Risk Prediction of Coronary Flow Reserve is Strongly Influenced by the Burden of Coronary Calcification

653 Background: The predictive significance of coronary flow reserve (CFR) and coronary artery calcium (CAC) is well established. However, the added value of CFR over CAC for the prediction of major adverse cardiovascular events (MACE) has not been investigated. Methods: We retrospectively identified 408 patients with native hearts undergoing cardiac PET/CT for evaluation of known or suspected coronary artery disease between 2012-2015 (mean age 58 ± 11 years; ejection fraction 65 ± 11%; creatinine 1.47 ± 1.7 mg/dL; male 36%; prior myocardial infarct 16%; prior stroke 9.1%, kidney disease 27%; diabetes 47%, hypertension 85%). CAC was visually estimated from ungated cardiac/chest CT into CAC 0-10, 11-400 and g P l 16%), including all-cause death (n=17; 4%), acute coronary syndrome (n=31; 8%) and/or stroke (n=22; 5%). Results: The combination of CAC and CFR yielded the following groups: 1) CAC ≤ 10 & CFR g 2) CAC ≤ 10 & CFR ≤ 1.5 (n=34); 3) CAC g and 4) CAC g P=0.037) and CAC g P < 0.0001) were important predictors of MACE. However, in a risk-adjusted model, CFR had comparable risk of MACE in patients with CAC ≤ 10 and only provided additional risk stratification in patients with CAC > 10 (Figure 1). Conclusions: Coronary flow reserve helps to risk stratify patients with CAC > 10. These findings have significant clinical implications but will need confirmation in larger studies.