ICD Therapies
NASPE Training
Lancashire & South Cumbria Cardiac
Network
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Ventricular therapies
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Antitachycardia Pacing
Low energy cardioversion
Defibrillation
Atrial Defibrillators
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Atrial Detection
Atrial Therapies
Antitachycardia Pacing
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Short bursts overdrive pacing – 10- 20 %
faster than tachycardia rate
Terminates 60 – 90 % of arrhythmias
eliminating need for shocks
Useful – re-entry tachycardia
Burst, ramp, combination
No scheme outshines any other
ATP accelerate arrhythmia – 10%
Is it worth inducing VT to enable
accurate termination programming?
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Emperical programming (3 scans)
ATP effective both groups – successfully
terminated 95% (tested) and 90% (non
tested)
5% difference – implies safe to program
emperical values in non-induced patients
Clinical situations Induction &
ATP testing preferred
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Initiation/change drug therapy
Significant change patient clinical status
Observed proarrhythmia post ATP
Frequent failure ATP
Patients separate pacemaker and ICD
Significant change pacing threshold
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ATP outputs – higher brady pacing outputs
- why?)
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Termination Success rates higher in
spontaneous tachycardia than induced
Acceleration rates lower in spontaneous
tachycardia than induced
Thought - Due to induced tacyhycardias
yielding faster rates than spontaneous
episodes
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Burst – train of pulses delivered at a fixed cycle
length that is a % of the tachycardia rate
Burst+ – burst followed by 2 extrastimulus at the
end of the train
Ramp – begins with coupling interval that is a %
of the tachycardia rate and is followed by
decremental coupling intervals throughout the
train
Scan – series of ramps that decrement in starting
coupling interval between each train
Low energy cardioversion
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Low energy – 1-5J synchronised
Usually following ATP to spare patient high
energy shock
Study comparing ATP to low energy shocks –
similar success rates & acceleration rates for both
types of treatment (no clinical advantage to
program low energy shocks as initial treatment
VT)
Some VT fails to respond to ATP – low energy
useful
Back up high energy should always be
programmed
Defibrillation
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Mainstay VF and fast VT termination
Efficacy – 98%
4 – 8 shocks of between 25 to 42J
Mean energy required successful
defibrillation – 10J
Retesting DFT – may be clinically
indicated
Atrial defibrillators
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Ventricular defibrillators diagnose atrial
arrhythmias to withhold therapy
Atrial defibrillators diagnose atrial
arrhythmias to deliver therapy
Atrial prevention therapies
Atrial termination therapies
Atrial detection
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PR logic (diagnoses ventricular
arrhythmias and to prevent ventricular
therapies for atrial arrhythmias
Separate detection algorithm – allow
therapies for atrial arrhythmias
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A fib / A flutter enhancement
Sinus rhythm enhancement
SVT discrimination
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AT or AF (depends average atrial cycle length
and regularity)
AT/AF evidence counter – increases when 2 or
more P waves occur in a RR interval and
decreases after the second RR interval that has 1
or less P waves associated
AT/SVT with 1:1 conduction may not be detected
as atrial arrhythmia
SVT falling in VT zone (rate criteria) may not
receive ventricular therapies (PR logic) but also
may not receive atrial therapies (atrial algorithm)
Episodes are terminated when;
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Sinus rhythm criteria is met (5 consecutive
beats when PR pattern of SR is seen) *
slow VT with long VA conduction*
Rhythm classification - longer than 3
minutes
Ventricular arrhythmia is detected
Inappropriate detection
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64 % - sinus rhythm with 1st degree block
classified as VT
17% SVT (1:1 SVT may be treated as a
ventricular episode – but this is often seen as
appropriate treatment anyway for fast SVT)
13% atrial sensing errors
6% ‘regular AF’ counted as double tachycardia
AF prevention
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High rate overdrive atrial pacing post atrial
arrhythmia – prevent early re-initiation (ERAF)
Atrial rate stabilisation – prevents long pauses
following PAC – prevent initiation AF
Atrial pacing preference – overdrive atrial pacing
above sinus rate – prevent initiation AF
Atrial septal lead placement – prevent initiation
AF (reduce intra-atrial conduction time)
AT/AF termination
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ATP – autodecremental bursts 10-20%
faster than atrial rate
Atrial 50HZ high frequency burst –
delivers AOO pacing every 20msec for
programmed duration (AT/AF has small
exitable gap)
Atrial shock - delivers shock over
independent electrodes
General principles
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Atrial pacing should be used liberally (approx
52% success)
1st shock energy should be sufficient to work
(clinically pain is more closely correlated with
number of shocks than shock strength (Jung)
Patient preference critical particularly for therapy
delivery (shock), time of day, self or auto
administered
Manual delivery can be undertaken at follow up * remember anticoagulation/risk of
thromboembolism if AF has been established for
any length of time*