What are the recommendations for holding warfarin (International Normalized Ratio (INR) anticoagulant) prior to surgery in patients with a mechanical (prosthetic) valve?

Perioperative Management of Warfarin in Patients with Mechanical Heart Valves

For patients with mechanical heart valves, warfarin should be stopped 48-72 hours before surgery, with bridging anticoagulation using therapeutic-dose intravenous unfractionated heparin (UFH) required only for high-risk patients, while low-risk patients can safely undergo surgery without bridging. 1

Risk Stratification for Thromboembolism

The decision to bridge anticoagulation depends on the patient's risk of thromboembolism:

High-Risk Patients (Require Bridging)

• Any mechanical mitral valve replacement
• Older-generation mechanical aortic valve (tilting-disc, caged-ball, Starr-Edwards)
• Mechanical aortic valve with risk factors:
  • Atrial fibrillation
  • Previous thromboembolism
  • LV dysfunction
  • Hypercoagulable condition
• Recent (<3 months) thromboembolic event
• History of perioperative stroke

Low-Risk Patients (No Bridging Required)

• Bileaflet mechanical aortic valve without risk factors 1

Perioperative Management Protocol

Pre-operative Management

1. Stop warfarin: 48-72 hours before surgery for all patients with mechanical valves 1
2. Check INR: Day before surgery (target INR <1.5 for safe surgery)
3. Bridging for high-risk patients:
   • Start therapeutic-dose IV UFH when INR falls below 2.0 (typically 48 hours before surgery)
   • Stop UFH 4-6 hours before procedure 1
   • Alternative: Therapeutic-dose LMWH (100 U/kg every 12 hours) may be considered 1

Post-operative Management

1. Resume warfarin: Within 24 hours after procedure if hemostasis is adequate
2. For high-risk patients:
   • Restart IV UFH as soon as bleeding stability allows
   • Continue until INR is therapeutic with warfarin 1
3. For low-risk patients:
   • Resume warfarin without bridging 1

Special Considerations

Management of Elevated Pre-operative INR

• If INR >1.5 1-2 days before surgery:
  • Do not routinely administer vitamin K (may create resistance to post-operative re-anticoagulation) 1
  • Consider delaying procedure if possible
  • For urgent surgery with elevated INR, fresh frozen plasma is preferable to high-dose vitamin K 1

Bleeding Risk Assessment

• For procedures with very low bleeding risk (simple dental extractions, minor skin excision), consider performing without interruption of warfarin 1
• For procedures with substantial bleeding risk, follow the interruption protocol above

Evidence Quality and Controversies

There is notable difference between guidelines regarding bridging recommendations. The 2008 ACC/AHA guidelines recommend a more selective approach to bridging 1, while older guidelines recommended routine bridging for all mechanical valve patients. The 2022 CHEST guidelines provide the most recent evidence supporting a more selective bridging approach 1.

Recent evidence suggests that bridging anticoagulation increases bleeding risk without significantly reducing thromboembolism in low-risk patients 1. The PERIOP-2 trial found no significant difference in thromboembolism rates between bridged and non-bridged patients with mechanical heart valves, but bridging was associated with increased bleeding risk 1.

Common Pitfalls to Avoid

1. Avoid high-dose vitamin K pre-operatively - May create a hypercoagulable state and resistance to re-anticoagulation 1
2. Don't delay resuming warfarin post-operatively - Should be restarted within 24 hours after surgery if hemostasis is adequate
3. Don't use bridging for low-risk patients - Increases bleeding risk without clear benefit 1
4. Don't use a one-size-fits-all approach - Risk stratification is essential for determining bridging need

By following this evidence-based protocol, clinicians can minimize both thrombotic and bleeding complications in patients with mechanical heart valves requiring temporary interruption of warfarin for surgery.