Electron-beam computed tomography for detecting coronary artery disease and cardiac events

Abstract

In this issue of the Journal, Harvey Hecht reviews the current status of electron-beam computed tomography (EBCT) and its implications for nuclear cardiology. Proponents of this technique for detection of coronary calcium deposits are at times overly enthusiastic about its accomplishments and promises. On the other hand, detractors of the technique are skeptical or frankly negative about its role in detecting preclinical coronary artery disease (CAD) and are often leery of the commercial overtones of some EBCT programs. In this scenario, the accumulated reported data are often cited with an emphasis on either the positive or negative findings, depending on the authors’ vested interests. Although Dr Hecht is correct in pointing out that the presence of calcium determined by EBCT is de facto proof of coronary atherosclerosis, the mere presence of calcium may not be a good predictor of future events: the vast majority of patients with coronary calcium deposits detected by EBCT do not have cardiac events during the next several years, and most patients probably will never have a cardiac event. Thus, although the presence of calcium is more direct evidence of coronary atherosclerosis than positive findings on a stress electrocardiogram or even a myocardial perfusion scan, the dilemma persists: it is easier to detect populations of patients who may be at higher risk for cardiac events than to “close in” on individual patients who will eventually have events. The acceptance of the guidelines developed by the Society of Atherosclerosis Imaging and reproduced by Dr Hecht in this issue may therefore be premature. To an impartial observer, it may appear that there is hardly any general agreement on what the appropriate indications are for this novel technique. The “evidence” in most cases is based on relatively few publications by a few groups of investigators who generally have a high degree of enthusiasm for EBCT. More studies reported from a larger number of institutions will be required before the results can be considered true “evidence.” These comments notwithstanding, EBCT does merit attention, if for no other reason than because CAD is the greatest health problem that Americans face. In the United States, 1 person dies each minute of a coronary event. Reducing the effects of CAD is a concern not only for this country but for the entire world. Great strides have been made in the daily treatment of CAD. Unfortunately, this treatment is targeting the disease after it has clinically revealed itself. Prevention of major cardiac disease events should be the main goal if we are to have a major impact on the outcome of CAD. Hence identifying persons with subclinical CAD before it becomes clinically apparent has great potential clinical applicability.