Antithrombotic Therapy for Mechanical Valve Replacement

Introduction to Antithrombotic Therapy

The American College of Cardiology recommends antithrombotic therapy for patients with mechanical valve replacement to prevent valve thrombosis and thromboembolic events, while managing bleeding risk 1, 2, 3, 4

The American College of Cardiology recommends a combination of warfarin (target INR 2.5), low-dose aspirin (75-100 mg), and subcutaneous heparin during the inpatient period after surgery for patients with mechanical SAVR 1
Bridging anticoagulation during subtherapeutic INR periods is reasonable for patients with mechanical AVR plus risk factors, older-generation AVR, or mechanical MVR, as recommended by the American College of Cardiology 4, 5, 1

For patients with bileaflet mechanical aortic valve without risk factors, the American College of Cardiology recommends warfarin with target INR 2.5 (range 2.0-3.0) plus aspirin 75-100 mg daily 1, 3, 4
For patients with mechanical aortic valve with risk factors (such as atrial fibrillation, previous thromboembolism, left ventricular dysfunction, or hypercoagulable state), the American College of Cardiology recommends warfarin with higher target INR 3.0 (range 2.5-3.5) plus aspirin 75-100 mg daily 1, 3, 6
Risk factors for mechanical AVR include atrial fibrillation, previous thromboembolism, left ventricular dysfunction, and hypercoagulable conditions, which warrant higher INR targets 3, 4

The American College of Cardiology recommends warfarin with target INR 2.5 (range 2.0-3.0) for 3-6 months after discharge 1, 7, 8, 4
After the initial 3-6 month period, transition to lifelong low-dose aspirin 75-100 mg daily is recommended (Class I; Level of Evidence B-NR) 1, 4, 3
For patients with On-X mechanical aortic valve without risk factors, lower-intensity warfarin (INR 1.5-2.0) plus aspirin 75-100 mg daily may be considered after 3 months of standard anticoagulation (Class IIb) 1, 9

Elderly patients have an increased risk of anticoagulation-related bleeding complications, and more frequent INR monitoring is needed due to potential drug interactions, as noted by the American Geriatrics Society 10
Avoid triple therapy (dual antiplatelet plus anticoagulant) unless absolutely necessary due to extremely high bleeding risk in elderly patients, according to the American Heart Association 6
INRs >4.0 significantly increase bleeding risk without additional antithrombotic benefit, and monitoring frequency should be adjusted accordingly, as recommended by the American Geriatrics Society 10

Regular INR monitoring is essential for safe warfarin therapy, with initial frequent monitoring (every few days) until stable, and then INR checks every 2-4 weeks 5, 1, 4
Aspirin 75-100 mg daily should be added once INR is stable, as suggested by the American College of Cardiology 3

For patients who cannot take warfarin, low-dose aspirin is indicated (Class I; Level of Evidence C) 11, 4
Direct oral anticoagulants (DOACs) should NOT be used in patients with mechanical valve prostheses 5, 4
Clopidogrel 75 mg daily may be reasonable for the first 6 months after TAVR in addition to lifelong aspirin 75-100 mg daily, as recommended by the American College of Cardiology 4

For minor procedures with easily controlled bleeding, continue VKA with therapeutic INR, while for invasive/surgical procedures in patients with bileaflet mechanical AVR without risk factors, temporary interruption of VKA without bridging is recommended, as recommended by the American College of Cardiology 4