Abstract

BackgroundDebate continues about the optimal anticoagulation level for elderly Japanese patients with non-valvular atrial fibrillation (NVAF) receiving warfarin. The Japanese Circulation Society guideline has recommended prothrombin time-international normalized ratios (PT-INR) of 1.6 – 2.6 for elderly patients and 2.0 – 3.0 for non-elderly patients, because previous observational studies indicated increased risk of bleeding when the ratio exceeded 2.6. We aimed to reappraise the relationship between PT-INR and the risk of major bleeding in elderly Japanese patients.MethodsFrom the electronic medical records, we selected a cohort of elderly (age ≥ 70 years) Japanese patients with NVAF who were prescribed warfarin for the prevention of thromboembolic diseases between November 2010 and March 2014 at Kanto Rosai Hospital. We identified those who developed major bleeding (cases). For each case, we randomly selected two matched controls by adopting a risk-set sampling method defined by calendar date, age, gender, length of warfarin administration, and the prescriber of warfarin. The risk of major bleeding in patients having PT-INR ≤ 1.49, 1.50 – 1.99, 2.00 – 2.49 (the reference), 2.50 – 2.99, and ≥ 3.00 were compared using the conditional logistic regression method. The study protocol was approved by the IRB before the study was begun.ResultsAmong the cohort of 806 elderly patients, we identified 32 cases and selected 64 matched controls. The overall incidence of major bleeding was 3.5 per 100 patient-years. The odds ratios (95 % confidence intervals) for the risk of developing major bleeding in patients with PT-INR ≤ 1.49 (n = 20), 1.50 – 1.99 (n = 32), 2.00 – 2.49 (n = 18), 2.50 – 2.99 (n = 10), and ≥ 3.00 (n = 16) were 1.0 (0.2, 5.9), 0.3 (0.1, 1.9), 1.0 (reference), 1.2 (0.2, 8.4), and 19.8 (2.0, 198.9), respectively, with a significant difference between ≥ 3.00 and reference.ConclusionsAmong elderly Japanese patients with NVAF, PT-INR 2.0 – 3.0 may be associated with a clinically permissible risk of major bleeding while PT-INR ≥ 3.00 a significant risk. Further studies are warranted to determine whether the risk of major bleeding is significantly lower for PT-INR 2.50 – 2.99 than for PT-INR ≥ 3.00.

Highlights

  • Debate continues about the optimal anticoagulation level for elderly Japanese patients with non-valvular atrial fibrillation (NVAF) receiving warfarin

  • Seven hundred and sixty-nine elderly patients who were diagnosed with atrial fibrillation were extracted from the electronic medical records

  • 1,048 elderly patients prescribed warfarin were extracted from the prescription record database

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Summary

Introduction

Debate continues about the optimal anticoagulation level for elderly Japanese patients with non-valvular atrial fibrillation (NVAF) receiving warfarin. The Japanese Circulation Society guideline has recommended prothrombin time-international normalized ratios (PT-INR) of 1.6 – 2.6 for elderly patients and 2.0 – 3.0 for non-elderly patients, because previous observational studies indicated increased risk of bleeding when the ratio exceeded 2.6. Non-valvular atrial fibrillation (NVAF) is the most prevalent arrhythmia in the elderly and poses substantial morbidity and mortality risks because of an increase in cardiogenic thromboembolic complications [1]. Debate continues regarding the optimal intensity of warfarin therapy in elderly Japanese patients with NVAF. While the prothrombin time-international normalized ratio (PT-INR) range of 2.0 – 3.0 is recommended for Caucasians regardless of age and for non-elderly Japanese patients, the range of 1.6 – 2.6 has been recommended for elderly (age ≥ 70 years) Japanese patients [6,7,8,9,10]

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