Real world battery longevity of the subcutaneous implantable cardioverter-defibrillator (S-ICD)
Authors: Van Der Stuijt W , Williams J L , Brisben A J , Koshiol A T , Carter N , Madias C , Ip J E , Link M S , Saba S F 
Published: November 2023

Abstract

Background
Subcutaneous implantable cardiac defibrillators (S-ICDs) protect against sudden cardiac death and avoid transvenous ICD lead complications.

Objective
To investigate S-ICD real-world battery longevity estimates and the impact of device parameters and advisory status.

Methods
Second and third generation S-ICD device longevity labeling is 7.3 years (yr) under normal use (e.g remote monitoring, pre-arrhythmia EGM storage, etc.). De-identified data from S-ICD devices implanted ≥3 months, with recent uploads from the patient devices to the LATITUDE system, were obtained in Nov 2022. For early to mid-life devices (15-100% battery life), longevity estimates were derived from storage time, implant time, and number of high voltage charges (HVC). For late-life devices, longevity estimates were calculated more accurately from battery voltage. Monte Carlo simulations estimated future HVCs. Multivariable maximum likelihood parameter models were used to analyze battery longevity determinants for the overall cohort and for patients who received &gt;1 shock, assuming 1 shock due to conversion testing at implant. Variables were considered clinically significant if univariable difference and multivariable estimate’s magnitude were both ≥0.2 yr. Results are reported in median and interquartile range.

Results
The 32,678 EMBLEM devices had a 2.5 yr [1.2,4.1] device dwell-time with 8.7 yr [8.3,8.9] longevity estimate. Of these patients, 28,544 (87.3%) received ≥1 shocks and 11,480 (35.1%) received &gt;2 shocks, including shocks delivered during conversion testing. Late life devices (n=3091, 9.5%) had a 5.2 yr [4.6,5.9] dwell time. For devices under the battery depletion advisory (n=13,900), the Monte Carlo model does not account for premature battery depletion (PBD), which is projected to impact 11.5% of advisory devices at 5 yrs. Longevity for PBD is 6.6 yr (Q4 2022 product performance report). While all variables except AF trend, AF episodes/yr, and post shock pacing statistically impact device longevity, only advisory status and number of device charges per yr impacted longevity by ≥0.2 yr (Figure, panel A). Patients who received &gt;1 shock have 8.5 yr [8.0,8.8] longevity estimates, vs 8.8 [8.4,8.9] for patients with 0 or 1 shock.
For patients with &gt;1 shock, (Figure, panel B), only advisory status had a ≥0.2 yr impact on longevity in multivariable and univariable analyses. Dwell time, shocks delivered per yr, and system impedance software upgrade impacted longevity by only 0.1 yr in univariable analysis.

Conclusion
Median EMBLEM S-ICD longevity estimate is 8.7 years, which is longer than device labeling. Longevity is reduced by 0.26 years for each device charge. AF monitoring and post shock pacing did not impact device longevity significantly. Low and high voltage impedance as well as remote monitoring transmission impacted longevity by less than 0.1 years. These data are important to consider during shared decision-making.Device Longevity Predictors