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Heparin versus placebo for acute coronary syndromes
K D Magee1, S G Campbell, D Moher
1Dalhousie University, Department of Emergency Medicine, Queen Elizabeth II Health Sciences Centre, Halifax Infirmary, 1796 Summer Street, Halifax, Nova Scotia, Canada B3H 3A7. kmagee@dal.ca
Insights
Heparins, including unfractionated heparin (UFH) and low molecular weight heparin (LMWH), did not significantly alter mortality in acute coronary syndromes (ACS). However, heparins did reduce myocardial infarction (MI) risk, but increased minor bleeding incidence.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Trials
Background:
- Acute coronary syndromes (ACS), encompassing unstable angina (UA) and non-ST segment myocardial infarction (NSTEMI), remain significant causes of morbidity and mortality.
- Current treatments for UA/NSTEMI, including aspirin, beta-blockers, and nitroglycerin, are not always sufficient.
- Emerging data suggest low molecular weight heparin (LMWH) may be more effective than unfractionated heparin (UFH), but comprehensive data on heparins as a class for ACS treatment is limited.
Purpose of the Study:
- To evaluate the efficacy and safety of heparins (UFH and LMWH) compared to placebo in the treatment of patients diagnosed with ACS.
- To synthesize evidence from randomized controlled trials to inform clinical practice regarding heparin use in ACS.
Main Methods:
- A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted.
- Searches were performed across major databases including Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and CINAHL up to May 2002.
- Eight RCTs involving 3118 participants met the inclusion criteria for parenteral UFH or LMWH versus placebo in patients with UA or NSTEMI.
Main Results:
- Heparin treatment demonstrated a significant reduction in the occurrence of myocardial infarction (MI) (RR = 0.40, 95% CI 0.25 to 0.63), with a number needed to treat (NNT) of 33.
- No significant difference was observed in overall mortality between heparin and placebo groups (RR = 0.84, 95% CI 0.36 to 1.98).
- An increased incidence of minor bleeding events was noted in the heparin group (RR = 6.80, 95% CI 1.23 to 37.49), with a number needed to harm (NNH) of 17.
Conclusions:
- While heparins did not impact overall mortality, revascularization, recurrent angina, major bleeding, or thrombocytopenia compared to placebo, they significantly decreased the risk of MI.
- The findings indicate a trade-off between reduced MI risk and an increased incidence of minor bleeding with heparin use in ACS.
- Further research may refine the role of specific heparin agents in ACS management.
Background:
Acute coronary syndromes (ACS) represent a spectrum of disease including unstable angina (UA) and non-ST segment myocardial infarction (NSTEMI). Despite treatment with aspirin, beta-blockers and nitroglycerin, UA/NSTEMI is still associated with significant morbidity and mortality. Although emerging evidence suggests that low molecular weight heparin (LMWH) is more efficacious compared to unfractionated heparin (UFH), there is limited data to support the role of heparins as a drug class in the treatment of ACS.
Objectives:
To determine the effect of heparins (UFH and LMWH) compared with placebo for the treatment of patients with ACS.
Search Strategy:
We searched the Cochrane Central Register of Controlled Trials on The Cochrane Library (issue 4, 2002), MEDLINE (1966 to May 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 which met the inclusion criteria were available.
Selection Criteria:
Randomized controlled trials of parenteral UFH or LMWH versus placebo in people with ACS (UA 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 (3118 participants) were included in this review. We found no evidence for difference in overall mortality between the groups treated with heparin and placebo (RR = 0.84, 95% CI 0.36 to 1.98). Heparins reduced the occurrence of MI (RR = 0.40, 95% CI 0.25 to 0.63, NNT = 33). An increase in the incidence of minor bleeds (RR = 6.80, 95% CI 1.23 to 37.49, NNH = 17).
Authors' Conclusions:
Compared to placebo, patients treated with heparins had similar risk of mortality, revascularization, recurrent angina, major bleeding and thrombocytopenia. However, those treated with heparins had decreased risk of MI and a higher incidence of minor bleeding.
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