Epidemiology of Coronary Artery Calcification

BACKGROUND:

Coronary artery disease (CAD) is a major cause of mortality and morbidity in the United States. Current noninvasive methods to identify individuals with atherosclerosis, such as exercise testing, are often insensitive until plaques have progressed enough to significantly impede blood flow or impair myocardial function. A large number of individuals destined to die suddenly or to experience myocardial infarction will experience no warning symptoms, having only mild non-flow limiting lesions which rupture and cause occlusive clot. Since coronary artery calcification (CAC) can identify individuals with mild, non-flow limiting lesions, CAC is a potent marker of atherosclerosis. The presence of calcium in mild, non-flow limiting lesions is hypothesized to be a predictor of coronary events in asymptomatic adults. Ultrafast Cardiac Computed Tomography (Ultrafast CT) provides a tool to obtain sensitive, noninvasive measures of both the presence and quantity of CAC.

DESIGN NARRATIVE:

Beginning in 1991, the study sought to establish if age and gender predict coronary artery calcification, a potent marker of atherosclerosis, in individuals who were sampled by the RFHS and who reported no symptoms of coronary artery disease. The study also sought to establish: if measures of lipid metabolism provide additional information in predicting CAC after accounting for variation in age and gender; if measures of blood pressure, body size, fat distribution, or smoking predict CAC after accounting for variation in age, gender, and measures of lipid metabolism; if the quantity of CAC aggregates in families; whether the predictors of CAC in asymptomatic individuals differ from predictors in those with symptoms of coronary artery disease. Ultrafast Cardiac Computed Tomography (Ultrafast CT) was used to obtain sensitive, noninvasive measures of both the presence and quantity of CAC.

The study was renewed in 2001 through February 2005 to: determine whether CAC predicts clinical events after 7.5 years of active followup; identify genetic determinants of change in CAC quantity; assess whether these genes act through measurable coronary artery disease risk factors. The full sample of 1,647 asymptomatic at baseline adults will be followed prospectively for clinical endpoints, while CAC quantity will be re-evaluated in a sub sample of 1,000 individuals.

The influence of newer inflammatory markers such as fibrinogen, C-reactive protein and antibodies to infective agents will be evaluated.

Individuals were recruited to participate if they had participated in the Rochester Family Heart Study or were siblings of those already in the ECAC study or had been in the GENOA Study or were identified to be at higher risk for having CAC. Potential participants were eligible if they were not pregnant, not lactating, and had never had coronary or non-coronary heart surgery. Eligibility for inclusion was independent of race, ethnicity, and country of birth.