Not all physicians are convinced that the exercise treadmill test (ETT) can reliably evaluate heart health in women.
However, a recent study carried out by UC Davis researchers shows that the ETT can in fact accurately predict coronary artery disease in women over 65. Two specific electrocardiogram (EKG) indicators of heart stress during an ETT were shown to further enhance its predictive power.
Published in the The American Journal of Cardiology, this study shows that the ETT is cheap and easy to administer, making clinical practice much more convenient for both doctor and patient. What’s more, it can also be used to select those who may require high-tech diagnostic tests.
During a typical ETT, a patient exercises on a treadmill at gradually increasing speed and elevation while undergoing blood pressure monitoring and an EKG to measure exercise-induced changes in the heart's electrical activity.
If the patient shows signs of heart disease, coronary angiography may also be carried out to determine if any blood vessels are narrowed or blocked by plaque. Coronary angiography produces a series of X-rays of the interior of the arteries by injecting dye into them to make them visible.
This study analyzed 111 women who had seen their physicians at UC Davis Medical Center because of chest pain and whose exercise treadmill tests were ‘positive’ - indicating the need for further cardiovascular testing. Coronary angiography was also performed on each patient and the researchers analyzed how often the angiography results showed definite evidence of arterial narrowing.
Initially, they found that only 50 percent of the women with positive treadmill tests had coronary artery disease. But when these test results were further segregated by age, the predictive value of ETT was seen to rise dramatically.
ETT predicted arterial disease in only 36 percent of the youngest group (aged 35 to 50 years) of study participants. However, it successfully identified this condition in 68 percent of those aged 65 years and older, which coincidentally is also when the prevalence of coronary artery disease rises sharply for women.
The investigators also found that two EKG parameters of heart stress that are related to poor blood flow - an ST-segment depression greater than 2.0 mm or ST-segment recovery time longer than three minutes - further added specificity to the diagnostic value of ETT.
In fact, longer ST-segment recovery time was the best predictor across all age groups of whether a positive treadmill test result could accurately identified coronary artery disease in eight out of 10 women older than 65.
These results finally provide physicians with a way to make a previously unreliable heart disease screening tool more reliable for women. They also add credibility to the guidelines of the American Heart Association and American College of Cardiology, both of which recommend that exercise treadmill testing should remain the initial test for both women and men who require evaluation for chest pain.