Cardiologists Debate Study Comparing CT Scans, Angiograms
Some cardiologists are questioning the findings of a new study published last week in the New England Journal of Medicine that compared the effectiveness of high-resolution CT scans at detecting blockages in patient arteries with conventional angiograms, the New York Times reports. Angiograms require the insertion of a catheter through a blood vessel in the groin, a procedure that carries risks of immediate complications, while CT scans are "faster and less invasive" but expose patients to higher doses of radiation, which could increase the risk of cancer, according to the New York Times. The New York Times reports that many physicians are embracing CT technology while others say it increases cost and offers no proven benefits (Caryn Rabin, New York Times, 12/2).
For the study, led by Julie Miller of the Johns Hopkins University School of Medicine, 291 patients with symptoms of coronary heart disease at nine hospitals in Brazil, Canada, Germany, Japan, the Netherlands, Singapore and the U.S. underwent CT scans before having conventional angiograms. The median age of the patients was 59 and 74% were men. Toshiba Medical Systems manufactured the CT scanner, which imaged the patients' hearts in 64 slices in 8.5 seconds, according to the Los Angeles Times (Kaplan, Los Angeles Times, 11/27). The study was paid for in part by Toshiba and many of the participating researchers had financial ties to the company, according to the New York Times (New York Times, 12/2).
The researchers found that the CT scans accurately identified 85% of patients with the largest blockages and 90% of the patients without significant blockage. The researchers found that 91% of patients whose CT scans indicated the presence of severe coronary artery disease and 83% of patients whose scans did not show large blockages received a correct diagnosis. In addition, among 163 patients with a narrowing of at least 50% in at least one artery, the researchers found that CT angiograms were 93% as accurate as conventional angiograms (Los Angeles Times, 11/27).
However, the scan failed to detect clogged arteries in 15% of cases among patients with significant blockages and incorrectly identified blockages in 10% of patients who did not have clogged arteries. The study's findings led the researchers to conclude that "CT angiography cannot replace conventional coronary angiography at present," according to the Wall Street Journal (Hechinger, Wall Street Journal, 11/28).
According to the American Heart Association, more than 1.2 million people in the U.S. undergo cardiac angiograms annually, and 1% to 2% of the procedures result in complications. Of the patients who have the procedure, 20% to 30% receive a clean bill of health, meaning that many patients are exposed to unnecessary risks -- such as heavy bleeding, damage to the blood vessels and possibly death -- Miller said. CDC's National Center for Health Statistics estimates that 25 people die each year from angiography, the Los Angeles Times reports (Los Angeles Times, 11/27).
According to the Journal, cardiologists are debating whether CT scans -- which cost $600 or more -- improve patient care or contribute to rising health care costs and radiation risk (Wall Street Journal, 11/28). Kim Allen Williams, director of nuclear cardiology at the University of Chicago, said the CT scan is a "tremendous test when applied to the right kind of people." However, Williams added that he believes the study's findings could lead to medical insurers refusing to pay for CT scans because of the authors' conclusion that CT is not yet a replacement for conventional angiography.
Steven Nissen, a cardiologist at the Cleveland Clinic, said he believes the study is "overly optimistic about CT angiography," adding, "In the real world, ... CT angiography does not perform as well as was reported in this study." Rita Redberg, director of women's cardiovascular services at UC San Francisco Medical Center, and colleague Judith Walsh in a perspective piece accompanying the study wrote that the use of CT scans has increased "despite a lack of evidence of outcome benefit," adding that a "pay now, benefits may follow" approach could contribute to significant health care cost increases (Desmon, Baltimore Sun, 11/27).
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