When diagnosing coronary heart disease in women, the Framingham 10-year risk scoring is commonly used to screen women to determine whether noninvasive testing is recommended.
Women who score higher than five percent may be advised by their doctors to undergo testing. Women with risk scores less than five percent don't need further testing if they show no symptoms of coronary heart disease; this is because false positive results are much more likely to occur if a woman's risk of coronary heart disease is low.
Women have more false positive results than men in tests for coronary
heart disease, so doctors often order imaging tests to be sure.
One form of noninvasive testing includes measuring levels of C-reactive protein (CRP). CRP is a marker of inflammation that appears to predict risk independent of LDL cholesterol in women; it may also be a good indicator of metabolic syndrome. Some infections and birth control may elevate CRP levels; weight loss, aspirin, and statins reduce CRP levels. If levels are measured at three or greater, risk is increased; however, it's recommended that a second test be administered six to eight weeks after the first to verify results.
Most people imagine treadmill stress electrocardiograms (ECG), which measure the electrical activity of the heart at each beat, when they think of noninvasive testing for coronary heart disease. Unfortunately, an ECG is not as accurate in women as it is in men; this is especially true of women who exercise and have normal ECGs when at rest.
It's known that women more often get a false positive ECG result, although the reason for this is unclear. Some researchers believe it may be related to hormones. Evidence from one study suggests that simple levels of fitness (indicated by how long it takes for the heart rate to drop after exercising and the total time spent exercising) predict coronary heart disease better than ECG tests in women.
To supplement the ECG stress test, most doctors order imaging tests, such as echocardiographs or nuclear perfusion techniques. Imaging tests are often used to confirm abnormal ECG results. Results from a stress echocardiograph, which uses sound waves to draw a picture of the heart while exercising, depend on a woman's level of fitness; results are most accurate in women who can sustain exercise at 90 percent of their predicted maximal heart rate.
Nuclear perfusion imaging that uses thallium, a radioactive substance, involves tracing the route of the thallium through the heart to determine if coronary arteries are blocked. This type of imaging, however, may be less accurate in women than men because breast tissue and women's smaller left ventricle chamber can interfere with the image.
Even invasive testing is not always as accurate in women as it is in men. The Women's Ischemia Syndrome Evaluation study examined differences in the way in which women and men experience coronary heart disease and the testing used for detection. Researchers found that approximately 50 percent of women who experience symptoms of coronary heart disease or have abnormal stress tests show no or minimal narrowing of the arteries when they undergo an angiogram (a test that creates a picture of the heart using dye injected into blood vessels). Yet, women with just minimal narrowing are more likely than women without it to have persistent symptoms of coronary heart disease requiring hospitalization.
Researchers concluded that symptoms such as angina might indicate a different underlying problem, such as endothelial dysfunction. This is a condition in which the cells that line the walls of blood vessels, called the endothelium, limit blood flow.
The information in the following articles will help you know what to expect when you visit your doctor for heart tests.
Dr. Neil Stone is a professor of clinical medicine in cardiology at the Feinberg School of Medicine of Northwestern University and a practicing internist-cardiologist-lipidologist at Northwestern Memorial Hospital. He also serves as the Medical Director of the Vascular Center for the Bluhm Cardiovascular Institute. Dr. Stone was a member of the first and third National Cholesterol Education Program Adult Treatment Panels and a past chairman of the American Heart Association Nutrition Committee and Clinical Affairs Committee.
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