By Melissa Schorr

NEW YORK, Mar 28 (Reuters Health) - A high-tech heart scan given while a patient is at rest works as well as a treadmill "stress test" for finding clogged arteries in people with chest pain, a research review has found. But the newer, more expensive test also has disadvantages, including the fact that it may be too sensitive.

"We found that the test is as accurate as exercise treadmill tests," lead author Dr. Brahmajee Nallamothu, a cardiology fellow at the University of Michigan Medical School in Ann Arbor, told Reuters Health. "I don't want to give the impression this will replace good tests we already have, but this is an additional test your doctor can use in certain circumstances."

Nallamothu and his colleagues conducted a meta-analysis--an extensive review of previously published research articles--to evaluate the accuracy of the new but costly technology, electron-beam computed tomography (EBCT).

EBCT scans a cross-section of the artery and measures calcium deposits in the blood vessel, which shows whether an artery is blocked and, if so, by how much. The test takes less than 15 minutes.

When blocked arteries narrow too much, they can eventually cut off the heart muscle's blood supply, causing a heart attack. Patients found to have artery blockage may be advised to simply take aspirin or cholesterol-lowering medications, or undergo more invasive procedures such as angioplasty or bypass surgery.

Although more than 100 medical centers across the country have already bought EBCT machines, researchers are still debating whether this is a cost-effective--and accurate--way to identify heart disease in patients with or without symptoms (usually chest pain). EBCT scans cost from $375 to $450, while the traditional treadmill test costs around $250 to $350.

This analysis, published in the March 26th issue of the Archives of Internal Medicine, sought to measure how accurate the test was in identifying blocked blood vessels in the heart in patients with symptoms such as chest pain or a recent heart attack. Nallamoth's team reviewed data on 1,662 patients compiled from nine previous studies. The EBCT was able to catch as many as 92% of arteries that had more than half their diameter blocked. However, with this high level of sensitivity, it also incorrectly diagnosed half of all healthy patients as diseased. Researchers determined the optimal measurement would pinpoint disease in 75% of patients, with only 25% diagnosed falsely.

False-positives are cause for concern, Nallamothu said, because they necessitate further testing, such as a heart catheterization, "which is invasive, has risks and costs a lot of money."

Overall, the EBCT test matched the accuracy of the stress test. One advantage to the EBCT test, Nallamothu said, is it is much quicker than a treadmill test and causes no physiological stress to the patient.

However, the EBCT machines also have some shortcomings that will need to be addressed by other technologies, Nallamothu pointed out. For example, they are not able to determine information about the heart muscle's ability to pump blood and on the health of heart valves, or the presence of dangerous lesions within the walls of the artery.

This analysis also may have had a bias by relying on prior published studies, which usually reported positive outcomes on the accuracy of EBCT technology. Studies not reporting favorable outcomes are less likely to be published, the authors note.

The analysis was funded by the Agency for Healthcare Research and Quality in Rockville, and the National Institutes of Health in Bethesda, Maryland.

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