Trouble shoooting ICD AND CRT

Introduction
 ICD are the cornerstone in the prevention of sudden death both in
patients at risk of life-threatening ventricular arrhythmias with or
without heart failure ---primary prevention
 in patients rescued from non-tolerated VT or ventricular fibrillation --
secondary prevention
 Therapy delivered for causes other than VT/VF is termed
“inappropriate”, and has been reported to occur in up to 17% of patients
of heart failure patients
 Shock delivery, whether appropriate or inappropriate, has been reported
to negatively impact patient survival, being closely associated to
progressive pump failure
TROUBLE SHOOTING OF ICD & CRT

ICD TROUBLE SHOOTING
 Evaluating patient with shocks
 Evaluating ineffective / absent treatment
 Preentive programming

Clinical presentation
four categories:
 Shocks (appropriate, inappropriate or failure to deliver therapy)
 Dizziness/syncope
 Palpitations
 Alerts (audible beeps or sensed vibrations originating from the ICD)

Avoiding Shocks Is Important
To Reduce Pain
and Anxiety
and Increase
Device
Acceptance1
To Reduce
Healthcare
Burden and
Improve Patient
Quality of Life1
Avoiding
Shocks May
Improve
Survival/Heart
Failure2
1 Wathen MS, DeGroot PJ, Sweeney MO, et al, for the PainFREE Rx II Investigators. Prospective randomized multicenter trial of empirical antitachycardia pacing versus
shocks for spontaneous rapid ventricular tachycardia in patients with implantable cardioverter-defibrillators: Pacing Fast Ventricular Tachycardia Reduces Shock
Therapies (PainFREE Rx II) trial results. Circulation. October 26, 2004;110(17):2591-2596.
2 Sweeney MO, et al. Differences in effects of electrical therapy type on health care utilization in the MVP ICD Trial. Presented at HRS 2010.

APPROACH TO A PATEINT WITH SHOCKS

APPROACH TO A PATEINT WITH SHOCKS
 When a patient presents with an ICD shock, a focused history and device
interrogation should be performed.
 Symptoms of palpitations/dyspnea/near-syncope prior to the shock go in
favor of an appropriate shock.
 A shock “out of the blue” should make one alert for the possibility of an
inappropriate shock.

 The two primary ICD EGMs are the shock or high-voltage EGM displayed on the
shock channel and the ventricular sensing EGM displayed on the sensing channel .
 The marker channel indicates the timing of sensing EGM that reachs the
amplitude threshold for a sensed event.
 The sensing EGM records a local (near-field) ventricular signal between the tip
electrode and the adjacent ring or RV coil.
 EGM recorded between the tip and the RV coil is referred to as integrated
bipolar EGM because the RV coil integrates both pace-sense and defibrillation
functions.
 recorded between the tip and a small proximal ring electrode are referred to as
dedicated (or true) bipolar EGM because the ring electrodeis dedicated to
pacing and sensing, not used for defibrillation.
 Leads designed for integrated bipolar sensing do not require a ring electrode and
are thus simpler than those designed for dedicated bipolar sensing.

Implantable cardioverter defibrillator (ICD) leads and electrograms (EGMs).
Charles D. Swerdlow et al. Circ Arrhythm Electrophysiol.
2014;7:1237-1261
Copyright © American Heart Association, Inc. All rights reserved.

 The shock EGM records a more global (far-field) signal between
widely separated, high-voltage electrodes, most commonly RV coil
and generator housing (can).
 In analyzing ventricular sensing, the shock EGM is used as a check
on the sensing EGM: signals sensed on the sensing channel that
do not correspond to signals on the shock channel indicate
oversensing.
 Dual-coil leads permit recording additional far-field signals,
including the shock EGM between RV and SVC coils and the
leadless ECG between the can and SVC coil.
 The left ventricular EGM in CRT-Ds provides another check on
ventricular sensing.

