When to Stop Heparin Drip for NSTEMI
For NSTEMI patients managed with medical therapy alone, continue intravenous unfractionated heparin (UFH) for at least 48 hours; for those undergoing PCI, discontinue anticoagulation immediately after the procedure if uncomplicated. 1
Post-Angiography Management Strategy
The timing of heparin discontinuation depends entirely on the revascularization strategy selected after diagnostic angiography:
For Patients Undergoing PCI
- Discontinue anticoagulant therapy immediately after PCI for uncomplicated cases (Level of Evidence: B) 1
- No post-procedural heparin infusions are recommended, particularly when GP IIb/IIIa inhibitors are used 1
- This applies to patients without residual high-risk features such as significant residual thrombus or dissections 1
For Patients Managed Medically (No Revascularization)
- Continue intravenous UFH for at least 48 hours (Level of Evidence: A) 1
- The 2007 ACC/AHA guidelines specifically recommend this duration for patients in whom medical therapy is selected as the post-angiography management strategy 1
- Heparin infusion after fibrinolytic therapy (though less relevant for NSTEMI) may be discontinued after 24-48 hours 1
For Patients Awaiting CABG
- Continue UFH until surgery (Level of Evidence: B) 1
- Do not discontinue heparin in patients scheduled for CABG, as ongoing anticoagulation is beneficial in the preoperative period 1
- If patients were on enoxaparin, discontinue 12-24 hours before CABG and transition to UFH per institutional practice 1
Critical Clinical Considerations
Close monitoring of aPTT is mandatory during UFH infusion: aPTT values >70 seconds are associated with higher likelihood of mortality, bleeding, and reinfarction 1. This represents a common pitfall where inadequate monitoring leads to supratherapeutic anticoagulation.
Avoid crossing over between anticoagulants: The SYNERGY trial demonstrated higher bleeding rates in patients who switched between different anticoagulant regimens 1, 2. If a patient is already on one form of anticoagulation (e.g., enoxaparin), do not add UFH to achieve a target ACT 1.
Special Populations
For patients on direct oral anticoagulants (DOACs) at home who present with NSTEMI, be aware that heparin anti-Xa assays are affected by DOACs, which may lead to falsely elevated levels and inappropriate delays in heparin administration 3. These elevated baseline levels typically normalize after 12 hours 3.
Duration Beyond Initial Hospitalization
Contemporary evidence supports that anticoagulation beyond the acute phase (48 hours for medical management, immediate post-PCI for interventional management) is not routinely indicated unless there are other indications such as atrial fibrillation, left ventricular thrombus, or extensive akinesis 1, 4. The focus shifts to dual antiplatelet therapy rather than continued anticoagulation for secondary prevention 5.
The key algorithmic decision point is: Did the patient undergo PCI? If yes, stop heparin immediately post-procedure. If no, continue for 48 hours minimum. If CABG is planned, continue until surgery.