Long-term treatment with warfarin in Chinese population

OBJECTIVE: To estimate the incidence of and risks for bleeding and thromboe mbolic events after warfarin anticoagulation. We also explored the dosage a nd international normalized ratio (INR) among Chinese patients during long- term warfarin therapy. METHODS: The population in this retrospective study consisted of inpatients of the only medical center for northern Taipei City, whose initial course of warfarin therapy continued for more than four weeks. Enrollment began in June 1995 and ended in February 1996. Follow-up was completed in March 199 8. Relevant data were collected by chart review. The rate of events was cal culated using the Kaplan-Meier method, and risk factors were identified by the Cox proportional hazard model. RESULTS: During the study period, 226 patients were identified. The total f ollow-up time was 248.7 patient-years. Sixty-one patients (27.0%) received anticoagulation for mechanical prosthetic valve, but their duration of ther apy accounted for 48.6% of the total patient-years of follow-up. The starti ng dosage (mean +/- SD) was 3.4 +/- 1.4 mg/d (range 1.3-10); the maintenanc e dosage was 3.1 +/- 1.2 mg/d (range 1.2-7.7). There were 1060 dosing adjus tments and 3398 INR measurements collected for these patients. The independ ent determinants of maintenance dosage were age, body weight, and indicatio n of mechanical prosthetic valve. The INR was 1.9 +/- 0.5 (range 1.0-3.7). The cumulative probabilities for hemorrhage at 12, 24, and 34 months were 2 4.5%, 32.3%, and 38.4%, respectively. The corresponding figures for thrombo embolism were 8.5%, 10.7%, and 10.7%, respectively. Three hemorrhages were fatal. After adjusting for other patient characteristics, increasing age wa s the only independent risk factor identified for bleeding. CONCLUSIONS: Antithrombotic efficacy seemed to be maintained, although the mean INR was 1.9. Even so, the substantial incidence of bleeding especially fatal bleeding, remains a concern. Low-intensity anticoagulation might be needed for Chinese patients during long-term warfarin therapy.