What is the treatment for thrombus formation on a mechanical Aortic Valve Replacement (AVR)?

From the Guidelines

Treatment for thrombus formation on a mechanical aortic valve replacement (AVR) should involve intensification of anticoagulation therapy, with an increase in the target INR range to 3.0-4.0 with warfarin, and addition of intravenous unfractionated heparin until the higher INR is achieved, as recommended by the 2020 ACC/AHA guideline for the management of patients with valvular heart disease 1.

Key Considerations

• The standard approach to managing thrombus formation on mechanical AVR involves increasing the target INR range to reduce the risk of thromboembolic events, as supported by the 2020 ACC/AHA guideline 1.
• The use of intravenous unfractionated heparin, with an initial bolus of 80 units/kg followed by a continuous infusion targeting an aPTT of 60-80 seconds, is a common practice in this setting.
• Thrombolytic therapy with tissue plasminogen activator (tPA) may be considered in cases with large thrombi causing hemodynamic compromise or systemic embolization, but this carries significant bleeding risks, as noted in the European Heart Journal recommendations 1.
• Surgical intervention with valve replacement may be necessary for patients with persistent large thrombi despite maximal medical therapy or those with severe valve dysfunction.

Long-term Management

• Following resolution of the acute thrombus, long-term management requires strict adherence to anticoagulation with a higher target INR (3.0-3.5), as recommended by the 2020 ACC/AHA guideline 1.
• The addition of low-dose aspirin (75-100 mg daily) may be considered, as suggested by the 2020 ACC/AHA guideline 1.
• Regular echocardiographic monitoring every 3-6 months is essential to detect any potential complications or recurrence of thrombus formation.

Importance of Anticoagulation Monitoring

• Thrombus formation on mechanical valves occurs due to inadequate anticoagulation, hypercoagulable states, or structural abnormalities that create flow disturbances, highlighting the importance of consistent anticoagulation monitoring and patient education about medication adherence, as emphasized by the European Heart Journal recommendations 1.
• Patient compliance with anticoagulation therapy is crucial to prevent thromboembolic events, and healthcare providers should ensure that patients are aware of the importance of adhering to their medication regimen.

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. For patients with tilting disk valves and bileaflet mechanical valves in the mitral position, the 7th ACCP recommends a target INR of 3.0 (range, 2.5 to 3.5).

Treatment for thrombus formation on mechanical AVR: Warfarin is recommended for all patients with mechanical prosthetic heart valves, with a target INR of 2.5 (range, 2.0 to 3.0) for patients with a St. Jude Medical bileaflet valve in the aortic position, and a target INR of 3.0 (range, 2.5 to 3.5) for patients with tilting disk valves and bileaflet mechanical valves in the mitral position 2.

From the Research

Treatment for Thrombus Formation on Mechanical AVR

• The treatment for thrombus formation on mechanical aortic valve replacement (AVR) involves anticoagulation therapy to prevent stroke and thromboembolism 3, 4, 5.
• The American College of Chest Physicians recommends anticoagulation with Warfarin at an INR range of 2-3 for patients with a bileaflet mechanical valve in the aortic position, and an INR of 2.5-3.5 for patients with a mechanical valve in the mitral position 3.
• Alternative recommendations include an INR of 2-3 in combination with aspirin (80 mg/day) for patients with a mechanical valve in the mitral position, and an INR of 2.5-3.5 combined with low-dose aspirin (80-100 mg) for patients with a mechanical valve and a history of systemic embolization 3.
• In patients who are hemodynamically unstable, surgical exploration with thrombectomy is indicated, with or without valve replacement 3.
• In patients who are hemodynamically stable, thrombolytic therapy is recommended initially 3.
• The use of dual-antiplatelet therapy (DAPT) with aspirin and clopidogrel has been studied as an alternative to warfarin, but it was associated with higher rates of thromboembolism and valve thrombosis compared to warfarin 4.
• Bridging anticoagulation therapy with intravenous unfractionated heparin or subcutaneous low-molecular weight heparin may increase the risk of bleeding complications 6, 5.

Anticoagulation Regimens

• The choice of anticoagulation regimen depends on the individual patient's risk factors and the type of mechanical valve used 3, 4, 5.
• Vitamin K antagonists, such as warfarin, are recommended for patients with mechanical valves and valvular atrial fibrillation 7.
• Direct oral anticoagulants, such as dabigatran, rivaroxaban, and apixaban, are not recommended for patients with mechanical valves, but may be used for patients with nonvalvular atrial fibrillation 7.
• Low-molecular-weight heparin may be used as a bridging anticoagulant or for patients with active cancer 7.