LAUSR

BACKGROUND Recent studies using an implantable loop recorder (ILR) have reported on clinical predictors of pacemaker implantation in patients with unexplained syncope. However, atrial fibrillation (AF) was not included as a risk factor; this may be because the precise mechanism of AF (persistent or paroxysmal) has not been explicitly investigated. Thus, this study aimed to investigate the relationship between paroxysmal AF and cardiac syncope recurrence requiring pacemaker implantation in patients with an ILR owing to unexplained syncope. METHODS We included consecutive patients who underwent ILR implantation for unexplained syncope between September 2010 and July 2020. ILR implantation was indicated for syncope that could not be explained even after comprehensive evaluation. RESULTS Overall, 128 patients (72 men; mean age, 62.5 ± 21.1 years) underwent ILR evaluation. Paroxysmal AF was diagnosed before ILR implantation in 32 patients. Bradyarrhythmia with an indication for pacemaker implantation was detected in 33 patients. The number of syncopal episodes (≥ 3) in the previous 2 years, history of paroxysmal AF/asymptomatic sinus arrest, and bundle branch block were independent predictors of pacemaker implantation. Among patients with a history of paroxysmal AF, the PR interval was longer in those who required pacemaker implantation than in those who did not (194.8 vs 168.8 ms; p = 0.0356). CONCLUSIONS Paroxysmal AF is a significant predictor of recurrent syncope, leading to pacemaker implantation in patients with unexplained syncope. Careful history taking of paroxysmal AF is essential, and aggressive use of ILR is recommended to detect bradycardic events.