The use of antithrombotics for acute coronary syndromes in the emergency department: considerations and impact.

Evidence-based guidelines for the management of acute coronary syndromes (ACS) identify a central role for unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). A recent study has suggested that interchanging between UFH and LMWH during the course of treatment may be associated with a worse outcome than continued therapy with either form of heparin. Because this has important implications for physicians in the emergency room, this review examines the current evidence for the efficacy and safety of heparins in ACS. In patients with acute myocardial infarction, several studies have shown that LMWHs represent an effective alternative to UFH as an adjunct to thrombolytic therapy and are not associated with an increased risk of major bleeding. In patients with unstable angina or non-ST-segment elevation myocardial infarction, the ESSENCE (Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q Wave Coronary Events) and TIMI 11B (Thrombolysis in Myocardial Infarction 11B) trials have shown that the LMWH enoxaparin significantly reduces the risk of cardiovascular events, compared with UFH, whereas other trials have shown that the combination of enoxaparin and a glycoprotein IIb/IIIa antagonist is not associated with an excess risk of bleeding. Recently, newer agents such as fondaparinux and bivalirudin have shown equivalent efficacy to the heparins with less bleeding and appear clinically attractive. Care paths for the use of antithrombotic therapy in patients with ACS are presented based on current US management guidelines and available clinical evidence.