TACHYARRHYTHMIAS
 after an episode, the retrieved signals are judged not to be due to
oversensing but to an actual tachycardia, further evaluation of the
arrhythmia has to be performed to verify appropriateness of the
shock since SVT-VT discrimination algorithms are not always
perfect.
 High ventricular rates during atrial fibrillation or atrial flutter are
the most frequent causes of inappropriate detection and therapy
 The Flashback memory (Medtronic) or Trending feature (Boston
Scientific) may provide helpful information to discriminate
between the different supraventricular arrhythmias.

 after a first unsuccessful shock in case of concurrent termination of the episode
of VT, SVT or device interpreted tachycardia, an inappropriate second shock
may be delivered.
 This second shock is so-called “committed”, meaning that it is delivered
without further pre-evaluation, for reasons of safety to prevent under-detection
and under-treatment of arrhythmias.
 Commitment also starts when the first therapy of an episode has been diverted
but the arrhythmia restarts before the episode has ended.
 It is also important to have a thorough awareness of discrimination algorithms
and their flaws to troubleshoot various inappropriate shocks in SVT

BostonScientific Rhythm ID algorithm

NONTACHYARRHYTHMIAS
 Oversensing can be classified by electrogram morphology, temporal pattern
(cyclic versus noncyclic), source type (physiological versus nonphysiological),
and source location (intracardiac versus extracardiac)
 temporal pattern of oversensed signals as varying consistently with the
ventricular cycle (cyclic) or independent of the ventricular cycle (noncyclic).

Ventricular oversensing in implantable cardioverter defibrillators (ICDs): classification and
common causes. *Oversensing atrial electrograms in atrial fibrillation (eg, ventricular lead
dislodged to atrium) also causes noncyclic oversensing.
2014;7:1237-1261

P-Wave Oversensing
 P waves may be oversensed if the proximal ventricular sensing electrode is close
to the tricuspid valve.
 Recording an atrial electrogram facilitates recognition of P-wave oversensing.
 Ventricular oversensing of atrial electrograms in AF may result in multiple
oversensed physiological signals for each true cardiac cycle, producing an
interval plot with short, irregular intervals, characteristic of nonphysiological
oversensing.
 P-wave oversensing is rare in adults because the ventricular sensing bipole is
usually far from the atrium. Thus, early after implant, P-wave oversensing
usually indicates RV lead dislodgement to a position closer the atrium.

 However, P-wave oversensing may occur in children with small right ventricles
and in adults with integrated bipolar sensing.
 first approach to clinically significant P-wave oversensing is to reduce the
programmed ventricular sensitivity.
 If this is unsuccessful or sensing of VF is not reliable at the reduced sensitivity,
the ventricular lead should be revised.
 As a temporary measure, P-wave oversensing in sinus rhythm may be mitigated
by forced atrial pacing, by introducing or increasing ventricular blanking after
each atrial event.

Spectrum of ventricular P-wave oversensing.
decreasing sensitivity increasing the ventricular blanking period
after atrial pacing.

R-Wave Double Counting
 R-wave double counting occurs if the duration of the sensed electrogram exceeds
the short ventricular blanking period in ICDs.
 Consistent double counting results in an alternation of ventricular cycle lengths.
 The expected sensed event early in the R wave is followed by a second, event as soon
as the ventricular blanking period ends, which always corresponds to an interval in
the VF zone.
 The duration of the device-detected interval that begins with the second event
approximates the difference between the spontaneous ventricular cycle length and
ICD’s blanking period.
 This produces a characteristic railroad track pattern on a plot of stored of
ventricular intervals.

Railroad track patterns on plot of stored ventricular intervals.
A, T-wave oversensing. B, R-wave double counting.

