The Italian subcutaneous implantable cardioverter-defibrillator survey: S-ICD, why not?
The Italian subcutaneous implantable cardioverter-defibrillator survey: S-ICD, why not?
Giovanni Luca Botto 0 1 2 11 12 13
Giovanni B. Forleo 0 1 2
Alessandro Capucci 0 1 2
Ennio Pisano 0 1 2 19 20
Antonio Rapacciuolo 0 1 2
Tommaso Infusino 0 1 2
Survey 0 1 2
Indication 0 1 2
Pacing 0 1 2
Ventricular 0 1 2
0 Implantable cardioverter-defibrillator
1 , Antonello Talarico
2 , Paola Ferrari
3 CRM dept, Boston Scientific , 20134 Milan , Italy
4 Cardiology, Ospedale Monaldi , 80131 Naples , Italy
5 Cardiology Department, University of Modena and Reggio Emilia, Policlinico di Modena , 41124 Modena , Italy
6 Cardiology, IRCCS MultiMedica , 20099 Sesto San Giovanni , Italy
7 Cardiology, Ospedale Papa Giovanni XXIII , 24127 Bergamo , Italy
8 Cardiology, Ospedale SS. Annunziata , 87100 Cosenza , Italy
9 Department of Cardiology, Fondazione Policlinico S. Matteo IRCCS , 27100 Pavia , Italy
10 Cardiology, Ospedale S. Anna e S. Sebastiano , 81100 Caserta , Italy
11 Cardiology and Arrhythmology Clinic, Universita Politecnica delle Marche , 60020 Ancona , Italy
12 Cardiology, University of Tor Vergata , 00133 Rome , Italy
13 Unit of Electrophysiology, S. Anna Hospital ASST Lariana , Via Ravona 1, San Fermo della Battaglia, 22020 Como , Italy
14 Department of Cardiovascular Surgery Sant'Anna Hospital , 88100 Catanzaro , Italy
15 Cardiology Unit, 'Card. G. Panico' Hospital , Tricase, 73039 Lecce , Italy
16 Electrophysiology, Ospedale San Martino , 161332 Genova , Italy
17 EP lab, A.S. Ospedaliera S. Croce e Carle , 12100 Cuneo , Italy
18 Cardiology, Casa di Cura Montevergine , Mercogliano, 83013 Avellino , Italy
19 Department of Advanced Biomedical Sciences, Federico II University , 80131 Naples , Italy
20 Cardiology, Ospedale Vito Fazzi , 73100 Lecce , Italy
Society of Cardiology Guidelines. However, the S-ICD is not ideally suitable for patients who need pacing. The aim of this The survey 'S-ICD Why Not?' was an independent initiative taken by the Italian Heart Rhythm Society (AIAC). Clinical characteristics, selection criteria, and factors guiding the choice of ICD type were collected in consecutive patients who underwent ICD implantation in 33 Italian centres from September to December 2015. A cardiac resynchronization therapy (CRT) device was implanted in 39% (369 of 947) of patients undergoing de novo ICD implantation. An S-ICD was implanted in 12% of patients with no CRT indication (62 of 510 with available data). S-ICD patients were younger than patients who received transvenous ICD, more often had channelopathies, and more frequently received their device for secondary prevention of sudden death. More frequently, the clinical reason for preferring a transvenous ICD over an SICD was the need for pacing (45%) or for antitachycardia pacing (36%). Nonetheless, only 7% of patients fulfilled conditions for recommending permanent pacing, and 4% of patients had a history of monomorphic ventricular tachycardia The vast majority of patients needing ICD therapy are suitable candidates for S-ICD implantation. Nevertheless, it currently seems to be preferentially adopted for secondary prevention of sudden death in young patients with channelopathies.
