May 12, 2003 -- Roughly half of all heart attacks and other coronary deaths occur in people without symptoms of heart disease. A new and somewhat controversial screening method that measures calcium deposits in the walls of the arteries that cover the heart offers the promise of predicting these events in this group of hard-to-identify patients.
In the largest study ever published assessing electron beam coronary artery calcium scanning as a screening tool for heart disease, researchers concluded that the diagnostic method was remarkably useful for identifying future trouble in people at moderate risk. Compared with men with the lowest levels of the calcium deposits in the coronary arteries, men with the highest levels of calcium scores were twice as likely to have heart attacks and 10 times as likely to need bypass surgery or angioplasty.
"Electron beam tomography (EBT) provided incremental information above the traditional risk factor assessment for this intermediate risk group," lead researcher George T. Kondos, MD, tells WebMD. "This appears to be much better than the traditional treadmill test for identifying people with asymptomatic disease."
In this study, Kondos and colleagues at the University of Illinois College of Medicine used EBT to evaluate the risk for coronary events among 5,635 men and women with no symptoms of heart disease. Participants were asked to hold their breath on two occasions for 30 seconds to one minute while lying on a special couch that slid into a hollow computed tomography (CT) scanner. During this time, electron beams create multiple images of the heart, and a computer measures the density of calcium deposits in the artery walls.
Within three-and-a-half years of having the test, 224 of the volunteers developed evidence of heart disease. They either required bypass surgery or angioplasty to open clogged arteries, had heart attacks, or died of coronary-related causes. EBT scanning detected high amounts of calcium deposits in 95% of these participants, but low amounts of calcium were detected in 67% of the participants who did not experience coronary events.
Compared with people with the lowest calcium levels, women with the highest levels were almost four times as likely to need heart bypass surgery or angioplasty during the follow-up, and men were 10 times as likely to require the procedures.
Kondos tells WebMD that EBT probably has little value in predicting future heart disease in people at very low or high risk for heart disease. Those at intermediate risk -- including men over 45 and women over 50 with at least one added risk factor, such as diabetes, high blood pressure, high cholesterol, family history, or vascular disease -- would benefit from this screening.
"This study reinforces (the idea) that the test is best reserved for individuals at intermediate risk in the population," American Heart Disease President Robert Bonow, MD, says in a news release.
In an editorial accompanying the study, cardiologist and epidemiologist William Weintraub, MD, wrote that it is clear that the cost of EBT can not be justified for people at high and low risk for heart disease. The 10-minute test can cost from $400 to $1,000 and it is rarely covered by insurance.
The jury is still out, he concludes, on whether the cost is justified in people in the intermediate-risk category. Critics of the scanning method say another new measure of heart disease risk -- blood testing for the presence of C-reactive protein -- may prove to be just as useful at a fraction of the cost.
Weintraub, who is a professor of medicine at Atlanta's Emory University, tells WebMD that he would recommend EBT as a diagnostic test for some, but not all, people in the intermediate-risk category.
"This is a powerful predictor of risk, but we are not quite sure what it adds to the other risk factors that we already measure," he says. "Within the next five years I do think it will have a bigger place in the diagnosis of coronary artery disease and its position will be better defined."