LEADLESS PACEMAKER AND SUBCUTANEOUS ICD

SUBCUTANEOUS ICD’S &
LEADLESS PACEMAKER
SUBCUTANEOUS ICD'S & LEADLESS
PACEMAKER

OUTLINE
• INTRODUCTION
• S-ICD
• LEADLESS PACEMAKER
• FUTURE PERSPECTIVE
• SUMMARY
PACEMAKER

INTRODUCTION
• Sudden cardiac death (SCD) resulting from cardiac arrhythmia is the
world's leading cause of cardiovascular mortality, accounting for
over 50 percent of cardiovascular deaths worldwide
• Conventional transvenous ICD (TV-ICD) systems come with the
inherent drawbacks of transvenous leads, including:
– Risks at the time of insertion – cardiac perforation, pericardial effusion,
cardiac tamponade, hemothorax, pneumothorax
– Delayed risks over the lifetime of the device – intravascular lead
infection, lead failure
• The subcutaneous ICD (S-ICD) has been developed in an attempt to
minimize some of the limitations of TV-ICD systems by avoiding
endovascular access entirely
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REQUIREMENTS FOR AN ICD SYSTEM
Effective Defibrillation
• Deliver adequate energy with an adequate safety margin to defibrillate.
• Deliver this energy in a sufficiently short time to minimize syncope while
still allowing the possibility of spontaneous termination.
Effective VT/VF Sensing
• Appropriate sensing of ventricular events at high rates while not oversensing
non-ventricular/non-cardiac events.
• Adequately distinguishing VT/VF events from supraventricular arrhythmias.
• Safe ICD System Implantation.
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PACEMAKER
The current S-ICD was originally conceived in
1994 by Dr. Gust Bardy
July 28, 2008 First Human Implant by Dr.
Margaret Hood and Dr. Warren Smith (Duke
EP Alum) in New Zealand

PACEMAKER
N Engl J Med 2010;363:36-44.

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PACEMAKER
Weighs 145 g
Volume 69 ml
Battery 5 years
Data per episode 120 sec
Max data storage 24episodes

COMPONENTS OF S-ICD
• As with a standard transvenous ICD (TV-ICD), the S-ICD is comprised of
a pulse generator and a shocking lead
• The pulse generator is implanted in a subcutaneous pocket in the left
lateral, mid-axillary thoracic position.
• The subcutaneous lead, which toward its terminal end contains an 8-cm
shocking coil electrode, is tunneled from the pulse generator to a position
along the left parasternal margin.
• There are proximal and distal sensing electrodes within the lead that flank
the 8-cm shocking coil.
• The distal electrode sits just below the sternal notch, and the proximal
electrode lies just above the xiphoid process.
• The cardiac rhythm is detected via a wide bipole between the two sensing
electrodes or between one of the sensing electrodes and the pulse generator
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S-ICD IMPLANTATION
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S-ICD
Sensing Lead Vectors
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FUNCTIONING OF S-ICD
• The S-ICD system detects changes in ventricular rate by using modified
subsurface electrocardiography through either a primary, secondary, or
alternate vector
• The device uses proprietary algorithms to automatically determine the
optimal sensing vector based on an R- to T- wave ratio that avoids double
QRS counting or T-wave oversensing.
• It measures the heart rate as the rolling average of 4 consecutive sensed
intervals, recognizing ventricular fibrillation (VF) when 18 of 24
consecutive sensed events exceed a pre-determined nonprogrammable
detection zone limit.
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EFFECTIVE SENSING
• Primarily rate sensing (common to all ICDs)
SICD Arrhythmia Discrimination Criteria
• Correlation between current beat and stored template – if <
50% favors VT
• Continuous beat-to-beat correlation – if polymorphic favors
VT –
• Continuous beat-to-beat QRS width – if wide QRS is noted
during monomorhpic relationship, favors VT
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• The device then charges its capacitors to deliver a biphasic-waveform
defibrillating pulse of up to 80 J.
• The S-ICD can provide post-shock bradycardia ventricular pacing support
for 30 s, activated only after more than 3.5 sec of post shock asystole.
• If vt or vf persists following the initial shock, the device will reverse
polarity between the electrodes and deliver subsequent shocks.
• The s-icd will deliver a maximum of five shocks for a single episode of a
ventricular arrhythmia.
• It can reverse shock polarity if the initial shock is unsuccessful
• During an event, the s-icd will store the electrocardiogram (ecg) tracing for
subsequent review
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Eligibility For S-ICD
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Placement of the surface electrodes during screening
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When To Consider The S-ICD
There are no formal guidelines for the selection of an S-ICD system.
1. S-icds may be considered in younger patients due to the expected
longevity of the implanted leads and a desire to avoid chronic
transvenous leads.
2. S-icd system might be an appropriate consideration in patients with
hypertrophic cardiomyopathy, congenital cardiomyopathies, or
inherited channelopathies.
3. S-icds may also be considered in patients at high risk for bacteremia,
such as patients on hemodialysis or with chronic indwelling
endovascular catheters.
4. Patients with challenging vascular access or prior complications with
tv-icds may be considered for s-icds.
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WHEN TO AVOID THE S-ICD
S-ICDs provide neither antitachycardia pacing as a therapy for ventricular
arrhythmias nor continuous bradycardia pacing in the event of symptomatic
bradyarrhythmias.
• Recurring ventricular tachycardia (vt) that is reliably terminated with
anti-tachycardia pacing (atp)
• In patients with sinus node dysfunction, atrioventricular block.
• S-ICD s are not indicated in patients requiring biventricular pacing for
cardiac resynchronization therapy.
• Unipolar pacing from a coexisting device is contraindicated
PACEMAKER

