Why is this test performed?
The test is used to:
- Determine your likelihood of having coronary artery disease
- Identify abnormal heart rhythms
- Evaluate the effectiveness of your cardiac treatment plan
- Help you develop a safe exercise program
Guidelines for people with diabetes
If you take insulin to control your blood sugar, ask your physician what amount of your medication you should take the day of the test. Often, your physician will tell you to take only half of your usual morning dose and to eat a light meal four hours before the test. If you take pills to control your blood sugar, do not take your medication until after the test is complete.
Do not take your diabetes medication and skip a meal before the test.
If you own a glucose monitor, bring it with you to check your blood sugar levels before and after your test. If you think your blood sugar is low, tell the lab personnel immediately. Plan to eat and take your diabetes medication following your test.
Exercise Testing in Women
Heart disease is an equal opportunity problem – it’s the number one killer of men and women in the United States. Yet, many scientific studies show that women don’t get equal care – they are less likely to have the appropriate testing to diagnose it, and less likely to be referred for treatment when a diagnosis of heart disease is made.
Why are men who go to the doctor with chest pain more likely to get referred for an exercise ECG than are women with the same complaint? An exercise ECG (electrocardiogram) – a test that measures the heartbeat’s electrical activity while the patient walks on a treadmill – is the gold standard for noninvasive testing in patients with suspected heart disease.
Part of the reason for the difference – sad but true – is that many physicians still are not tuned in to heart disease risk in women. When a woman comes into the office with chest pain, some doctors will first look for other problems, like gastric reflux, before considering the possibility of heart disease.
To complicate the issue further, there are true gender differences in heart disease symptoms. While men are more likely to have classic symptoms – pain in the chest and arm – women just as often experience nausea, vomiting, jaw pain, back pain or shortness of breath. A doctor easily can mistake these for symptoms of other problems, unless he or she is really on the ball about women and heart disease.
Finally, the truth is that some noninvasive diagnostic tests simply are not as accurate in women as they are in men for detecting early heart disease. Physicians who are aware of this may not refer women for testing simply because they don’t believe the test will detect a problem.
In fact, several studies have shown that women with existing heart disease are more likely than men to have a normal ECG. The problem, according to American Heart Association research, is that an exercise ECG is not very good at detecting heart disease in only one vessel, and that’s the kind that women usually have. Men, on the other hand, usually have more than one clogged vessel, and an exercise ECG can pick that up more easily.
Inaccuracies in ECG results also can be caused by older women’s physical limitations – they simply cannot exercise hard enough for the test to be effective.
Improving on the status quo
The good news is that the diagnostic situation for women is improving, with new techniques being developed to improve testing accuracy. For example, researchers with the National Institutes of Health Women’s Health Initiative have determined that an exercise ECG is more accurate in women when the test interpretation takes women’s smaller heart size into consideration.
Even more encouraging, some medical centers such as the Sydell and Arnold Miller Family Heart & Vascular Institute use heart imaging technology such as stress echocardiography or nuclear imaging along with the exercise ECG to get a more complete and accurate idea of a woman’s heart health. Both of these technologies are good; if you need to have this type of testing, your doctor will pick the one he is more familiar with.
Echocardiography uses ultrasound to create an image of the heart‘s blood vessels. One large study compared exercise echocardiography to exercise ECG in 161 women who also underwent coronary angiography, a definitive, invasive procedure for diagnosing coronary artery disease by taking X-ray images of the blood vessels from the inside. By comparing angiography results with the results of the exercise echo and exercise ECG, researchers concluded that exercise echocardiography was more specific and accurate than exercise ECG for detecting coronary artery disease.
Nuclear imaging involves injecting a radioactive tracer into the coronary circulation. By tracking the radioactive signals emitted by the tracer, physicians can identify areas of the heart where coronary artery disease has reduced the blood flow.
Originally, physicians used thallium-201 as the radiotracer, but they found that dense breast tissue inhibits the radioactivity from thallium and distorts the image. Today, nuclear cardiac imaging usually is performed with technetium-99m, a different radiotracer agent that has considerably less distortion problems than does thallium. Several studies in which imaging results were confirmed by angiography have proven that technetium imaging is very sensitive and accurate for detecting coronary artery disease in women.
So what are the practical implications of this discussion if you are a woman concerned about heart disease?
- Start by asking your doctor what tests would be most appropriate for you.
- Don’t hesitate to get a second opinion if you aren’t comfortable with the
- Most importantly, if you have significant risk factors and/or symptoms of heart disease
(remember to think beyond chest pain), you should consider being evaluated at a center with a lot
of experience in diagnosing and treating women.
Doctors at large, multidisciplinary heart centers are more likely to be familiar with gender differences in heart disease symptoms and have all of the latest technology to ensure that you receive the most appropriate testing, depending on your symptoms and risk factors.
Cardiac CTA is a newly available imaging modality that may be used to detect coronary atherosclerosis plaques at an early stage and coronary blockages. This test is indicated for patients with symptoms of chest pain with risk factors for coronary disease.