Abstract 4350763: Baseline Severity of Coronary Artery Calcium Among Patients Enrolled in the CorCal Trial Compared to those Enrolled in the MESA Study

Background: CorCal is an ongoing clinical outcomes trial in which men over 50 and women over 60 without ASCVD, diabetes, or statins were randomized to use the Pooled Cohort Risk Equation or the coronary artery calcium score (CACS) to determine the need for statin therapy. The trial is event-driven and is delayed in its completion due to a significantly lower than predicted overall event rate. Whether a lower-than-expected baseline severity of CACS among the CorCal patients might explain the reduced event rate is unknown. Methods: All CorCal subjects who received a CACS were included. The overall CACS were placed into 0, 1-100, and >100 categories. The results were evaluated according to various baseline clinical characteristics and compared to the historically reported CACS of subjects enrolled in the MESA study. Results: Table 1 shows baseline CACS according to various clinical characteristics. Overall, 62.1% of men, but only 40% of women, had a CACS ≥1. Additionally, relatively few subjects (Men = 24.6%; Women 12.2%) had a CACS >100. The most significant age-related increase in CACS began at 70 years and expanded rapidly with age after that. There was no correlation between CACS and LDL-cholesterol levels. Table 2 shows the differences in prevalence of CACS ≥1 by age and sex between the MESA and CorCal study populations. Even after adjusting for age at enrollment, fewer CorCal than MESA subjects showed evidence of coronary calcium. Conclusions: Nearly half of CorCal subjects had a CACS=0, and less than 20% had a CACS >100. Additionally, the coronary calcium burden among subjects enrolled in the CorCal Study was substantially less than the reported number in the MESA study. These findings may explain the lower-than-expected event rate thus far observed in the entire CorCal study.