INR optimization based on stroke risk factors in patients with non-valvular atrial fibrillation

Background Bleeding complications have been frequently reported in East Asian patients on warfarin with a target international normalized ratio (INR) of 2.0–3.0. Objective This study aimed to identify the optimal therapeutic range of the INR in Korean patients with non-valvular atrial fibrillation (NVAF). Setting Cardiovascular department of a 1320 inpatient bed Korean hospital. Method Retrospective chart review was conducted on 1014 patients for a total follow-up period of 2249.2 patient years. Major thromboembolic and bleeding complications were evaluated. The INR incidence of complication curve was plotted, and the optimal therapeutic range of INR was determined from the intersection of curves to ensure the lowest incidences of both thromboembolic and bleeding complications. For subgroup analysis, all patients were stratified by the following factors: age (above 75), disease (presence of hypertension, diabetes, congestive heart failure, and a history of stroke or thromboembolism), rhythm control procedure, and concurrent aspirin therapy. Main outcome measure Optimal therapeutic ranges of INR according to the risk factors. Results A total of 41 thromboembolic and 91 bleeding events occurred during the follow-up period. The complication rates were the lowest at an INR of 1.9 and the optimal therapeutic range was estimated to be 1.7–2.2 for the overall patients. The optimal therapeutic ranges of INR in the stratified patients were determined as follows: 1.3–1.8 in the patients ≥75 years of age; 1.5–2.0 in patients with hypertension, diabetes and concurrent aspirin therapy; 1.8–2.3 in patients with congestive heart failure; 1.9–2.4 in patients with previous stroke or thromboembolism; 1.7–2.2 in patients who had undergone rhythm control procedures. It has been shown that, by keeping the INR within these ranges, complication risks could be significantly reduced by up to 81 %. Conclusion The intensity of anticoagulation therapy for Korean patients with NVAF is optimal when INR is between 1.7 and 2.2.