Twelve RCTs were included in the review with 17,157 participants.
Six RCTs (1,353 participants) reviewed short-term UFH versus placebo or untreated control.
Two RCTs (1,639 participants) reviewed short-term LMWH versus placebo or untreated control.
Five RCTs (12,171 participants) reviewed short-term LMWH versus UFH.
Five RCTs (12,099 participants) reviewed long-term LMWH versus placebo.
The pooled OR for MI or death during short-term (up to 7 days) UFH compared with placebo or untreated control was 0.67 (95% CI: 0.45, 0.99; p = 0.045), without statistical heterogeneity (chi-square = 2.90, p = 0.82).
The pooled OR for MI or death during short-term (up to 7 days) LMWH compared with placebo or untreated control was 0.34 (95% CI: 0.20, 0.58; p < 0.0001). There was no report of heterogeneity for this result.
The pooled OR for MI or death during short-term (up to 7 days) UFH or LMWH compared with placebo or untreated control was 0.53 (95% CI: 0.38, 0.73; p = 0.0001) or 29 events prevented per 1,000 patients treated. There was no statistical evidence of heterogeneity (chi-square = 6.52, p = 0.37). The pooled OR for MI or death during short-term (up to 7 days) LMWH compared with UFH was 0.88 (95% CI: 0.69, 1.12; p = 0.34) which was not statistically significant. There was no statistical evidence of heterogeneity (chi-square = 4.49, p = 0.49). The pooled OR for MI or death during long-term (up to 3 months) LMWH compared with placebo or untreated control was 0.98 (95% CI: 0.81, 1.17; p = 0.80) which was not statistically significant. Statistical heterogeneity test not reported. Long-term LMWH was associated with a significantly increased risk of major bleeding (OR 2.26, 95% CI: 1.63, 3.14; p < 0.0001) which is equivalent to 12 major bleeds per 1,000 patients treated.