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Coronary Artery Calcium Scans

CT scanning to detect coronary artery disease

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Updated November 13, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Are calcium scans useful in coronary artery disease?

In coronary artery disease (CAD), atherosclerosis causes the smooth, elastic lining of the coronary arteries to become hardened, stiffened and swollen because of "plaques," which are deposits of calcium, fats and abnormal inflammatory cells. Among other things, this means that if you have calcium deposits in your coronary arteries, you have at least some CAD.

For many years, doctors have known that certain sophisticated computerized tomography (CT) scans can detect and measure coronary artery calcium deposits. (The names given to the various kinds of cardiac CT scans can be confusing, but any CT scan used to measure coronary artery calcium is usually referred to simply as a "calcium scan.")

How are calcium scans done?

Having a calcium scans is very much like having any x-ray. You will lie on an x-ray table, wires will be attached to your chest to record an ECG and the table will slide in to the scanner. You will be asked to hold your breath for a minute or so, so that a clear image can be obtained. The resulting computerized x-ray image will be examined for the telltale "white spots" that indicate calcium deposits in the coronary arteries, and the amount of calcium will be quantified into a score.

The calcium score

The amount of calcium present in the coronary arteries is scored according to the Agatson scale, as follows:
  • 0 - no identifiable disease
  • 1 to 99 - mild disease
  • 100 to 399 - moderate disease
  • 400 or higher - severe disease

How are calcium scans used?

There has been a lot of controversy about who should have calcium scans and how the results should be used. The controversy arose largely because, originally, doctors tended to use these scans to screen patients for obstructive CAD; that is, for partial blockages in the coronary arteries that may need to be treated by stenting. It turns out, though, that calcium scans are not particularly good for this purpose. Many patients who have high calcium scores, while they, indeed, have a lot of CAD, do not have significant blockages. So early on, calcium scans led many patients to have unnecessary cardiac catheterizations, and when the catheterizations showed no significant blockages, the calcium scans were (wrongly) considered to have been "false positives."

Today, doctors realize that the chief benefit of calcium scans is not to find specific areas of blockage, but to instead identify whether or not a patient has CAD, and if so, to estimate its severity. This information can be very useful in deciding how aggressive to be in pursuing risk factor modification.

What are the risks to the calcium scan?

The only risk to a calcium scan is the exposure to radiation, which occurs with any x-ray test. The amount of radiation a person receives with a calcium scan varies quite a bit depending on the equipment used, and before you agree to the test, you should ask the lab how much radiation exposure you will get in that facility. A reasonable amount of radiation with a calcium scan is 2 to 3 mSv (millisievert), which is equivalent to about 8 to 12 months of naturally occurring radiation.

Who should have calcium scans?

The usefulness of calcium scans largely depends on your level of risk for CAD. You can easily estimate your own risk level (into the categories low, intermediate or high) by answering a few simple questions. To estimate your own risk of heart disease, go here.

People in the low risk category have such a low probability of having a positive scan that it is currently recommended that they not have calcium scanning.

People in the high risk category have such a high probability of having a positive calcium scan that very little is gained by actually doing the scan.

It is people in the intermediate risk category who can benefit from calcium scans. These individuals often are apparently quite healthy, except for two or three risk factors that may be only "borderline" abnormal. Deciding whether to engage in aggressive lifestyle changes or to take statins or aspirin prophylactically can be difficult for such individuals. Here, a calcium scan can be quite helpful. If the calcium score is moderate or high, then active CAD is already present and these people should consider themselves to be at high (and not intermediate) risk for heart attacks. Aggressive steps for risk factor modification should be taken, often including statins and aspirin. On the other hand, if the calcium score is low, then little or no CAD is likely to be present and less aggressive risk factor modification (such as improving lifestyle choices) would be reasonable. Read here for more information on controlling heart disease risk factors.

The bottom line, as with any test, is that if the results of the calcium scan would be helpful in guiding your treatment or your behavior, then it is a good idea to consider having this test. Otherwise, pass it up.

Sources:

1) Agatston AS, Janowitz WR, Hildner FJ, et al. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol 1990 Mar 15;15(4):827-32

2) Greenland, P, Bonow, RO, Brundage, BH, et al. ACCF/AHA 2007 clinical expert consensus document on coronary artery calcium scoring by computed tomography in global cardiovascular risk assessment and in evaluation of patients with chest pain: a report of the American College of Cardiology Foundation Clinical Expert Consensus Task Force (ACCF/AHA Writing Committee to Update the 2000 Expert Consensus Document on Electron Beam Computed Tomography) developed in collaboration with the Society of Atherosclerosis Imaging and Prevention and the Society of Cardiovascular Computed Tomography. J Am Coll Cardiol 2007; 49:378.

3) Radiology Exposure in X-ray Examinations. Radiologyinfo.com (American College of Radiology and Radiological Society of North America). http://www.radiologyinfo.org/en/safety/index.cfm?pg=sfty_xray&bhcp=1&bhhash=1#3

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