Recently, the clinical entity embolic stroke of undetermined source (ESUS) has been defined for patients with ischemic strokes, where neither a cardioembolic nor a non-cardiac source can be detected. These patients may suffer from asymptomatic atrial fibrillation (AF), terminating spontaneously and thus eluding detection. Implantable loop recorders (ILR) with automatic AF detection algorithms can detect short-lasting, subclinical AF. The aim of this study was to prospectively assess and predict AF detection in patients with ESUS using ILR with daily remote interrogation. Patients with acute ESUS received an ILR, were seen every 6 months and additionally interrogated their ILR daily using remote monitoring. The incidence of AF detection was assessed and parameters which might predict AF detection (clinical and from magnetic resonance tomography) were analysed. ILR implantation was performed in 123 patients on average 20 days after stroke. During a mean follow-up of 12.7±5.5 months, AF was documented and manually confirmed in 29 of 123 patients (23.6 %). First AF detection occurred on average after 3.6±3.4 months of monitoring. Patients with AF were on average older, had a higher CHADS-VASc score and more often cerebral microangiopathy. In conclusion, AF can be documented in approximately 25 % of patients with the diagnosis of ESUS after careful work-up within a year of monitoring by an ILR and daily remote interrogation. This had important therapeutic consequences (initiation of anticoagulation for secondary stroke prevention) in these patients.

Background: 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. Methods: 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. Results: 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. Conclusions: 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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Introduction: The embolic stroke of unknown source concept was introduced as a more rigid analysis of patients with cryptogenic stroke representing a superselection of patients with cardioembolic stroke. These patients are particularly candidates for intermittent AF. As long as AF has not been documented, current concepts do not recommend oral anticoagulation.Implantable loop recorders (ILR) in patients with ESUS may detect AF and establish the indication for oral anticoagulation. The aim of this study was to prospectively assess and predict AF occurrence in patients with ILR after ESUS. Methods: In patients with ESUS (MR imaging based cardioembolic stroke, exclusion of structural cardiac stroke source by TEE, no AF detectable by 72h Stroke Unit monitoring and 24h holter ECG, exclusion of other stroke causes such as symptomatic carotid stenosis) an ILR was implanted and AF detection assessed by daily remote monitoring. The ILR was implanted on average 20 days after stroke. We analyzed the predictive value of different clinical and imaging characteristics for AF detection. Results: By daily remote monitoring of 124 Patients over a period of 12.7±5.5 months, AF was documented and manually confirmed in 29 of 124 patients (23.4%). First AF detection occurred on average after 3.6±3.4 months of monitoring. Characteristics of patients with and without AF detection are shown in the table. Conclusions: Patients with ESUS and asymptomatic AF detected only by long-term continuous monitoring with an ILR were on average older, had a higher CHA2DS2-VASc score and had more often microangiopathy. Other clinical parameters and features of cerebral imaging in ESUS did not increase the probability of AF detection in these preselected patients with ESUS. Importantly, ESUS selection almost doubled AF detection rate compared to recent studies such as the ILR group of the Crystal-AF trial (23.4% in 12.7±5.5 months compared to 12.4% in 12 months).