What is the recommended anticoagulation therapy for patients with mechanical aortic valves?

From the Guidelines

Patients with mechanical aortic valves require lifelong anticoagulation with warfarin, targeting an INR of 2.0-3.0 for bileaflet or current-generation tilting disc valves without additional risk factors, and 2.5-3.0 for those with risk factors or older-generation valves. This recommendation is based on the most recent guidelines from the American College of Cardiology/American Heart Association, as outlined in the 2020 ACC/AHA guideline for the management of patients with valvular heart disease 1. The guideline recommends anticoagulation with a vitamin K antagonist (VKA) to achieve an INR of 2.5 for patients with a mechanical bileaflet or current-generation single-tilting disk aortic valve replacement (AVR) and no risk factors for thromboembolism. For patients with a mechanical AVR and additional risk factors for thromboembolism, or an older-generation prosthesis, anticoagulation with a VKA to achieve an INR of 3.0 is recommended.

Key considerations for anticoagulation therapy in patients with mechanical aortic valves include:

• The type of valve prosthesis, with bileaflet or current-generation tilting disc valves generally requiring lower INR targets than older-generation valves
• The presence of additional risk factors for thromboembolism, such as atrial fibrillation, previous thromboembolism, left ventricular dysfunction, or hypercoagulable conditions
• The need for regular INR monitoring, typically every 2-4 weeks once stable, to ensure optimal anticoagulation and minimize the risk of bleeding or thromboembolic complications
• The potential addition of low-dose aspirin (75-100 mg daily) to warfarin therapy for additional protection, especially in higher-risk patients, though this increases bleeding risk

It is essential to note that direct oral anticoagulants (DOACs) like apixaban and rivaroxaban are contraindicated in patients with mechanical heart valves, as they have not been shown to be effective in preventing valve thrombosis and systemic embolism in this population 1. Anticoagulation is necessary because the artificial valve surfaces activate the coagulation cascade, potentially leading to valve thrombosis and systemic embolism, which can cause stroke or other serious complications if left untreated. The 2021 guideline provides the most up-to-date recommendations for anticoagulation therapy in patients with mechanical aortic valves, and should be consulted for guidance on individual patient management 1.

From the FDA Drug Label

For all patients with mechanical prosthetic heart valves, warfarin is recommended. For patients with a St. Jude Medical (St. Paul, MN) bileaflet valve in the aortic position, a target INR of 2.5 (range, 2.0 to 3. 0) is recommended.

The recommended anticoagulation therapy for patients with mechanical aortic valves is warfarin. The duration of warfarin treatment is not explicitly stated as a specific length of time, but rather it is recommended to be continued until the danger of thrombosis and embolism has passed. The target INR range for patients with a mechanical aortic valve is 2.0 to 3.0, with a target INR of 2.5 2.

From the Research

Mechanical Aortic Valve Anticoagulation Therapy

• The recommended anticoagulation therapy for patients with mechanical aortic valves varies based on the type of valve, position, and risk factors for stroke 3.
• For mechanical heart valves in the aortic position, anticoagulation with Warfarin at an INR range of 2-3 is recommended 3.
• In patients with a mechanical valve and a history of systemic embolization, an INR of 2.5-3.5 combined with low-dose aspirin (80-100 mg) is recommended 3.
• The American College of Chest Physicians recommends an INR range of 2-3 for patients with a bileaflet mechanical valve in the aortic position 3.

Alternative Anticoagulation Therapies

• Enoxaparin has been shown to be a successful alternative anticoagulation therapy for patients with mechanical heart valves who do not tolerate or fail warfarin 4.
• A case study reported successful long-term anticoagulation with enoxaparin in a patient with a mechanical aortic valve who had a contraindication to warfarin 4.
• The use of enoxaparin requires meticulous monitoring of anti-factor Xa levels and dosage adjustments to ensure treatment success 4.

Low-Dose Warfarin and Aspirin Therapy

• A prospective, observational registry study found that warfarin targeted to an INR of 1.8 (range 1.5-2.0) plus daily aspirin (75-100 mg) is safe and effective for patients with an On-X aortic mechanical valve 5.
• The study reported a 57% reduction in the primary composite end point rate compared to standard-dose warfarin (INR 2.0-3.0) plus daily aspirin 81 mg 5.
• The results suggest that warfarin targeted at an INR of 1.8 (range 1.5-2.0) plus aspirin is a viable option for patients with an On-X aortic mechanical valve 5.

Standard Versus Higher Intensity Anticoagulation

• A study found that standard-intensity anticoagulation (INR goal 2.5) was associated with a lower risk of thromboembolic events, bleeding, or all-cause death compared to higher-intensity anticoagulation (INR goal 3.0) in patients with mechanical aortic valve replacement and additional risk factors for thromboembolism 6.
• The results challenge current guideline recommendations for anticoagulation management of mechanical aortic valve replacement in patients with additional risk factors 6.

Optimal Intensity of Warfarin Therapy

• A review of current guidelines and published literature found that the evidence-based INR goal in patients with a mechanical aortic valve is 2-3 for low-risk recipients with most bileaflet mechanical aortic valves 7.
• The review suggests that an INR range of 2.5-3.5 may be justified in patients with risk factors for thromboembolism with low thrombogenic valves, except for On-X valve 7.
• The INR goal in high-risk On-X aortic valve recipients can be managed at 1.5-2.5 with low-dose aspirin 3 months after valve implantation 7.