Heparins for Unstable Angina and Non-ST Segment Elevation Myocardial Infarction

Background: Acute coronary syndrome represents a spectrum of disease that includes unstable angina and non-ST segment elevation myocardial infarction (NSTEMI). Despite treatment with aspirin, beta blockers, and nitroglycerin, unstable angina or NSTEMI are still associated with significant morbidity and mortality. Although emerging evidence suggests that low-molecular-weight heparin (LMWH) is more effective compared with unfractionated heparin (UFH), there are limited data to support the role of heparins as a drug class in the treatment of acute coronary syndrome. Objectives: To determine the effect of heparins (UFH and LMWH) compared with placebo for the treatment of patients with acute coronary syndrome. Search Strategy: The authors searched the Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 4, 2002), Medline (1966 to Mali 2002), EMBASE (1980 to May 2002), and CINAHL (1982 to May 2002). Authors of included studies and pharmaceutical industry representatives were contacted to determine if unpublished studies that met the inclusion criteria were available. Selection Criteria: Randomized controlled trials of parenteral UFH or LMWH versus placebo in persons with acute coronary syndrome (unstable angina or NSTEMI). Data Collection and Analysis: Two reviewers independently assessed quality of studies. Data were extracted independently by two reviewers. Study authors were contacted to verify and clarify missing data. Main Results: Eight studies (3,318 participants) were included in this review. We found no evidence for difference in overall mortality between the groups treated with heparin and placebo (relative risk [RR] = 0.84; 95% confidence interval [CI], 0.36 to 1.98). Heparins reduced the occurrence of myocardial infarction (RR = 0.40; 95% Cl, 125 to 0.63; number needed to treat = 33), and increased the incidence if minor bleeds (RR = 6.80; 95% Cl, 1.23 to 37.49; number needed to harm = 17). Authors' Conclusions: Compared with placebo, patients treated with heparins had similar risks of mortality, revascularization, recurrent angina, major bleeding, and thrombocytopenia. However, those treated with heparins had a decreased risk of myocardial infarction and a higher incidence of minor bleeding.