 R-wave double counting often results from local ventricular conduction delay.
 In conducted rhythm, it is most common when ICDs with short ventricular
blanking periods ≤120 ms are connected to integrated bipolar leads.
 If the blanking period is programmable, it may be increased when using these
generators with integrated bipolar sensing.
 R-wave double counting may be precipitated by reversible conduction block
caused by hyperkalemia or sodium channel blocking antiarrhythmic drugs.
 The primary troubleshooting intervention is to increase the ventricular
blanking period

R-Wave Double Counting

R-wave double counting.
2014;7:1237-1261

T-Wave Oversensing
 T-wave oversensing presents as alternating morphologies of device-detected
sensing electrograms: Higher frequency R waves alternate with the lower
frequency T waves.
 hallmark of T-wave oversensing is alternation of electrogram signal frequency
content, not device-measured cycle length, which is easier to appreciate on
wideband electrograms than narrowband electrograms.
 A simultaneous shock electrogram confirms that alternate low-frequency
electrograms represent T waves.

 T-wave oversensing was a major problem for early ICDs: oversensing that
could not be treated by reprogramming accounted for 13% of lead revisions in
a multicenter study conducted from 1993 to 2004.
 emerged as the leading cause of oversensing for the subcutaneous ICD.
 To reduce T-wave oversensing associated with a fixed-low sensing threshold
while retaining sensitivity for VF, ICDs adjust sensitivity dynamically to
become progressively more sensitive after each sensed or paced event
 automatic control of sensitivity affect the trade-off between preventing T-
wave oversensing and minimizing VF undersensing

 T-wave oversensing with large R waves is caused by an absolute increase in T-
wave amplitude.
 Clinical correlates include pediatric patients, hypertrophic cardiomyopathy,
long QT syndrome, short QT syndrome, hyperkalemia,and, rarely, other drug
and metabolic abnormalities.
 with small R waves, resolution usually requires an alternative approach
 small R waves, oversensed T waves usually have normal amplitude, such as in
Brugada Syndrome or advanced myocardial disease.
 The root cause relates to a fundamental limitation of automatically adjusted
sensitivity, which links the initial value of sensitivity to the amplitude of the
preceding R wave.

Ventricular dynamic sensing in St JudeMedical ICD &
programming to prevent T-wave oversensing.

T-Wave Oversensing: Prevention and Remediation
 Minimum Sensing Threshold
 Dynamic Sensitivity
 Filtering and Rectification
 Algorithmic Rejection of T Waves
 New Sensing Lead

Features to minimize T-wave oversensing.
Copyright © American Heart Association, Inc. All rights reserved.TROUBLE SHOOTING OF ICD & CRT
applied during initial detection and
redetection, but not during pacing.

Oversensing Physiological Extracardiac Signals: Myopotentials
 Diaphragmatic Myopotentials
 These low-amplitude, high-frequency signals are more prominent on the sensing
electrogram than the shock electrogram because the sensing bipole is closer to the
source.
 Their amplitude varies with respiration, but not the cardiac cycle .
 Oversensing is most common with integrated bipolar sensing at the RV apex and
rare with dedicated bipolar sensing or leads in the RV outflow tract.
 it commonly occurs in pacemaker-dependent patients, in whom inhibition of
pacing maintains high ventricular sensitivity, resulting in persistent oversensing
and inappropriate detection of VF
 Oversensing may be corrected by reducing ventricular sensitivity if VF sensing is
reliable. In pacemaker-dependent patients, pacing at a faster rate may prevent
oversensing by not allowing sensitivity to reach its minimum value
 The nonprogrammable Boston Scientific noise rejection algorithm operates
continuously and may reduce oversensing. Occasionally, correction requires
inserting a new sensing or defibrillation lead away from the diaphragm.

Pectoral Myopotentials
 These high-frequency, variable amplitude signals are prominent on
electrograms that include the ICD can, including shock electrograms and
leadless ECG.
 They may be reproduced by pectoral muscle exercise. ICDs do not use these
signals as primary sensing channels, pectoral myopotentials do not cause
oversensing if the lead is intact.
 they may cause misclassification of exercise-induced sinus tachycardia as VT
because algorithms that discriminate VT from SVT based on ventricular
electrogram morphology use the RV coil-can vector as the default signal .
 The diagnosis may be confirmed by monitoring the real-time sensing
electrogram during pectoral muscle exercise.
 Oversensing of pectoral myopotentials on dedicated bipolar electrograms
typically indicates an in-pocket insulation breach.

