Role of the implantable loop recorder in clinical practice: insights on indications, diagnostic yield and therapeutic implications from a single, high volume, tertiary care centre experience

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. INTRODUCTION: Besides the established class I indication for the evaluation of patients with recurrent syncope of uncertain origin, implantable loop recorders (ILRs) have been increasingly used for other diagnostic purposes (e.g. detection of atrial fibrillation (AF) following cryptogenic stroke). PURPOSE: To describe the main indications to ILR and to investigate procedural parameters, outcomes and diagnostic yield of ILR in a single, high-volume tertiary care centre. METHODS: All patients undergoing ILR implantation between November 2007 and April 2022 were consecutively enrolled in this study. Clinical characteristics of patients, procedural data and outcomes were collected. The indications to ILR implantation were divided into four categories: 1) AF detection in patients with recent cryptogenic stroke or peripheral thromboembolism [CRYSP], 2) recurrent syncope of uncertain origin [RSUO], 3) monitoring of ventricular arrhythmic events [VAE] in patients with predisposing cardiomyopathy/channelopathy, 4) monitoring of AF burden or relapse [AFB]. The main endpoint of the study was the diagnostic yield (number of definitive diagnoses made) and the time to diagnosis following ILR implantation. The occurrence of acute or subacute complications was used as a secondary safety endpoint. RESULTS: Overall, 1442 patients underwent ILR implantation (mean age 65 years, 43% female). The two main indications to ILR were AF detection following CRYSP and RSUO (42% and 34% of all implantations respectively, table 1). The commonest site of implantation was the left parasternal position (902 patients, 63%), median procedural time was 20 minutes (IQR 15-25). During a median follow-up of 397 days (134-1094), infections requiring ILR extraction or pocket revision occurred in 13 patients (0.9%). A definitive diagnosis was achieved in 500 (35%) patients after a median time of 206 days (IQR 60-533) [table 1 shows details and action taken following diagnosis for each indication subgroup]. At multivariable analysis, age and PR interval duration were significantly associated with the need for PM/ICD implantation among patients receiving ILR for RSUO whilst age was associated with AF detection among those with CRYSP (table 2). CONCLUSIONS: In this cohort of patients use of ILR was associated with a good diagnostic yield regardless of the initial indication, triggered timely therapeutic actions and was overall safe. [Figure: see text] [Figure: see text]