S-ICD Candidate Selection +
FAVORABLE FACTORS RELATIVE CONTRAINDICATIONS
Young and active Recurrent monomorphic VT
CHD that limits lead placement Bradycardia requiring pacing
Indwelling catheters Indication for CRT
Immunocompromsed High risk for VT( sarcoidosis,
ARVD)
Inherited channelopathies Preference for remote
monitoring
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+S-ICD :is it the future? Chapter 159; cardiac update by dr.o.sai satish
md dm

EFFICACY OF S-ICD
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COMPARISON WITH TV-ICD
• In the START (Subcutaneous versus Transvenous Arrhythmia Recognition
Testing) trial, which compared simulated sensing performance of the S-ICD
with that of standard TV-ICDs in 64 patients, both S-ICD and TV-ICD
devices were successful in detecting 100 % of ventricular arrhythmias.
• In this trial, the S-ICD also had greater success in discriminating
supraventricular tachycardias from ventricular tachycardias (VTs) (98 % S-
ICD versus 76.7 % for single-chamber TV-ICD versus 68 % for dual-
chamber TV-ICD)
• In a case-control study of 69 patients with S-ICD who were matched with
control patients with TV-ICDs, successful conversion of induced
ventricular fibrillation (VF) occurred in 89.5 percent of initial shocks
delivered by S-ICD (95.5 percent including reverse polarity defibrillation),
compared with 90.8 percent success in conversion with traditional TV-ICD
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PRAETORIAN Trial
• Currently is underway and should be the first multicenter, randomized trial
to directly compare S-ICDs with TV-ICD.
• The study is designed to enroll a total of 700 patients, powered to prove
non-inferiority of the S-ICD with the composite primary endpoint being
inappropriate shocks and ICD-related complications, along with secondary
endpoints of shock efficacy and patient mortality
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POTENTIAL COMPLICATIONS
PACEMAKER

Inappropriate Shocks
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• Most common and concerning complications seen with s-icds,( 4 to 16%).
• The majority of inappropriate shocks are due to oversensing (85%) most frequently
of cardiac signals (94% of over sensed episodes) mainly consisting of T waves or
low amplitude signals.
• Most common cause for inappropriate shocks from S-ICD’s is oversensing of t-
waves, for tv-icd systems, due to supraventricular arrhythmias or lead malfunction .
• Inappropriate sensing of myopotentials from chest muscle activity may also be a
source of inappropriate shocks.
• Inappropriate shocks are more likely to occur in younger, physically active patients,
who are also those commonly selected for placement of an S-ICD system.