Pectoral Myopotentials

Oversensing Nonphysiological Signals: Electromagnetic Interference
 it typically presents as rapid, noncyclic signals on multiple channels; and the
diagnosis can often be confirmed by a history of exposure at the time of the
stored episode.
 EMI may not be recorded on every channel because of differences in electrode
surface area, interelectrode distance, antenna spatial orientation, amplifier
sensitivity, and bandpass filters.
 External EMI usually has lower amplitude on channels recorded from small,
closely spaced electrodes than on those recorded from widely spaced electrodes
or those that include a large defibrillation electrode.

Electromagnetic interference (EMI).

Oversensing in the Diagnosis of ICD Lead Failure
 Of all the causes of oversensing, early diagnosis may be most important in
lead failure, which commonly presents with repetitive inappropriate shocks
and less commonly causes loss of bradycardia pacing or failure to deliver
therapeutic shocks.
 Pace-sense malfunctions, either conductor fractures or insulation breaches,
account for the majority of clinically diagnosed lead failures

Oversensed Signals in Pace-Sense Conductor Fractures and
Connection Problems
 conductor fractures cause nonphysiological signals often are referred to as
make-break potentials because indistinguishable signals can be generated by
connecting and disconnecting cables from the sensing circuit.
 typical signal has 6 characteristics, of which the first 3 are almost always
present : (1) signals are intermittent and have a high dominant frequency. (2)
They display ≥1 types of variability including amplitude, morphology, or
frequency. (3) In dedicated bipolar leads, they are not recorded on the shock
channel. (4) Usually, at least some signals are not cyclic. (5) Often, some
intervals are nonphysiological, shorter than typical physiological intervals. (6)
Signal amplitude may exceed the range of the sensing amplifier and thus appear
truncated.

Nonphysiological signals of pace-sense conductor fracture and lead-header connection
problem.
2014;7:1237-1261

Oversensed Signals in Insulation Breaches
 Unlike conductor fractures, insulation breaches themselves do not generate
abnormal signals. Instead, oversensing occurs because signals enter the intact
conductor at the insulation breach. Thus, electrogram patterns vary, reflecting
the physiological or nonphysiological source signal.
 Intermittent, high-amplitude pectoral myopotentials on the sensing channel
suggest in-pocket, outside-in abrasion .
 Inside-out insulation breaches may cause mechanical interactions between the
2 shock components, the 2 pace-sense components (ring cable and central
helix), or 1 pace-sense and 1 shock component. The latter 2 may present as
oversensing.
 Inside-out breaches of Riata leads often have characteristic spikes on the
sensing channel or both sensing and shock channels that may represent such
mechanical interactions

UNSUCCESSFUL SHOCK
 SVT MUST BE RULED OUT
 SUBSTRATE RE-EVALUATION-ISCHEMIA,SCAR
 DRUG THERAPY
 REASSES DFT (DEFIB THRESHOLD) IN LAB

 If no episodes of tachyarrhythmia or bradyarrhythmia are stored in device memory and
if the patient is not pacemaker dependent, cardiac arrhythmia probably did not cause
the syncopal episode.
 In pacemaker-dependent patients, special attention should be paid to the exclusion of
oversensing (with pacing inhibition) as the cause of syncope.
 If no oversensing is manifest at rest or on the stored EGM, such physical maneuvers as
deep breathing and upper-extremity isometric exercises should be tried in an effort to
recreate oversensing, before ruling that out as the cause of syncope.
 VT with a cycle length below the cut-off rate, unless ongoing during clinical evaluation,
is less easily detectable since the detection criteria have not been met and no episodes
will be stored. However, clues hidden in the cardiac flash back (Medtronic) or the
Trending (Boston Scientific) help to reveal the arrhythmia.
 antiarrhythmic drugs or ablation may be reasonable alternatives.

