How to bridge warfarin (anticoagulant) in patients with Non-ST-Elevation Myocardial Infarction (NSTEMI)?

Bridging Warfarin in NSTEMI Patients

Do not initiate additional anticoagulant therapy (bridging) until the INR falls below 2.0 in NSTEMI patients already therapeutically anticoagulated with warfarin, but start antiplatelet therapy immediately regardless of INR, especially if an invasive strategy is planned. 1

Acute Management of Warfarin-Anticoagulated NSTEMI Patients

Initial Assessment and Antiplatelet Therapy

• Initiate antiplatelet therapy immediately even in patients therapeutically anticoagulated with warfarin, particularly when an invasive strategy with anticipated stent implantation is planned 1
• Hold additional anticoagulant therapy (UFH, enoxaparin, fondaparinux) until INR decreases to <2.0 to avoid unacceptably high bleeding risk 1
• For supratherapeutic INR, urgent surgical needs, or unacceptably high bleeding risk, consider warfarin reversal with vitamin K or fresh-frozen plasma based on clinical judgment 1

Triple Antithrombotic Therapy Protocol

When warfarin must be continued for established indications (atrial fibrillation, mechanical prosthetic valves, left ventricular thrombus):

• Use triple therapy (warfarin + aspirin + P2Y12 inhibitor) for the minimum time necessary at minimally effective doses 1
• Target INR 2.0-3.0 (preferably 2.0-2.5 in older patients and those with bleeding risk factors) 1
• Use low-dose aspirin 75-81 mg daily (not 162-325 mg) to minimize bleeding risk 1, 2
• Add clopidogrel 75 mg daily as the P2Y12 inhibitor 1
• This carries a Class IIb recommendation with Level of Evidence B, acknowledging limited prospective trial data and increased bleeding risk 1

Duration of Antithrombotic Therapy

Triple Therapy Duration

• Maximum 6 months for most patients, with consideration of 1 month for very high bleeding risk 2
• After completing triple therapy, transition to dual therapy with warfarin (INR 2.0-3.0) plus either aspirin or clopidogrel for an additional 6 months 2
• Continue warfarin monotherapy long-term for the underlying indication (atrial fibrillation, mechanical valves, LV thrombus) 1, 2

Post-Stent Considerations

• For bare metal stents: aspirin 162-325 mg daily for at least 1 month, then 75-162 mg indefinitely; P2Y12 inhibitor for at least 12 months 1
• For drug-eluting stents: aspirin 162-325 mg daily for 3-6 months (depending on stent type), then 75-162 mg indefinitely; P2Y12 inhibitor for at least 12 months 1

Critical Safety Monitoring

Bleeding Risk Management

• Mandatory proton pump inhibitor therapy during triple therapy to reduce gastrointestinal bleeding 2
• Monitor INR strictly between 2.0-3.0 with more frequent checks during triple therapy 2
• Watch for bleeding complications, especially gastrointestinal, which are 2-3 fold higher with triple therapy 1
• Major and minor bleeding rates with combination warfarin-aspirin therapy: 2% and 15% respectively 1

Specific Warfarin Indications That Require Continuation

Warfarin should be prescribed for NSTEMI patients with established indications including:

• Atrial fibrillation 1
• Left ventricular thrombus 1
• Mechanical prosthetic heart valves (INR ≥2.5 based on prosthesis type) 1

What NOT to Do

Routine Long-Term Warfarin

• Low- or moderate-intensity anticoagulation with warfarin is NOT recommended for routine use after NSTEMI hospitalization without specific indications 1
• Multiple trials (CARS, CHAMP, OASIS-2) showed no benefit of warfarin plus aspirin versus aspirin alone for mortality, cardiovascular death, stroke, or nonfatal MI 1

Heparin Bridging

• Do not use heparin bridging in warfarin-treated NSTEMI patients - recent evidence shows 2-3 fold increased major bleeding risk with no reduction in stroke or systemic embolism 3
• The concept of "bridging" applies to elective procedures, not acute coronary syndromes where the management strategy differs fundamentally 3

Common Pitfalls to Avoid

• Initiating anticoagulant therapy before INR falls below 2.0 creates excessive bleeding risk 1
• Using high-dose aspirin (162-325 mg) with warfarin instead of low-dose (75-81 mg) increases bleeding without additional benefit 1, 2
• Continuing triple therapy beyond 6 months without reassessing bleeding versus ischemic risk 2
• Failing to provide gastric protection with PPI during triple therapy 2
• Delaying antiplatelet therapy in therapeutically anticoagulated patients when invasive strategy is planned 1