To Evaluate The Efficacy Of Antiplatelet Regimen And The Response To Clopidogrel In Patients With Acute Coronary Syndrome

Objectives To investigate the antiplatelet efficacy and the response to clopidogrel in patients with acute coronary syndrome using ex vivo measures of the platelet vasodilator-stimulated phosphoprotein (VASP) phosphorylation and the activation of glycoproteinⅡb/Ⅲa receptor.Methods Included patients were treated with aspirin, clopidogrel, and heparin. Tirofiban was used in patients undergoing emergency PCI. At baseline and 7th day, the platelet VASP phosphorylation at resting (+PGE1) and activated (PGE1+ADP) status and PAC-1 assay were conducted by flow cytometry. The platelet reactivity (PRI), expressed as percentage, is the difference in mean fluorescence intensity of phosphorylated VASP between resting and activated platelets.Results 33 patients were included and there were not significant differences in clinical characteristics between unstable angina, non-ST elevated MI and ST elevated MI patients. The distribution of PRI and PAC-1 was nearly normal at baseline and 7th day. But the values of PAC-1 and PRI at 7th day were widely dispersed(PAC-1: 12.14%±4.84%, from 5.9% to 24.6%;PRI: 57.05%±13.69%, from 17.8% to 80.1%). The PRI was strongly correlated with PAC-1 (r=0.798, P﹤0.001). The changes of PRI and PAC-1 between pre- and post-clopidogrel regimen were extremely significant (77.52%±5.60% vs. 57.05%±13.69, P﹤0.001 and 19.81%±3.35% vs. 12.14%±4.84%,P﹤0.01). However, the distribution of inhibitory extent widely dispersed (PAC-1 reduction: 39.65%±18.36%, from -20.59% to 68.62%; PRI reduction: 26.55%±16.12%, from -9.61% to 76.14%). At 7th day, nearly 30% of these patients (9/33) had PRI and PAC-1 values equivalent to baseline with the criteria of mean±2SD. 8 patients (24.2%) had a reduction of PAC-1 less than 30% and about one-third (10/33) patients had a reduction of PRI less than 20%.Conclusions 1. Clopidogrel combined with aspirin and heparin can inhibit the platelet activity significantly in patients with ACS. However, a part of patients didn't demonstrate adequate inhibition of platelet function. The response to clopidogrel varied, nearly one-third patients failed to achieve enough platelet inhibition. 2. Addition to PAC-1, the platelet VASP phosphorylation assay at pre- and post anti- platelet regimen may evaluate the inhibitory efficacy and the response to clopidogrel.