A recommendation for a subcutaneous-implantable cardioverter-defibrillator (S-ICD) has been added to recent European
, Giovanni Russo ,
, Luigi Padeletti
, Mariolina Lovecchio
, Sergio Valsecchi ,
, on behalf of ‘AIAC S-ICD
Why Not’ Survey Investigators
Aims Methods and results
• This nation-wide survey provided original data on the current
practice of implantable cardioverter-defibrillator (ICD)
implantation, and specifically on the adoption of subcutaneous-ICD
• The typical profile of an S-ICD recipient is different from that
of the overall ICD population, in that an S-ICD seems to be
preferred in young patients with channelopathies, mainly in the
context of secondary prevention.
• The most common reasons for preferring a transvenous ICD
over an S-ICD are not supported by specific conditions, such
as the need for permanent pacing or antitachycardia pacing.
Implantable cardioverter-defibrillators (ICDs) are an established
therapy for the prevention of sudden cardiac death (SCD).1
Conventional ICDs rely on transvenous leads to deliver defibrillation
shocks [transvenous-ICD (T-ICD)] and, if necessary, to provide
cardiac pacing. Implantable cardioverter-defibrillator therapy is not free
from procedural complications; these are mainly associated with the
insertion of transvenous leads, e.g. pneumothorax, cardiac
tamponade, and vascular damage.2 Moreover, the long-term risks of
devicerelated complications are of great concern, especially in view of the
improved survival of ICD recipients.3 In order to avoid the risks
involved in accessing the heart via the vascular system and to
overcome recurring problems with transvenous leads, a subcutaneous
ICD (S-ICD) has recently been developed in which the electrode
system is placed entirely subcutaneously, outside the chest. The available
data suggest that S-ICDs are effective in terminating life-threatening
ventricular arrhythmias (VAs).4–6 Consequently, a Class IIa
recommendation for S-ICD has been added to the most recent European
Society of Cardiology (ESC) Guidelines for patients with VAs.1
However, S-ICDs are not suitable for patients who require pacing for
bradycardia or cardiac resynchronization therapy (CRT), nor for
those who suffer from VAs that can easily be terminated by
antitachycardia pacing (ATP).
The Italian survey ‘S-ICD Why Not?’ was an independent initiative
taken by the Italian Heart Rhythm Society (Associazione Italiana
Aritmologia e Cardiostimolazione—AIAC). The primary aim of this
survey was to provide information, including clinical characteristics,
selection criteria, and factors guiding the choice of ICD type, in a
representative sample of consecutive patients who underwent ICD
implantation in Italian clinical practice. Data were analysed to measure
the actual suitability for S-ICD and to evaluate the adoption of this
All Italian centres with experience in S-ICD implantation were invited
to participate. Centres were asked to enrol consecutive patients at the
time of de novo implantation of a new single- or dual-chamber T-ICD or
an S-ICD, in a 3 month row, between
1 September 2015
. At the time of implantation, all patients provided
written informed consent for data storage and analysis. Data were collected
by means of online internet entry. An electronic case report form was
created to capture demographics and clinical characteristics, selection
criteria assessed prior to implantation, and factors guiding the choice of ICD
type. The contents of the form are detailed in Appendix. All centres were
also asked to report the total number of implantation procedures
performed during the observation period, i.e. de novo, replacement and
upgrade implantations of single-or dual-chamber T-ICD, ICD for CRT
(CRT-D), and S-ICD. Secondary prevention of SCD was defined as the
ICD implantation in patients with documented ventricular fibrillation,
haemodynamically not tolerated or recurrent sustained ventricular
tachycardia in the absence of reversible causes.1 The prevalence of conditions
for a recommendation for pacing according to ESC Guidelines8 was
measured to quantify the actual need for permanent pacing.
Descriptive statistics are reported as means 6 SD for normally
distributed continuous variables or medians with 25th–75th percentiles in the
case of skewed distribution. Categorical variables are reported as
percentages. Differences between mean data were compared by means of a
t-test for Gaussian variables, and by the Mann–Whitney non-parametric
test for non-Gaussian variables. Differences in proportions were
compared by means of v2 analysis or Fisher’s exact test, as appropriate. A
Pvalue <0.05 was considered significant for all tests. All statistical analyses
were performed by means of STATISTICA software, version 7.1
(StatSoft, Inc., Tulsa, OK, USA).
