AICD programming

Programming AICD
Presenter
Dr Praveen Gupta
Moderator
Dr Raja Selveraj
Department of Cardiology
05.09.2017
JIPMER
Pondicherry
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Detection and treatment of ventricular tachyarrhythmias by an ICD involves a series of
sequential steps, each of which provides an opportunity to minimize unnecessary shocks
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Optimal ICD programming
 Programming of the detection rate
 Detection duration
 Antitachycardia pacing (ATP)
 Discriminate supraventricular tachycardia (SVT) from VT
 Programming to minimize the sensing of noise
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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.

Rate and Duration for Initial Detection
 ICDs detect VT/VF if the RR intervals are shorter than the detection interval for a
programmable number of intervals or duration
 An increased detection rate or prolonged duration is the most robust programming tool for
prevention of unnecessary ICD therapy
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Primary prevention patients experience faster VTs with rates less likely to overlap SVT than secondary prevention
patients Permits programming of faster VT rate cutoffs, ,minimizes unnecessary shocks in primary prevention patients

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PREPARE (Primary Prevention Parameters Evaluation) study
The Detection rates 182 bpm, duration set for 30 of 40 intervals (≈9 seconds), patients less likely to receive a shock
(9% versus 17%, P<0. .01), No difference in arrhythmic syncope between groups

SVT-VT Discrimination
 Withhold inappropriate therapy
 Hardware dependent
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Single chamber discrimination
 Sudden onset
 Rate stability
 Ventricular complexes morphology
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Single-Chamber Algorithms
Sudden onset
 Sudden onset criterion bases action on the past
8 intervals:
 Takes the interval average of every other
detected ventricular event (4 out of 8)
 Compares the current interval average to each
of the four previous interval averages
 If the sudden onset difference is less than the
programmed delta, the onset is classified as
gradual, favoring sinus tachycardia. Otherwise,
the onset is classified as sudden, favoring VT.
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Stability
 The stability delta is the widest difference
between the second longest and second
shortest cycles, among 12 (programmable
value) consecutive cycles of tachycardia
detection (discards the fastest and the slowest
intervals and subtracts the shortest interval
from the longest interval).
If the stability difference is less than the
programmed delta, the rhythm is VT.
Otherwise favors AF
Does not, discriminate sinus tachycardia,
atrial tachycardia or atrial flutter from VT.
In this example: stability ignores longest
(395 ms) and shortest (268 ms) intervals
and subtracts second longest (378 ms)
from second shortest (271 ms): 378 ms -
271 ms = 107 m (> 80 ms the
programmed value); therefore interval
stability indicates SVT (AF)
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Compare electrograms during tachycardia with a template acquired during normal rhythm
Morphology

Morphology
 Tachycardia morphology similar
from template by programmable
threshold is SVT
Example: SVT = Match (% match above 60% threshold)
The algorithm breaks the waveform apart into triangular chunks and compares the A
pieces, the B pieces, etc. At each point, it determines how much discrepancy there is between
template and test. In this case, there is none, which results in a 100% match. In such a
scenario, the algorithm would determine the rhythm was an SVT (sinus in origin) rather
than a VT.
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Morphology
 Tachycardia morphology differs
from template by programmable
threshold is VT
Example: VT = Non-Match (35% match is less than 60% threshold)
Each part is compared (A to A, B to B) etc. This drawing shows how these particular pieces do not
match exactly; the far right shows areas that one waveform has and the other does not (in other words,
the blue areas is the one that does not match). The MD algorithm assesses this numerically; in this case,
the waveforms are only a 35% match (in favor of VT).
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 Morphology algorithm greater sensitivity and specificity
 Sensitivity 92% to 99% and specificities of 90% to 97%
 Interval algorithms (onset and stability) unreliable at higher rates (>180–200 bpm
 Morphology is the only SVT-VT discriminator reliably applied at rates >200 bpm
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Dual-Chamber SVT-VT Discriminators
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 Use information collected simultaneously from the atria and ventricles
 Dual chamber devices discriminators, depending on the AV relationship used to classify the
arrhythmia (V>A, V<A, V=A).

