The role of low-molecular-weight heparins in non-ST-segment elevation acute coronary syndromes

Acute coronary syndromes are believed to be mediated by plaque rupture, initiation of the coagulation cascade, and platelet activation and aggregation. Compared to unfractionated heparin, the low molecular weight heparins possess several important theoretical advantages for the treatment of patients with acute coronary syndromes, including less non-specific binding, resistance to inactivation by platelet factor-4, more reliable anticoagulation effects, and greater factor anti-Xa activity. Four large studies have compared low-molecular-weight heparin therapy with unfractionated heparin therapy in patients with acute coronary syndromes. Two studies involving enoxaparin (Lovenox) have demonstrated that this therapy results in a lower incidence of adverse events compared to treatment with unfractionated heparin. One study of dalteparin (Fragmin) and one of nadroparin (Fraxiparin) have demonstrated comparable results between these low-molecular-weight heparins and unfractionated heparin. Several studies of modest size have demonstrated that low-molecular-weight heparins can be safely combined with platelet glycoprotein IIb/IIIa inhibitors. Ongoing and upcoming studies should add to current knowledge of the utilization of low-molecular-weight heparins.