CORONARY-ARTERY SCREENING BY ELECTRON-BEAM COMPUTED-TOMOGRAPHY - FACTS, CONTROVERSY, AND FUTURE

Coronary calcium as detected by electron beam computed tomography always signifies at least some atherosclerosis, appears to be correlated with coronary risk factors, cardiac history, and overall angiographic severity of disease, but is inconsistently related to degree of atherosclerotic lesion stenosis in a given artery. Increasing evidence, however, suggests an association between coronary artery calcium, atherosclerosis, and coronary risk. But atherosclerosis is a very common condition, its prevalence increasing with age. No fully validated method for determining the quantity of coronary calcium is available, and we do not know whether the amount of calcium is a consistently accurate reflection of the amount of atherosclerosis or whether the amount of atherosclerosis reflects the degree of risk. Furthermore, the prognostic significance of coronary calcium in any given atherosclerotic lesion is not yet established. What is clear from cohort studies, however, is that at least three quarters of asymptomatic individuals, at least half of whom would have 'positive' coronary calcium electron beam computed tomographic scans, will live for at least 10 years without cardiac problems of any kind. Investigation is needed to determine whether medical intervention may impact the clinical outcome of the rest of those identified with a positive scan but destined to suffer future clinical events. Despite lack of validation, this test has widespread appeal, both to the public as a means of being able to find out the condition of their coronary arteries 'without injections or dye' and to hospitals and private medical groups who view this both as an innovation in cardiovascular diagnosis and as a potentially profitable diagnostic procedure. Physicians asked to explain the results of the test must clearly delineate to patients the meaning of their results. Since the clinical value and cost- effectiveness of identifying individuals at risk over and above the existing methods of risk-factor evaluation are not known, it is not possible to recommend universal screening at this time. However, active research and emerging findings by many investigators may soon make it possible to recommend whether specific risk subgroups of individuals might benefit from coronary calcium screening.