Despite advances in medical treatment, improvements in medical technology and a greater focus on women and their risk, cardiovascular disease remains the number one cause of death for women in the United States.
According to Gulati, in addition to better outcomes, significant cost savings may be achieved by following the guidelines and appropriately using the exercise stress test. The article points out that diagnostic imaging is the fastest growing cost for Medicare, and has been targeted by the U.S. Department of Health & Human Services Office of Inspector General.
In addition to interpreting electrocardiogram (EKG) changes with exercise, evaluation of exercise capacity, chronotropic index, heart rate recovery, blood pressure response and the Duke Treadmill Score can be used to enhance the effectiveness of exercise stress testing.
“Historically, exercise stress testing is women has been thought to have decreased diagnostic accuracy, but most early studies evaluating its effectiveness included very few women,” says Gulati. “As research on exercise stress testing in women has increased, we have an improved understanding of its diagnostic and prognostic value.”
ST-segment depression that occurs with exercise stress testing is thought to be less accurate in identifying coronary artery disease in women than in men. While it has been thought that women have more ST-segment depression with exercise testing, larger and more recent studies of asymptomatic women have shown that ST-segment depression appears far less common than previously noted.
Gulati, who has a specific interest in fitness and prevention and has co-authored two books on heart health, says exercise capacity, which is an indicator of cardio-respiratory fitness, has emerged as one of the most important diagnostic and prognostic markers that can easily be assessed with exercise stress testing.
“Research shows that exercise capacity, or fitness level, is among the best measures for predicting the presence of coronary artery disease in women,” she says. “By understanding exercise capacity as early as possible, we can work with patients to identify easy things they can do to improve their fitness level.”
Gulati, who holds the Sarah Ross Soter Chair in Women’s Cardiovascular Health at Ohio State, also developed a new method to calculate a women’s maximum age-predicted heart rate. Since most previous studies involved men, the common heart-rate calculation (220 minus your age) doesn’t necessarily apply to women. By analyzing data, Gulati and her colleague developed an algorithm for calculating the maximum heart rate for women. The formula takes into account a patient’s low, intermediate or high risk as determined by a self-administered pre-test questionnaire to assess exercise capacity.
The article concludes that exercise EKG should continue to serve as the method for distinguishing those women not requiring any further testing from those who would benefit from further exercise stress testing with imaging. Although imaging can improve diagnostic accuracy of exercise stress testing, these tests have significant additional costs associated with them and should only be used when appropriate.
“The standard exercise stress test is the recommended initial stress test of choice in most patients,” adds Gulati. “To better understand the differences in men and women, and develop customize approaches for each patient, we need to closely examine the valuable information that comes with any exercise stress test.”
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