What is the optimal level of anticoagulation in adult patients receiving warfarin following implantation of a mechanical prosthetic mitral valve?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was what is the optimal target INR for warfarin therapy in patients who have undergone implantation of a prosthetic mechanical mitral heart valves? Altogether 894 papers were identified on Medline and 1235 on Embase using the reported search including all major international guidelines. Twelve papers and publications represented the best evidence on the topic. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that after implantation of new generation prosthetic mechanical mitral valves, patients should receive warfarin to a target INR of 2.5-3.5. For older types of valve the target INR should be 3.5-4.5. Warfarin therapy should be administered to maintain stable INR values ensuring lowest possible variation in the intensity of anticoagulation. In selected patients with a history of thromboembolic disease and/or coronary artery disease warfarin therapy consideration should be given to supplementing warfarin with low-dose aspirin.