Do mechanical heart valves require anticoagulation (anticoagulant) therapy?

Anticoagulation for Mechanical Heart Valves

All patients with mechanical heart valves require lifelong anticoagulation with a vitamin K antagonist (VKA) such as warfarin to prevent potentially fatal valve thrombosis and thromboembolic events. 1

Rationale for Anticoagulation

Mechanical heart valves necessitate anticoagulation for several key reasons:

• The thrombogenicity of the intravascular prosthetic material
• Abnormal flow conditions created by mechanical valves, with:
  • Zones of low flow within valve components
  • Areas of high-shear stress causing platelet activation
  • Risk of valve thrombosis and embolic events

Research demonstrates that anticoagulation with a VKA significantly reduces:

• Valve thrombosis (relative risk: 0.11; 95% CI: 0.07-0.2)
• Thromboembolic events (relative risk: 0.21; 95% CI: 0.16-0.27) 1

Target INR Ranges

The target INR varies based on valve position and patient risk factors:

Aortic Position

• For bileaflet mechanical AVR without risk factors: INR 2.0-3.0 (target 2.5) 1, 2
• For older-generation mechanical AVR (ball-cage or tilting disc): INR 2.5-3.5 (target 3.0) 2

Mitral Position

• For all mechanical mitral valves: INR 2.5-3.5 (target 3.0) 3, 2
• Higher targets are needed due to increased thrombogenicity in the mitral position

Additional Risk Factors

For patients with:

• Previous thromboembolism
• Atrial fibrillation
• Hypercoagulable conditions
• Left ventricular dysfunction
• Multiple mechanical valves

Consider maintaining the higher end of the recommended INR range and adding aspirin therapy 1, 3

Adjunctive Therapy

• Low-dose aspirin (75-100 mg daily) is recommended in addition to warfarin for patients with mechanical heart valves who have low bleeding risk 1
• The addition of aspirin reduces thromboembolic risk but increases bleeding risk approximately 1.5-fold 3

Contraindicated Medications

• Direct oral anticoagulants (DOACs) are contraindicated in patients with mechanical heart valves:
  • Dabigatran is specifically contraindicated (Class III: Harm, Level B-R) 1
  • Anti-Xa direct oral anticoagulants have not been assessed and are not recommended (Class III: Harm, Level C-EO) 1

Management During Procedures

For patients requiring procedures:

• Minor procedures with easily controlled bleeding: Continue VKA with therapeutic INR 1
• For bileaflet mechanical AVR without risk factors: Temporary interruption without bridging is reasonable 1
• For higher-risk valves (mitral position, older-generation valves) or patients with risk factors: Bridging with heparin is recommended when INR is subtherapeutic 1

Common Pitfalls and Caveats

1. Inadequate anticoagulation: Maintaining consistent therapeutic INR is essential; fluctuations increase complication risk 1

2. Inappropriate DOAC use: Never substitute DOACs for warfarin in mechanical valve patients 1

3. Interrupting anticoagulation: Bridging therapy decisions should be individualized based on valve type, position, and patient risk factors 1

4. Monitoring challenges: Specify a single INR target for each patient with an acceptable range of 0.5 INR units on each side to reduce the likelihood of consistently being at range boundaries 1

5. Emergency situations: For patients requiring emergency procedures, 4-factor prothrombin complex concentrate can be used to rapidly reverse anticoagulation 1

The evidence is clear and consistent across multiple guidelines that mechanical heart valves require lifelong anticoagulation with VKAs to prevent potentially devastating thromboembolic complications and valve thrombosis, with the specific INR target determined by valve position and patient risk factors.