Past research in stable patients with coronary artery disease and those with non-ST elevation acute coronary syndromes (NSTEMI) has demonstrated the safety and efficacy of enoxaparin as an anticoagulant strategy in patients undergoing percutaneous coronary intervention 1-3.~In patients with ST-elevations myocardial infarction (STEMI) receiving pharmacological reperfusion (fibrinolysis), enoxaparin has been shown to be an attractive alternative to unfractionated heparin based upon past modest scale trials (HART-2, ENTIRE TIMI 23, ASSENT-3, ASSENT-3+)4-6. These results were definitively extended by the ExTRACT-TIMI 25 trial which compared fibrinolysis with unfractionated heparin versus enoxaparin in 20,506 patients with STEMI 7. The primary endpoint of death and re-MI occurred in 9.9% of patients with enoxaparin and 12.0% of patients in the unfractionated heparin group (17% RR, p<0.001); major bleeding occurred in 2.1% and 1.4% respectively (p<0.001). This was achieved using a dose reduction strategy in the elderly (>75yrs) that omitted the intravenous enoxaparin bolus and decreased the subcutaneous injection to 0.75 mg/kg. After initial fibrinolysis, fewer patients underwent PCI through 30 days in the enoxaparin group versus the unfractionated heparin group (22.8% vs 24.2%, p=0.027). Among those who underwent PCI (n=4674) by 30 days the primary endpoint occurred in 10.7% with enoxaparin versus 13.8% unfractionated heparin randomization (0.77 RR, p<0.001); major bleeding was not different (1.4% vs. 1.6%, p=NS) 8.~Despite existing data in stable coronary artery disease, NSTEMI, and STEMI patients treated with fibrinolysis there is limited data regarding the approach to anticoagulation therapy with enoxaparin in those STEMI patients undergoing primary PCI. Within a sub-study of the Which Early ST Elevation Myocardial Infarction Therapy study (WEST) we undertook systematic anti-Xa sampling to address the adequacy of anticoagulation with an enoxaparin based regime9, 10. WEST patients undergoing primary PCI received aspirin, clopidogrel, and subcutaneous enoxaparin (1mg/kg) at the time of randomization. Subsequent administration of intravenous enoxaparin and abciximab at the time of PCI was encouraged. Those receiving supplemental intravenous enoxaparin (0.3 - 0.5 mg/kg) in addition to subcutaneous enoxaparin achieved anti-Xa levels > 0.5 units/ml (the proposed therapeutic concentration). Amongst those receiving 1 mg/kg of enoxaparin subcutaneous at randomization and 0.3 mg/kg intravenous enoxaparin at time of PCI, none had excessive anticoagulation (anti-Xa > 1.5 units/ml) suggesting that this may be an attractive dosing strategy.~Recently a non-randomized comparison of unfractionated heparin and enoxaparin within the FINNESSE study was presented in STEMI patients undergoing primary PCI. Preliminary reports indicate superior outcomes amongst those receiving enoxaparin 0.5mg/kg intravenous as compared to unfractionated heparin intravenously.~The STREAM study provides a unique and important opportunity to acquire randomized safety and efficacy data on anticoagulation with enoxaparin vs. unfractionated heparin in STEMI patients undergoing primary PCI.
The purpose of this study is to assess the safety and efficacy of Enoxaparin and Unfractionated Heparin in St Elevation Myocardial Infarction patients undergoing primary percutaneous coronary intervention.