Recurrent Ischemic Stroke in Patients With Atrial Fibrillation While Receiving Oral Anticoagulants

IMPORTANCE: Patients with atrial fibrillation (AF) can have an ischemic stroke (IS) despite oral anticoagulant (OAC) treatment. Knowledge regarding the association between OAC discontinuation and the subsequent risk of recurrent IS in patients with AF is limited. OBJECTIVES: To determine the risk of recurrent IS in patients with AF receiving OAC and to evaluate the association between OAC discontinuation and the risk of recurrent IS. DESIGN, SETTING, AND PARTICIPANTS: This is a nationwide cohort study of patients aged 50 years or older in Denmark who had AF and an IS (entry IS) and were initiating or restarting subsequent OAC treatment after being discharged between January 2014 and December 2021. Patients were followed up for recurrent IS until June 2022. Within this study cohort, a nested case-control analysis was performed in which patients with recurrent IS were matched to patients receiving OAC who had not yet experienced a stroke. Data were analyzed from May 25, 2023, to April 18, 2024. EXPOSURE: Use of OAC at the time of recurrent IS or the equivalent date in matched controls based on redeemed prescriptions. MAIN OUTCOMES AND MEASURES: The primary outcome was recurrent IS. Crude and adjusted cumulative incidences of recurrent IS and all-cause mortality were calculated in cohort analyses, and adjusted odds ratios (aORs) were determined for recurrent IS associated with OAC discontinuation in nested case-control analyses. RESULTS: The study cohort included 8119 patients (4392 [54.1%] male; mean [SD] age, 78.4 [9.6] years; median (IQR) CHA2DS2-VASc score, 4.0 [3.0-5.0]). Over a mean (SD) follow-up of 2.9 (2.2) years, 663 patients had a recurrent IS, of whom 533 (80.4%) were receiving OAC at the time of their recurrent IS. The crude cumulative incidence of recurrent IS at 1 year was 4.3% (95% CI, 5.9%-7.1%), and the crude cumulative incidence of all-cause mortality was 15.4% (95% CI, 14.7%-16.2%). Adjusted analysis showed similar results. Patients who discontinued OACs had a higher risk of recurrent IS (89 cases [13.4%], 180 controls [6.8%]; aOR, 2.13; 95% CI, 1.57-2.89) compared with patients still receiving OAC. CONCLUSIONS AND RELEVANCE: The risks of recurrent IS and mortality were high in patients with AF despite secondary prevention with OAC, and OAC discontinuation doubled the risk of recurrent IS compared with patients who continued OAC. This finding highlights the importance of OAC continuation and the need for improved secondary stroke preventio