Coronary Artery Calcium and Primary Prevention Risk Assessment: What Is the Evidence?

Over 600 000 myocardial infarctions (MIs) occur yearly in the United States, and more than half of patients whose MI presents as sudden cardiac death have no antecedent symptoms.1 Furthermore, men >40 years of age have an almost 50% lifetime risk of developing coronary heart disease (CHD) and women of the same age have a risk of approximately 1 in 3.2 The Framingham Risk Score (FRS) is the most commonly used CHD risk prediction model and is an integral component of cardiovascular screening and lipid-lowering guidelines.3 Although the FRS provides a reasonable estimation of risk in certain subgroups, it was derived from a relatively homogenous population in an era when pharmacological treatment options and use were limited.4 Furthermore, chronologic age is the dominant risk factor in the FRS equation, although it is a poor surrogate for atherosclerotic burden and limits the personalization of risk estimates.5 As a result, the majority of MIs occur in individuals classified as low or moderate risk who therefore do not meet the Adult Treatment Panel (ATP) III criteria for statin therapy.3,6To improve risk estimation, recent research has focused on identifying novel risk predictors. However, when they are added to existing risk prediction models, there is little improvement in CHD risk stratification.7,8 As a result, there is an increasing interest in selectively using atherosclerosis imaging to increase the accuracy of traditional risk prediction models in persons broadly classified as intermediate risk.9 Coronary artery calcium (CAC), measured using noncontrast cardiac CT, is a relatively low-cost and noninvasive imaging technique. CAC testing provides an individualized measure of atherosclerotic burden that integrates an individual’s cumulative lifetime risk factor exposure that cannot be obtained from serum markers.10,11The use of CAC screening in select …