Background and Objectives: Aspirin and clopidogrel are the commonly using anti-platelet agents for reducing cardiovascular (CV) event and preventing stent thrombosis. Recently, drug resistance to antiplatelet agents is known as one of the risk factors for CV events. The object of this study is to evaluate the clinical factors affecting aspirin and clopidogrel resistance. Methods: Four hundred thirty patients(290 men, mean age 62.910.1 years) undergoing percutanenous coronary intervention (PCI) were enrolled in this study. We measured aspirin reaction unit (ARU) for aspirin and percentage platelet inhibition (PPI) for clopidgogrel by Ultegra Rapid Platelet Function assay(RPFA) and Ultegra RPFA-P2Y12(VerifyNow TM Assay), respectively. Aspirin resistance was defined as ARU ≥ 550, whereas clopidogrel resistance was defined as PPI < 20%. Clinical factors such as age, sex, cardiovascular risk factors, LV ejection fraction, lipid profile, CRP, and medications were analyzed. Results: Average of ARU and PPI were 446.960.0 and 27.724.3. On aspirin, thirty patient (7%) was resistant and there was no statistically significant factor affecting aspirin resistance. On clopidogrel, 195 patients (48%) were resistanant and age, sex, abdominal circumference (AC), smoking, HDL, LDL, the use of cilostazol and ACE inhibitor were correlated with clopidogrel resistance using univariate analysis. Multiple logistic regression analysis of the variables showed that the AC (RR 1.04, CI=1.006-1.076, p=0.021) and the use of cilostazol (RR 0.337, CI=0.173-0.656, p=0.001) were independent predictors of clopidogrel resistance.
Conclusion: Here, we found that aspirin resistance is uncommon, whereas clopidogrel resistance occurred in half of patients undergoing PCI. Furthermore, some clinical factors are related with clopidogrel resistance and we should focused on dosage and alternative medications in these patients.
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