Perioperative Bridging for Mechanical Valve Replacement
Direct Answer
For a 63-year-old woman with a mechanical heart valve on warfarin requiring a painful injection procedure, stop warfarin 3–4 days before the procedure, start therapeutic-dose LMWH (100 U/kg subcutaneously every 12 hours) when the INR falls below 2.0 (typically 48 hours pre-procedure), hold the last LMWH dose 24 hours before the procedure, and resume both warfarin and LMWH 12–24 hours post-procedure once hemostasis is adequate, continuing LMWH until the INR is therapeutic (≥2.0) on two consecutive measurements. 1
Pre-Procedure Management
Stop Warfarin
- Stop warfarin 3–4 days before the procedure to allow the INR to fall below 1.5 for major procedures or below 2.0 for minor procedures 1
Initiate Bridging Anticoagulation
Start therapeutic-dose subcutaneous LMWH at 100 U/kg every 12 hours (or alternatively 1 mg/kg enoxaparin every 12 hours) when the INR falls below 2.0, which typically occurs 36–48 hours before surgery 1, 2
Alternatively, intravenous unfractionated heparin can be used at an initial bolus of 80 U/kg followed by 18 U/kg/hour infusion, targeting an aPTT of 60–80 seconds, though LMWH is preferred for outpatient management 1, 3, 4
All mechanical mitral valves require bridging—this is a Class I recommendation with no exceptions for "low-risk" patients, unlike bileaflet aortic valves 1
Hold Bridging Before Procedure
Stop LMWH 24 hours before the procedure to allow adequate clearance and minimize bleeding risk 1, 2
If using intravenous UFH, stop 4–6 hours before the procedure 1
Post-Procedure Management
Resume Anticoagulation
Restart warfarin at the previous maintenance dose on the evening of the procedure (typically 12–24 hours post-operatively) once adequate hemostasis is achieved 1
Resume therapeutic-dose LMWH 12–24 hours after the procedure if hemostasis is secure and bleeding risk is acceptable 1, 2
Continue both warfarin and LMWH together until the INR reaches the therapeutic range (2.5–3.5 for mitral valves) on two consecutive measurements at least 24 hours apart 1
Target INR
For mechanical mitral valves, the target INR is 2.5–3.5 (higher than aortic valves due to greater thrombotic risk) 1, 3
For bileaflet mechanical aortic valves without risk factors, the target INR is 2.0–3.0 1
Critical Valve Position Considerations
Why Mitral Valves Require Aggressive Bridging
Mechanical mitral valves carry markedly higher thrombotic risk than aortic valves and can develop valve thrombosis within days of subtherapeutic anticoagulation 1, 5, 6
The 2024 AHA/ACC guidelines note that recent evidence questions routine bridging in many scenarios, but mechanical mitral valves remain the one absolute indication where bridging cannot be safely omitted 1
Low-Risk Exception (Does NOT Apply Here)
Only patients with bileaflet mechanical aortic valves AND no additional risk factors (no atrial fibrillation, no prior thromboembolism, no LV dysfunction, age <65) can safely undergo temporary warfarin interruption without bridging 1
This patient has a valve replacement (position unspecified), so assume high-risk and bridge accordingly 1
Common Pitfalls to Avoid
Never Use High-Dose Vitamin K
Do not give high-dose vitamin K (>2.5 mg) routinely for pre-operative INR reversal, as this creates warfarin resistance lasting weeks and increases thrombotic risk in mechanical valve patients 1, 7
If emergency reversal is needed, use fresh frozen plasma or 4-factor prothrombin complex concentrate plus low-dose (1–2 mg) oral vitamin K 1
Do Not Delay Post-Procedure Bridging
Delaying LMWH resumption excessively puts the patient at risk of valve thrombosis, which can occur within 48–72 hours of subtherapeutic anticoagulation 5, 6
The 2024 guidelines emphasize that while post-operative bridging increases bleeding risk in atrial fibrillation patients, mechanical mitral valves are the exception where thrombotic risk outweighs bleeding concerns 1
Ensure Adequate Overlap
- Continue LMWH for at least 24 hours after achieving therapeutic INR to ensure adequate anticoagulation, as warfarin's full effect requires synthesis of new clotting factors 1
Monitoring Protocol
Pre-Procedure
- Check INR 1–2 days before the procedure to confirm it has fallen to <1.5 for major surgery 1
Post-Procedure
Check INR daily starting 24–48 hours after restarting warfarin until two consecutive therapeutic values are obtained 1, 5
Monitor aPTT if using intravenous UFH (target 60–80 seconds) 1, 3
After achieving stable therapeutic INR, continue monitoring every 2–3 days for 1–2 weeks, then weekly for the first month 5
Evidence Quality Note
The 2024 AHA/ACC guidelines note that bridging recommendations are based primarily on observational cohort studies with poor or no comparator groups (Level C evidence), as adequately powered randomized trials in mechanical valve patients are lacking. However, the consistent finding across multiple cohorts is that mechanical mitral valves have unacceptably high thrombotic risk without bridging, making this a Class I recommendation despite limited trial data. 1