Abstract 2759: Elevated Coronary Calcium Scores Measured by Multi-Slice Computed Tomography are Associated with Low Response to Clopidogrel in Patients with Stable Angina pectoris

Cardiac multi-detector computed tomography (MDCT) with retrospective ECG-gating permits the determination and quantification of coronary calcifications. High calcium scores are known to be associated with elevated all-cause mortality. Moreover, low response to clopidogrel influences cardiovascular outcome after coronary stent placement. We sought to evaluate whether elevated calcium scores are associated with a low response to clopidogrel. Methods 62 patients were enrolled in this trial (52 male, mean age 64.8 ± 8.9 years). Coronary calcium scoring (expressed as Agatston score equivalent, ASE) was measured with multi-slice computed tomography (Sensation 64™ [n=19] and Somatom Definition ™ [n=43], Siemens, Forchheim, Germany) prior to stent implantation. Responsiveness to clopidogrel was assessed by ADP (20 micromol/L)-induced aggregometry at least 6 h after administration of a loading dose of 600 mg clopidogrel. Results Median calcium score was 736 ASE [range 0 –3126] and mean platelet inhibition was 35±19% [range 0 –70]. There was a significant negative correlation between ASE and response to clopidogrel (r 2 =0.135, p=0.0033, slope 7.809 ± 2.549). Patients within the first quartile of ASE had significantly better response to clopidogrel than other patients (p<0.05). Establishing a threshold of 200 ASE responsiveness to clopidogrel could be predicted with a positive predictive value of 80% and a specificity of 91%. Conclusions We could demonstrate that elevated ASE is associated with a low response to clopidogrel. Patients with a low coronary plaque burden are more likely to have a good response to clopidogrel. Coronary calcium scoring might help to identify low responders to clopidogrel prior to stent placement and aggregometry.