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January 21, 2011

Best use for popular CAD assessment procedure is misunderstood

What is the best way to determine if you are developing the nation’s most deadly condition, coronary artery disease (CAD)?

An increasing number of doctors are encouraging patients – especially those deemed to be at high-risk for developing CAD – to undergo a non-invasive imaging procedure called coronary computed tomography angiography, or coronary CTA, to see if plaque deposits are accumulating in their arteries.

According to Dr. Christopher M. Kramer, a professor of Radiology and Medicine at the University of Virginia Health System, widespread use of CTA for screening purposes may be inappropriate. “There seems to be a lot of misunderstanding about CTA. People need to know that it is not intended to be a screening test,” he says.

In a recent article in Circulation , Dr. Kramer asserted that doctors should not order coronary CTA to assess every high-risk patient. “This procedure exposes people to radiation and contrast dye, both of which can have adverse affects,” he notes. “When individuals don’t have symptoms of CAD, such as chest pain, coronary CTA may pose more risk than benefit.”

Nationally, much study and debate surrounds the use and clinical value of coronary CTA as a screening tool. Medicare reimbursement is also under review. Currently, all 50 states provide Medicare coverage when coronary CTA is performed on patients with symptoms, but U.S. Centers for Medicare and Medicaid Services (CMS) has expressed uncertainty about its benefits. CMS recently postponed implementation of more stringent coverage limits for coronary CTA until further research is completed.

Coronary CTA has been gaining in popularity because it is a fast and relatively inexpensive way to see exactly how much plaque has accumulated in arteries that supply blood to the heart. It is the only noninvasive test that shows what kinds of plaque are building up – either the hard, calcified type or soft, fatty deposits – and directly reveals if blockages are forming.

From start to finish, the procedure takes about 10 minutes. Preparations begin with an injection of iodine-containing contrast dye into an intravenous (IV) line in the patient’s arm. Some patients also receive medication to slow or stabilize their heart rate. During a coronary CTA, doctors use a high-resolution, three-dimensional scanner to take X-rays of a patient’s beating heart and surrounding blood vessels.

Whether or not patients have symptoms, they are considered to be at high risk for CAD when they have several of the following factors: elevated blood pressure, smoking, high cholesterol, excess body weight, diabetes, stress, poor diet and/or lack of proper exercise. Being older, male and having a family history of CAD increases risk levels.

As Dr. Kramer sees it, understanding the best use of coronary CTA will require more time and studies. So far, it has proven useful in three groups: patients with low-to-intermediate CAD risk factors who have chest pain; patients with CAD symptoms and left bundle-branch block – a blockage that causes the left ventricle of the heart to contract later than the right ventricle; and, patients preparing for cardiac valve surgery.

Current medical guidelines call for doctors to aggressively treat all patients at high risk for CAD without ordering tests like coronary CTA. According to Dr. Kramer, a CT procedure called calcium scoring, which uses no contrast dye and much less radiation, may be appropriate for screening patients who are at risk for CAD and have not developed symptoms.

Reference: Christopher M. Kramer, All High-Risk Patients Should Not Be Screened With Computed Tomographic Angiography, Circulation 117, pp 133-139, March 11, 2008.

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