New test for coronary artery disease linked to higher rates of cardiac procedures and greater costs

A new, noninvasive diagnostic test for coronary artery disease is associated with a higher rate of subsequent invasive cardiac procedures and higher health-care spending. That's according to an observational study of Medicare recipients conducted by researchers at the Stanford University School of Medicine.

In the study, which will be published in the Nov. 16 issue of the Journal of the American Medical Association, patients who underwent coronary CT angiography were about twice as likely to have a subsequent invasive cardiac procedure as patients who underwent a stress test, a more common diagnostic procedure. CT angiography was also associated with higher total health-care spending.

Senior author Mark Hlatky, MD, professor of medicine and of health research and policy, said the findings raise questions of whether patients are benefiting from the additional procedures. "We don't know if those extra procedures will ultimately save lives and lead to better quality of life," he said, noting that they definitely increased costs. "Our study suggests that we need more definitive clinical trials to show whether patients are better off as a result of having CT angiography instead of a stress test."

When coronary artery disease is suspected, current clinical guidelines recommend an initial evaluation with a type of stress test that enables doctors to see how a patient's heart works during physical exertion. If the results suggest the presence of blocked coronary arteries, the next step is usually cardiac catheterization with an invasive coronary angiogram, which displays the size and location of plaque in a patient's artery.

The coronary CT angiography recently emerged as an alternative to the stress test: It uses intravenous dye and CT scanning to provide an inside view of the coronary arteries. "CT angiography is a potential game-changer with respect to how we evaluate patients with suspected heart disease," said Hlatky, adding that the number of coronary CT angiography procedures conducted on Medicare beneficiaries has increased steadily since the procedure first became eligible for reimbursement in 2006.

Experts predict a substantive growth in the use of coronary CT angiography over the next decade, but the impact of the test in practice hasn't been known. "Most prior studies have simply evaluated the accuracy of coronary CT angiography compared with the results of a standard invasive coronary angiogram, and haven't looked at how the information was used," said Hlatky. "Before we did this study, it wasn't clear whether a CT angiogram would lead to more testing and more unnecessary procedures, or whether it would reduce the need for further testing and save money. We needed real data to document how coronary CT angiography would be used in practice."

For this study, Hlatky and his colleagues — internal medicine resident and first author Jacqueline Baras Shreibati, MD, and Laurence Baker, PhD, professor of health research and policy — examined the health-care use and spending among patients evaluated for suspected heart disease. This issue hadn't been addressed in previous studies.