Background The aetiology of syncope can be challenging to undermine because of its sporadic nature. Implantable loop recorders (ILR) are recommended to be used early in undetermined syncope to establish a symptom – rhythm correlation if cardiac syncope is suspected. Real world diagnostic yield of ILR is not well established.

Purpose To evaluate the diagnostic yield of ILR devices in patients with undetermined syncope.

Methods This single centre, retrospective study, reviewed the electronic medical records of all patients, who underwent ILR insertion for syncope from January 2017 to June 2022. Abnormal rhythm strips on ILR were reviewed by a cardiac physiologist and cardiology consultant to determine its significance.

Primary outcome was the total number of cardiac implantable electronic devices (CIEDs) inserted due to ILR findings. Secondary outcomes included (1) a baseline characteristics comparison between the group of patients who had an arrhythmia detected on ILR and patients who had detected no arrhythmia, and (2) the total number of clinical significant events (CSEs), defined as a symptomatic arrhythmia, an asymptomatic arrhythmia deemed clinically related to the patients’ history of syncope, and the absence of an arrhythmia when the patient experienced syncope. Complications of ILR insertion were recorded.

Given that normality was not assumed, a non-parametric analysis was utilised to compare baseline characteristics.

Results A total of 215 patients were included in this study, of which 43 (20%) had a CIED inserted due to ILR findings. Baseline characteristics were similar between the groups except age (Table 1).

103 (47.9%) of the patients had a CSE (Figure 1). Symptomatic arrhythmias were the most common clinically significant events, out of which a sinus pause of greater than 6 seconds was most prevalent arrhythmia. There were no complications that required early explant of the ILR in this cohort.

Conclusion ILR detected a clinically significant arrhythmia and the absence of an arrhythmia in 42.7% and 5.1% of patients with undetermined syncope, respectively. ILR use is a valuable diagnostic tool in this cohort of patients. Further studies looking at cost-effectiveness would be beneficial.

Conflict of Interest Nil