How do you bridge a patient from Lovenox (enoxaparin) to Coumadin (warfarin) in cases of mechanical valve replacement?

Bridging from Lovenox to Coumadin in Mechanical Valve Replacement

Bridging anticoagulation with enoxaparin (Lovenox) to warfarin (Coumadin) in patients with mechanical heart valves should be individualized based on thrombotic risk factors, with therapeutic-dose LMWH started when INR falls below therapeutic threshold and continued until the INR returns to therapeutic range. 1

Risk Assessment for Bridging

• Bridging therapy is reasonable for patients with:

  1. Mechanical mitral valve replacement (MVR) 1
  2. Mechanical aortic valve replacement (AVR) with any thromboembolic risk factor 1
  3. Older-generation mechanical AVR (ball-cage or tilting disc) 1
  4. Additional risk factors (atrial fibrillation, previous thromboembolism, hypercoagulable condition, LV dysfunction, or multiple mechanical valves) 1

• Temporary interruption of VKA without bridging is recommended for patients with bileaflet mechanical AVR and no other risk factors for thrombosis 1

Bridging Protocol

• When interrupting warfarin for procedures:
  • Stop warfarin 3-4 days before the procedure 1
  • Begin bridging with enoxaparin when INR falls below therapeutic threshold (2.0-2.5) 1
  • This typically occurs 36-48 hours before surgery 1
  • Stop enoxaparin 12 hours before the procedure 1
  • Resume warfarin postoperatively as soon as bleeding risk allows (typically 12-24 hours after surgery) 1
  • Continue enoxaparin until INR returns to therapeutic range 1, 2

Dosing Recommendations

• For therapeutic-dose enoxaparin: 1 mg/kg twice daily or 1.5 mg/kg once daily 2
• Target INR for mechanical valves:
  • Aortic position (bileaflet/St. Jude): 2.5 (range 2.0-3.0) 3
  • Mitral position or tilting disk valves: 3.0 (range 2.5-3.5) 3
  • Caged ball/disk valves: 3.0 (range 2.5-3.5) plus aspirin 75-100 mg/day 3

Monitoring Recommendations

• Monitor anti-Xa levels when using enoxaparin for bridging in mechanical valve patients 4
  • Target anti-Xa level: 0.6-1.0 IU/mL 4
• Check INR frequently during bridging period to ensure adequate anticoagulation 2

Important Considerations and Pitfalls

• Direct oral anticoagulants (DOACs) are contraindicated in patients with mechanical heart valves 1
• Patients with mechanical valves may be more sensitive to warfarin in the immediate post-operative period; reduced initial dosages may be necessary 5
• Consider adding low-dose aspirin (75-100 mg daily) to warfarin therapy for mechanical valves to reduce thromboembolic events without significantly increasing bleeding risk 6
• Be aware that bridging therapy may expose patients to higher bleeding risks; decisions should account for the trade-offs between thrombosis and bleeding 1
• For emergency reversal of anticoagulation in patients with mechanical valves and uncontrollable bleeding, 4-factor prothrombin complex concentrate is reasonable 1

Special Situations

• For patients with subtherapeutic INR during routine monitoring, outpatient bridging with enoxaparin is indicated until therapeutic INR is reached 1
• In cases where warfarin is contraindicated, long-term enoxaparin with anti-Xa monitoring may be considered as an alternative, though this is not standard practice 4