Expanding the Role of Implantable Loop Recorders: Diagnostic and Therapeutic Yields Across Seven Clinical Indications in 388 Real-World Patients

<b>Background/Objectives</b>: Implantable loop recorders (ILRs) enable long-term electrocadiographic monitoring and are established diagnostic tools for syncope and atrial fibrillation (AF). However, their diagnostic yield and therapeutic impact in other clinical settings remain less well defined. We aimed to evaluate the diagnostic yield and clinical impact of ILR implantation across contemporary clinical indications. <b>Methods</b>: In this retrospective single-center study, 388 patients who underwent ILR implantation between 2011 and 2018 were included. Indications were categorized into seven groups: unexplained syncope, presyncope, cryptogenic stroke or transient ischemic attack (TIA), AF detection, AF recurrence after atrial flutter (AFL) ablation, risk stratification in structural or inherited heart disease, and palpitations. <b>Results</b>: Among 388 patients (median age 63 [51.8-71.8] years, 57.5% male; median follow-up 17.0 [IQR 6.4-32.4] months), ILRs were most frequently implanted for syncope (44.6%), AF (20.4%), and stroke/TIA (12.9%). ILR-detected arrhythmias occurred in 241 patients (62.1%), with the highest detection rates in AF (83.5%) and AFL (73.7%). Indication-fulfilling diagnoses were established in 155 patients (39.9%), most frequently in AF (73.4%) and AFL (71.1%), after a median of 4.4 months (IQR 2.4-12.5). Nearly three quarters (72.9%) of diagnoses were made within the first year. ILR findings prompted therapeutic interventions in 156 patients (40.2%), including pacemaker implantation in syncope and rhythm- or anticoagulation-based therapies in AF. AF and AFL independently predicted higher diagnostic yield, while diagnostic yield and AF history predicted ILR-triggered therapy. AF, AFL, stroke/TIA, and AF history were associated with shorter time to first arrhythmia detection. Arrhythmia-free survival differed significantly across indication groups (<i>p</i> < 0.0001) and was lowest in AF and AFL, which demonstrated the highest cumulative incidence of indication-fulfilling arrhythmias. <b>Conclusions</b>: ILRs provide substantial diagnostic and therapeutic value across a broad range of indications. Beyond established uses in syncope and AF, clinically relevant yields were observed in presyncope, risk stratification, and AFL post-ablation, supporting broader consideration of ILRs and optimized patient selection.