Participating centres and study population
The participating centres numbered 33 (the complete list is reported
in Appendix), 29 (88%) of which belonged to the fourth quartile of
the ICD volume distribution (>50 ICDs per year), according to the
Italian ICD Registry of AIAC.
A total of 1371 consecutive ICD procedures were performed
during the 3 month observation period. The procedure was a
replacement or an upgrade of a previous ICD system in 424 (31%) patients
and a de novo implantation in 947 (69%) patients. Of the latter, 369
(39%) were CRT-Ds; the remaining 578 (61%) cases were eligible for
inclusion, i.e. single- or dual-chamber T-ICDs and S-ICDs (Figure 1). In
68 (12%) of these cases, data were not available or consent was not
The remaining 510 patients constituted the population in analysis.
The device implanted was a single-chamber T-ICD in 221 (43%)
patients, a single-lead T-ICD with atrial sensing (VDD) in 8 (2%)
patients, a dual-chamber ICD in 219 (43%) patients, and an S-ICD in 62
Table 1 shows the baseline clinical variables in the overall population
and in patients who underwent implantation of T-ICD and S-ICD.
The two groups differed greatly, in that S-ICD patients were younger,
showed better systolic function and functional status, less frequently
presented with structural cardiomyopathy and more often had
inherited channelopathies. Patients who received an S-ICD also had
less coronary artery disease and fewer comorbidities, and more
frequently received their device for secondary prevention of SCD.
Electrocardiogram on implantation and clinical indications for pacing
The findings of the baseline electrocardiogram (ECG) and the
arrhythmic history of the patients are presented in Table 2. Twenty-eight (5%)
patients presented with sick sinus syndrome, and 8 (2%) with
seconddegree Mobitz II or third-degree atrioventricular block. Overall,
conditions for a Class I recommendation for permanent pacing were present
in 36 (7%) patients. An additional 10 (2%) patients had conditions for a
Class IIa (should be considered) recommendation and 3 (1%) patients for
a Class IIb (may be considered) recommendation.
Analysis of the arrhythmic history revealed the occurrence of
monomorphic ventricular tachycardia (MVT) with syncope in 19
Factors guiding the choice of implantable cardioverter-defibrillator type
The main reasons for choosing a T-ICD over an S-ICD (n ¼ 448)
are reported in Figure 2. Among clinical factors, the current or
expected need for pacing was reported in 203 (45%) patients. Of
these, only 28 had conditions for a Class I recommendation for
permanent pacing on implantation. In 163 (36%) patients, a T-ICD
was preferred owing to the potential need for ATP therapy.
Of these, only nine had a history of MVT with syncope. The
possible development of CRT indications during follow-up, to be
managed in future by device upgrade, was reported as the reason
for preferring a T-ICD in 117 (26%) patients. In this group, only
seven patients had a left bundle branch block, and 25 patients had
a QRS duration >120 ms.
The cost of the system was reported as the reason for preferring a
T-ICD in 172 (38%) patients.
The drivers for S-ICD implantation (n ¼ 62) are reported in
Figure 3. The most frequent were young age, long life expectancy, and
the possibility of avoiding complications.
The results of this survey demonstrate that, in current Italian clinical
practice, the typical profile of an S-ICD recipient is different from that
of the overall T-ICD population, in that an S-ICD seems to be
preferred in young patients with channelopathies, mainly in the context
of secondary SCD prevention. We also found that a high proportion
of patients necessitating therapy for the prevention of SCD might be
suitable candidates for S-ICD implantation. Actually, the most
common reasons for preferring a T-ICD over an S-ICD are not supported
by specific conditions, such as the need for permanent pacing or ATP
As the body of evidence on the safety and efficacy of S-ICD
continues to grow,4–7 a Class IIa recommendation for S-ICD has been
added to the most recent ESC Guidelines for patients with VAs.1
However, as the S-ICD does not provide pacing, it is not ideally
suitable for patients who need pacing therapy for bradycardia support,
CRT, or ATP therapy.
