DALLAS, June 30--By detecting calcium deposits in the coronary arteries, a special "CAT-scan" technique may help guide appropriate treatment for patients with coronary artery disease. However, in most situations, there is not enough compelling evidence to warrant widespread use at this time, according to a new consensus statement by the American College of Cardiology (ACC) and the American Heart Association (AHA).
Although an imaging method called electron-beam computed tomography (EBCT)--a type of "CAT-scan" technique--can detect these calcium deposits, which can lead to atherosclerosis, or hardening of the arteries, there have been conflicting reports as to the appropriateness of the technique in different types of patients.
Now a group of experts from ACC and AHA has reached consensus on this often-controversial topic. The resulting "ACC/AHA Expert Consensus Document on EBCT for the Diagnosis and Prognosis of Coronary Artery Disease" will be published in the July 2000 issue of the Journal of the American College of Cardiology and the July 4 issue of Circulation: Journal of the American Heart Association.
The ACC/AHA Writing Group reviewed the literature on EBCT published between 1988 and 1999, obtained information from articles in press, and examined data from EBCT research centers. The group also reviewed the Blue Cross/Blue Shield Technology Evaluation Center's assessment of EBCT. After performing meta-analyses, the group came to consensus on the use of EBCT in three different situations.
First, the writing group noted that a positive calcium score might be valuable in determining whether a patient who appears to be at intermediate risk is actually at high risk of developing coronary artery disease. Conversely, a low or absent EBCT calcium score may also prove useful in determining a low likelihood of developing heart disease.
An example of someone with intermediate risk would be a middle-aged person who has slightly elevated cholesterol, normal or slightly elevated blood pressure, and possibly an immediate family member who has had a heart attack. A high EBCT score may indicate this patient's need for cholesterol- and blood pressure-lowering drugs to reduce the chance of further damage to the blood vessels or a possible heart attack. A low EBCT score would mean this patient has a lower risk than expected and that lifestyle changes, rather than aggressive treatment and drug therapy, may be necessary to prevent heart disease.
Second, the writing group decided against recommending EBCT as a method for diagnosing obstructive coronary artery disease in asymptomatic people without multiple risk factors, citing the excessively high percentage of false positive results and the unnecessary and expensive additional tests that follow. "Some physicians are suggesting that electron-beam computed tomography be done on every person in the country over age 20," explains writing group chair Robert A. O'Rourke, M.D., of the University of Texas Health Science Center in San Antonio. "They're even advertising it to the lay person." Although the writing group noted that preliminary data are intriguing with respect to risk prediction, they believe that the data are insufficient to warrant widespread use, especially in light of more proven risk assessment models.
Finally, the writing group concluded that EBCT in asymptomatic patients can be justified only when performed in the context of a medical assessment, only after the more standard cardiac risk assessment is considered insufficient by the physician to direct further therapy plans. Commenting on the ACC/AHA report, Sidney Smith, Jr., M.D., past president of the American Heart Association says, "EBCT should be reserved for patients whose heart disease risk status is uncertain." He added that current imaging techniques such as angiography are better tools to determine if a patient's blood vessels are blocked with atherosclerotic build-up and need clinical intervention.
"We don't state that EBCT isn't useful," explains O'Rourke. "What we would like to see are additional properly designed studies to determine when the procedure is useful and when it's not."
Committee members include Bruce H. Brundage, M.D.; Victor F. Froelicher, M.D., Philip Greenland, M.D.; Scott M. Grundy, M.D., Ph.D.; Rory Hachamovitch, M.D.; Gerald M. Pohost, M.D., Leslee J. Shaw, Ph.D.; William S. Weintraub, M.D.; and William L. Winters, Jr., M.D.
Media advisory: Dr. Smith can be reached by phone at 919-966-0732 or email at scs@med.uncedu .; Dr. O'Rourke can be reached at 210-617-5100 (Please do not publish telephone numbers.)
For journal copies only,
please call: 214-706-1173
For other information, call:
Carole Bullock: AHA 214-706-1279 caroleb@heart.org
Beth Cassady: (ACC) 301-897-2628