Coronary Calcium Independently Predicts Incident Premature Coronary Heart Disease over Measured Cardiovascular Risk Factors: Mean Three-year Outcomes in the Prospective Army Coronary Calcium (PACC) Project

Objectives: We sought to examine the independent predictive value of coronary artery calcium detection for coronary outcomes in a non-referred cohort of healthy men and women ages 40 to 50 years.

Background: Existing studies have suggested that coronary calcium might have incremental predictive value for coronary outcomes above standard coronary risk factors. However, additional data from non-referred and younger populations are needed.

Methods: Participants (n = 2,000; mean age 43 years) were evaluated with measured coronary risk variables and coronary calcium detected with electron beam tomography. Incident acute coronary syndromes and sudden cardiac death were ascertained via annual telephonic contacts, with follow-up (mean, 3.0 +/- 1.4 years; range, 1 to 6 years) in 99.2% of the cohort.

Results: Coronary calcium was found in 22.4% of men and 7.9% of women. A total of 9 acute events occurred in men at a mean age of 46 years, including 7 of 364 men with coronary calcium (1.95%) and 2 of 1,263 men without coronary calcium (0.16%; p < 0.0001 by log-rank). No events occurred in women. In these men, coronary calcium was associated with an 11.8-fold increased risk for incident coronary heart disease (CHD) (p = 0.002) in a Cox model controlling for the Framingham risk score. Among those with coronary artery calcification, the risk of coronary events increased incrementally across tertiles of coronary calcium severity (hazard ratio 4.3 per tertile). A family history of premature CHD was also predictive of incident events. The marginal cost effectiveness, assuming a 30% improvement in survival associated with primary prevention among at-risk men, was modeled to be 37,633 dollars per quality-adjusted life year saved.

Conclusions: In young, asymptomatic men, the presence of coronary artery calcification provides substantial, cost-effective, independent prognostic value in predicting incident CHD that is incremental to measured coronary risk factors.