From the Guidelines
Low molecular weight heparin (LMWH) in acute myocardial infarction should be administered as an adjunctive anticoagulant therapy alongside other standard treatments, with enoxaparin given at 1 mg/kg subcutaneously every 12 hours for non-ST-elevation MI (NSTEMI) and 30 mg IV bolus followed by 1 mg/kg subcutaneously every 12 hours for ST-elevation MI (STEMI), with dose adjustments for renal impairment and age. The administration of LMWH in acute MI is supported by several studies, including the ESSENCE trial, which showed a significant reduction in recurrent ischemic events and invasive diagnostic and therapeutic procedures with enoxaparin therapy 1. The SYNERGY trial also found no significant difference in death or MI at 30 days between enoxaparin and unfractionated heparin, but with more TIMI major bleeding in the enoxaparin group 1. Key considerations for LMWH administration in acute MI include:
- Dose adjustment for renal impairment, with a reduction to 1 mg/kg SC once daily for patients with CrCl <30 mL per minute 1
- No initial bolus for NSTEMI patients 1
- Monitoring for bleeding complications and heparin-induced thrombocytopenia 1
- Preference for LMWH over unfractionated heparin due to its more predictable anticoagulant response and lower risk of heparin-induced thrombocytopenia 1 The most recent and highest quality study, the 2014 AHA/ACC guideline, recommends the use of LMWH as an adjunctive anticoagulant therapy in acute MI, with enoxaparin as the preferred agent 1.
From the Research
Administration of Low Molecular Weight Heparin in Acute Myocardial Infarction
- The administration of low molecular weight heparin (LMWH) in acute myocardial infarction (MI) has been studied in several clinical trials 2, 3, 4, 5, 6.
- Enoxaparin, a type of LMWH, has been shown to be effective in reducing the risk of recurrent MI and death in patients with ST-segment elevation MI (STEMI) 2.
- The recommended dosage of enoxaparin is an initial 30 mg intravenous bolus, followed by 1 mg/kg subcutaneously every 12 hours for up to 8 days 2.
- However, in patients older than 75 years, the initial bolus should be omitted, and the 12-hourly dosages should be reduced to 0.75 mg/kg 2.
- In patients with renal impairment (estimated creatinine clearance <30 mL/min), the dose should be reduced to 1 mg/kg every 24 hours 2.
Comparison with Unfractionated Heparin
- LMWH has been compared to unfractionated heparin (UFH) in several studies, and has been shown to be at least as effective and safe as UFH in patients with acute coronary syndromes 3, 4, 6.
- LMWH has the advantage of not requiring laboratory monitoring, and can be administered subcutaneously, allowing for early mobilization and rehabilitation of patients 6.