Palpitations
 Although not emergency , a frequent complaint at regular ICD follow-up.
 interrogation - underlying cause since it may reveal the occurrence of irregular or
fast atrial arrhythmias, PVCs or non-sustained VTs.
 Sustained VTs with a cycle length below the cut-off rate are especially difficult to
diagnose when the VT is not ongoing during follow-up.
 If history is pointing in this direction, the monitor zone can be adjusted to store
these arrhythmias.
 Decreasing the lower rate of the pacemaker or lowering the beta-blocker dosage
may resolve these complaints.
 If a careful analysis of the stored EGMs does not help to answer the question,
Holter monitor or an event monitor—has to be used.

Alerts
 Most ICDs have alerts that notify the patient of undesired settings or electrical
events of the ICD and/or leads.
 The alerts produce audible signals (Medtronic, Boston Scientific) or a
vibrational sensation (St Jude).
 Alerts are repetitive, discontinuous signals that can be programmed to a
specified time.
 Most alerts are programmable (on/off), except “system alerts” that convey
debilitated functioning with respect to proper treatment of tachycardia.

goals of ICD programming
 -detect high rate NSVT, as they are predictive of ICD discharge for life-
threatening arrhythmias and all-cause mortality
 -avoid unnecessary treatment of NSVT by delaying ICD intervention as
tolerated by the patient
 -discriminate SVTs
 -terminate sustained VT and VF while minimizing shock therapy
 -monitor AF, SVTs, and slow VTs for stroke prevention management, ablative
and/or drug therapy
 -provide alert on technical (lead integrity and device) and patient-related
(atrial fibrillation, heart failure) medical issues

ICD programming
 comprehensive process based on the patient's clinical
history and encompasses:
 -Arrhythmia detection:
Zones setting
Detection duration of each programmed zone
SVT discrimination
 -Termination of ventricular arrhythmias
 -Choice of the device type
 -Monitor zone programming
 -Device and clinical alerts

Overview of detection& treatment of ventricular
arrhythmia by ICD

CRT OPTIMISATION -Aortic VTI
Method
 Objective:
 Identify the AV Delay that yields the maximum cardiac
output as determined by an aortic VTI measurement
 Procedure:
 Obtain continuous wave Doppler echo of aortic valve
outflow to obtain VTI measurement
 Record VTI values over a range of programmed AV Delays
 Program the AV Delay value that yields the maximum aortic
VTI
TIPS & TRICKS OF CRT

Iterative Method
 Objective:
 Identify the AV Delay that maximizes LV filling using mitral velocity
echocardiographic measurements1
 Procedure
 Obtain transmitral Doppler echo at a “long” programmed AV Delay
during ventricular pacing
 Shorten the programmed AV Delay by 10-20 ms until the echo
Doppler A-wave becomes truncated (A wave is atrial contraction)
 Lengthen the programmed AV Delay back to the value where there is
no A-wave cutoff. This timing should enable ventricular contraction
to occur just at the end of atrial systole

 to maximize DFT
(i.e. separation of
the E- and A-
waves).
 to allow complete
end-diastolic
filling(marked by
the end of the A-
wave)before the
onset of LV
contraction.

Diastolic mitral regurgitation (Ishikawa)
method
 Aims to minimize diastolic MR.
 optimal AV delay = long AV delay - duration of
diastolic MRTIPS & TRICKS OF CRT

Mitral inflow velocity time integral
 VTI is calculated representing the stroke volume of
mitral inflow as a surrogate of LV filling volume.
 The AV delay with the largest VTI is considered the
optimal setting.
 good correlation with optimization by LV dP/dtmax
(r=0.96) in a small study of 30 patients

Trouble shoooting ICD AND CRT

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