Comparison of enoxaparin versus unfractionated heparin in patients with unstable angina pectoris/non-ST-segment elevation acute myocardial infarction having subsequent percutaneous coronary intervention

Patients with unstable angina or non-ST-segment elevation myocardial infarction (MI) may undergo invasive revascularization procedures shortly after admission to hospital or after a brief period of stabilization. In the Thrombolysis In Myocardial Infarction (TIMI) 11B trial and Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-Wave Coronary Events (ESSENCE) trial 1,326 patients underwent percutaneous coronary intervention (PCI). A total of 924 patients underwent PCI during the initial hospitalization period, and of these, 445 patients did so while receiving treatment with unfractionated heparin (UFH) or the low-molecular-weight heparin, enoxaparin. This analysis compared efficacy and clinical events in the enoxaparin and UFH groups in patients who: (1) underwent PCI while on treatment versus those who did not, and (2) underwent PCI in hospital. We also compared those who did not undergo PCI. Treatment with enoxaparin (1 mg/kg given as twice daily subcutaneous injections) was beneficial and well tolerated in patients with unstable angina and non-ST-segment elevation MI who underwent PCI. Compared with UFH, enoxaparin significantly reduced the likelihood of clinical events (death and nonfatal MI after PCI) in patients who underwent PCI after 1 year (p = 0.003 for in-hospital PCI; p = 0.005 for on-treatment PCI), with a trend toward a reduced event rate at 43 days. In addition, patients treated with enoxaparin who did not undergo PCI also showed a reduction in the risk of death, nonfatal MI, and urgent revascularization when compared with those treated with UFH (significant at 43 days, with a trend persisting at 1 year). Study limitations were that PCI was nonrandomized, the analysis was post hoc, and the sample size was relatively small. Nevertheless, in the absence of large clinical trials, this study suggests that treatment with enoxaparin was well tolerated, and exhibited a similar risk of major hemorrhage to UFH in patients who underwent PCI.