The findings build upon initial reports from 1993 that the non-invasive imaging technique is a safe, convenient alternative to angiography, long considered the gold standard among coronary diagnostic tests.
“This new technology requires no needles, no exposure to contrast dye, and no exposure to radiation,” according to the study's principal investigator Warren J. Manning, M.D., co-director of the Cardiac MR Center at BIDMC and Associate Professor of Medicine and Radiology at Harvard Medical School. By using a powerful magnet and radio waves to provide images of the heart's arteries, MRA eliminates the discomfort and potential complications of an invasive X-ray procedure that detects artery blockages by injecting an iodinated contrast dye into the blood vessels using a catheter inserted in the groin or arm. As a result, the patient's risk of complications, including infection and bleeding, is eliminated, and the level of comfort is greatly improved, with the time spent in the hospital reduced from as long as eight hours to as little as 45 minutes. Costs are also substantially reduced.
The study of 109 patients was conducted at seven sites in the United States and Europe among individuals referred for their first coronary X-ray angiogram. At each site, the MRA procedure used standardized Philips Medical Systems MR hardware and BIDMC-developed software and scanning protocol. The MRA was generally performed within a day prior to X-ray angiography. For each patient – and each coronary vessel – the sensitivity, specificity and accuracy of the MRA scan were assessed and compared with the results of the X-ray technique. Overall, it was found that the MRA had an accuracy of 72 percent in diagnosing coronary artery disease; that figure rose to 87 percent in the specific identification of three-vessel coronary disease or left main artery disease. Furthermore, the “negative predictive value” of the technology was 81 percent for any coronary disease and 100 percent for left-main or three-vessel disease. In other words, patients whose coronary MRAs were interpreted as “normal” were, indeed, unlikely to have any significant disease.
A secondary benefit of the imaging technology is its usefulness in ruling out coronary disease. “Many patients who are referred for an angiogram are found to not have any blockages,” says Manning, noting that 41 percent of the subjects in this study were found to have no clinically significant disease, as shown on X-ray angiography. If, instead, a patient underwent an MRA – and results were normal – then they could likely avoid the invasive angiogram altogether. Left untreated, coronary artery disease can lead to heart attacks, and has been implicated in 900,000 deaths each year at a cost of $60 billion. Early identification of coronary artery disease provides the opportunity for surgical intervention, which has produced good long-term survival benefits among patients.
“This study was not designed to examine the use of coronary MRA as a screening test for coronary artery disease,” Manning emphasizes. “But, if there is a question regarding the presence of multi-vessel disease, the coronary MRA appears to be very accurate.”
The study was funded, in part, by Philips Medical System, and by a grant from the American Heart Association.
Co-authors include BIDMC investigators W. Yong Kim, M.D., Ph.D., Peter G. Danias, M.D., Ph.D., Matthias Stuber, Ph.D., and Rene M. Botnar, Ph.D.; Erik M. Pedersen, M.D., Ph.D., of Aarhus University Hospital, Denmark; Scott D. Flamm, M.D., of St. Luke's Episcopal Hospital, Houston; Sven Plein, M.D., of the Yorkshire Heart Center, United Kingdom; Eike Nagel, M.D., of the German Heart Institute, Berlin, Germany; Susan E. Kangerak, M.Sc., of Leiden University Medical Center, Netherlands; Oliver M. Weber, Ph.D., of the University of Zurich, Switzerland; and Matthias Schmidt, M.D., University of Cologne, Germany.
Beth Israel Deaconess Medical Center is a major patient care, research and teaching affiliate of Harvard Medical School and a founding member of CareGroup Healthcare System. Beth Israel Deaconess is the fourth largest recipient of National Institutes of Health research funding among independent U.S. teaching hospitals.
Journal
New England Journal of Medicine