The ventricular rate is faster than the atrial one in the majority (more than 80%) of the ventricular tachycardias or
fibrillations, this proportion even increases with very fast rhythms. Therefore, the 2 other branches (V=A and V<A) apply
for less than 20% of ventricular tachycardias
VT arm (V>A), When the ventricular rate is faster than the atrial rate, the tachycardia is classified as
VT. No other discrimination criterion is analyzed
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 When the ventricular rate is slower than
the atrial rate, one must distinguish AF,
atrial tachycardia or flutter, and VT,
 Rate stability
 Stability of AV association
 QRS morphology
The rate stability and morphology criteria operate as described for single chamber devices. AV association operates on the same
principle as rate stability, i.e. the AV association delta measures the difference between the second longest and second shortest AV
intervals among the 12 tachycardia detection cycles. When Interval Stability classifies a rhythm disorder as VT, AV association goes into
effect.
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 Ventricular and the atrial rates are same, using the following criteria:
 AV interval delta
 Sudden onset
 QRS morphology

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 AV Interval discrimination is evaluated first.
 If AV interval points to VT, then no other discrimination is applied, and VT therapy begins.
 If AV interval points to SVT, then the rhythm is evaluated by 2 other discriminators in the
V=A rate branch: the sudden onset and morphology criteria

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 Use atrioventricular (AV) association to distinguish SVT from VT
 Proper atrial and ventricular sensing is essential
 Atrial undersensing caused by AF, lead dislodgement, functional, resulting from
the atrial blanking that occurs during and immediately after ventricular sensed or
paced events
 Atrial undersensing lead to misclassification of SVT as VT
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 Oversensing by large FFRWs , misclassification of VT as SVT, inappropriately withheld
therapy
 Prevent both far-field R-wave (FFRW) oversensing and the undersensing of small fibrillation
waves on the atrial channel
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Single- Versus Dual-Chamber ICD
 No benefit of dual-chamber over single-chamber
 Dual-chamber discrimination is superior when overlap in VT and SVT rates
 Dual-chamber ICDs for secondary prevention and for patients with slow VT
 In primary prevention patients, little overlap between SVT and VT heart rates, the
benefit of using high rate cutoffs and prolonged detection appears to overwhelm
any modest additional contribution of dual-chamber SVT-VT discrimination
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Antitachycardia Pacing
 ATP is rapid pacing at a cycle length
shorter than VT
 Terminates VT by penetrating the circuit
 ATP terminate slow VT (<188–200
bpm),
 Success 85% to 90% and a 1% to 5%
risk of acceleration
 VT in primary prevention are
monomorphic, potential application of
ATP
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ATP
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 Rate of ATP programmed at 69% to 88% of VT cycle length
 Each drive train typically has 8 stimuli
 First ATP most effective, 95% of responsive fast VTs terminated successfully
 Only a small minority of patients are responsive to >3 or 4 ATPs

Factors affecting efficacy of ATP
 Burst ATP-Interstimulus interval in the
train remains constant
 Ramp ATP-Each subsequent stimulus in
a train is decremented
 Burst and ramp pacing have similar
efficacy and safety for slow VT
 Fast VT, burst pacing
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Redetection and Reconfirmation
 Contemporary devices reconfirm the
persistence of arrhythmia during and
after charging.
 Charge is dissipated if arrhythmia
terminates
 Noncommitted shock if possible
 The ADVANCE-CRT trial reported
greater efficacy of biventricular ATP in
patients with ischemic cardiomyopathy.
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Antitachycardia Pacing
Analysis of the response to ATP
 Used to optimize programming
 Provides measure of temporal proximity of the pacing site to the VT
 Differential diagnosis of SVT and VT
 Transient VA and AV block during ATP is diagnostic of VT and SVT, respectively
 An AAV response is diagnostic of atrial tachycardia, and a VVA response is diagnostic of VT
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Programming Therapy Zones
 ICDs have 2 to 3 zones defined by the longest RR interval in each zone
 The lower boundary between sinus and VT zone is programmed at approximately
180 to 188 bpm in primary prevention patients and at 30 to 60 ms greater than the
cycle length of the slowest observed VT (150–160 bpm in most trials) in secondary
prevention patients
 Programming in the VT zone is focused on preventing therapy for SVT and
nonsustained VT
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 If 2 VT zones are programmed, the rate
at which fewer trials of ATP therapy are
desired forms the boundary between the
2 zones.
 In secondary prevention, slower VT zone
is programmed with 3 to 4 sequences of
ramp/burst ATP compared with 1-burst
ATP followed by shocks in the faster VT
zone.
 SVT discriminators are programmed on
in VT zones. Implantable cardioverter defibrillator (ICD) rate detection zones. Some
ICDs permit programming of an additional monitor-only zone. The upper
panel shows programming for secondary prevention patients. The lower
panel shows programming for primary prevention patients.
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 The boundary between the VT and VF zones is determined by the rate at which
ATP before charge is no longer desired
 SVT discriminators are either not programmable in the VF zone (Boston Scientific
and St Jude Medical) or are applied with some limitations (Medtronic)
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ATP should not be routinely programmed
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 Inherited channelopathies (Brugada syndrome, Long and Short QT
syndrome)
 Catecholaminergic polymorphic VT
 Early repolarization syndromes
 Arrhythmia is polymorphic VT or VF
 Arrhythmias lack reentry and not interrupted by pacing

