Clinical Value of Implantable Loop Recorders in Syncope of Unclear Aetiology: A Single-Centre Experience.

Background The aetiology of syncope can be challenging to undermine because of its sporadic nature. Implantable loop recorders (ILRs) are recommended to be used early in undetermined syncope to establish a symptom-rhythm correlation if cardiac syncope is suspected. The real-world diagnostic yield of ILRs is not well established. Purpose This study aimed 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 ILRs were reviewed by a cardiac physiologist and cardiology consultant to determine their significance. The primary outcome was the total number of cardiac implantable electronic devices (CIEDs) inserted due to ILR findings. Secondary outcomes included (1) a comparison of baseline characteristics between the group of patients who had an arrhythmia detected on ILRs and patients who had no detected arrhythmia and (2) the total number of clinically significant events (CSEs), defined as symptomatic arrhythmia, asymptomatic arrhythmia deemed clinically related to the patients' history of syncope, and the absence of arrhythmia when the patient experienced syncope. Complications of ILR insertion were recorded. Given that normality was not assumed, a non-parametric analysis was utilized 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 group of patients who had an arrhythmia detected on ILRs and patients who had no detected arrhythmia, except for age. One hundred three (47.9%) of the patients had CSEs. Symptomatic arrhythmias were the most common CSEs, out of which a sinus pause of greater than six seconds was the most prevalent arrhythmia. There were no complications that required early explant of the ILR in this cohort. Conclusion ILRs detected a clinically significant arrhythmia and the absence of an arrhythmia in 92 (42.7%) and 11 (5.1%) patients with undetermined syncope, respectively. ILR is a valuable diagnostic tool in this cohort of patients. Further studies looking at its cost-effectiveness would be beneficial.