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SAFE, PAINLESS CT EXAM MAY REPLACE CORONARY ANGIOGRAMS
FOR SOME PATIENTS WITH BLOCKED HEART ARTERIES
CHICAGO -- The most common test used to diagnose blocked arteries in the heart -- coronary angiogram -- is being challenged by a safe, painless and less expensive technology that researchers say may soon be widely available.
The technique, called electron-beam computed tomography (CT), also called "Ultrafast CT," has been under investigation at medical centers in the United States for the past years. "Even now, we're ready to say it can replace coronary angiograms in some patient groups, particularly those who are not known to have a coronary artery blockage and are undergoing tests to rule it out," said Charles B. Higgins, M.D., professor and vice chairman of radiology, University of California, San Francisco, who presented results of his study today at the 83rd Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
Currently, a coronary angiogram -- also called coronary angiography, angiocardiography or coronary arteriography -- still is required in patients with known blockages to assess the disease prior to surgery or angioplasty to open the artery, Dr. Higgins said.
According to the National Center for Health Statistics, nearly 2 million coronary angiograms are performed in the United States every year, and it is the most common diagnostic exam to assess coronary artery blockage.
Advantages of the new technique compared to coronary angiograms include:
ï It is noninvasive. The new CT scan requires only that a small amount of contrast agent, or dye, be injected intravenously. For a coronary angiogram, a puncture is made in the patient's groin, a catheter is threaded into the coronary arteries and a contrast agent is injected.
ï It is painless.
ï It is virtually risk-free. With coronary angiography, there is a 1 percent to 2 percent risk of complications, and some high-risk patients must be hospitalized for the procedure.
ï It is less expensive. "Electron-beam CT is approximately one-fifth the cost of a coronary angiogram," Dr. Higgins said. "If a patient requires hospitalization for the angiogram, the cost can be 20 times more than CT."
ï There is less exposure to radiation.
In the study reported by Dr. Higgins, co-author Dr. Gautham Reddy and their colleagues, 23 patients were imaged with angiography and electron-beam CT. Doctors who were blinded to the results of the angiograms were able to correctly correlate the findings of CT with angiographic findings in from 71 percent to 100 percent of the blocked arteries that were evaluated.
The exam is performed with a special CT scanner that acquires images more rapidly than conventional CT. "The images must be acquired in milliseconds, during the resting cycle of the heart," Dr. Higgins said. "Currently, there are about 40 electron-beam CT scanners in the United States, but as this new technique is validated and acquires widespread acceptance, that number will grow."
"With advances in radiologic imaging, we are increasingly able to image the heart and other structures of the body noninvasively," Dr. Higgins said. "For example, another emerging technology that promises to improve the diagnosis of heart disease and avoid coronary angiography for some patients is magnetic resonance angiography (MRA)," he said.
Co-authors of a paper on the topic presented by Drs. Higgins and Reddy during the RSNA meeting are D. Chernoff, M.D., Ph.D.; S. Siripornpitak, M.D.; J. Adams, M.D.; and R. Outtrim, M.D.
The RSNA is an association of 30,000 radiologists and physicists in medicine dedicated to education and research in the science of radiology. The Society's headquarters are located at 2021 Spring Road, Suite 600, Oak Brook, Illinois 60523-1860.
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Copies of 1997 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Dec. 1.
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