Abstract 15858: Patterns of International Normalized Ratio Stability Among Newly Initiated Warfarin Patients With Nonvalvular Atrial Fibrillation
OBJECTIVES: In patients with nonvalvular atrial fibrillation (NVAF), the use of warfarin can be challenging due to difficulties in achieving stable control of the international normalized ratio (INR). This analysis characterized the INR patterns among new warfarin patients in a large anticoagulation management service database.
METHODS: We analyzed longitudinal patient-level anticoagulation management records collected between 2006 and 2010 by decision support software, CoagClinic™. Adult patients with NVAF were followed from warfarin initiation to the first 90-day gap. INR stabilization is operationally defined as having 3 consecutive INR values within 2.0≤ INR≤3.0. The Rosendaal method was used to calculate TTR. INR patterns were compared 1) between those who achieved stabilization and those who did not, and 2) before and after INR stabilization.
RESULTS: We identified 100,800 patients who met all inclusion criteria, with mean age of 72 years and 56% male patients. About 37% of patients never achieved INR stabilization and they discontinued from follow-up sooner (figure). Mean [median] follow-up was 81  days for never-stabilized patients (mean TTR 37.6%), and 522  days for those who achieved stabilization (mean TTR 67.5%). Among those who achieved stabilization, mean [median] time-to-INR-stabilization was 148  days. Before stabilization, the mean (SD; range) number of changes in weekly total dose was 4.0 (4.2; 0-91), and there were 7.2 (6.8; 1-124) INR measures. After stabilization, a mean of 29% of INR values were out of range. There were more INR values above 3 before stabilization than after (16.7% vs. 11.8%).
CONCLUSIONS: Use of warfarin is associated with complex management. More than 1/3 of warfarin patients failed to achieve INR stabilization, and a majority of them appeared to have discontinued warfarin therapy in < 3 months. After a mean of nearly 5 months to achieve stabilization, more than 1 in 4 INR was out of range after stabilization.
- © 2013 by American Heart Association, Inc.