Electron beam computed tomographic coronary calcium as a predictor of coronary events: comparison of two protocols

We assessed the accuracy of two electron beam computed tomography (EBCT) protocols for predicting coronary events.

In 1994, 24 months after enrollment in a longitudinal study, 326 high-risk adults underwent both 3- and 6-mm image-slice thickness EBCT scanning and were followed up for 32.0+/-4.0 additional months. Events were defined as either coronary death, myocardial infarction, or revascularization. We monitored these subjects for the 32-month postscanning period with yearly phone calls and acquisition of records for all hospital admissions. At the time of scanning, 11 subjects (3%) had already suffered 12 events (5 infarctions and 7 revascularizations) during the 24-month prescanning period. During the postscanning period, 18 subjects (6%) suffered 23 events (5 coronary deaths, 6 infarctions, and 12 revascularizations). Thus, 28 subjects (9%) suffered 35 events. Calcium quantities calculated for both protocols, performed on the same subjects, were sorted in ascending order and divided into equal quartiles. When revascularizations were included, there was a significant trend toward higher frequencies of events with increasing calcium quantity (P<.01). However, coronary death and infarction were not significantly more frequent in higher quartiles. These relationships were preserved in the subjects without prior events at the time of scanning.

Calcium quantities from the 3-mm and the more reproducible 6-mm scanning are equally accurate for predicting events. Coronary calcium amount appears to be a weak predictor of coronary death and infarction. Its predictive accuracy is superior for predicting revascularization.