Should warfarin be bridged every time the International Normalized Ratio (INR) is below the therapeutic range?

Bridging Anticoagulation for Subtherapeutic INR

Bridging therapy with heparin or low-molecular-weight heparin is NOT recommended for routine management of isolated subtherapeutic INR values in patients on warfarin therapy. 1, 2

Risk-Based Approach to Subtherapeutic INR

The decision to bridge anticoagulation when INR falls below therapeutic range should be based on a careful assessment of individual thrombotic risk factors:

High Thrombotic Risk (Consider Bridging)

• Mechanical mitral valve replacement 1
• Mechanical aortic valve with additional risk factors:
  • Atrial fibrillation
  • Previous thromboembolism
  • Hypercoagulable condition
  • Older-generation mechanical valves (ball-cage or tilting disc)
  • LV systolic dysfunction
  • Multiple mechanical valves 1
• Recent thromboembolism (<3 months) 1
• Active cancer 1

Low Thrombotic Risk (No Bridging Needed)

• Bileaflet mechanical aortic valve without additional risk factors 1
• Isolated atrial fibrillation without recent stroke 1
• Stable warfarin therapy with temporary, isolated subtherapeutic INR 2, 3

Management Algorithm for Subtherapeutic INR

1. For mildly subtherapeutic INR (0.5 below target range):

   • Continue current dose
   • Retest within 1-2 weeks 2
   • No bridging needed

2. For moderately subtherapeutic INR:

   • Consider increasing warfarin dose by 10-20% 2
   • More frequent monitoring
   • No bridging unless high thrombotic risk factors present

3. For severely subtherapeutic INR in high-risk patients:

   • Consider bridging with therapeutic doses of LMWH or UFH 1
   • Increase warfarin dose
   • Monitor INR more frequently until therapeutic

Evidence Analysis

The 2017 AHA/ACC guidelines for valvular heart disease downgraded the recommendation for bridging therapy from Class I to Class IIa, acknowledging that bridging may increase bleeding risk without necessarily reducing thromboembolic events 1. The American College of Chest Physicians guidelines do not recommend routine bridging for subtherapeutic INR values found during regular monitoring 1.

A retrospective study examining bridging for isolated subtherapeutic INR found no significant difference in thrombotic events between bridged and non-bridged patients (2.0% vs. 0.7%), but noted increased costs and potentially increased bleeding complications with bridging 3.

Important Considerations

• Bridging therapy increases healthcare costs significantly ($967 higher per episode) 3
• Bridging may increase bleeding risk without clear evidence of thrombotic risk reduction 1, 3
• The FDA label for warfarin does not recommend routine bridging for isolated subtherapeutic INR values 4
• Time to return to therapeutic range is shorter with bridging (6.8 vs. 18.9 days) but requires more frequent monitoring 3

Common Pitfalls to Avoid

• Overuse of bridging therapy: Bridging all patients with subtherapeutic INRs leads to unnecessary costs and potential bleeding complications 3
• Making frequent dose changes: Minor INR fluctuations should not trigger immediate dose adjustments, as this can lead to INR instability 2
• Neglecting risk stratification: Failing to consider individual patient risk factors when deciding on bridging therapy 1
• Inadequate follow-up: Patients with subtherapeutic INRs require appropriate monitoring regardless of bridging decision 2

In conclusion, routine bridging anticoagulation is not recommended for isolated subtherapeutic INR values. Instead, a risk-stratified approach should be used, reserving bridging for patients at high risk of thromboembolism while considering the increased bleeding risk associated with bridging therapy.