Antiplatelet Therapy in Patients with Mechanical Heart Valves
Antiplatelet agents alone are contraindicated in patients with mechanical heart valves, as vitamin K antagonist (VKA) therapy is required for all patients with mechanical valves to prevent thromboembolism and valve thrombosis. 1
Primary Antithrombotic Management for Mechanical Valves
- For all patients with mechanical heart valves, VKA therapy (warfarin) is recommended over no VKA therapy for long-term management (Grade 1B) 1
- For patients with mechanical aortic or mitral valves, VKA therapy is strongly recommended over antiplatelet agents alone (Grade 1B) 1
- Antiplatelet therapy alone does not provide adequate protection against thromboembolism in patients with mechanical heart valves 2
Appropriate INR Targets for Mechanical Valves
- For patients with a mechanical aortic valve (bileaflet or current-generation single tilting disk), the target INR should be 2.5 (range 2.0-3.0) 1
- For patients with a mechanical mitral valve, the target INR should be 3.0 (range 2.5-3.5) 1
- For patients with a mechanical aortic valve and additional risk factors for thromboembolism (e.g., atrial fibrillation, previous thromboembolism, LV dysfunction, hypercoagulable state) or an older-generation prosthesis (e.g., ball-in-cage), the target INR should be 3.0 1
Role of Aspirin as Adjunctive Therapy
- In patients with a mechanical mitral or aortic valve at low risk of bleeding, adding low-dose aspirin (50-100 mg/d) to VKA therapy is suggested (Grade 1B) 1
- The addition of aspirin to VKA therapy has been shown to reduce mortality and major systemic embolism in patients with mechanical heart valves 3
- Caution should be used when adding aspirin to VKA therapy in patients at increased bleeding risk, such as those with a history of GI bleeding 1
Evidence Supporting Combined Therapy
- Combined low-dose aspirin and warfarin therapy following mechanical heart valve replacement has been associated with a greater reduction in thromboembolic events than warfarin therapy alone without significantly increasing major bleeding risk 4
- Low-intensity oral anticoagulation (INR 2.5-3.5) plus low-dose aspirin (100 mg/day) provides similar antithrombotic protection as high-intensity oral anticoagulation alone (INR 3.5-4.5), with potentially fewer bleeding complications 5
Special Considerations and Pitfalls
- Direct oral anticoagulants (DOACs) such as dabigatran and anti-Xa agents are contraindicated in patients with mechanical valve prostheses 1
- Triple antithrombotic therapy (VKA plus dual antiplatelet therapy) may be necessary in patients with mechanical valves who also have drug-eluting stents, but this significantly increases bleeding risk and should be limited to the shortest necessary duration 6
- When VKA therapy is combined with antiplatelet agents, careful monitoring for bleeding complications is essential, and the INR should be maintained at the lower end of the therapeutic range 7
Conclusion
For patients with mechanical heart valves, antiplatelet therapy alone is inadequate and contraindicated. VKA therapy is mandatory, with target INR based on valve type and position. Low-dose aspirin may be added to VKA therapy in patients at low bleeding risk to further reduce thromboembolic events.