Qualitative coronary artery calcium assessment on CT lung screening exam helps predict first cardiac events

Background: Qualitative assessment of coronary artery calcium (CAC) burden on CT lung screening (CTLS) exams offers an opportunity to improve cardiac risk stratification among millions of current and former heavy smokers at no additional cost or radiation exposure. Methods: Qualitative CAC scores and subsequent myocardial infarction or revascularization (cardiac events) among individuals undergoing CTLS at our institution from January 1, 2012 through August 26, 2014 with follow-up through December 31, 2015 were retrospectively reviewed. Correlations were assessed through multivariable logistic regression modeling and time to event analysis. Results: A total of 1,513 individuals underwent CTLS. Downstream data, pre-test cardiac risk factors and CAC scores were available for 88.3% (1,336/1,513). The average length of follow-up was 2.64 (SD +/- 0.72) years. There were a total of 43 events, occurring in 1.55% (6/386) of patients with mild CAC, 3.24% (11/339) of patients with moderate CAC, and 8.90% (26/292) of patients with marked CAC. There were no events among patients with no reported CAC (0/319). Using multivariable logistic modeling, the increased odds of an initial cardiac event was 2.56 (95% CI, 1.76-3.92, P<0.001) for mild CAC, 6.57 (95% CI, 3.10-15.4, P<0.001) for moderate CAC, and 16.8 (95% CI, 5.46-60.3, P<0.001) for marked CAC, as compared to individuals with no CAC. Time to event analysis showed distinct differences among the four CAC categories (P<0.001). Conclusions: Qualitative coronary artery calcification scoring of CTLS exams may provide a novel method to help select individuals at elevated risk for an initial cardiac event.