Many, but not all, atherosclerotic plaques contain calcium. In recent years, a test called EBCT (electron beam computed tomography), which measures the amount of calcium in the coronary arteries (CAC), has been used to assess a person's risk of a heart attack.

Studies have shown that the larger the amount of calcium in the coronary arteries, the greater the risk of a heart attack. Despite its widespread use, the value of this test remains controversial.

In 2000, a joint statement from the American Heart Association (AHA) and the American College of Cardiology concluded that published studies could not answer whether EBCT was useful in identifying asymptomatic people who were at increased risk for heart attacks.

Several years later a commentary in the Journal of the American Medical Association by a physician at Harvard Medical School said the test should not be used in people with no symptoms of coronary heart disease.

Another recent and quite different recommendation was made this year by the SHAPE Task Force on heart attack prevention. They stated that, except for those with no risk factors, all asymptomatic men between 45 and 75 years of age and asymptomatic women between ages 55 and 75 should have either a measurement of coronary artery calcium or carotid artery thickness by ultrasonography.

Now, the AHA has finally published its much-awaited statement on coronary artery calcium. They concluded that CAC "identifies individuals at elevated risk for myocardial infarction [heart attack] and cardiovascular deaths, and adds significant predictive ability to the Framingham score."

The Framingham score uses a group of risk factors to estimate the risk of a heart attack in the next 10 years. It was recommended by the National Cholesterol Education Program as the way to judge when and how aggressively to treat LDL cholesterol levels. (To be truthful with you, in my opinion and experience, the Framingham score is frequently mentioned in learned medical journals but rarely if ever used by physicians.)

The AHA statement wisely recommended that CAC should not be measured in individuals at low or high risk because neither group of people benefits from the test. They go on to say "it may be reasonable" to measure CAC in "clinically selected, intermediate-risk patients" as a way of selecting people for more aggressive cholesterol-lowering therapy.

These recommendations are not really an about-face from the AHA statement made six years earlier; rather, they reflect the growing amount of evidence supporting the value of CAC. The statement is couched in a cautious and conservative tone because the AHA fears the costs that would result from excessive use of CAC measurements.   

I agree with the AHA statement that measurements of CAC can be valuable in selected patients at intermediate risk, even if they have no symptoms. I am not yet ready to accept the SHAPE Task Force recommendation that all asymptomatic older men and women should have a scan for CAC.