Antithrombotic treatments in patients with acute ischemic stroke and non-valvular atrial fibrillation before introduction of non-vitamin K antagonist oral anticoagulants into practice in Korea

Background This study aimed to describe patterns of long-term antithrombotic use in acute ischemic stroke (AIS) patients with non-valvular atrial fibrillation (NVAF) in Korea and their impacts on clinical events before introduction of non-vitamin K antagonist oral anticoagulants (NOAC) into practice in 2015. Methods Patients with NVAF who were admitted due to the AIS and discharged no later than 2008 were enrolled retrospectively. Data were collected at 11 time points during the first 3 years of follow-up. The primary outcome event was a composite of stroke recurrence, major bleeding, and death. Vitamin K antagonist (VKA) users were categorized into a well-controlled INR group and a poorly-controlled INR group (modified TTR >= 47.0% vs <47.0%). Results Of 1,350 patients enrolled in this study, 95% were on antithrombotic medications at discharge. The rate of VKA usage decreased over time (77% and 40% at discharge and 3 years, respectively). The cumulative event rates of the primary outcome differed by treatment patterns. Among the 10 most frequent treatment types, the highest outcome rate was observed in patients who started with VKA-only therapy but discontinued VKAs during follow-up without restarting (70.2%); this was followed by those starting with antiplatelet-only therapy and stopping it without restart (66.7%). Among VKA users, the 3-year cumulative primary outcome rates were higher in the poorly-controlled INR group than the well-controlled INR group (24.5% vs 15.7%; p= 0.015). Conclusion Our study revealed that, in pre-NOAC era, there was a wide spectrum of long-term antithrombotic use. The incidence of the composite outcome also varied by patterns of antithrombotic use.