Anticoagulation for Prosthetic Valves

Implantation of prosthetic valve requires consideration for anticoagulation. The current guideline recommends warfarin on all mechanical valves. Dabigatran is the new generation anticoagulation medication which is taken orally and does not require frequent monitoring. This drug is approved for treatment for atrial fibrillation and venous thromboembolism, but the latest large trial showed that this drug increases adverse events when used for mechanical valve anticoagulation. On-X valve is the new generation mechanical valve which is considered to require less anticoagulation due to its flow dynamics. The latest study showed that lower anticoagulation level lowers the incidence of bleeding, while the risk of thromboembolism and thrombosis remained the same. Anticoagulation poses dilemma in cases such as pregnancy and major bleeding event. During pregnancy, warfarin can be continued throughout pregnancy and switched to heparin derivative during 6–12 weeks and >36 weeks of gestation. Warfarin can be safely started after 1-2 weeks of discontinuation following major bleeding episode. 1. Introduction Prosthetic valves require consideration for anticoagulation postoperatively to prevent thrombotic events. The traditional method of anticoagulation is warfarin which requires frequent blood test to check prothrombin (PT) time and International ratio (INR). American College of Cardiology and American Heart Association (ACC/AHA) have a guideline to show the adequate anticoagulation level for each position depending on the valve type: mechanical or biologic. However, anticoagulation is not without a risk. As mentioned earlier, frequent blood testing is required and being off the target level exposes patients to risk of thrombosis and bleeding. Also, patients who are on anticoagulation have restrictions on activities to prevent bleeding events which limits lifestyle to the young patients. Warfarin carries a risk during childbearing which necessitates conversion to alternative anticoagulation method. In this paper, we will discuss the current guideline and show evolving new evidence which may change the way of anticoagulation with prosthetic valves. 2. Current Guideline The latest guideline from ACC/AHA in 2008 on anticoagulation for prosthesis is as follows [1]. 2.1. Class I (1) After aortic valve replacement (AVR) with mechanical prostheses, warfarin is indicated to achieve an INR of 2.0 to 3.0. If the patient has risk factors, warfarin is indicated to achieve an INR of 2.5 to 3.5. (2) After mitral valve replacement (MVR) with mechanical valve, is indicated warfarin