Key result
Clopidogrel administration is associated with an ~18% reduction in coated-platelet levels at 24 hours.
Why the study?
Excessive coated-platelets increase thrombotic risk and the effect of clopidogrel on coated-platelet formation in vivo was unknown.
Does clopidogrel reduce coated-platelet formation in patients undergoing elective coronary angiography?
Observational (n=27)
Does clopidogrel reduce coated-platelet formation in patients undergoing elective coronary angiography?
Absolute Risk Reduction: 7.2
Absolute Event Rate: 32.8% vs 40%
Absolute Risk Reduction: 7.2%
p-value: p=<0.0001
In vivo administration of clopidogrel significantly attenuates coated-platelet formation in patients undergoing elective coronary angiography, suggesting a potential new antithrombotic mechanism beyond ADP-induced aggregation inhibition.
Clopidogrel modestly attenuates coated-platelet formation; leaves open its contribution to antithrombotic efficacy and need for prospective trials.
INTRODUCTION: Coated-platelets are a subclass of highly thrombotic activated platelets with an enhanced ability to generate thrombin. Excessive numbers of coated-platelets are believed to increase thrombotic risk. A previous report demonstrated that P2Y12 inhibition in vitro attenuates coated-platelet formation. The aim of this study was to determine the effect clopidogrel has on coated-platelet formation. METHODS AND RESULTS: We enrolled 27 patients undergoing elective coronary angiography. A total of 3 blood samples were taken from eligible patients: baseline, 24-hour postclopidogrel (preangiography), and 6-hour postangiography. Coated-platelet levels, expressed as percentage of total platelets, were determined with convulxin and thrombin with or without 1.5 or 6 microM adenosine diphosphate (ADP). Baseline levels of coated-platelets were 40.0% +/- 14.3% (mean +/- 1 SD). After clopidogrel exposure, the coated-platelet level was 32.8% +/- 13.6%, representing a significant 7.2% absolute reduction (AR) (17.8% relative reduction (RR); P < 0.0001). Clopidogrel significantly lowered the convulxin, thrombin plus ADP coated-platelet production (11.0% AR; 20.1% RR for 1.5 microM and 11.2% AR; 19.1% RR for 6 microM). CONCLUSIONS: This is the first report on the impact of in vivo administration of a P2Y12 antagonist on coated-platelet formation. The significance of a partial attenuation in coated-platelet potential has yet to be determined, but this could represent a new antithrombotic mechanism of clopidogrel beyond inhibition of ADP-induced aggregation.
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Norgard et al. (2008) conducted an observational in Elective coronary angiography (n=27). Clopidogrel vs. Baseline was evaluated on Coated-platelet levels (ARR 7.2%, p=<0.0001). Clopidogrel administration significantly reduced coated-platelet levels from 40.0% at baseline to 32.8% at 24 hours (7.2% absolute reduction; P<0.0001).
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