Coronary Artery Disease Screening Tests (CAD) (cont.)
Daniel Lee Kulick, MD, FACC, FSCAI
Dr. Kulick received his undergraduate and medical degrees from the University of Southern California, School of Medicine. He performed his residency in internal medicine at the Harbor-University of California Los Angeles Medical Center and a fellowship in the section of cardiology at the Los Angeles County-University of Southern California Medical Center. He is board certified in Internal Medicine and Cardiology.
Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
In this Article
- What is coronary artery disease?
- What is the purpose of screening tests for CAD?
- What are common initial screening tests for CAD?
- Exercise cardiac stress test (treadmill stress test or ECST)
- Radionuclide stress test
- Stress echocardiography
- Pharmacologic stress test
- Are there other tests for CAD that are noninvasive?
- What is the most accurate method of defining CAD?
- Coronary angiography
- Find a local Cardiologist in your town
Pharmacologic stress test
During a pharmacologic stress test, certain medications are administered which stimulate the heart to mimic the physiologic effects of exercise. One of these medications is dobutamine, which is similar to adrenaline. Dobutamine is carefully administered to gradually increase the heart rate and strength of the contractions of the heart muscle. Simultaneously, echocardiography or radionuclide imaging is performed.
Alternatively, a medicine called adenosine is administered, which simulates the physiology of the coronary artery circulation during exercise. Adenosine is combined with radionuclide isotope imaging to provide a very accurate test for the detection of significant CAD. A newer agent, regadenoson (Lexiscan), is often used as it seems to be better tolerated. Pharmacological stress testing is commonly performed in patients who are thought to be at high risk for significant CAD and who are scheduled for major non-cardiac surgical procedures. These patients are often unable to perform exercise stress testing due to the underlying condition for which they require surgery. In this setting, pharmacological stress testing is invaluable in assessing the cardiac risk of patients prior to surgery.
Are there other tests for CAD that are noninvasive?
A new noninvasive test for the detection of CAD is electron beam computerized tomography (EBCT), or calcium scoring. Unlike the above mentioned stress tests that measure the heart's physiology, EBCT is designed to measure calcium deposits in the coronary arteries.
In patients with CAD, the plaques which make up the blockages contain significant amounts of calcium, which can be detected with the CT scanner and the amount of blockage is calculated by calcium scoring. This test will identify calcium in blockages as mild as 10%-20%, which would not be detected by standard physiological testing. When such mild blockages are detected, however, the only recommended therapy is risk factor modification (cholesterol lowering and cessation of smoking if applicable), and adjunctive use of aspirin and certain vitamins; such therapy would be advised in all patients with risk factors for CAD, regardless of the results of any noninvasive tests.
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Calcium scoring may be very helpful in convincing patients to change their lifestyle or take their medicines, as a score that is not zero implies that the blockage process is starting, and likely will progress unless lifestyle changes are made. It is important to realize that calcification is a function of age, and in younger patients (men under 50, women under 60) the calcium score is less helpful when low.
A more elaborate modality is CT angiography (ultrafast CT). This is a non-invasive (no catheter involved) form of angiogram, but still involves dye exposure and radiation, and is less precise than a coronary angiogram. This is still a rather new modality, and its role is still being defined.
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