PCI and clopidogrel: antiplatelet responsiveness and patient characteristics.

Objective: This study on responsiveness to clopidogrel and aspirin evaluates its interaction with: (i) patient characteristics; (ii) procedure characteristics; (iii) antiplatelet dose.

Methods And Results: After elective PCI, 60 patients receiving aspirin 100 mg daily, and clopidogrel 75 mg daily were monitored with the PFA 100 test and VASP assay. Non-responsiveness to aspirin and clopidogrel was found in 23 (38%) and 18 (30%) of 60 patients, respectively. Seven (12%) patients were dual nonresponders. Non-responders to both aspirin and clopidogrel were more often smokers. Non-responders to clopidogrel, in addition had elevated inflammatory markers (P < 0.05). Dual non-responders had (i) a higher platelet count, LDL, and CRP; (ii) a lower HDL (P < 0.05). Clopidogrel non-responders were receiving 150 mg clopidogrel, with a positive response in 72%. Eighty % of non-responders to 150 mg clopidogrel were also non-responders to aspirin.

Conclusion: Baseline patient characteristics and clopidogrel dose modify the antiplatelet response. Also, patients resistant to both aspirin and clopidogrel do no benefit from an increased clopidogrel dose.