Warfarin in patients with mechanical heart valves

### What you need to know A 55 year old woman with severe aortic stenosis underwent valve replacement with a mechanical valve. She has been started on warfarin and is maintaining an international normalised ratio (INR) within the target range of 2.0-3.0. She finds monitoring INR levels cumbersome. She has heard about newer direct oral anticoagulants and asks if she can switch to one of these. Valve replacement or repair is the definitive treatment in those with severe valvular heart disease. The choice of valve depends on valve durability, the need for antithrombotic therapy, and patient preferences.12 Mechanical heart valves are preferred in patients under 65.3 Bioprosthetic valves do not require lifelong anticoagulation but have a greater rate of primary failure and are associated with a higher reoperation rate. They last only 10 to 15 years compared with 20 to 30 years for mechanical heart valves.3 Warfarin is an anticoagulant prescribed to patients with mechanical heart valves. Patients with mechanical heart valves have a risk of thrombosis on the valve and subsequent embolism. Blood flows at high shear stress around the valve, which activates platelets and local coagulation. Latest European, US, and National Institute of Health and Care Excellence (NICE) guidelines recommend lifelong treatment with warfarin to prevent this.1245 Warfarin is a vitamin K antagonist. Other drugs in this group are acenocoumarol and dicoumarol. Warfarin inhibits the synthesis of the vitamin K dependent …