Enoxaparin is superior to unfractionated heparin for preventing clinical events at 1-year follow-up of TIMI 11B and ESSENCE

Abstract

Background: Enoxaparin treatment is associated with a 20% reduction in clinical events during the acute phase of management of patients with unstable angina/non ST elevation myocardial infarction. Interest in the use of enoxaparin would be enhanced further if evidence of a durable treatment benefit over the long term could be provided.

Methods: Event rates at 1 year for the composite end-point of death/non-fatal myocardial infarction/urgent revascularization and its individual components were ascertained from the TIMI 11B and ESSENCE databases.

Results: There was no evidence of heterogeneity between TIMI 11B and ESSENCE in tests for interactions between treatment and trial. A significant treatment benefit of enoxaparin on the rate of death/non-fatal myocardial infarction/urgent revascularization was observed at 1 year (hazard ratio 0.88;P=0.008). The event rate was 25.8% in the unfractionated heparin group and 23.3% in the enoxaparin group, an absolute difference of 2.5%. A progressively greater treatment benefit of enoxaparin was observed as the level of patient risk at baseline increased. Treatment effects for the individual end-point elements ranged from 9-14%, favouring enoxaparin.

Conclusions: The stable absolute difference in event rates of 2.5% seen at 8 days and again at 1 year favouring enoxaparin may be due to more effective control of the thrombotic process surrounding the index event. Once the pharmacological effect of enoxaparin had dissipated there was no rebound increase in events. Thus, those patients who had received enoxaparin acutely were protected from experiencing a deterioration of the original therapeutic benefit. These findings regarding enoxaparin add to the data to be considered by clinicians when selecting an antithrombin for the acute phase of management of unstable angina/non-ST elevation myocardial infarction.