UNFRACTIONED HEPARIN/CLOPIDOGREL INTERACTION IN PATIENTS WITH STEMI NOT UNDERGOING REPERFUSION

Background: A substantial proportion of patients with ST-segment elevation myocardial infarction (STEMI) do not receive reperfusion therapy.The aim of our study was to investigate the relative benefits of enoxaparine compared to unfractioned heparin (UFH) in association with clopidogrel in STEMI patients not undergoing reperfusion therapy. Methods: We enrolled 1440 consecutive patients with STEMI from 2007 to 2011. A total of 584 patients (40.6 %) did not receive reperfusion therapy. At admission, 223 were treated with enoxaparine and 292 patients with UFH. All patients received aspirin and/or clopidogrel. No significant differences were found in the concomitant medications between the group treated with enoxaparine compared to UFH treated patients. Results: We found a significant interaction (p<0.001) between UFH and clopidogrel, consequently, we performed separate analysis for clopidogrel users and non users. After adjustment for cardiovascular risk factors, clinical history, time to hospitalization and in-hospital treatment with clopidogrel and/or aspirin. UFH was associated (p=o.oo2) with a lower risk of in-hospital death in clopidogrel users (adjusted OR 0.38; 95%CI 0.30- 0.70). The rate of mortality in the association of enoxaparine and clopidogrel or enoxaparine and UFH alone, was not statistically significant (Figure). Conclusions: We found evidence of UFH - clopidogrel interaction. The effect of UFH was favorable only in concomitant treatment with clopidogrel.