"Our study is the largest meta-analysis done in this context," Dr. Singh said. "It included all contemporary clinical trials, with over 37,000 patients in total."

Dr. Singh and colleagues evaluated cardiac outcomes and the risk of major bleeding with LMWH versus UFH in the management of acute MI in seven randomised trials.

Primary endpoints were death and nonfatal recurrent MI through 30 days, and secondary endpoints included death, recurrent MI, and major bleeding during the first 7 days following hospitalisation.

Combined relative risks for LMWH versus UFH regarding primary endpoint outcomes across the seven studies were heterogeneous and were computed using the random effect model. Secondary endpoints and net clinical benefits were homogenous in their outcomes and were computed using the Mantel-Haenszel fixed effect model.

Analysis of the results showed that the risk of death and reinfarction was significantly lower (P <.01 and P <.001, respectively) at seven days in patients treated with LMWH compared with those treated with UFH.

At 30 days, mortality risks were identical in the two groups (P = 1.067), but there was a trend toward lower reinfarction rates in the LMWH group versus UFH (P =.139). Patients treated with LMWH had a significantly higher risk of major bleeding compared with those receiving UFH (P <.001).

These results show that LMWH reduces the incidence of reinfarction compared with UFH during the first seven days after hospitalisation for MI, and that this effect is maintained at 30 days with no reduction in mortality, Dr. Singh said.

"The reduction in the incidence of reinfarction suggests that low-molecular-weight heparins have superior antithrombotic effects compared with currently recommended intravenous unfractionated heparin, and may be preferable as an adjunct to fibrinolytic therapy in patients with acute ST-segment elevation MI," he concluded.


REFERENCES:
1. Enoxaparin and Thrombolysis Reperfusion for Acute Myocardial Infarction Treatment—Thrombolysis in Myocardial Infarction 25 (EXTRACT-TIMI 25, 2006)
2. Assessment of the Safety and Efficacy of a New Thrombolytic 3 PLUS (ASSENT 3 PLUS, 2003)
3. Assessment of the Safety and Efficacy of a New Thrombolytic PLUS (ASSENT 3 PLUS, 2003)
4. Enoxaparin and TNK-tPA with or without GP IIb/IIIa Inhibitor as Reperfusion strategy – Thrombolysis in Myocardial Infarction 23 (ENTIRE TIMI-23, 2002)
5. Baird et al. Eur Heart J. 2002 Apr;23(8):627-32.
6. Heparin and Aspirin Reperfusion Therapy (HART II, 2001)
7. Assessment of the Safety and Efficacy of a New Thrombolytic 3 (ASSENT 3, 2001)


[Presentation title: Adjunctive Low Molecular Weight Heparin to Fibrinolytic Therapy in Acute ST-Segment Elevation Myocardial Infarction: A Meta-Analysis of Randomized Controlled Studies. Abstract A-2]

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