How do you determine if a patient needs a bridge anticoagulant, such as unfractionated heparin (UFH) or low molecular weight heparin (LMWH), when interrupting oral anticoagulants like warfarin?

Determining the Need for Bridge Anticoagulation

Bridge anticoagulation should be reserved only for patients at high thromboembolic risk, as bridging increases bleeding risk without reducing thrombotic events in most patients. 1, 2

Risk Stratification Framework

The decision to bridge depends on assessing the patient's thromboembolic risk against the procedural bleeding risk. 3

High-Risk Patients Who May Require Bridging

These patients should be considered for bridging therapy:

• Mechanical mitral valve (any type) 3, 1, 2
• Older-generation mechanical aortic valve (ball-cage or tilting disc) 3, 2
• Bileaflet mechanical aortic valve PLUS any additional thromboembolic risk factor (atrial fibrillation, prior thromboembolism, hypercoagulable condition, LV dysfunction, or >1 mechanical valve) 3, 2
• Recent thromboembolism (<3 months from stroke, TIA, or VTE) 1, 4, 2
• Severe thrombophilia (protein C or S deficiency, antiphospholipid syndrome) 1
• Very high-risk atrial fibrillation (CHA₂DS₂-VASc score ≥7 or CHADS₂ score 5-6) 4, 2

Patients Who Do NOT Require Bridging

Bridging should be avoided in these patients:

• Bileaflet mechanical aortic valve without other risk factors 3, 2
• Atrial fibrillation without mechanical valves and CHA₂DS₂-VASc score ≤5 1, 4
• Remote venous thromboembolism (>3 months ago) 1, 2
• Bioprosthetic valves 3, 2
• Low-risk thrombophilias (Factor V Leiden, prothrombin mutation F2G20210A) 1

The landmark BRIDGE trial definitively demonstrated that bridging causes more harm than benefit in atrial fibrillation patients, showing non-inferior thromboembolism rates but significantly higher bleeding rates in bridged patients. 2, 5

Procedural Bleeding Risk Considerations

Minor Procedures That Do NOT Require Warfarin Interruption

Continue warfarin with therapeutic INR for:

• Dental extractions 3, 1
• Cataract surgery 3, 1
• Skin biopsies 1
• Pacemaker/defibrillator implantation 1
• Catheter ablation 1

These procedures have minimal bleeding risk that is easily controlled, making continued anticoagulation safer than bridging. 3

Major Procedures Requiring Warfarin Interruption

For procedures with significant bleeding risk, warfarin must be stopped 5-6 days before surgery. 1, 4 The decision to bridge during this interruption depends entirely on the thromboembolic risk stratification above. 3, 1

Bridging Protocol for High-Risk Patients

When bridging is indicated:

Preoperative Management

• Stop warfarin 5-6 days before procedure 1, 4
• Start LMWH when INR falls below 2.0 (typically 3 days before procedure) at 1 mg/kg twice daily or 1.5 mg/kg once daily 1, 2
• Last pre-procedure LMWH dose: Give at half the total daily dose, no less than 24 hours before surgery 1
• Proceed if INR ≤1.5; consider low-dose vitamin K (1-2.5 mg) if INR 1.5-1.8 1

Postoperative Management

For low bleeding risk procedures:

• Resume warfarin evening of procedure 1, 4
• Restart LMWH at previous dose 24 hours post-procedure 1
• Continue LMWH until INR ≥2.0 1

For high bleeding risk procedures:

• Resume warfarin evening of procedure 1, 4
• Delay LMWH for 48-72 hours post-procedure 1, 2
• Continue LMWH until INR ≥2.0 1

Critical Pitfalls to Avoid

The most common error is over-bridging patients who don't need it. Most patients with atrial fibrillation and no mechanical valve do not require bridging, and doing so significantly increases bleeding risk without reducing stroke risk. 2, 5

For patients with severe renal insufficiency, adjust LMWH dosing or consider unfractionated heparin instead. 1, 6

Inadequate risk assessment leads to inappropriate bridging decisions—always stratify thromboembolic risk using the specific criteria above rather than defaulting to bridging. 4

Delayed resumption of anticoagulation unnecessarily increases thromboembolic risk—resume warfarin the evening of the procedure in nearly all cases. 1, 4