Proportion of appropriate and inappropriate therapies and their
etiologies
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• A preimplantation surface electrocardiogram (ECG) screening tool has also
been developed to minimize the number of patients at risk for inappropriate
shock due to T-wave oversensing error.
• The tool identifies patients who have large and or late T-waves relative to
the QRS using three vectors that mimic the device sensing vectors.
• Studies suggest that between 8 and 15 percent of patients are ineligible for
an S-ICD due to susceptibility to T-wave oversensing and thus high risk of
inappropriate shocks.
PACEMAKER

• The programming of an arrhythmia discrimination zone can reduce the
frequency of inappropriate S-ICD shocks due to supraventricular
arrhythmias.
• Inappropriate shocks due to oversensing may be minimized by appropriate
patient screening prior to implantation and appropriate device programming
following implantation.
PACEMAKER

Pocket Infections
• 1 to 10 % of S-ICD recipients , 1 to 4% requiring device explantation.
• The rate of pocket infection with the S-ICD exceeds that with the T-ICD.
• The 3 incisions required for s-icd implantation provide a greater probability
for bacterial entry.
• The increased bulk of the s-icd may exert more pressure on the skin and
increase the risk of tissue necrosis and erosion.
• S-icd infections can be treated conservatively with a course of antibiotics.
• S-icd device does not contain any endovascular leads, the risk of infection
causing bacteremia/endocarditis is reduced.
• The infection rate may decrease with more operator experience,
introduction of smaller pulse generators, and use of a 2-incision technique
for system implantation.
PACEMAKER

Lead Movement
• Lead dislodgement or migration had been noted to occur in( 3 to 11%).
• Lead dislodgement or migration results from vigorous physical activity occurring
without adequate fixation of the parasternal lead.
• Requires reoperation to reposition the lead.
• Suture sleeves are now used to anchor the proximal segment of the parasternal lead
PACEMAKER

• Other less common complications that may require reintervention may
include
– skin erosion,
– premature battery depletion,
– explantation due to need for antitachycardia/bradycardia pacing or a new indication for
resynchronization therapy
• Complication rates have been shown to improve as operators and centers
gain experience with S-ICD implantation.
PACEMAKER

APPROACH TO S-ICD DEVICE SELECTION
1. Does the patient have an indication for antitachycardia pacing or known
to respond to antitachycardia pacing?
2. Does the patient have an indication for standard transvenous pacing?
3. Is the patient a candidate for biventricular pacing and cardiac
resynchronization therapy?
4. Is the patient relatively young with anticipated prolonged ICD therapy or
multiple ICD systems in the course of one’s lifetime?
5. Does the patient have other indwelling venous catheters or leads?
6. Is the patient at high risk for systemic infection?
PACEMAKER

Algorithm for choosing subcutaneous ICD
PACEMAKER

Advantages of S-ICD
1. obviates some of the mechanical complications associated with
transvenous lead implantation (eg, cardiac perforation leading to
pericardial effusion and cardiac tamponade, hemothorax, pneumothorax,
endovascular lead infection)
2. solid core design of the S-ICD lead and its lack of exposure to the
repeated mechanical stresses of myocardial contraction improves lead
durability when compared with transvenous ICD (TV-ICD) leads.
3. No transvenous lead
4. Fluoroscopy not required for implant
5. Ultra far ﬁeld signals for arrhythmia discrimination.
PACEMAKER

6. The S-ICD system delivers energy to the heart in a more homogenously
distributed pattern than the endocardial shock delivered by the T-ICD .
7. Endocardial shocks produce significant troponin release; shocks delivered
from subcutaneous electrodes do not.
• The uneven distribution of energy across the myocardium after an endocardial
shock can produce voltage gradients and electroporation resulting in
myocardial stunning and damage.
• Myocardial injury and stunning associated with ICD discharge might explain
the increased mortality seen in heart failure patients receiving multiple shocks.
PACEMAKER

Limitations of S-ICD
1. Does not provide pacing for bradyarrhythmias
2. CRT is not available
3. No ATP
4. No atrial lead for monitoring of atrial tachyarrhythmias
5. No remote monitoring
6. Larger size
7. Long charge times
8. Battery life is shorter approximately 5 years
9. NO mortality data or long term experioence
10. 80J shock
11. Inappropriate shocks, might be associated with reduced longevity and
quality of life
PACEMAKER

Future of S-ICD
• The S-ICD is a promising technology that could fill a gap in the treatment
of ventricular tachyarrhythamias by extending this vital therapy to patients
in countries where the facilities to implant T-ICDs are not available.
• Indeed, if this new device that is based on simplicity and ease of implan-
tation can be deployed at less cost and with non inferior clinical outcomes,
it could become a breakthrough therapy.
• But it is a new technology and, as such, requires the scrutiny of a
comparative effectiveness trial.
• Only then can we tell patients that it is as effective as existing ICDs.
Otherwise, a fully informed patient who is offered this device today should
not want one.
PACEMAKER

