Abstract 346: Platelet Reactivity to Aspirin and Clopidogrel in Patients with Acute ST Elevation Myocardial Infarction and its Correlation with High Sensitivity C- Reactive Protein

Abstract

INTRODUCTION Implantation of bare metal or drug eluting stents supported by dual antiplatelet therapy (DAPT) is standard treatment for the management of patients with ST elevation myocardial infarction (STEMI). Individual response to aspirin and clopidogrel is heterogeneous, and decreased response is associated with thrombotic events following stenting. We postulated that systemic inflammation at the time of STEMI would diminish responsiveness to DAPT. The aim of this study is to evaluate the correlation between elevated high-sensitivity C-reactive protein (hs-CRP) as a marker of inflammation and decreased platelet sensitivity to DAPT in STEMI. METHODS We recruited patients with STEMI undergoing percutaneous coronary intervention (PCI) who received oral clopidogrel 600 mg loading dose followed by 75 mg daily maintenance dose and aspirin 325 mg daily. Platelet reactivity and hs-CRP were measured within 72 hours of PCI and at 6 weeks. For patients receiving eptifibatide, blood samples were taken 48 hours after discontinuation. Platelet reactivity was assessed using the VerifyNow platelet function analyzer. A cut-off value of 208 platelet reaction units (PRU) was used to define high on-clopidogrel platelet reactivity (HCPR) and a value of 454 aspirin reaction units (ARU) was used to define high on-aspirin platelet reactivity (HAPR). RESULTS In 20 patients aged 31 to 85, in hospital and 6 weeks after STEMI, hs-CRP was 6.7 (SD 4.0) and 2.6 (SD 3.2) respectively, p< 0.01. Changes in ARU from 408.3 (SD 54.3) to 425.2 (SD 68.2) and PRU from 157.8 (SD 74.7) to 164.2 (SD 75) were not statistically significant. 2 patients had HAPR in hospital; 1 became sensitive at follow up. 2 patients developed HAPR and HCPR. We saw a trend towards higher PRU in diabetic patients and those prescribed statins. CONCLUSIONS Although we found a significant difference in hs-CRP levels between the first and second time point, no significant difference was found in on-aspirin and on-clopidogrel platelet reactivity between the time points.Thus, in this small series, the acute inflammatory state associated with STEMI did not appear to influence the on-DAPT reactivity at the dosages used. Trends among those with diabetics and prescribed statins will be discussed