Anticoagulant Therapy for Aortic Valve Replacement
For mechanical aortic valve replacement, lifelong warfarin targeting INR 2.5 (range 2.0-3.0) plus aspirin 75-100 mg daily is mandatory; for bioprosthetic aortic valve replacement, warfarin targeting INR 2.5 for 3-6 months followed by lifelong aspirin 75-100 mg daily is recommended. 1
Mechanical Aortic Valve Replacement
Anticoagulation Regimen
Warfarin is the only acceptable anticoagulant for mechanical valves—direct oral anticoagulants (DOACs) including dabigatran, apixaban, and rivaroxaban are absolutely contraindicated due to increased thrombotic and bleeding complications. 1, 2
Target INR 2.5 (range 2.0-3.0) for modern bileaflet or current-generation single-tilting disc mechanical aortic valves in patients without additional risk factors. 1
Target INR 3.0 (range 2.5-3.5) is required if the patient has any of the following risk factors: atrial fibrillation, previous thromboembolism, left ventricular dysfunction, hypercoagulable conditions, or older-generation mechanical valves (ball-in-cage). 1
Aspirin Addition
- Aspirin 75-100 mg daily must be added to warfarin therapy for all patients with mechanical aortic valves—this is a Class I, Level A recommendation. 1
Bridging Therapy
- Heparin should be initiated within 6-48 hours postoperatively (target aPTT 55-70 seconds) as soon as surgical bleeding risk is acceptable, continuing until therapeutic INR is achieved, because the highest thromboembolism risk occurs within the first 72 hours post-procedure. 1
Bioprosthetic Aortic Valve Replacement (Surgical)
Initial Anticoagulation Period
Warfarin targeting INR 2.5 (range 2.0-3.0) for 3-6 months is reasonable in patients at low bleeding risk, as stroke risk and mortality are lower with anticoagulation during this period when the valve is not yet fully endothelialized. 1
The evidence supporting this comes from a Danish registry of 4,075 patients showing lower thromboembolic events and mortality with warfarin for up to 6 months, though this recommendation is Class IIa (reasonable) rather than Class I (mandatory). 1
Aspirin 75-100 mg daily alone is an alternative for patients at higher bleeding risk during the initial 3-6 month period. 1
Long-Term Management
After 3-6 months, transition to aspirin 75-100 mg daily alone for lifelong therapy in patients without other indications for anticoagulation. 1, 2
Continue warfarin indefinitely (INR 2.5, range 2.0-3.0) if the patient has atrial fibrillation, previous thromboembolism, left ventricular dysfunction, or hypercoagulable conditions. 1, 3
Transcatheter Aortic Valve Replacement (TAVR)
Standard Post-TAVR Regimen
Dual antiplatelet therapy with aspirin 75-100 mg plus clopidogrel 75 mg daily for 6 months is the standard approach, though this is based on clinical trial protocols rather than direct evidence of benefit. 1, 2
Warfarin for at least 3 months may be reasonable in patients at low bleeding risk, as subclinical valve thrombosis occurs in 7-40% of TAVR patients on antiplatelet therapy alone but not in those receiving warfarin. 1, 2
Long-Term TAVR Management
Lifelong aspirin 75-100 mg daily alone after the initial 6-month period in patients without other anticoagulation indications. 2
Rivaroxaban was shown to cause harm compared to antiplatelet therapy in the GALILEO trial, reinforcing that DOACs should not be used. 1
Critical Pitfalls and Caveats
DOAC Prohibition
- Never use DOACs for any prosthetic valve—this is a Class III (harm) recommendation with Level B evidence showing increased thrombotic complications. 1
Combination Antiplatelet-Anticoagulation Risks
When warfarin is combined with aspirin during the initial post-bioprosthetic valve period, bleeding risk increases (1.4% vs 2.8% at 3 months) while thrombotic events decrease only marginally (1.0% vs 0.6%). 1
Aspirin dose should never exceed 100 mg when combined with warfarin to minimize bleeding risk. 1
Add a proton pump inhibitor when combining aspirin with warfarin in high-risk thrombotic patients to reduce gastrointestinal bleeding. 1
Drug Interactions
Verapamil should be avoided if risk factors for DOAC accumulation are present, though this is less relevant given DOACs are contraindicated; however, verapamil does not significantly affect warfarin clearance. 1
Diltiazem is preferred over verapamil if a calcium channel blocker is needed, as it does not impair warfarin clearance. 1
Special Valve Considerations
- The On-X mechanical valve in the aortic position may allow a lower INR target of 1.5-2.0 in patients without additional risk factors, but this is a Class IIb recommendation requiring very close INR monitoring and is not universally accepted. 1