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CT Scan Helps With Heart Predictions, But …

April 30, 2010
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Using a computed tomography (CT) test to measure calcium in coronary arteries can help predict future heart disease, according to a new study. But a second study is needed to determine whether the improvement is worth the extra cost and extra risk from radiation exposure.

The research, published April 28 in The Journal of the American Medical Association, studied 5,878 participants from July 2000 through May 2008. (It excluded persons with diabetes.) The study tested two models to predict the five-year risk of coronary heart disease “events,” including heart attack, cardiac arrest from which the patient was resuscitated, and death from coronary heart disease. The first model used the following traditional risk factors: age, sex, tobacco use, systolic blood pressure, use of antihypertensive drugs, total and HDL cholesterol, and race/ethnicity. The second model added the coronary artery calcium score (CACS), as measured by a CT scan.

The second model predicted an additional 23 percent of participants who eventually experienced a serious cardiovascular event. Also, an additional 13 percent whom the second model had reclassified as low risk (compared to the first model) did not experience such cardiovascular problems.

So does it make sense to add the CACS to the list of standard heart risk factors in order to identify patients who merit further treatment—or who might be able to avoid unnecessary treatment?

“We didn’t look at that,” said Philip Greenland, MD, a professor of preventive medicine at Northwestern University Feinberg School of Medicine and a member of the team reporting the study. Dr. Greenland told HealthDay:

What we can say here is that additional testing looks like it improves prediction. Whether it improves clinical outcome requires a different kind of study.

Dr. Greenland said his team has been discussing just such a study with the National Heart, Lung and Blood Institute of the National Institutes of Health. That study might involve tens of thousands of participants and cost anywhere from $29 million–$50 million (Dr. Greenland’s estimate) to more than $100 million (the guess of Andrew J. Einstein, MD, director of cardiac computed tomography research at Columbia University Medical Center in New York).

According to Dr. Greenland, a CT scan yields about twice the radiation exposure of a mammogram, and the cost of a CACS scan is estimated at between $200 and $600.

He seems optimistic that a follow-up study will be funded. However, we obviously won’t see any results—or changes in screening recommendations—for several years.

Related seminar: Cardiac Imaging

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