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Despite risks and costs, CT heart scans are about to become more ubiquitous

The American College of Cardiologists and other medical societies have just widened the criteria under which computerized tomography (CT) scans are considered “appropriate” for the diagnosis of heart disease.

That means doctors will be recommending CT scans of the heart to many more people than in the past, including people who are at low risk for heart disease but who have a symptom or two, such as chest pain or shortness of breath.

In addition, under the new criteria, which were published online Monday in the Journal of the American College of Cardiology, scans may now be used to look for calcium deposits in the arteries of some people (such as those with a family history of heart disease) who have no symptoms at all.

As I reported earlier this year, CT scans for coronary calcium in asymptomatic people is controversial, for in many cases calcium deposits can be false-positives — invalid indications of heart disease.

The use of CT scans on asymptomatic people is also controversial because of their cost; they tend to be much more expensive than other screening tests. But the major objection to using these scans on people without symptoms has to do with the large amount of radiation they deliver. Indeed, their widening use in recent years has been linked to an increase in the incidence of cancer. A study published late last year estimated that 15,000 Americans may die from cancer over the next two decades as a direct result of CT scans they received in 2007 alone.

One of the common assumptions among radiologists and others who support expanding the use of CT scans has been that the risk of cancer from these tests is lower among middle-aged people. (Most CT heart scans are done on older adults.) But a study published Monday in the Journal of the National Cancer Institute knocks down that assumption. Using mathematical modeling of Japanese atomic bomb survivor data, the authors of that study concluded that radiation exposures in middle age can promote the expansion of existing premalignant cells in the body. In fact, they found that the cancer risk is twice what was predicted in previous models.

Dissenting voices
The committee of cardiologists and radiologists who drafted the new, expanded CT scan criteria believe, of course, that the benefits outweigh the risks.

But not all experts are convinced, as Reuters’ Frederik Joelving reports:

[T]he expanded criteria may be more geared to benefitting medical professionals than patients, according to some experts who say the scans are little more than pretty pictures with a big price tag — and potentially serious side effects.

Joelving cites the concerns of Dr. Rita F. Redberg, a cardiologist at the University of California, San Francisco, who wrote an editorial in the Archives of Internal Medicine last spring about the radiation risks of CT scans.

“Right now we don’t have any data showing that cardiac CT is as good as or better than other tests we have,” Redberg told Joelving. For people without congenital heart defects, CT scans are little more than “pretty pictures,” she added.

“A test cannot predict whether or not you are going to have a heart attack, and it can’t prevent getting one,” she said. “You get more false information than you get real information.”

Another doctor interviewed by Joelving, internist Dr. Patrick G. O’Malley of the Uniformed Services University in Bethesda, Md., also expressed concern that the new criteria will lead to overtesting. He noted that the physicians who drew up the criteria have a vested interest, for they use the technology every day.

“They didn’t include people who are not involved in this research,” O’Malley told Joelving. “They didn’t include a patient perspective.”

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