Background We aimed to determine the relative frequency of affected cerebrovascular territories in patients with atrial fibrillation (AF) suffering an ischemic stroke.

Methods Altogether, 1,976 patients who suffered their first-ever ischemic stroke during 2003–2012 and were diagnosed with AF either before or within 30 days after the event were included in this retrospective multicenter cohort study. Strokes were classified radiographically to be located either within the anterior or the posterior cerebrovascular territory, and the effect of the CHA2DS2-VASc score, oral anticoagulant (OAC) use, and timing of AF diagnosis on lesion localization was determined.

Results The median age of the patients was 78.4 (interquartile range: 71.7–84.2) years, 1,137 (57.5%) of them were women, their mean CHA2DS2-VASc score was 3.5 (95% confidence interval: 3.4–3.5), 656 (33.2%) were receiving OAC drugs, and altogether, 1,450 (73%) had a previous AF diagnosis. The localization of ischemic lesions between the anterior and the posterior cerebrovascular territories was not affected by the timing of AF diagnosis (p = 0.46), use of OACs (p = 0.70), or the CHA2DS2-VASc score (p = 0.10). Within the anterior territory, altogether 774 strokes (53.2%) were located in the left hemisphere and 3 (0.2%) were bilateral. The timing of AF diagnosis (p = 0.84), use of OACs (p = 0.90), or the CHA2DS2-VASc score (p = 0.21) did not affect the location of the ischemic lesion between the hemispheres.

Conclusions The timing of AF diagnosis, use of OAC drugs, or the CHA2DS2-VASc score did not affect the distribution of ischemic strokes. Anterior territory strokes were slightly more often located within the left hemisphere.