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).
| Outcome or subgroup title | Effect size (95% CI) | Participants (studies) |
|---|---|---|
| Myocardial infarction: heparin vs placebo or untreated control | RR 0.40 (0.25 to 0.63) | 2 426 (6 studies) |
| RR 0.28 (0.14 to 0.55) | 1 602 (2 studies) |
| RR 0.55 (0.23 to 1.34) | 541 (3 studies) |
| Recurrent angina: heparin vs placebo or untreated control | RR 0.81 (0.60 to 1.09) | 2 426 (6 studies) |
| RR 0.52 (0.36 to 0.74) | 1 602 (2 studies) |
| RR 0.99 (0.78 to 1.24) | 541 (3 studies) |
| Revascularization procedures: heparin vs placebo or untreated control | RR 0.93 (0.76 to 1.15) | 2 520 (6 studies) |
| RR 0.26 (0.09 to 0.78) | 1 602 (2 studies) |
| 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.
Primary/Secondary Keywords