Randomized comparison of enoxaparin with unfractionated heparin following fibrinolytic therapy for acute myocardial infarction

Aims To compare the efficacy and safety of low molecular weight heparin with unfractionated heparin following fibrinolytic therapy for acute myocardial infarction. Methods and Results Three-hundred patients receiving fibrinolytic therapy following acute myocardial infarction were randomly assigned to low molecular weight heparin as enoxaparin (40mg intravenous bolus, then 40mg subcutaneously every 8h, n=149) or unfractionated heparin (5000U intravenous bolus, then 30000U.24h−1, adjusted to an activated partial thromboplastin time 2–2·5× normal, n=151) for 4 days in conjunction with routine therapy. Clinical and therapeutic variables were analysed, in addition to use of enoxaparin or unfractionated heparin, to determine independent predictors of the 90-day composite triple end-point (death, non-fatal reinfarction, or readmission with unstable angina). The triple end-point occurred more frequently in patients receiving unfractionated heparin rather than enoxaparin (36% vs. 26%;P =0·04). Logistic regression modelling of baseline and clinical variables identified the only independent risk factors for recurrent events as left ventricular failure, hypertension, and use of unfractionated heparin rather than enoxaparin. There was no difference in major haemorrhage between those receiving enoxaparin (3%) and unfractionated heparin (4%). Conclusion Use of enoxaparin compared with unfractionated heparin in patients receiving fibrinolytic therapy for acute myocardial infarction was associated with fewer recurrent cardiac events at 90 days. This benefit was independent of other important clinical and therapeutic factors.