Is anticoagulation needed post bioprosthetic Mitral Valve Replacement (MVR)?

Anticoagulation After Bioprosthetic Mitral Valve Replacement

Anticoagulation with a Vitamin K Antagonist (VKA) to achieve an INR of 2.5 is reasonable for at least 3 months and for as long as 6 months after surgical bioprosthetic mitral valve replacement (MVR) in patients at low risk of bleeding. 1

Evidence-Based Recommendations

The 2017 AHA/ACC Focused Update on Valvular Heart Disease provides clear guidance on anticoagulation following bioprosthetic MVR:

• First 3-6 months post-op: Anticoagulation with a VKA (warfarin) targeting INR of 2.5 (range 2.0-3.0) is reasonable for patients at low bleeding risk 1
• Lifelong therapy: Low-dose aspirin (75-100 mg daily) is reasonable for all patients with a bioprosthetic mitral valve 1, 2

Rationale for Early Anticoagulation

There is compelling evidence supporting temporary anticoagulation after bioprosthetic MVR:

• Lower stroke risk and mortality rates in patients receiving anticoagulation for up to 6 months compared to those who don't 1
• Increased risk of ischemic stroke early after operation, particularly in the first 90-180 days 1
• Potential for bioprosthetic valve thrombosis that may be warfarin-responsive 1
• In a non-randomized study, patients with bioprosthetic MVR who received anticoagulation had a lower rate of thromboembolism (2.5% vs 3.9% per year) 1

Clinical Considerations and Pitfalls

Risk Assessment

• Balance the benefit of anticoagulation against bleeding risk
• The incidence of ischemic stroke within the first 30 postoperative days is higher after bioprosthetic valve replacement (4.6%) compared to mechanical prosthesis (1.3%) 1

Practice Variation

Despite guidelines, significant practice variation exists:

• Only about 67% of surgeons follow anticoagulation guidelines for bioprosthetic MVR 3, 4
• A Society of Thoracic Surgeons Database analysis found only 58% of patients were prescribed warfarin after BMVR 3

Bleeding Risk

• Compared with oral anticoagulation alone, adding dual-antiplatelet therapy increases bleeding complications 2-3 fold 1
• Recent data shows warfarin is associated with increased bleeding in BMVR patients (HR 1.32) but also provides a modest survival benefit 5

Alternative Anticoagulants

• NOACs (direct oral anticoagulants) have been associated with increased adverse outcomes after mitral valve operations and should not be used 5

Anticoagulation Algorithm for Bioprosthetic MVR

1. Immediate post-operative period:

   • Begin warfarin therapy targeting INR 2.5 (range 2.0-3.0)
   • Continue for at least 3 months, preferably up to 6 months in patients at low bleeding risk

2. After initial anticoagulation period:

   • Discontinue warfarin
   • Start lifelong low-dose aspirin (75-100 mg daily)

3. Special considerations:

   • For patients with other indications for anticoagulation (atrial fibrillation, previous thromboembolism, etc.), continue warfarin indefinitely
   • Monitor INR regularly during warfarin therapy, initially every few days until stable, then every 2-4 weeks

Conclusion

The evidence strongly supports temporary anticoagulation with warfarin for 3-6 months following bioprosthetic MVR, followed by lifelong low-dose aspirin therapy. This approach balances the risk of thromboembolism against bleeding complications.