NEW ORLEANS -- Two routine tests that have been used almost exclusively in men have been shown to be just as accurate in detecting heart disease and predicting outcomes in women.
By demonstrating in two separate studies the reliability of exercise treadmill tests and myocardial perfusion imaging (MPI) in women, researchers at Duke University Medical Center said physicians will be much better equipped to screen and treat their women patients.
Treadmill testing will provide an accurate way to screen those women who have symptoms but who, in fact, do not have heart disease, the researchers concluded after screening more than 1,600 women tested at Duke.
That treadmill testing, the reliable and inexpensive workhorse of cardiology, can predict heart disease as accurately in women as in men is significant, the Duke researchers said, since cardiologists traditionally skip treadmill testing in favor of more high-priced and high-tech radiological tests for women patients with chest pain.
"There has long been the perception that we can't rely on non-invasive techniques for women heart patients," said Leslee Shaw, research associate at the Duke Clinical Research Institute (DCRI). "However, our data demonstrate that the Duke Treadmill Score (DTS) provides equally accurate information for women and men.
"This is a good message for women -- treadmill testing is tried and true, and cost-effective," she said. "We will be able to screen out those women who don't, in fact, have heart disease without sending them on for more invasive diagnostic procedures. It is wonderful to have a screening test for women that works, is inexpensive and is non-invasive."
Heart disease is the leading cause of death for both women and men, and the way women report symptoms makes it more difficult for physicians to quickly diagnose heart disease, Shaw said.
"Because these clinical histories can be difficult to interpret, many physicians tend to send their women heart patients directly to the more expensive and invasive tests," Shaw said.
The DTS is a composite score based on three different measurements taken while patients are undergoing an exercise treadmill test -- duration of exertion, changes in the EKG readings during the test, and the amount of chest pain reported by patients. The DTS was developed by Duke in 1983 and is widely used by cardiologists across the country.
"After adjusting for such variables as age, prior heart attacks, diabetes, hypertension and other factors, we found that the DTS was the most important predictor of cardiac survival," said study statistician Karen Kesler, who prepared the findings for presentation Wednesday (Nov. 13) at the annual scientific meeting of the American Heart Association. "The DTS reliably predicted the risk of death in both men and women."
For the treadmill study, researchers looked at 5,665 patients who were referred to Duke for treadmill testing and subsequent catheterization from 1969 to 1991. Of those patients, 1,617 were women. The study was supported by the Duke Clinical Research Institute, which has been collecting and analyzing data about heart disease for 27 years.
In the second study, researchers demonstrated that the sophisticated MPI system can now be used with confidence in detecting damaged heart muscle in women.
In the past, cardiologists had tended to avoid MPI in women because it was thought that breast tissue between the heart and the MPI camera could lead to misleading images. However, the development of new radioisotopes has allowed the cameras to make accurate readings in women and heavy-set patients.
In an MPI test, trace amounts of radioactive isotopes are injected into the patient undergoing a stress test.
"The isotope is taken up by the blood and goes wherever it goes," said Shaw, principal investigator of the END (Economics of Non-Invasive Diagnostics) study, which looked at 8,411 patients. "Areas where there is no flow show up as a 'hole' or a 'cold spot.' We can then clearly see any areas of the heart that aren't receiving adequate blood flow."
Heart disease, once was thought to be a man's disease, is killing men and women in equal numbers, though the rates are increasing for women as the rates for white men decrease, Shaw said.
"This decrease is due to early detection of heart disease," Shaw said. "It is important that in studies like these we can study large numbers of women and develop accurate detection tools for women. Women also tend to be more concerned about breast cancer than they are about heart disease, which is unfortunate, because more women die from heart disease. The good news is that we now have non-invasive tools to accurately diagnose heart disease in women."
The findings about MPI were presented Nov. 10 at the heart association meeting by Shaw's colleague, Dr. Tom Marwick of the Cleveland Clinic, as a part of END, which was supported by The Pharmaceuticals Division of the DuPont Merck Pharmaceuticals Co., maker of the radioisotopes used in the study.