Abstract
Background Although patients undergoing coronary stenting routinely receive dual antiplatelet treatment to reduce the risk of stent thrombosis, this undesired event still occurs. A suboptimal response to clopidogrel treatment (low responders) has been suggested to contribute to stent thrombosis. In the present study, platelet function profiles were assessed in patients undergoing coronary stenting receiving a standard 300-mg clopidogrel loading dose with the aim to identify low clopidogrel responders. Materials and methods Platelet aggregation was assessed by light transmittance aggregometry following 6 μM ADP stimuli in 48 patients before and 10 min, 4 and 24 h after receiving clopidogrel front-loading. Patients having ≥40% inhibition of platelet aggregation 24 h after clopidogrel administration were defined as normal responders, whereas those having <40% inhibition were low responders. Glycoprotein (GP) IIb/IIIa activation and P-selectin expression were assessed by whole blood flow cytometry following 2 μM ADP stimuli at the same time points. Platelet function profiles were compared between normal and low clopidogrel responders. Results Twenty-seven patients (56%) were normal responders and 21 (44%) low responders. Baseline GP IIb/IIIa activation was higher in low responders (74.6±16.6% vs. 58.2±24.5%, p=0.03). Although GP IIb/IIIa activation reduced following clopidogrel front-loading in both groups, it remained increased among low responders at 24 h (58.6±21.3% vs. 40.2±28.7%, p=0.05) and during the overall study time course ( p=0.02). There were no differences in P-selectin expression. Conclusions A considerable proportion of patients have an early suboptimal response to a 300-mg clopidogrel loading dose. An increased GP IIb/IIIa activation before intervention may identify this group of patients suggesting the use of a more aggressive antithrombotic treatment in these individuals.
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