Predictive factors for pacemaker implantation in patients receiving an implantable loop recorder for syncope remained unexplained after an extensive cardiac and neurological workup.

Background Several previous implantable loop recorder (ILR) studies have shown bradyarrhythmic events requiring a pacemaker implantation in a significant proportion of patients with unexplained syncope (US). The aim of this observational, two-centre, study was to identify the predictive factors for pacemaker implantation in a population of patients receiving an ILR for US with suspected arrhythmic aetiology. Methods Fifty-six patients (mean age 68 years, 61% male) with a history of US and negative cardiac and neurological workup, who underwent ILR implantation, were enrolled. After the implantation, a follow-up visit was undertaken after symptomatic events or every 3 months in asymptomatic subjects. The end-point of the study was the detection of a bradyarrhythmia (with or without a syncopal recurrence) requiring pacemaker implantation. Results After a median ILR observation of 22 months, a clinically significant bradyarrhythmia was detected in 11 patients (20%), of which 9 cases related to syncopal relapses. In the multivariable analysis, three independent predictive factors for pacemaker implantation were identified: an age > 75 years (odd ratio [OR]: 29.9; p = 0.035); a history of trauma secondary to syncope (OR: 26.8; p = 0.039); and the detection of periods of asymptomatic bradycardia, not sufficient to explain the mechanism of syncope, during conventional ECG monitoring (through 24 h Holter or in hospital telemetry), performed before ILR implantation (OR: 24.7; p = 0.045). Conclusions An advanced age, a history of trauma secondary to syncope, and the detection of periods of asymptomatic bradycardia during conventional ECG monitoring were independent predictive factors for bradyarrhythmias requiring pacemaker implantation in patients receiving an ILR for US.