Abstract 3410: Coronary Calcium Screening for CHD Risk Assessment: For Intermediate Risk Only? Findings in Low-risk Men and Women
Background The AHA Scientific Statement (2006) regarding coronary artery calcium (CAC) scanning states that CAC measurements are “reasonable in clinically selected intermediate risk patients” and that “low risk (<10% FRS) patients do not benefit from coronary calcium assessment”. To test this, we prospectively examined the incremental predictive value of CAC measurements in patients aged 40 –50 years of age at low risk of CHD.
Methods We enrolled 2000 healthy men and women (mean age 42) and evaluated them with measured traditional coronary risk variables, CAC detected with electron beam tomography, and annual follow up for hard events (hospitalized unstable angina, myocardial infarction and CHD death) and coronary revascularization. A Cox proportional hazard regression analysis was performed to investigate the association of coronary calcium and total CHD events, hard CHD events and revascularization events after controlling for the Framingham risk score and other CHD risk factors such as family history and CRP.
Results 1990 patients (99.5% of the cohort) were successfully followed for a mean of 5.6 years ± 1.5 years (range: 1.0 to 8.3 years). Among the 1634 male participants (mean FRS 4.6%, CAC prevalence 22.4%), there were 22 total CHD events, 14 hard events and 8 revascularization events. The cumulative event rate was significantly higher among those with CAC (3.8% vs. 0.5%; P<0.0001) and incremental across tertiles of calcium scores (Log-rank P < .0001). The presence of any CAC was an independent and incremental prognostic factor of total CHD events, hard CHD events and revascularization events with hazard ratios of 6.1 (95% confidence interval (CI): 2.6 –14.5; P<0.0001), 8.6 (95% CI: 2.7–27.5: P<0.0001) and 3.5 (95%CI: 1.4 –18.9; P=0.02), respectively. Adjustment for additional CHD risk factors such as family history and CRP did not change the association between the coronary calcium and CHD events. Among women (mean FRS 1.3%, CAC prevalence 7.9%) only 1 participant (with CAC) had an event.
Conclusion CAC is independently predictive of coronary events over 6 years among unselected low risk men ≤ 50 years of age. Low risk women of similar age are not suitable for CAC screening.