Real-world battery longevity of implantable loop recorders implanted for unexplained syncope: Results from a large single-center registry.

Background/purpose: Implantable loop recorders (ILR) are increasingly used in cardiac rhythm monitoring and diagnostic work-up of unexplained syncope. ILR battery longevity, according to manufacturers' product performance specifications, typically ranges between 2 and 4 years, but real-world data in this population are lacking.

Methods: This monocentric, prospective, observational study included consecutive patients with unexplained syncope undergoing ILR implantation between October 2007 and 2019. The main purpose was to determine real-world battery longevity of ILRs. Diagnostic yield and relationship between arrhythmogenic diagnosis and duration of ILR monitoring were explored.

Results: The study included 309 patients (59 years [38-73], 49% female) with ILR implantation for unexplained syncope. Median battery longevity was 42 [40-45] months. A total of 99.5% of ILRs reached prespecified battery longevity. The time to end-of-life varied by up to 33 months among the same ILR models. Overall arrhythmogenic diagnostic yield counted 27% (73% sick sinus syndrome, 20% atrioventricular block, and 7% ventricular tachycardia). Median time to diagnosis was 10 [2-25] months, with the latest event at 43 months. The cumulative diagnostic yield for arrhythmogenic event explaining syncope was 4.2%, 6.1%, 9.4%, 14.6%, 19.4%, and 26.7% at 1, 2, 6, 12, 24, and 48 months, respectively. In univariate analysis, first degree AV block and prolonged HV time on EP study were predictors of diagnosis, while QRS duration abnormality borderline missed significance.

Conclusions: Real-world battery longevity of ILRs matched industry projected longevity in 99.5% of patients implanted with ILR for unexplained syncope. A battery longevity of minimum 3.5 years is recommended to maximize the diagnostic yield in this population.