Discussion:
In this retrospective cohort study, an S-ICD extraction rate of 5.9%
was identified over a median follow-up period of 4.4 [2.0-6.5] years
with a median length of implantation of 39.6 [8.3-4.6] months. The
most common indications for S-ICD extraction or removal were need for
bradycardia pacing, infection, and inappropriate shocks due to
oversensing. Both a history of smoking and a higher BMI were
independently associated with S-ICD extraction.
Prior studies have investigated common complications leading to S-ICD
extraction. A pooled analysis of patients from the S-ICD IDE study and
EFFORTLESS registry cited an incidence of S-ICD extraction for pacing
needs of 0.4% and an incidence of infection requiring extraction or
revision of 1.7%.18 A secondary analysis on the
PRAETORIAN trial showed that though S-ICDs caused lower rates of
lead-related complications (1.4% in S-ICDs vs. 6.6% in TV-ICDs,
p<0.001) and systemic infection (0% in S-ICDs vs. 1.2% in
TV-ICDs, p=0.03), they were still shown to cause greater rates of pocket
bleeding (22.2% in S-ICDs vs. 4.1% in TV-ICDs).18,19A large tertiary center study at the University Hospital Münster cited
several complications of S-ICDs including oversensing with inappropriate
shock delivery, need for pacing, hematoma, infection, hypermobility and
ineffective shocks; however, those requiring S-ICD extraction were only
in patients who had a need due to oversensing (incidence, 0.85%), new
pacing requirements (0.57%), ineffective shock (0.28%), and infection
(0.57%) with a total extraction rate of 2.85%. Other complications,
such as pocket hematomas, device position change, and re-programming to
correct oversensing, were corrected via revisions
only.13 In April 2022, the University of Pennsylvania
published a study which cited an incidence rate of S-ICD extraction rate
of 12.9% with a mean dwell time of 20 months. Indications for
extraction cited in this study included infection (incidence rate,
5.12%), improper device sensing (3.90%), pacing need (2.93%), heart
transplantation (1.71%), patient discomfort (0.73%), and other less
common device technical issues.14 These two studies by
the University Hospital Münster and the University of Pennsylvania have
shown a wide variability in rates of S-ICD extraction, demonstrating
that current understanding of the nature of S-ICD extraction is
limited.13,14 The S-ICD extraction rate found in the
current study adds to this limited literature, demonstrating a low S-ICD
extraction rate of 5.9% with appropriate patient selection. The present
study also found that need for bradycardia pacing (1.08%), infection
(1.34%), and inappropriate shocks due to oversensing (1.34%) were the
most common specified indications for extraction, consistent with
findings from prior studies. Other, less common, indications for
extraction included chronic resynchronization therapy needs (0.54%),
patient preference (0.81%), heart transplantation (0.54%), and failure
to shock (0.27%) (Figure 1).
In addition, several studies have also attempted to identify risk
factors associated with S-ICD extraction. The S-ICD Post Approval Study
identified four risk factors of S-ICD-related infection: patients with
previous ICD implantation (extracted for any reason), age ≤ 55 years
old, left ventricular ejection fraction ≤ 30%, and patients with
diabetes.20 Other studies evaluating risk factors for
S-ICD extraction have shown that a history of repeat or multiple
implantation procedures, perioperative fever, use of temporary pacing,
diabetes requiring insulin, end stage renal disease requiring
hemodialysis, crowded operating theaters, immunosuppression,
corticosteroid use, the presence of central lines, and malignancy all
confer a higher risk for infection associated with the new
device.21-25 Results from the current study add to
these prior data and suggest that a history of smoking, elevated BMI,
and prior pocket infection are also associated with S-ICD extraction due
to infection. While elevated BMI is a factor associated with S-ICD
extraction for inappropriate shocks in the present study, it is to be
noted that S-ICD implantation in obese patients can be safe and feasible
if using appropriate technique.26
These results suggest that the S-ICD is usually well tolerated in
appropriately selected patients, but care should be taken during S-ICD
evaluation in patients with a history of smoking or elevated BMI.
Further work must be done to determine whether this study’s findings
regarding rates of, and indications for, S-ICD extraction are
transferrable to other health systems.
Limitations:
The results of this study are limited by its retrospective nature and
focus on a single healthcare system. The present study occurred in a
large metropolitan center and could capture clinical and
sociodemographic characteristics that differ from cohort profiles in
other studies. Additionally, there is wide variability in provider
preferences when it comes to opting for device implantation in patients
who are considered borderline in candidacy for S-ICDs and extracting
devices in the setting of local pocket infection rather than treating
with antibiotic therapy.6 Future analyses may compare
indications for S-ICD vs TV-ICD extraction to provide results which may
shed light on relative benefits of one ICD system in specific patient
populations. Furthermore, device technology improved dramatically during
2010-2022 and could have impacted device-related complication rates and
provider preferences. Finally, contemporary studies examining patient
outcomes and cost effectiveness have sparked an evolution of device
guidelines and expansion of indications for S-ICD implantation, changing
how S-ICDs have been implemented over the years.2, 3,
27 Other factors influencing device selection could be further analyzed
including patient’s socioeconomic status, patient preferences, and
cost.