Discontinuation of Enoxaparin After Myocardial Infarction
Enoxaparin should be discontinued immediately after successful PCI in uncomplicated cases, but continued for the duration of hospitalization (up to 8 days) in patients managed medically without revascularization. 1
Post-PCI Management
For patients who undergo successful PCI, discontinue all parenteral anticoagulation including enoxaparin immediately after the procedure. 1 The mechanical revascularization eliminates the acute thrombotic risk that necessitated anticoagulation, and continued anticoagulation provides no additional benefit while only increasing bleeding risk once adequate antiplatelet therapy (aspirin plus clopidogrel) is established. 1
Critical Timing Considerations for PCI
The timing of the last enoxaparin dose relative to PCI determines periprocedural management: 1
- If last subcutaneous dose was <8 hours before PCI: No additional anticoagulation needed during PCI 1
- If last dose was 8-12 hours before PCI: Give 0.3 mg/kg IV enoxaparin at time of PCI 1
- If last dose was >12 hours before PCI: Treat as de novo anticoagulation with full-dose UFH or bivalirudin 1
Critical pitfall: Never add UFH to patients already on enoxaparin within 8-12 hours of the last dose, as this creates dangerous over-anticoagulation and significantly increases bleeding risk. 1 Additionally, do not rely on activated clotting time (ACT) to guide anticoagulation decisions in enoxaparin-treated patients, as LMWHs have minimal effect on ACT measurements despite significant anticoagulation. 1
Medical Management Without Revascularization
For patients who undergo angiography but do not proceed to PCI, continue enoxaparin for the duration of hospitalization (typically up to 8 days). 2 Evidence from the FRISC-II trial demonstrated that prolonged LMWH administration (minimum 5 days) significantly reduced the composite endpoint of death or MI at 30 days (3.1% vs 5.9%, p=0.002) in medically managed patients. 2
Duration of Therapy in Medical Management
The benefits of prolonged dalteparin administration were particularly evident in: 2
- Patients managed medically throughout their hospitalization
- Patients with elevated troponin T levels at baseline
Low-risk patients may discontinue LMWH after the observational period when no ECG changes are apparent and a second troponin measurement is negative. 2
Special Considerations for Renal Impairment
In patients with impaired renal function (creatinine clearance <30 mL/min), reduce enoxaparin to 1 mg/kg subcutaneously once daily, or alternatively manage with UFH. 2 This is critical because severe renal insufficiency substantially increases bleeding risk with enoxaparin. 3, 4, 5
The ExTRACT-TIMI 25 trial demonstrated that: 3
- Patients with CrCl >60 mL/min (79.1% of population) had significant net clinical benefit with enoxaparin over UFH
- With more severe renal dysfunction, the net clinical benefit between enoxaparin and UFH did not differ, despite rising adverse events in both groups
- Major bleeding and intracranial hemorrhage progressively increased with worsening renal function in enoxaparin-treated patients
Patients aged ≥75 years with severe renal insufficiency experienced significantly more bleeding events with enoxaparin compared to UFH (p=0.024). 4
Surgical Planning
For patients receiving subcutaneous LMWH in whom CABG is planned, discontinue LMWH and switch to UFH for the operation. 2 This recommendation applies because of the longer half-life of LMWH and difficulty in reversing its anticoagulant effects perioperatively.
If clopidogrel is being administered and CABG is planned, stop clopidogrel approximately 5 days before operation. 2
Standard Dosing for STEMI
For patients with STEMI receiving fibrinolytic therapy, the standard enoxaparin regimen is: 6
- Initial 30 mg IV bolus
- 1 mg/kg subcutaneously within 15 minutes, then every 12 hours for up to 8 days
- Age ≥75 years: No initial bolus; reduce to 0.75 mg/kg subcutaneously every 12 hours
- CrCl <30 mL/min (any age): 1 mg/kg subcutaneously every 24 hours