Significant proportions of LVO strokes are due to previously undiagnosed AF and therefore would benefit from aggressive monitoring for occult AF.

Effective risk factor modification for secondary stroke prevention depends on accurate identification of stroke etiology. While endovascular intervention of large vessel occlusions (LVOs) can achieve excellent outcomes in the acute setting, far less is known about secondary prevention after an LVO stroke. Based on the major LVO endovascular treatment trials, atrial fibrillation preexists in 24-40% of patients prior to stroke but few studies have identified the rates of atrial fibrillation discovered during and after hospitalization

Retrospective review of LVO patients without severe ipsilateral carotid stenosis as defined by NASCET or other non-AF cardioembolic etiology. AF was defined as pre-existing or diagnosed via inpatient telemetry, electrocardiogram, 30 day event monitor, loop recorder.

172 LVO patients fulfilled criteria for inclusion. 75 (44%) had known AF upon presentation. Of the remaining 97, AF was discovered during admission in 17 (17%) of these patients. 10(6%) patients died prior to discharge and 9 (12%) were lost to follow up. Out of the 61 remaining patients, AF was discovered in 8 (13%); overall, AF accounted for 100 (58%) patients as the most likely LVO etiology.

Our study shows that over half (58%) of the LVO strokes were due to atrial fibrillation. New atrial fibrillation was discovered during inpatient admission (17%) and during follow up (13%). These results underscore the importance of aggressive pursuit of occult AF in this population. Given the high risk of atrial fibrillation, future studies with empiric anticoagulation could be considered. Limitations to our study include our relatively small sample, number of patients lost to follow up, and the lack of systematic AF screening practice for all LVO patients.