The Detection of Atrial Fibrillation by Implantable Event Recorders: A Study of Patients Who Have Had a Cryptogenic...

Arial fibrillation (AF) plays a role in approximately one-third of ischemic strokes. In embolic strokes of undetermined source (ESUS), paroxysmal atrial fibrillation often escapes detection; if detected, it could be an indication for oral anticoagulation. In the ARTESiA trial, the absolute benefit of anticoagulation was higher in patients who had already had a stroke or transient ischemic attack (TIA) than in those who had not.

We retrospectively analyzed data from 233 consecutive ESUS patients at the Jena University Hospital who had received an implanted loop recorder (ILR) over the period 2021-2025. We additionally provide a narrative review on the detection rates associated with various monitoring strategies based on pertinent publications that were retrieved by a literature search.

The 12-month detection rate of paroxysmal AF was 24.0% (56/233, 95% confidence interval [19.0; 29.9]). 73.2% of the initial detections were within the first 90 days. All patients in whom AF was detected were orally anticoagulated. The 12-month detection rate was higher than in the CRYSTAL-AF trial (12.4%) and the PER-DIEM trial (15.3%), but lower than was reported by Pikija et al. (31.3%). The cutoff values with the highest positive predictive value were a stroke risk analysis (SRA) index of 2 or above (38.4%) and age 75 or above (37.9%).

Early, risk-adapted diagnostic testing with ILR in selected ESUS patients can detect clinically relevant AF. Advanced age and an elevated SRA index may be useful patient selection criteria. A robust number needed to treat (NNT) for the ILR strategy cannot be derived from the available one-armed registry data. The indication for ILR should be linked to its therapeutic relevance, the probability of detecting AF, and the individual hemorrhagic risk.