In a patient with a mechanical mitral valve on warfarin presenting for a non‑cardiac elective surgery with a subtherapeutic INR, what is the appropriate peri‑operative anticoagulation management?

Management of INR 1.52 in a Patient with Mechanical Mitral Valve Presenting for Non-Cardiac Elective Surgery

Consider postponing the elective surgery if the INR is >1.5, and initiate bridging anticoagulation with therapeutic-dose heparin immediately. 1

Immediate Decision: Postpone vs Proceed

The 2009 European Heart Journal guidelines explicitly state that "consideration should be given to postponing the procedure if the INR is >1.5" 1. Your patient's INR of 1.52 falls into this category, making postponement the preferred option for an elective procedure.

If Surgery Cannot Be Postponed:

Do NOT administer vitamin K. The 2022 CHEST guidelines recommend against routine use of pre-operative vitamin K in patients with elevated INR (>1.5) 1-2 days before surgery 1. This is critical because:

• Vitamin K can create warfarin resistance lasting weeks, putting your patient at severe thrombotic risk postoperatively 2, 3
• Mechanical mitral valves carry extremely high thrombotic risk and can develop valve thrombosis within days of subtherapeutic anticoagulation 4, 2
• The American Heart Association explicitly advises never giving vitamin K to a patient with subtherapeutic INR and a mechanical heart valve 2

Bridging Anticoagulation Protocol

Mechanical mitral valves are high-risk and require bridging therapy. 1

Pre-operative Management:

• Initiate therapeutic-dose intravenous unfractionated heparin (UFH) immediately with target aPTT of 60-80 seconds 1, 2
• Continue UFH until 4 hours before surgery 1
• Alternative: therapeutic-dose LMWH (70 U/kg twice daily) with last dose at least 12 hours before procedure 1

The 2009 European guidelines note that "in patients with mechanical prosthetic heart valves, the evidence for i.v. UFH is more solid" 1, making this the preferred approach over LMWH for your high-risk patient.

Post-operative Management:

• Resume therapeutic-dose heparin 12-24 hours after surgery depending on hemostatic status 1
• Restart warfarin on postoperative day 1-2 at the pre-operative maintenance dose plus a 50% boost dose for two consecutive days 1
• Continue heparin until INR reaches therapeutic range (2.5-3.5) on two consecutive measurements 4
• Maintain both warfarin and heparin together for at least 24 hours with therapeutic INR before discontinuing heparin 4

Target INR for Mechanical Mitral Valves

The target INR for all mechanical mitral valves is 2.5-3.5 (specifically targeting 3.0), regardless of valve type 4, 5. This higher target compared to aortic valves reflects the greater thromboembolic risk with mitral position valves 4.

Monitoring Protocol

• Check INR on the day of procedure 1
• Monitor aPTT to maintain 60-80 seconds when on heparin bridge 4, 2
• Check INR daily during acute postoperative phase 4, 2
• Once stable on warfarin, transition to INR monitoring every 2-3 days, then weekly, then monthly 4

Critical Pitfalls to Avoid

Never give vitamin K in this scenario - it will worsen the situation by creating a hypercoagulable state and warfarin resistance 2, 3. The 2022 CHEST guidelines specifically recommend against routine pre-operative vitamin K for elevated INR >1.5 1.

Do not delay heparin bridging - mechanical mitral valves can thrombose within days of subtherapeutic anticoagulation 4, 2, 3. The PERIOP-2 trial showed that in patients with mechanical mitral valves, bridging did not increase thromboembolism risk but did increase bleeding risk slightly 1, yet the consensus remains that high-risk patients (mechanical mitral valves) should receive bridging 1.

Do not use prophylactic-dose heparin - mechanical mitral valves require therapeutic-dose anticoagulation, not prophylactic doses 1.