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Heart Imaging Tool Under the Microscope

Usefulness of CTA Screening Unknown in People With No Symptoms
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WebMD Health News

CTA Scans Heart Disease

July 22, 2008 -- The death of newsman Tim Russert last month from a massive heart attack raised interest in new technologies that may better identify people at risk for life-threatening cardiac events.

A test that one expert calls "the iPod of medical imaging" is emerging as an important tool for visualizing plaque buildup in patients with known coronary artery disease.

But a new study offers little support for the use of computed tomography angiography (CTA) as an early screening tool for people with no symptoms of artery disease, such as chest pain or an abnormal stress test.

And researchers conclude that the safety of CTA must be established before the test can be recommended for the routine screening of people with no symptoms.

CTA-associated radiation exposure has been linked to an increase in the lifetime risk of cancer, especially in women and young people.

"CTA has promise, but at present we simply don't have the data to confirm its usefulness and safety in an asymptomatic population," study co-author Hyuk-Jae Chang, MD, PhD, of South Korea's Seoul National University Bundang Hospital, tells WebMD.

CTA-Detected Plaque

Also known as multislice computed tomography or 64-slice CT, CTA screening is being prematurely marketed to the public as a screening tool for low-risk populations, even though there are no guidelines recommending its use for this purpose, Chang says.

"Everyone wants the latest technology, and this is something like the iPod of medical imaging," says cardiologist Ann F. Bolger, MD, of the University of California, San Francisco. "Unfortunately, the technology is only as useful as the science behind it."

In one of the first studies to examine the value of CTA for identifying coronary artery disease in presumably low-risk populations, Chang and colleagues followed 1,000 asymptomatic people without established artery disease for about a year and a half following CTA screening.

Although the test did identify significant and severe plaque buildup in 5% and 2% of the people, respectively, the sample size was too small and the follow-up too short to determine the value of CTA screening in people without symptoms, Chang says.

The researchers plan to follow 5,000 asymptomatic patients for five years following CTA screening.

"We do not yet have the data to show that the risks outweigh the benefits in this population, but we also don't have the data to show that the benefits outweigh the risks," Chang says. "So we must wait."

Radiation Risk a Concern

One big problem with the test is that it is not clear what the findings mean in patients with few risk factors for heart disease, Bolger tells WebMD.

"If you don't see coronary disease, is that person off the hook, and if you do see it does that mean that the person will have a coronary event in a year, or two, or five?" she says. "We can't answer these questions yet."

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