This nation-wide survey analysed the practice of ICD implantation
in a large number of centres. The participating centres constituted a
representative sample (about 40%) of the Italian ICD centres
belonging to the fourth quartile of the ICD volume distribution (>50 ICDs
per year), according to the Italian ICD Registry of AIAC.9 Similarly,
the devices in analysis constituted a sample of about 40% of all ICD
implantation procedures performed in Italy during the observation
The preliminary studies on the therapy with S-ICD mostly included
patients that were considered more suitable, e.g. patients with
difficult venous access, young patients facing a lifetime of device therapy,
or those at particular risk of bacteraemia. Similarly to our S-ICD
population, the mean age at implantation in the pooled analysis of
two large prospective studies [IDE (S-ICD System IDE Clinical
Investigation) and EFFORTLESS (Post-Market S-ICD Registry)]6 was
as low as 50 years. Interestingly, compared with published studies we
observed an even higher proportion of secondary prevention
indications (52% vs. 30%) and a higher mean value of ejection fraction (49%
vs. 39%). This demonstrates that the patients currently receiving
SICD in Italian clinical practice represent a very selected group out of
the general population currently indicated for ICD and thus
potentially suitable for S-ICD, according to the most recent guidelines.1
In order to quantify the actual need for permanent pacing in the
study population, we prospectively looked for the prevalence of
conditions for a Class I recommendation for pacing on implantation; we
found a proportion of 7%, whereas criteria for a weaker
recommendation were met by an additional 3% of patients. Considering the
possibility of developing the need for pacing after implantation, de Bie
et al.10 performed a single-centre retrospective study on patients
without a pre-existing indication for pacing. Among predictors of the
unsuitability for an S-ICD, they found a prolonged QRS duration,
which was present in 12% of patients in our population. Similarly, in a
post hoc analysis of the MADIT-II study,11 it was shown that the need
for pacing or CRT was very low (<2% per year), during follow-up in
patients with an ICD indication, and even lower in those with normal
PR interval (PR >200 ms was present in 12% of patients in our
survey). Nonetheless, the relationship between right ventricular pacing
and adverse outcomes in patients with ICD was previously shown,12
thus providing the rationale for implementing strategies and pacing
modalities that minimize ventricular pacing.13 Similarly, it has been
suggested to reduce atrial pacing, as an increasing risk relationship
was shown between its cumulative percentage and the severity of
atrioventricular decoupling in ICD patients.14
In this study, the proportion of patients with a CRT indication was
39% of all consecutive patients undergoing de novo ICD implantations.
However, the possible development of CRT indications after
implantation, i.e. need for device upgrade to a CRT-D system, was
previously shown to be very rare (0.3% at 1-year follow-up, and <6% of
the cases of S-ICD unsuitability) and not associated with additional
risks.10 Nonetheless, the best strategy for ICD candidates considered
at risk of the future development of CRT-D indications is still unclear,
mainly in the light of the well-known complications associated with
transvenous device replacement and upgrade.15 Indeed, de novo
CRT-D implantation after removal of an S-ICD could be safer than
upgrading a single- or dual-chamber T-ICD to a CRT-D system.
The need for ATP therapy constitutes an additional potential
barrier to the adoption of S-ICD. However, the role of ATP therapy has
recently been questioned. ATP utilization has increased significantly
in the last decade without notable effects on shock incidence and
survival.16 In the delayed-therapy arm of the Multicenter Automatic
Defibrillator Implantation Trial—Reduce Inappropriate Therapy
(MADIT-RIT), a primary prevention trial, the 1-year incidence of
pacing therapies was only 4%, with low rates of appropriate shocks and
unnecessary ATP therapies.17 Similarly, the PainFree SST secondary
prevention trial18 showed recently a 1-year rate of ATP therapies
equal to 5.4%, adopting a prolonged detection programming strategy.
