Electron-beam tomography coronary artery calcium and cardiac events: a 37-month follow-up of 5635 initially asymptomatic low- to intermediate-risk adults.

BACKGROUND Conventional coronary artery disease (CAD) risk factors fail to explain nearly 50% of CAD events. This study examines the association between electron-beam tomography (EBT) coronary artery calcium (CAC) and cardiac events in initially asymptomatic low- to intermediate-risk individuals, with adjustment for the presence of hypercholesterolemia, hypertension, diabetes, and a history of cigarette smoking. METHODS AND RESULTS The study was performed in 8855 initially asymptomatic adults 30 to 76 years old (26% women) who self-referred for EBT CAC screening. Conventional CAD risk factors were elicited by use of a questionnaire. After 37+/-12 months, information on the occurrence of cardiac events was collected and confirmed by use of medical records and death certificates. In men, events (n=192) were associated with the presence of CAC (RR=10.5, P<0.001), diabetes (RR=1.98, P=0.008), and smoking (RR=1.4, P=0.025), whereas in women, events (n=32) were linked to the presence of CAC (RR=2.6, P=0.037) and not risk factors. The presence of CAC provided incremental prognostic information in addition to age and other risk factors. CONCLUSIONS The association between EBT CAC and cardiac events observed in this study of initially asymptomatic, middle-aged, low to intermediate-risk individuals presenting for screening suggests that in this group, knowledge of the presence of EBT CAC provides incremental information in addition to that defined by conventional CAD risk assessment.