Shock Strength, Polarity, and Defibrillation Threshold
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 Implant testing assesses VF sensing and defibrillation effectiveness
 SAFE-ICD study (Safety of Two Strategies of ICD Management at Implantation) revealed
comparable rates of ICD complications and long-term sudden death in patients who did and
did not undergo routine DFT testing

 Strongly considered in nonstandard lead
positioning, right-sided devices,
amiodarone therapy, pediatric
implantations, and use of an s-ICD
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 If the DFT is known, the first shock in the VT zone is programmed ≥10 J above it,
and subsequent shocks are set to maximal energy
 The advantage of lower-energy shocks (conservation of battery life, diminished
postshock stunning or block) is minimal with current biphasic technology.
 High-energy shocks are more likely to be successful for VT/VF and SVT without
patient discomfort or increase in charge time
 Low-energy shocks also convey a risk of conversion of VT to VF
 Maximal shock strength is generally preferred
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 Right ventricular coil as the anode resulted in slightly lower DFT in some patients
 Reverse-shock polarity, can be tried in patients with high DFTs.
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Optimization of Sensing to Prevent Shocks
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 ICD should reliably sense every QRS complex during normal rhythm and small fibrillatory
waves during VF
 Do not sense T waves
 Ignore extracardiac and nonphysiological signals
 ICDs use dynamic sensitivity or gain to achieve these sensing requirements

Optimization of Sensing to Prevent Shocks
 After a sensed or paced ventricular event,
sensitivity is reduced as a function of the
amplitude of the R wave after the
postventricular blanking period expires.
 Sensitivity is increased until a subsequent
event is sensed or the maximum
programmed sensitivity is reached
 Strategy reduces risk of T-wave
oversensing while maintaining sensitivity
for the small deflections of VF
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Preventing T-Wave Oversensing
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 Low-amplitude R waves (<3 mV), large T waves, or long QT intervals promote T-wave
oversensing, result in double counting and inappropriate therapy.
 Hypertrophic cardiomyopathy, long-QT syndrome, and Brugada syndrome predispose T-
wave oversensing
 Decreasing ventricular sensitivity reduces the risk of T-wave oversensing but requires a
sufficiently large R- to T-wave ratio and may risk VF undersensing

Surveillance of Lead Fracture
 Lead Integrity Alert algorithm for detection
of lead fracture based on sudden changes in
lead impedance and noise detection
 The lead-integrity alert is triggered if 2 of 3
events occur:
 (1) Sudden increase in lead impedance
 (2) ≥2 nonsustained tachycardia events (≥5
beats) with intervals <220 ms
 (3) sensing integrity counters with ≥30 short
RR-interval counts <140 ms within 3
consecutive days indicative of
nonphysiological signals
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Noise-Detection Algorithms
 Algorithms for discrimination of VT from myopotentials and nonphysiological noise such as
electromagnetic interference
 Noise have higher frequency with very short intervals
 If noise is detected, the device raises the floor of the dynamic sensitivity above the level of
the noise to prevent oversensing
 This is most useful to prevent myopotential detection
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ICD Programming During Electrical Storm
 Recurrent ICD shocks in the course of
electrical storm (defined as ≥3 VT/VF
episodes in 24 hours)
 Lead to heart failure, sympathetic
overdrive, and psychological trauma,
which potentiates the risk for recurrent
VT.
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ICD Programming During Electrical Storm
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 Programming for minimizing the number of shocks
 Duration to detection is increased
 Number of intervals to declare an end of episode decreased
 Increasing the lower pacing rate may help suppress recurrent VT/VF
 Hospitalized patients, ICD therapies are turned off during electrical storm

Remote Monitoring
 Automated, wireless remote
monitoring with clinician and
patient alerts shortens the time to
detection of changes in clinical
status and device function and may
reduce mortality risk
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Conclusions
 Proper ICD programming minimizes unnecessary ICD therapy to reduce patient
morbidity and mortality.
 Current evidence supports the use of various strategies to reduce shocks without
compromising therapy effectiveness.
 The extension of detection duration to prevent treatment of self-terminating
tachycardia has proven to be the most useful of these strategies, followed by the
application of SVT-VT discrimination and the use of ATP to terminate VT
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Disclosures
 Dr Friedman has received research support from Medtronic (grant administered by
Mayo Clinic for investigator-initiated study), Biotronik, and Cameron Health, and
is a speaker or consultant for Bard, Biotronik, Leadex, and Sorin.
 Dr Madhavan reports no conflicts
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AICD programming

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