Abstract 2784: Quantitative Relation between Coronary Artery Calcium Content and Coronary Vasodilator Reserve as Assessed by Integrated PET-CT Imaging
Background: Coronary artery calcium (CAC) score is a marker of atherosclerosis. Whether epicardial calcium reflects more widespread consequences of atherosclerosis on coronary vascular function is unknown. Our objective was to determine the relation between CAC and coronary vasodilator reserve (CVR).
Methods: We evaluated 52 consecutive patients without known coronary disease (60 ±12 years, 64 % females) undergoing rest-dipyridamole stress Rb82 PET imaging and CAC scoring on hybrid PET-CT scanner. CAC score was quantified in each individual coronary artery by the Agatston method. A group of 20 asymptomatic healthy volunteers without CAC were also included. Myocardial blood flow and CVR was assessed using generalized factor analysis and 2 compartment kinetic model. A total of 195 coronary artery territories without reversible or fixed perfusion defects on rest-stress PET imaging were analyzed.
Results: In per vessel analysis: CAC scores were inversely related to estimated CVR (r= −0.32, p<0.001). Mean CVR stratified into tertiles of CAC score is presented in the figure⇓. In per patient analysis: Univariable predictors of CVR included age (p<0.001), hypertension (p<0.001), hyperlipidemia (p<0.008), peripheral arterial disease (p=0.03), diabetes (p=0.05) and CAC score (p<0.001). In multivariable modeling only hypertension (p=0.007) and the CAC score (p=0.005) remained predictive.
Conclusion: CAC score is a predictor of decreased CVR independent of traditional coronary risk factors. Possible mechanisms of the altered CVR in territories with high CAC may include a combination of epicardial stenosis and impaired coronary function independent of upstream stenosis.