Abstract： Background Aspirin and clopidogrel resistance plays a significant role in the development of cardiovascular ischemic events for ninety patients undergoing percutaneous coronary intervention.Recent studies have indicated that increasing the dose of antiplatelet drugs maybe a potent method to improve the inhibition of platelet aggregation.Methods Thrombelastograph (TEG) determinations were used to evaluate the effect of antiplatelet therapy.According to the results,90 patients were divided into three groups and given different doses of aspirin and clopidogrel.Thirty patients with both an inhibition rate of aspirin ＞50％ and an inhibition rate of clopidogrel ＞50％ were defined as the control group.Sixty patients with an inhibition rate for aspirin ＜50％ and an inhibition rate for clopidogrel ＜50％ were defined as the resistance group.Patients in resistance group were randomly assigned to be given a routine dose (100 mg aspirin plus 75 mg clopidogrel per day,which we called a resistance plus routine dose group,R+R) and a loading dose (200 mg aspirin and 150 mg clopidogrel per day,which we called resistance plus loading dose group,R+L) of antiplatelet therapy.A 12-month follow-up was observed to examine the change of inhibition rate of antiplatelet therapy and to estimate the relationship between inhibition rate and the occurrence of cardiovascular ischemic events.Results After 6 months of antiplatelet therapy,the inhibition rate of aspirin in the R+L group increased from (31.4±3.7)％ to (68.6±7.1)％,which was significantly higher than that in R+R group,(51.9±8.2)％ (P ＜0.01).The inhibition rate of clopidogrel in the R+L group increased from (22.1±3.8)％ to (60.2±7.4)％,which was significantly higher than in the R+R group,(45.9±4.3)％ (P ＜0.01).The occurrence rates of cardiovascular ischemic events,stent thrombosis,recurrent unstable angina and myocardial infarction in the R+R group were 20％,36％ and 17％,respectively.Occurrence was significantly increased compared with that in the control group,3％,10％ and 1％,respectively (P ＜0.01).In contrast,the occurrence rates in the R+L group (10％,23％ and 6％,respectively) were attenuated compared with those in the R+R group (P ＜0.01 ),although still higher than in the control group (P ＜0.01).Conclusions Almost all of the cardiovascular ischemic events occurred in the first six months after percutaneous coronary intervention.According to the result of TEG determinations,earlier application of a loading dose of aspirin and clopidogrel can decrease the rate of recurrent cardiovascular ischemic events.