Effect of Thrombocytopenia on Outcomes Following Treatment With Either Enoxaparin or Unfractionated Heparin in Patients Presenting With Acute Coronary Syndromes

Thrombocytopenia is associated with an increased risk for adverse cardiac events and bleeding in patients presenting with acute coronary syndromes (ACS) treated with unfractionated heparin (UFH). Enoxaparin has been shown to improve outcomes in ACS; however, its effect on the development of thrombocytopenia in this population is not well documented. This study was conducted to examine the incidence and clinical importance of thrombocytopenia in patients presenting with non–ST-elevation ACS randomized to treatment with enoxaparin or UFH. Thrombocytopenia was defined as a platelet count <100 × 109/L or a >50% decrease from baseline. Thrombocytopenia developed in a total of 93 of 3,910 patients during the follow-up period of 14 days; the incidence was similar between study arms. The development of thrombocytopenia was associated with more frequent death, nonfatal myocardial infarction, and urgent revascularization during the study period (odds ratio 2.96, p = 0.001). This association was independent of assignment to treatment with enoxaparin or UFH (p for interaction = 0.47). Major bleeding was also more common in patients with thrombocytopenia regardless of treatment. In conclusion, thrombocytopenia is a significant correlate of adverse events in patients presenting with non–ST-elevation ACS treated with either enoxaparin or UFH.