Warfarin to prevent thromboembolic events in atrial fibrillation

Warfarin reduces the stroke risk in patients with atrial fibrillation by 60% and can be used for long-term anticoagulant therapy to prevent thromboembolism and strokeHart, 2007.

Warfarin is recommended for patients with atrial fibrillation who have rheumatic mitral stenosis and/or a mechanical heart valve. The term ‘valvular’ atrial fibrillation has previously described this patient group—this term should be avoided as it can cause confusionHindricks, 2021. There is no evidence to support the use of DOACs in patients with rheumatic mitral stenosis and/or a mechanical heart valve, and data shows that DOACs may be harmful compared with warfarin in these patientsConnolly, 2022Eikelboom, 2013.

Warfarin may also be preferred over DOACs for patients with atrial fibrillation who have concomitant severe kidney impairment or another indication for warfarin therapy (eg antiphospholipid syndrome)Steffel, 2021.

Warfarin’s use is limited by its narrow therapeutic index, interactions with drugs and food, and the need to perform regular blood tests to monitor anticoagulation.

In patients with atrial fibrillation, follow a local protocol to determine the warfarin dose. Use:

Adjust the warfarin dose to achieve an INR from 2 to 3. The INR range can be higher for patients with rheumatic mitral stenosis and/or a mechanical heart valve as the range can depend upon the type of valve lesion or prosthesis; seek specialist advice.

See Practical information on using warfarin for information about dosing, monitoring and management of bleeding and overanticoagulation.