Undocumented atrial fibrillation (AF) is suspected as a main stroke cause in patients with ESUS, but its prevalence is largely unknown. This prospective study therefore aimed at delineating the prevalence of AF in patients with ESUS using continuous cardiac monitoring by implantable loop recorder (ILR) with daily remote interrogation over a period of 3 years and its clinical consequences, including recurrent stroke.
In consecutive patients with an ESUS diagnosis after complete work-up, an ILR was implanted and followed by daily remote monitoring until AF was detected or a follow-up of at least 3 years was completed. Additionally the ILR was interrogated in-hospital in 6-month intervals.
A total of 123 patients (74 male, mean age 65±9 years) were enrolledand completed the 3 years study period. AF was detected in 51 patients (41.4%). In 42 of the 51 AF positive patients (82%) oral anticoagulation was established. Recurrent strokes occurred in 28 patients (23%) of this ESUS population, 11 of these patients (21%) being AF positive, 17 (23%) AF negative. Patients with AF were slightly older than patients without AF (63.1±8.8 versus 67.5±9.6 years, p=0.12). Other parameters such as CHA2DS2-VASc score, infarct localization, micro- and macroangiopathy, carotid- or aortic plaques or stroke recurrence were not significantly different between groups.
In ESUS patients, early implantation of an ILR with cardiac monitoring and remote transmission over a 3-year period detects AF in 41.4 % and results in oral anticoagulation in 82% of these patients.

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