Low Molecular Weight Heparin and Unfractionated Heparin in the Early Pharmacologic Management of Acute Coronary Syndromes: A Meta-analysis of Randomized Clinical Trials

Background: The standard of care in Acute Coronary Syndromes (ACS) includes a full complement of antischemic and antithrombotic therapy. Although aspirin is used widely and concomitant anticoagulation is recommended, the comparative benefits of low molecular weight heparin (LMWH) and unfractionated heparin (UFH) have not been defined.Methods/Results: A meta-analysis including all randomized clinical trials comparing LMWH and UFH for the treatment of non-ST segment elevation acute coronary syndromes was performed. Risk ratios (RR), using the DerSimonian-Laird Model, were calculated from a total of 13,320 patients. Death (RR 0.98, 95% CI 0.73–1.31), death and myocardial infarction (MI) (RR 0.86, 95% CI 0.74–1.01), death, MI, recurrent angina or revascularization (RR 0.89, 95% CI 0.74–1.07) and major hemorrhage (RR 1.01, 95% CI 0.81–1.25) occurred with similar frequencies for the anticoagulant-based strategies.Conclusions: Fixed dose LMWH therapy given subcutaneously compares favorably with UFH titrated to a target level of anticoagulation and should be considered a safe, effective, and clinically acceptable alternative in the early management of patients with non-ST segment elevation ACS. The superiority of LMWH preparations characterized by high in vitro factor Xa to thrombin inhibitory capacity is supported by clinic trial data but requires further investigation.