Incidence and parameters associated with early diagnosis in unexplained syncope patients undergoing implantable loop recorder.

INTRODUCTION

ESC Guidelines recommend implantable loop recorder (ILR) use in unexplained syncope patients, given their high diagnostic value compared with external loop recorders (ELR). At times, syncope diagnosis is made shortly after ILR implantation, suggesting ELR may suffice.

PURPOSE: Evaluate prevalence and characteristics of patients with early syncope diagnosis, within <1 month of ILR implant, potentially enabling ELR-based diagnosis.

METHODS

Retrospective cohort of unexplained syncope post-ILR patients in two tertiary centers (2013-2023). Study endpoint was early ILR-based syncope diagnosis. Clinical characteristics associated with early diagnosis were assessed using univariable and multivariable penalized regression analyses.

RESULTS

Study included 106 unexplained syncope post-ILR patients. During a 33-month median follow-up, 49/106 reached an ILR-based diagnosis. Fifteen (30.6%) achieved early diagnosis, including high-degree atrio-ventricular block (AVB) (n = 9), non-arrhythmic syncope (n = 5), and ventricular tachycardia (n = 1). Older age (≥70 y/o), diabetes, and intraventricular conduction delay (IVCD) were significantly associated with early AVB diagnosis in univariable analysis, whereas only age and IVCD remained associated with early AVB on penalized multivariable analysis. Young age (<50 y/o), normal ECG, and normal echocardiography were associated with early non-arrhythmic etiology.

CONCLUSIONS

Our study revealed a 30.6% prevalence of early ILR-based diagnoses, raising the hypothesis that selected unexplained syncope patients might be diagnosed using 1-month ELR. Future studies are needed to confirm these results.