What is the recommended peri-procedural anticoagulation management for patients with mechanical heart valves, specifically regarding the use of warfarin (anticoagulant) and heparin (unfractionated heparin or low molecular weight heparin)?

Perioperative Anticoagulation Management for Mechanical Heart Valves

For patients with mechanical heart valves requiring perioperative anticoagulation management, bridging therapy with intravenous unfractionated heparin (UFH) is recommended for high-risk patients when the INR falls below 2.0, while low-risk patients with bileaflet aortic valve replacements can safely interrupt warfarin without bridging. 1

Risk Stratification for Perioperative Management

High-Risk Patients (Require Bridging)

• Mechanical mitral valve replacement (any type)
• Older-generation mechanical valves (ball-cage or tilting disc)
• Mechanical aortic valve with additional risk factors:
  • Atrial fibrillation
  • Previous thromboembolism
  • Hypercoagulable condition
  • Left ventricular dysfunction
  • Multiple mechanical valves
  • Recent (<3 months) thromboembolic event

Low-Risk Patients (No Bridging Required)

• Bileaflet mechanical aortic valve replacement without additional risk factors

Perioperative Management Protocol

For Low-Risk Patients (Bileaflet Mechanical AVR Without Risk Factors):

1. Stop warfarin 48-72 hours before procedure
2. Allow INR to fall below 1.5
3. Resume warfarin within 24 hours after procedure
4. Heparin bridging is unnecessary 1

For High-Risk Patients:

1. Pre-procedure management:

   • Stop warfarin 5 days before procedure
   • Start therapeutic-dose UFH intravenously when INR falls below 2.0 (typically 48 hours before surgery)
   • Stop UFH 4-6 hours before procedure 1

2. Post-procedure management:

   • Resume UFH as soon as hemostatic stability is achieved (typically 12-24 hours after surgery)
   • Restart warfarin at pre-operative maintenance dose within 24 hours when bleeding risk allows
   • Continue UFH until INR returns to therapeutic range (2.5-3.5 for mitral valves; 2.0-3.0 for aortic valves) 1, 2

Important Considerations

Therapeutic Targets

• For mechanical aortic valves: INR 2.0-3.0 (bileaflet and Medtronic Hall valves)
• For mechanical mitral valves: INR 2.5-3.5 (all types)
• For older generation valves (Starr-Edwards): INR 2.5-3.5 1, 2

Heparin Dosing

• Initial IV bolus: 80 U/kg
• Continuous infusion: 18 U/kg/hour
• Target aPTT: 60-80 seconds (1.5-2.5 times control value) 3, 4, 5

Potential Alternative Bridging Options

• Low molecular weight heparin (LMWH) may be considered in high-risk patients at a dose of 100 U/kg every 12 hours, though evidence is limited and this remains an off-label use 1, 6
• For subcutaneous UFH, 15,000 units every 12 hours may be used 1

Special Situations

Emergency Procedures

• If INR is elevated (>1.5) 1-2 days before urgent surgery:
  • Fresh frozen plasma is preferable to high-dose vitamin K1 1
  • High-dose vitamin K should not be given routinely as it may create a hypercoagulable condition 1

Minor Procedures with Low Bleeding Risk

• For procedures with minimal bleeding risk (dental extractions, cataract surgery):
  • Continue warfarin at therapeutic INR 1
  • No need to interrupt anticoagulation

Pitfalls to Avoid

1. Avoid complete reversal of anticoagulation unless life-threatening bleeding occurs, as this creates high thrombotic risk for mechanical valves 3
2. Avoid prolonged interruption of anticoagulation, especially for mitral mechanical valves which have high thrombotic risk when unprotected 3
3. Avoid high-dose vitamin K for reversal as it may create rebound hypercoagulability 1
4. Avoid delaying reinitiation of anticoagulation after procedure, as the early postoperative period carries increased thrombotic risk 1
5. Avoid using direct thrombin inhibitors or factor Xa inhibitors in patients with mechanical heart valves 1

Recent evidence from the PERIOP-2 trial suggests that the risk of thromboembolism may be lower than previously thought even without post-operative bridging, but this remains an area where clinical judgment is needed, particularly for high-risk patients 1.