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Evidence summaries

Low Molecular Weight Heparins for Acute Coronary Syndromes

Low-molecular weight heparins are superior to placebo and unfractionated heparin in acute coronary syndromes (unstable angina or non-ST segment elevation myocardial infarction). Level of evidence: "A"

A Cochrane review [Abstract] 1 included 8 studies with a total of 3 118 subjects to determine the effect of heparins (UFH and LMWH) compared with placebo for the treatment of patients with non-ST elevation acute coronary syndromes (unstable angina or non-ST segment elevation myocardial infarction (NSTEMI)). 1 602 patients (52%) were eligible to receive low molecular weight heparin (LMWH) and 1 508 patients (48%) were eligible to receive unfractionated heparin (UFH). Two different LMWHs were used: dalteparin (n=1498) and nadroparin (n=104). The incidence of death in the placebo group was 0.9% (11/1188) compared to 0.7% (9/1238) in the heparin group (RR 0.84, 95% CI 0.36 to 1.98). Heparins reduced the occurrence of myocardial infarction (RR 0.40, 95% CI 0.25 to 0.63; NNT 33). The pooled analysis from the LMWH subgroup showed statistically significant benefit with respect to the incidence of recurrent angina and revascularization procedures, even though this benefit was lost when all heparins were grouped together (table T1). There was a trend towards more major bleeds in the heparin studies compared to control studies (RR 2.05, 95% CI 0.91 to 4.60).

Incidence of myocardial infarction (MI), recurrent angina, and revascularization procedures over all time periods

Outcome or subgroup titleEffect size (95% CI)Participants (studies)
Myocardial infarction: heparin vs placebo or untreated controlRR 0.40 (0.25 to 0.63)2 426 (6 studies)
  • LMWH
RR 0.28 (0.14 to 0.55)1 602 (2 studies)
  • UFH
RR 0.55 (0.23 to 1.34)541 (3 studies)
Recurrent angina: heparin vs placebo or untreated controlRR 0.81 (0.60 to 1.09)2 426 (6 studies)
  • LMWH
RR 0.52 (0.36 to 0.74)1 602 (2 studies)
  • UFH
RR 0.99 (0.78 to 1.24)541 (3 studies)
Revascularization procedures: heparin vs placebo or untreated controlRR 0.93 (0.76 to 1.15)2 520 (6 studies)
  • LMWH
RR 0.26 (0.09 to 0.78)1 602 (2 studies)
  • UFH
RR 0.98 (0.76 to 1.25)635 (3 studies)

Another Cochrane review [Abstract] 2 included 7 studies with a total of 11 092 patients to assess the effects of LMWH compared to UFH for acute coronary syndromes (unstable angina or NSTEMI). Four different LMWHs were involved: enoxaparin (n=7045), nadroparin (n=2535 patients), dalteparin (n=1482), and tinzaparin (n=40). There was no evidence for difference in overall mortality between the groups treated with LMWH and UFH (RR 1.0, 95% CI 0.69 to 1.44). LMWH reduced the occurrence of MI (RR 0.83, 95% CI 0.70 to 0.99) and the need for revascularization procedures (RR 0.88, 95% CI 0.82 to 0.95). There was no evidence for difference in occurrence of recurrent angina (RR 0.83, 95% CI 0.68 to 1.02), major bleeds (RR 1.00, 95% CI 0.80 to 1.24) or minor bleeds (RR 1.40, 95% CI 0.66 to 2.90). A decrease in the incidence of thrombocytopenia (RR 0.64, 95% CI 0.44 to 0.94) was observed for patients given LMWH. Insufficient data exist to compare different types of LMWH.

    References

    • Andrade-Castellanos CA, Colunga-Lozano LE, Delgado-Figueroa N et al. Heparin versus placebo for non-ST elevation acute coronary syndromes. Cochrane Database Syst Rev 2014;(6):CD003462. [PubMed].
    • Magee KD, Sevcik W, Moher D et al. Low molecular weight heparins versus unfractionated heparin for acute coronary syndromes. Cochrane Database Syst Rev 2003;(1):CD002132. [PubMed].

Primary/Secondary Keywords