CONCLUSIONS
.
• The clinical experience from the introduction of the S-ICD system
underscores its role as a reliable alternative for preventing SCD.
The exclusive use of a subcutaneous lead for sensing and
defibrillation represents the greatest advantage of this novel
technology; the S-ICD eliminates the drawbacks associated with
endovascular electrodes. However, the lack of demand bradycardia
or anti-tachycardia pacing limits its utility in patients with
conduction system disease or pace-terminable VT. The first-
generation device raises concerns about an increased risk of pocket
infection, battery longevity, and inappropriate shocks compared
with the newest T-ICD systems. No study to date directly compared
the T-ICD and the S-ICD in patients indicated for ICD therapy as
primary prevention of SCD. The clinical experience does suggest
that its use be considered in relatively
PACEMAKER

LEADLESS PACEMAKER
PACEMAKER

• In response to the limitations of both transvenous and epicardial pacing
systems, efforts have been made to develop leadless cardiac pacing
systems.
• leadless systems have a self-contained system which includes both the
pulse generator and the electrode within a single unit that is placed into the
right ventricle via a transvenous approach.
• Leadless cardiac pacing systems have been approved for use in Europe
since 2013, and in April 2016, the first leadless cardiac pacing system was
approved for use in the United States
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PACEMAKER
MICRA
NANOSTIM

PACEMAKER
NANOSTIM LEADLESS CARDIAC PACEMAKER

MICRA TRANSCATHETER PACING SYSTEM
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CLINICAL TRAILS
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LEADLESS Trial
• The, a first-in-human, single-arm, multicenter study of the safety and
clinical performance of the LCP.
• patients were considered eligible if they had indications for single-chamber,
right ventricular pacing (VVI [R]).
Indications included:
1) permanent atrial fibrillation with atrioventricular block (including atrial
fibrillation with a slow ventricular response).
2) normal sinus rhythm with second- or third-degree atrioventricular block
with a low level of physical activity or short expected life span.
3) sinus bradycardia with infrequent pauses or un- explained syncope with
electrophysiologic findings.
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 Thirty-three patients were enrolled in the LEADLESS trial.
 The implantation success rate was 97% (32 of 33 patients),
 the mean procedure duration was 28 +/-17 min
 the overall complication-free rate was 94% (31 of 33 patients).
The 1-year follow-up results of the LEADLESS trial were recently reported
and demonstrated that:
1) performance measures (pacing threshold, impedance, and sensing)
remained stable;
2) there were further no complications related to the device (beyond the
index procedure);
3) there were no premature battery depletions or under/oversensing issues;
4) adequate rate response, defined as 80% of the predicted maximal heart
adjusted for age, was observed in those patients for whom it was activated
PACEMAKER

PACEMAKER
n engl j med 373;12 :September 17, 2015

• In the leadless II trial, a prospective, non-randomized, multicenter trial of
self-contained leadless device (nanostim leadless cardiac pacemaker , st.
Jude medical ) enrolled patients with an indication for single chamber RV
pacing.
• 93 % met the primary efficacy endpoint of acceptable pacing capture
threshold (<2v at 0.4 milliseconds) and sensing amplitude (R wave ≥5 mv).
• The primary safety endpoint (freedom from device-related adverse events)
was also achieved in 93 percent of patients (280 out of 300).
• On the basis of the observed device-use conditions (e.g Heart rate,
percentage of ventricular pacing, and pacing impedance) of the 300-patient
cohort followed for 6 months, the battery longevity is estimated to be
15.0±6.7 years
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Complications of conventional and leadless pacemaker
LEADLESS PACEMAKER (6.7%)
• Device dislodgement in 1.7%
• Cardiac perforation in 1.3%
• Elevated pacing thresholds requiring device retrieval and re implantation in
1.3%
• Vascular complications in 1.3%
CONVENTIONAL VENTRICULAR PACEMAKERS (3.2%)
• Pneumothorax in 1.1%
• Lead dislodgement in 0.8%
• Infection in 0.5%
• Cardiac perforation 0.6 to 5.0%
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LIMITATIONS
• This pacemaker was safely retrievable; however, most of the devices that
were retrieved were explanted within 1 year after implantation, and there
are few data on the feasibility of the removal of leadless cardiac
pacemakers beyond this point
• This study was limited by the observational design that did not directly
compare the leadless cardiac pacemaker with conventional pacemakers,
thereby limiting our ability to draw conclusions about the relative safety
and efficacy of these devices.
• Furthermore, the mean follow-up was only 6 months, again limiting
understanding of long-term efficacy and pacemaker-related complications,
particularly in comparison with conventional pacemaker systems.
PACEMAKER

