For a patient with a mechanical mitral valve on nicoumalone, how should peri‑operative anticoagulation be managed using therapeutic‑dose unfractionated heparin (UFH) bridging?

Perioperative Anticoagulation Management for Mechanical Mitral Valve with Nicoumalone and UFH Bridging

For a patient with a mechanical mitral valve on nicoumalone (acenocoumarol) requiring surgery, therapeutic-dose unfractionated heparin (UFH) bridging is recommended with intravenous administration preferred over subcutaneous, targeting an aPTT of 1.5-2.5 times control, due to the high thromboembolic risk (>10% annually) associated with mechanical mitral valves. 1, 2

Pre-operative Management

Stop nicoumalone 5 days before surgery to allow adequate time for the INR to decline, given acenocoumarol's half-life of 36-42 hours. 1, 3

• Check INR 36-48 hours after stopping nicoumalone (typically when INR falls below 2.0-2.5) to determine when to initiate UFH bridging. 1, 2
• Begin therapeutic-dose intravenous UFH when INR drops below 2.0, targeting an aPTT of 1.5-2.5 times control or anti-factor Xa level of 0.3-0.7 IU/mL. 1, 4
• Verify INR <1.5 on the day of surgery to ensure safe hemostasis. 2, 3

Stop intravenous UFH 4-6 hours before the procedure to minimize bleeding risk while maintaining anticoagulation as long as safely possible. 1, 2

Intraoperative Considerations

The European Society of Cardiology emphasizes that intravenous UFH administration should be favored over subcutaneous routes in patients at high thrombotic risk, which includes all mechanical mitral valve patients regardless of additional risk factors. 1

• Mechanical mitral valves carry substantially higher thromboembolic risk than aortic valves, making bridging a Class I recommendation. 2
• UFH remains the only approved heparin treatment specifically for patients with mechanical prostheses according to ESC guidelines. 1

Post-operative Management

Resume nicoumalone on the evening of surgery at the usual maintenance dose, and consider a 50% boost dose for two consecutive days to accelerate return to therapeutic anticoagulation. 2, 4

Restart therapeutic-dose intravenous UFH 4-6 hours after surgery once adequate hemostasis is secured, continuing the same aPTT target of 1.5-2.5 times control. 1

• For high-bleeding-risk orthopedic procedures, delay UFH resumption to 24-48 hours post-operatively. 2
• Continue UFH bridging until INR reaches therapeutic range (2.5-3.5 for mitral valves) on two consecutive measurements. 2, 4
• Check INR at least weekly during warfarin re-initiation until stable therapeutic levels are achieved. 2, 4

Monitoring Protocol

Monitor aPTT every 6 hours initially when using intravenous UFH, adjusting infusion rates to maintain 1.5-2.5 times control. 1, 4

• Baseline hemoglobin and platelet counts must be obtained before initiating UFH and repeated if clinical bleeding is suspected. 2
• The 2017 ESC guidelines recommend bridging for subtherapeutic INR levels noted during routine monitoring, which is particularly relevant given nicoumalone's shorter half-life compared to warfarin. 1

Critical Risk-Benefit Analysis

Bridging carries a 2.8% major bleeding risk but is essential for mechanical mitral valves given their exceptionally high thromboembolic risk without anticoagulation. 2, 5

• Observational data show thromboembolic risk of 0.9% with bridging versus substantially higher without bridging in mechanical mitral valve patients. 2
• Studies consistently demonstrate increased bleeding with bridging (3.3-5.5% major bleeding rate), but the alternative of no bridging in mechanical mitral valves is unacceptable given stroke risk. 1, 5

Common Pitfalls to Avoid

Never use prophylactic-dose UFH for mechanical mitral valves—therapeutic dosing is mandatory due to the high thromboembolic risk, unlike lower-risk mechanical aortic valves where some data support prophylactic dosing. 2, 6

Do not resume UFH within 4-6 hours of surgery for standard procedures, and wait 24-48 hours for high-bleeding-risk operations to avoid catastrophic hemorrhage. 1, 2

Continue UFH until INR is therapeutic on two consecutive measurements, not just one reading, as warfarin takes several days to achieve stable anticoagulation even after INR appears therapeutic. 2, 4

Avoid adding aspirin during the perioperative period unless there is a specific indication (such as recent coronary stenting), as triple therapy significantly increases bleeding risk without reducing thromboembolism in this context. 1, 3