Though coronary artery disease (CAD) remains the first cause of morbidity and mortality in the United States (http://www.americanheart.org), screening for asymptomatic disease has been at the center of a vivid debate for a long time. Several councils and professional associations have endorsed screening for subclinical atherosclerosis in selected patients. The American Heart Association/American College of Cardiology1 and experts of the National Cholesterol Education Program III (NCEP-III)2 suggested that screening may provide incrementally useful information in subjects judged to be at intermediate risk by traditional risk factors. The European Society of Cardiology3 recently noted that CAC is a sensitive marker of atherosclerosis, and it should not be used as a marker for underlying coronary luminal stenosis. Rather it should be used as a tool to improve risk assessment in individual patients. This organization further acknowledged that the prognostic relevance of CAC has been demonstrated in several prospective studies, not only in asymptomatic individuals but also in patients undergoing coronary angiography. However, screening for CAC should be reserved to individuals at intermediate risk and in men older than 45 years and women older than 55 yeears.3 These opinions are based on the analysis of available data on imaging along with an analysis of the distribution of cardiovascular risk in the adult population of Western countries. In the United States, among individuals older than 20 years, 40% to 45% are classifiable at intermediate risk (6%-20% risk of hard cardiovascular events at 10 years), 30% to 35% at low risk, and 25% at high risk. Because the largest proportion of the population is in the intermediate risk group, this is the group that experiences the bulk of events and therefore is the most expensive group for society. The cost of caring for cardiovascular disease is calculated at ap proximately $300 billion in the United States per year (http://www.americanheart.org), and early detection of disease and effective management of risk should guarantee an improved outcome with a related cost reduction due to the reduction in advanced forms of disease. Nonetheless, there are substantial limitations to this axiom: patients' adherence to risk-reducing practices is discontinuous, and current medical therapies are incompletely effective to eradicate disease. Furthermore, there are substantial costs inherent in the insufficient societal awareness of risk and the missed opportunity to screen for risk at the primary office level.4 Lack of awareness of risk, leading to disease development, is certainly more costly than effective screening and preventive programs.
Proposed use of subclinical atherosclerosis imaging in asymptomatic subjects with a preliminary assessment of risk based on Framingham risk score categories. The choice of a coronary artery calcium (CAC) score of 100, a carotid wall thickness of 1 mm and any of the 2 measurements higher than the 75th percentile for age- and sex-matched individuals was based on publications demonstrating the prognostic relevance of these measures. A measure of atherosclerosis higher than the 75th percentile for age and sex defines a vascular age older than the biological age of the individual. EBCT indicates electron-beam computed tomography; EF, ejection fraction; IMT, intima-media thickness.
Proposed approach to the diagnosis of obstructive coronary artery disease (CAD) in symptomatic patients according to the pretest probability of disease and level of coronary calcification. Several publications showed that the probability of obstructive CAD increases significantly when the coronary artery calcium (CAC) score rises above 400. That is why this score was chosen as the threshold beyond which further testing could be warranted. EBCT indicates electron-beam computed tomography; EF, ejection fraction.
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