PACEMAKER
n engl j med 374;6 February 11, 2016

• In the Micra Transcatheter Pacing Study, which enrolled 725
patients with an indication for single chamber RV pacing, the
leadless device was successfully placed in 719 patients (99.2
percent).
• The primary safety end point was freedom from system-related or
procedure- related major complications. The primary efficacy end
point was the percentage of patients with low and stable pacing
capture thresholds at 6 months (≤2.0 V).
• The Kaplan-Meier estimate of freedom from device-related adverse
events at six months was 96 percent.
• The second primary endpoint, <2V mean pacing capture threshold at
0.24 millisecond pulse width, was assessed at six months in a subset
of 297 patients, among whom 292 (98.3 percent) reached the
primary endpoint
PACEMAKER

POTENTIAL BENEFITS OF LEADLESS CARDIAC PACING
1. Mitigates the risk of complications of transvenous lead.
2. Inherent benefit of preventing intrasystem connection errors because the
pulse generator pace/sense electrodes are a single unit.
3. The single-component systems do not require a surgical
incision/subcutaneous pocket, which mitigates the risk of surgical
complications and may provide a more favorable cosmetic profile.
4. Smaller size.
PACEMAKER

5. LCP have projected battery longevity that is comparable to that of
standard single-chamber transvenous pacemakers.
Less internal current drain ,approximately 1mA
The lack of “lost” energy through the lead
High-density lithium carbon monofluoride battery
Use of energy-efficient conductive (vs. Inductive) telemetry
6. The LCP and TPS are also believed to be safe for use with magnetic
resonance imaging, because of their lack of ferrous material
7. There is potentially less radiation exposure for the implanting physician.
PACEMAKER

POTENTIAL LIMITATIONS OF LEADLESS CARDIAC PACING
1. Most important limitation is their ability to perform only single-chamber
pacing, specifically right ventricular pacing , not appropriate for patients
with sinus node dysfunction.
1. Chance of device embolization with single- component systems.
1. The optimal fixation mechanism, with regard to both chronic performance
and the need for future extraction, remains to be seen.
1. The portion of the device that interacts with the endocardium has a wider
diameter, which has raised the possibility of proarrhythmia.
2. Although leadless pacemakers are reportedly retrievable acutely, the
ability to remove a chronically-implanted device remains untested in
humans.
PACEMAKER

5. The larger caliber of the delivery units has the potential to increase
complications related to either the femoral access site or catheter
manipulation within the right ventricle.(Large venous 24-F for the TPS and 18-F
for the LCP)
6. As such, the strategy for device management (retrieval vs. Abandonment)
once the battery has been depleted remains to be determined.
7. The leadless cardiac pacemaker also cannot provide electrographic data.
8. Higher chance of Perforations related to leadless cardiac pacemakers due
to the relatively large diameter of the device.
9. Special training will be required to develop proficiency in lcp
implantation.
PACEMAKER

CONCLUSIONS
Leadless cardiac pacing holds promise as a long-term permanent cardiac
pacing option for patients requiring single ventricle (RV only) pacing.
• However, longer-term follow-up is needed to assess the safety and efficacy
of these devices.
• The potential for and incidence of long-term deleterious effects of pacing
only the RV will also need to be assessed.
• Randomized clinical trials will be necessary to definitively determine
whether the theoretical benefits of leadless systems will be superior to
those of conventional pacemakers both from a safety perspective and in
terms of long-term pacing and sensing performance.
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FUTURE PERSPECTIVE
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SUMMARY
• S-ICD
• LEADLESS PACEMAKER
PACEMAKER

THANK YOU
PACEMAKER

LEADLESS PACEMAKER AND SUBCUTANEOUS ICD

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