Current guidelines provide recommendations for customized ATP
programming in cases of previous MVT.19 In our study, the
prevalence of unstable MVT was 4%. This kind of patient is suitable for
different approaches: early implantation of a T-ICD, a hybrid approach
by combining S-ICD implantation and catheter ablation,20 or even
SICD followed by possible additional implantation of the upcoming
leadless system capable of delivering ATP therapy.21 Additional
investigations are warranted in order to compare strategies and measure
Overall, our results on S-ICD suitability seem to be in agreement
with preliminary S-ICD experiences. In a recent analysis of 882
patients who received an S-ICD, extraction of the S-ICD because of the
need for pacing occurred in four patients (0.4%) over 22 months.6
Specifically, one patient developed a new bradycardia indication, one
device was extracted in order to upgrade to a CRT, one patient
needed ATP, and one patient with arrhythmic storms underwent
replacement with a T-ICD in an attempt to suppress arrhythmias by
means of overdrive pacing.
Among factors for preferring a transvenous ICD over an S-ICD,
the need for dual-chamber detection algorithms was reported in 6%
of patients, suggesting that this may not be a relevant concern.
Plausibly, this can be explained by the inconclusive literature on the
superiority of dual-chamber ICD in reducing inappropriate shocks.
However, it should be considered that in our population a
dualchamber ICD was adopted in 43% of patients, in the majority of cases
in the absence of an indication for pacing. This is an additional finding
confirming that patient characteristics play a small role in the decision
to place a specific ICD type.
In addition to clinical considerations, in this survey the cost of the
system proved to be an additional barrier to the adoption of S-ICD in
current clinical practice. However, this may be specific to the Italian
situation and not applicable to other healthcare systems.
In summary, our results seem to suggest that a treatment gap
exists between the guidelines and the clinical care of patients.
Ongoing studies on the S-ICD will serve to confirm the efficacy of
the therapy22 and to build confidence in its usefulness. The addition
of S-ICD to the tools for treating patients at risk of SCD has been a
significant advance. The application of strategies to facilitate the
implementation of guidelines (e.g. clinical decision support and
reminder systems) could enhance the use of a novel recommended
therapy, such as the S-ICD, thereby improving outcomes.
Our findings might be affected by a bias, in that the participation
in present survey was limited to centres with experience in S-ICD
implantation. In particular, data about the therapy adoption and the
factors guiding the choice of device could have been different if a
larger sample of implanting centres was considered. Moreover, our
results may not be applicable to other populations with different
underlying demographics or to other healthcare systems. In addition,
although the importance of consecutive inclusion was emphasized
repeatedly to all participants, we cannot confirm that all patients were
included consecutively. Similarly, the accuracy of the data was not
audited. In addition, it should be mentioned that some patients
suitable for S-ICD according to the absence of a pacing indication or
previous MVT may be ineligible according to the manufacturer’s surface
ECG screening template. A previous study that explored this issue
found a proportion of 15% of patients who did not satisfy ECG
The present nation-wide survey revealed that an S-ICD was
implanted in 12% of patients with no CRT indication, and was adopted
preferentially for secondary prevention of SCD in young patients
with channelopathies. Moreover, although the most common
reasons for preferring a T-ICD over an S-ICD were the need for
permanent pacing or ATP therapy, at the time of ICD implantation, only
7% of patients fulfilled conditions for Class I recommendation for
permanent pacing. An additional 4% of patients presented with a
history of unstable MVT that might have been treatable with ATP. The
vast majority of patients needing therapy for SCD prevention might
therefore be suitable candidates for S-ICD implantation.
Conflict of interest: M.L. and S.V. are employees of Boston
Scientific. The other authors report no conflicts.
This was an independent study. No external funding was received for this
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