Scientists doubt utility of CT scan as heart test

By Gene Emery

BOSTON (Reuters) - The U.S. health insurance program for the elderly, Medicare, is spending money on state-of-the-art CT scanners without clear evidence showing their usefulness in combating heart problems, commentators in the New England Journal of Medicine said on Wednesday.

CT scanning, used to diagnose coronary artery blockages, is one case where the U.S. government appears to be wasting money because pressures to pay for high-tech testing have overridden scientific evidence, they said in a commentary accompanying a study on the scans in the journal.

Another example is PET scans to assess dementia in patients with Alzheimer's, said commentary co-author, cardiologist Dr. Rita Redberg of the University of California, San Francisco.

The study published by the journal found that the expensive CT scans can detect narrowed blood vessels in people with suspected heart disease nearly as well as the conventional test in which doctors thread a catheter directly into the heart.

Researchers at Johns Hopkins University in Baltimore found that so-called 64-row computed tomography, or CT, scans were 93 percent as precise as conventional cardiac catheterization without subjecting a patient to an invasive procedure.

In a statement, Johns Hopkins cardiologist Dr. Joao Lima, one of the researchers, said CT scans are "an alternative diagnostic tool" that doctors can use to rule in or rule out coronary blockages when other, more indirect tests for reduced blood flow, such as cardiac stress testing, are unclear or unsafe for a particular patient.

The study, sponsored in part by the company that makes one brand of scanners, Toshiba Medical Systems, concluded scanners "cannot replace conventional coronary angiography at present." Toshiba Medical Systems is a unit of Japanese electronics maker Toshiba Corp.

About 5,000 of the $2 million units have been sold.

Redberg, in a telephone interview, said the concerns of a Medicare review panel that raised questions about the usefulness of the scans were not heeded. During a review earlier this year, "once again, enthusiasm for unfettered use of new technology prevailed," she and coauthor Dr. Judith Walsh, also of UCSF, wrote.

"The more scanners sold, the more people are invested in a technology," making it is less likely they will look at it critically, Redberg said. "Once that train leaves the station, it's harder to pull it back and say, 'Is this something that's really good for patients?'"

The problem is not just that the scans are not yet as good as conventional angiography, she said. The amount of radiation received with a CT heart scan is double, triple or quadruple the exposure in conventional angiography.

"We're talking about 500 chest X-rays with one of these cardiac CTs, so it's a lot of radiation," she said.

That could increase the risk of breast or lung cancer, another issue that should be studied, said Redberg.

And even if a correctable problem is found in a CT scan of the heart, doctors must do further testing and possibly more procedures. With conventional angiography, if doctors find a blocked blood vessel, they can often open it on the spot.

Another issue is cost.