Abstract Body (Do not enter title and authors here): Background: Subcutaneous insertable cardiac monitors (ICM) have the capability to detect tachycardia (tachy) which are occasionally ventricular tachycardia and fibrillation (VT/VF).

Objective: We investigated the incidence of spontaneous VT/VF in patients (pts) implanted with an ICM and clinical history (Hx) of heart failure (HF) with reduced or preserved left ventricular ejection fraction (LVEF).

Methods: Pts with Hx of HF admissions who were implanted with an ICM were identified from the aggregated and de-identified Optum^® electronic health record (EHR) database during 2007-2021. The ICM collected data were merged with EHR data to create a de-identified database of real-world patients. Pts were included if they had ≥180 days of device follow-up. ICMs detect tachy if 30 of 40 recent intervals are shorter than 260 ms or if 16 consecutive intervals are shorter than tachy interval (nominally 340 ms) that is adjusted with age. Tachy episodes were first classified as VT/VF, SVT, or oversensing using an artificial intelligence (AI) model that was pre-trained using over 50K manually adjudicated ICM detected tachy episodes. If the AI model output probability for VT/VF was greater than 0.2, then those episodes were manually adjudicated for true incidence of non-induced spontaneous VT/VF. The Kaplan-Meier incidence curves for VT/VF incidence are reported as a function of reduced vs preserved ejection fraction.

Results: A total of 1020 ICM pts with Hx of HF admission were identified from the real-world dataset. In 889 pts (87%) with available LVEF, 394 (44%) had EF<50%, and 495 (56%) had EF≥50%. In 296 pts (29%) with available NYHA class, 13%, 43%, 38%, 6% were class I, II, III, and IV respectively. Pts had an avg. age of 68±13 yrs with 52% being males and Hx of hypertension in 95%, diabetes in 56%, coronary artery disease in 75%, atrial fibrillation in 57%, stroke/TIA in 51%, and renal dysfunction in 53%. A total of 911 pts with an average follow-up of 25.8 months were included. A total of 90 tachy episodes (41 pts) were adjudicated as true VT/VF. Incidence of true VT/VF, as detected by an ICM over 36 months of follow-up, was estimated to be 5.6% with VT/VF incidence being 8.2% vs 3.8% in HF pts with reduced versus preserved LVEF (Figure).

Conclusion: Incidence of VT/VF over 3 years of follow-up was estimated to be more than 5% in pts with ICM and Hx of HF events. VT/VF incidence was higher in HF pts with reduced versus preserved LVEF in this real-world cohort.