Low-molecular-weight heparins for acute coronary syndromes

OBJECTIVE: To review published literature regarding the use of low-molecular-weight heparins (LMWHs) for the acute coronary syndromes of unstable angina and acute myocardial infarction (MI). METHODS: A MEDLINE search (January 1986-August 1997) was performed to identify all pertinent articles. Selected references from these articles and abstracts of recent clinical trials were also included. DISCUSSION: LMWHs have several distinct advantages over standard unfractionated heparin (UFH). These advantages include convenient once- or twice-daily standardized administration without the need for activated partial thromboplastin time monitoring. While the use of LMWHs as prophylaxis and treatment of venous thromboembolism is fairly well-established, the use of LMWHs for treating acute myocardial ischemia is evolving. Published studies and abstracts have shown LMWHs to be as effective as or more effective than UFH in preventing death, myocardial infarction, and recurrent ischemia in patients with unstable angina or acute MI. The comparative incidence of bleeding between LMWHs and UFH is controversial, with some studies reporting lower or similar rates of bleeding with LMWHs, while one study demonstrated a higher bleeding rate than with UFH. The cost-effectiveness of using LMWHs over UFH for acute coronary syndromes also remains to be established. CONCLUSIONS: LMWHs appear to be as effective as, and potentially more effective than, UFH in preventing complications of acute coronary syndromes. However, further studies are needed to better define the comparative bleeding risks of LMWHs and UFH. This, plus the lack of published peer-reviewed trial results and pharmaco-economic analyses, preclude the recommendation of routinely using LMWHs for treating unstable angina and acute MI at this time.

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