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.
Combining cardiac magnetic resonance and computed tomography coronary calcium scoring: added value for the assessment of morphological coronary disease?
