Abstract 3719: Using the Framingham Risk Score to Select Low-risk Men for CAC Screening
Background Although coronary artery calcium (CAC) is predictive of future CHD, screening for CAC in low risk populations is controversial. Criteria are needed to narrow the screening population to those in whom CAC measurement is most efficient (vs. unselected screening). In this analysis, we report the relationship between CAC and CHD outcomes across Framingham risk score (FRS) subgroups to test whether there is a differential relationship between CAC and outcomes across baseline risk.
Methods In 1634 unselected male volunteers (mean age 42, mean 10 year CHD FRS 4.6%, CAC prevalence 22.4%), we evaluated the independent relationship between CAC and incident CHD over 5.6 years including hard events (hospitalized unstable angina, myocardial infarction and CHD death) and coronary revascularization. The cohort was stratified into tertiles of FRS to explore the relationship between CAC and CHD outcomes.
Results FRS tertile cutpoints were 0 –3%, 3–5%, and >5% 10 year CHD risk. Over a mean 5.6 years ± 1.5 year of follow-up (range: 1.0 to 8.3 years), there were 22 total CHD events, including 14 hard events and 8 revascularizations. The majority of events occurred in the highest FRS tertile (n = 14), versus the middle (n= 6) and lowest risk tertiles (n=2; P = 0.005). Only in the highest FRS tertile was there a significant relationship between CAC and CHD outcomes.
Conclusion Among asymptomatic low risk men, the presence of CAC demonstrates substantial discriminating power in predicting events, but appears to be most clinically useful when the 10-year FRS exceeds approximately 5%. If screening with CAC is pursued among low risk men, it should be preceded by a FRS and restricted to those with scores >5%.