Warfarin Resumption After Interruption in Valve Replacement Patients
Immediate Management
- The American College of Cardiology and the American Heart Association recommend resuming warfarin immediately at the usual maintenance dose and restarting bridging anticoagulation with therapeutic-dose heparin until the INR returns to therapeutic range (2.5-3.5 for mechanical valves) 1, 2
- Obtain stat INR to assess current anticoagulation status, as the INR is almost certainly subtherapeutic (<1.5) given warfarin's 42-hour half-life 1, 3
- The patient is currently at high risk for valve thrombosis during this unprotected period 1, 2
Bridging Anticoagulation
- For mechanical valve patients, bridging is mandatory, which is a Class I recommendation, and should be initiated immediately with either IV unfractionated heparin or subcutaneous LMWH 1, 2
- The American College of Cardiology recommends adjusting IV unfractionated heparin to maintain aPTT at 1.5-2.5 times control (or anti-Xa 0.3-0.6 IU/mL) 1, 3, 4
- The American College of Cardiology also recommends giving therapeutic dose subcutaneous LMWH twice daily, with a dose of 1 mg/kg enoxaparin every 12 hours (or equivalent LMWH), and monitoring anti-Xa levels 4-6 hours after dose, targeting 0.8-1.2 U/mL 1, 2
Critical Risk Assessment
- All mechanical valve patients who have been off anticoagulation for 5 days are at high thrombotic risk and require bridging, according to the American College of Cardiology and the American Heart Association 1, 2
- Mechanical valves (especially mitral position) carry the highest thrombotic risk, and five days without anticoagulation represents significant unprotected time 1, 4
INR Monitoring Schedule
- The American College of Cardiology and the American Heart Association recommend checking INR daily until therapeutic range is achieved, with a target INR of 2.5-3.5 for mechanical valves 1, 2