7. 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
7
8. 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
8
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
9. 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
9
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
10. 10
Rate and Duration for Initial Detection
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
12. 12
Rate and Duration for Initial Detection
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
13. SVT-VT Discrimination
Withhold inappropriate therapy
Hardware dependent
13
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
14. Single chamber discrimination
Sudden onset
Rate stability
Ventricular complexes morphology
14
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
15. 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.
15
16. Single-Chamber Algorithms
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)
16
17. 17
Compare electrograms during tachycardia with a template acquired during normal rhythm
Single-Chamber Algorithms
Morphology
18. Single-Chamber Algorithms
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.
18
19. Single-Chamber Algorithms
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).
19
20. Single-Chamber Algorithms
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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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
21. Dual-Chamber SVT-VT Discriminators
21
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).
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
22. Dual-Chamber SVT-VT Discriminators
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
22
23. Dual-Chamber SVT-VT Discriminators
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.
23
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
24. Dual-Chamber SVT-VT Discriminators
24
Ventricular and the atrial rates are same, using the following criteria:
AV interval delta
Sudden onset
QRS morphology
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
25. Dual-Chamber SVT-VT Discriminators
25
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
27. Dual-Chamber SVT-VT Discriminators
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
27
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
28. Dual-Chamber SVT-VT Discriminators
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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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
29. 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
29
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
30. 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
30
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
31. ATP
31
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
32. 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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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
33. 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.
33
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
34. 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
34
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
35. 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
35
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
36. Programming Therapy Zones
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.
36
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
37. Programming Therapy Zones
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)
37
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
38. ATP should not be routinely programmed
38
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
39. Shock Strength, Polarity, and Defibrillation Threshold
39
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
40. Shock Strength, Polarity, and Defibrillation Threshold
Strongly considered in nonstandard lead
positioning, right-sided devices,
amiodarone therapy, pediatric
implantations, and use of an s-ICD
40
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
41. Shock Strength, Polarity, and Defibrillation Threshold
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
41
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
42. Shock Strength, Polarity, and Defibrillation Threshold
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.
42
43. Optimization of Sensing to Prevent Shocks
43
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
44. 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
44
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
45. Preventing T-Wave Oversensing
45
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
46. 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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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
47. 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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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
48. 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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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
49. ICD Programming During Electrical Storm
49
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
Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
50. 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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Madhavan M, Friedman PA. Optimal programming of implantable cardiac-defibrillators. Circulation. 2013 Aug 6;128(6):659-72.
51. 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
51
52. 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
52