Electron beam computed tomography: screening for coronary artery disease.

The need to detect coronary atherosclerosis early in its course has been well recognized by clinicians and epidemiologists for decades. The ability to identify populations with a greater prevalence of coronary disease prior to manifestation of illness would greatly reduce cardiac morbidity and mortality. Electron beam computed tomography (EBCT) uniquely combines the characteristics of speed and excellent density resolution that have led to a rebirth of interest in detecting coronary calcium as a means of screening asymptomatic populations for coronary atherosclerosis. Electron beam computed tomography is noninvasive and widely applicable. It can both detect and quantitate the presence of coronary atherosclerosis. A positive test has diagnostic and prognostic significance, predicting future cardiac events and the extent of atherosclerosis, including the probability of obstructive coronary artery disease (CAD). Multiple studies demonstrate a 6- to 35-fold increased risk of developing a cardiac event with elevated calcium scores. A negative test is highly predictive for excluding obstructive CAD. The cost ranges from $300 to $400, similar to that of an exercise treadmill test. Moreover, scanning for coronary calcium does not require injection of contrast medium, requiring no patient preparation or exercise; therefore, a CT technician can perform the study without supervision. The entire procedure takes < 10 min to perform. These features make EBCT a potential screening test for occult CAD in symptomatic and asymptomatic persons.