Anticoagulant therapy in Japanese patients with mechanical mitral valves.

There are no guidelines for the optimal therapeutic range of anticoagulant therapy in Japanese patients with mechanical heart valves. A total of 214 patients were followed retrospectively after mitral mechanical valve replacement (mean duration of follow-up, 4.8 years; total duration of follow-up, 1,027 patient-years). The target range of the international normalized ratio (INR) for oral anticoagulation was between 1.5 and 2.5. For all patients 10,416 measurements of the INR were obtained during the follow-up period and approximately 76% of the intensity measurements were within the target range. Thromboembolism occurred in 8 patients (0.8 per 100 patient-years) and major bleeding in 5 patients (0.5 per 100 patient-years). There was no correlation between the distribution of the INR and the occurrence of thromboembolic or bleeding complications. In the univariate analysis of the various risk factors, patients who had a tilting valve or did not receive antiplatelet therapy had an increased risk of thromboembolism. However, there were no risk factors with respect to bleeding complications. A target range of 1.5 to 2.5 INR appears to be the optimal range and is safe for thromboembolism or bleeding complications. Thromboembolism may be reduced by additional antiplatelet therapy, and a tilting valve needs more intense anticoagulation.