American College of Cardiology/American Heart Association Expert Consensus document on electron-beam computed tomography for the diagnosis and prognosis of coronary artery disease.

Executive Summary Coronary artery calcification is part of the development of atherosclerosis; it occurs exclusively in atherosclerotic arteries and is absent in the normal vessel wall. Electron-beam computed tomography (EBCT), the focus of this document, is a highly sensitive technique for detecting coronary artery calcium and is being used with increasing frequency for the screening of asymptomatic people to assess those at high risk for developing coronary heart disease (CHD) and cardiac events, as well as for the diagnosis of obstructive coronary artery disease (CAD) in symptomatic patients. The use of EBCT has the greatest potential for further determination of risk, particularly in elderly asymptomatic patients and others at intermediate risk. The calcium score has been advocated by some as a potential surrogate for age in risk-assessment models. EBCT has also been proposed as a useful technique for assessing the progression or regression of coronary artery stenosis in response to treatment of risk factors such as hypercholesterolemia. EBCT uses an electron beam in stationary tungsten targets, which permits very rapid scanning times. Serial transaxial images are obtained in 100 ms with a thickness of 3 to 6 mm for purposes of detecting coronary artery calcium. Thirty to 40 adjacent axial scans are obtained during 1 to 2 breathholding sequences. Current EBCT software permits quantification of calcium area and density. Histological studies support the association of tissue densities of 130 Hounsfield units (HU) with calcified plaque. However, a plaque vulnerable to fissure or erosion can be present in the absence of calcium. Also, sex differences play a role in the development of coronary calcium, the prevalence of calcium in women being half that of men until age 60 years. EBCT calcium scores have correlated with pathological examination of the atherosclerotic plaque. This American College of Cardiology (ACC)/American Heart Association (AHA) Writing Group reviewed the literature on EBCT published between 1988 and 1999 and also used information obtained when possible from articles in press and data sets from EBCT research centers. We also reviewed the Blue Cross/Blue Shield (BC/BS) Technology Evaluation Center (TEC) assessment of EBCT for screening asymptomatic patients for CAD and for diagnosing CHD in symptomatic patients. Three members of this Writing Group attended the recent AHA Prevention V Conference on “Identification of the High-Risk Patient for Primary Prevention,” and one of our members is also a participant in the design of the National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI) forthcoming Multiethnic Study