A perspective on trials comparing enoxaparin and unfractionated heparin in the treatment of non–ST-elevation acute coronary syndromes

Background Non–ST-elevation (NSTE) acute coronary syndrome (ACS) is a serious, acute illness characterized by a high rate of death and morbid events, and antithrombin therapy is integral to its management. Contemporary guidelines from the American College of Cardiology/American Heart Association call for use of low-molecular-weight heparin or unfractionated heparin (UFH). Methods A systematic overview of six randomized, controlled trials comparing enoxaparin to UFH in the treatment of NSTE ACS was performed using a random-effects empirical Bayes model. Efficacy end points included the incidence of death or the composite of death and myocardial infarction (MI) at 30 days. Safety end points included major bleeding and transfusion at 7 days. Results For the aggregate of 21,946 patients, the incidence of the composite of death and MI at 30 days was lower in enoxaparin-treated patients (10.1% vs 11.0% for UFH, OR 0.91, 95% CI 0.83–0.99, number need to treat 107). For the 9,835 patients in these trials who received no prerandomization antithrombin therapy, the composite of death and MI at 30 days occurred in 8.0% and 9.4% of enoxaparin- and UFH-treated patients, respectively (OR 0.81, 95% CI 0.70–0.94, number need to treat 94). There was no significant difference in the incidence of death at 30 days in either population. A nonsignificant trend toward higher rates of major bleeding was seen at 7 days for enoxaparin-treated patients, in both the overall safety population and the population of patients who did not receive antithrombin treatment before randomization, but there was no difference in blood transfusions. Conclusion In a systematic overview of six randomized, controlled trials comparing enoxaparin to UFH in the treatment of NSTE ACS in approximately 22,000 patients, the use of enoxaparin rather than UFH was associated with a modest reduction in the incidence of the composite of death and MI at 30 days without a significant increase in the rate of major bleeding or transfusion at 7 days