Restoration of effective myocardial perfusion by percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI) is a life-saving therapy. Selection of the optimum anticoagulation regimen to support primary PCI is essential. Unfractionated heparin, low molecular weight heparins, the factor Xa inhibitor fondaparinux, and the direct thrombin (factor IIa) inhibitor bivalirudin have all been studied in this setting. These agents have different mechanisms of action, binding specificity, pharmacokinetic and pharmacodynamic consistency, risks of heparin-induced thrombocytopenia, and half-lives ().