Prognostic Value of PET-Derived Myocardial Flow Reserve in Patients With Very High Coronary Artery Calcium Score

BACKGROUND: Coronary artery calcium (CAC) is a strong predictor of cardiovascular outcomes, with patients having high CAC experiencing event rates similar to those in secondary prevention populations. Emerging evidence suggests that patients with extremely high CAC (≥1000) represent a distinct high-risk group. Therefore, this study aims to evaluate the prognostic value of myocardial flow reserve (MFR) in patients with very high CAC. METHODS: Consecutive patients who had a clinically indicated positron emission tomography were enrolled and followed prospectively for incident outcomes (all-cause death and myocardial infarction). Multivariable-adjusted Cox proportional hazards models were used to study the association between MFR and incident events (composite of all-cause death and myocardial infarction) among those with CAC ≥400. RESULTS: The study population consisted of 3091 patients; mean (SD) age 69.6 (10.1) years, 36.8% female, 64.5% White, 46.0% with a CAC score of 400 to 999, and 54.0% with a CAC score of ≥1000. The median (interquartile range) MFR was 1.9 (1.45–2.35). Over a median (interquartile range) follow-up time of 1.36 (0.45–2.50) years, there were 278 incident events (81 myocardial infarctions and 217 deaths). In adjusted analyses, an MFR ≥2 was inversely associated with a lower risk of incident events; hazard ratio, 0.65 (95% CI, 0.38–1.12) for a CAC score of 400 to 999 and hazard ratio, 0.44 (95% CI, 0.28–0.69) for a CAC score of ≥ 1000. There was no significant interaction between MFR and CAC score; P =0.53. CONCLUSIONS: Among patients with CAC ≥400, positron emission tomography–derived MFR ≥2 is inversely associated with a lower risk of all-cause death and myocardial infarction.