Download Pacemakers and AICD`s

Pacemakers
and
AICD’s
Pacemaker Basics
Provides electrical stimuli to cause cardiac
contraction when intrinsic cardiac activity
is inappropriately slow or absent
Sense intrinsic cardiac electric potentials
ICD Basics
Designed to treat a cardiac tachydysrythmia
Performs cardioversion/defibrillation

Ventricular rate exceeds programmed cut-off
rate
ATP (antitachycardia pacing)
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Overdrive pacing in an attempt to terminate
ventricular tachycardias
Some have pacemaker function (combo
devices)
Pacemaker and ICD Basics
Pulse Generators
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Placed subcutaneously or submuscularly
Connected to leads
Battery
Most commonly lithium-iodide type
Life span 5 to 8 years
Output voltage decreases gradually
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Makes sudden battery failure unlikely
Pacemaker and ICD Basics
Asynchronous
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Fixed rate
Impulse produced at a set rate
No relation to patients intrinsic cardiac activity
Susceptible to Torsades if impulse coincides
with t wave
Pacemaker and ICD Basics
Synchronous
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Demand mode
Sensing circuit searches for intrinsic
depolarization potential
If absent, a pacing response is generated
Can mimic intrinsic electrical activity pattern of
the heart
Pacemaker Nomenclature
I
II
III
IV
V
Chamber
Paced
Chamber
Sensed
Response to
Sensing
Rate Modulation,
Programmability
Antitachycardia
Features
A=Atrium
A=Atrium
T=Triggered
P=Simple
P=Pacing
V=Ventricle V=Ventricle I=Inhibited
M=Multiprogrammable
S=Shock
D=Dual
D=Dual
D=Dual
R=Rate Adaptive
D=Dual
O=None
O=None
O=None
C=Communicating
O=None
Examples
VVI
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Paces ventricle
Senses ventricle
Inhibited by a sensed ventricular event
Pacing Nomenclature
Examples
AAT
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Paces atria
Senses atria
Triggers generator to fire if atria sensed
DDD
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Paces atria and ventricle
Senses atria and ventricle
Atrial triggered and ventricular inhibited
EKG – 2 spikes
DDD
Atrial Spike
Ventricular Spike
Pacemaker Lead System
Endocardial leads placed via central
access

Placed in right ventricle and/or atria
Fixed to the endocardium via screws or
tines
Experimental pacing systems
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2 atrial leads (minimize afib)
Biventricular pacing
Magnet Inhibition
Closes an internal reed switch

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Causes sensing to be inhibited
Temporarily turns pacemaker into
“asynchronous” mode (set rate)
Does NOT turn pacemaker off
Rate can confer info regarding battery life

Distinct rates for BOL, ERI, EOL
Pacemaker Indications
Absolute indications
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Sick sinus syndrome
Symptomatic sinus bradycardia
Tachy-brady syndrome
Afib with slow ventricular response
3rd degree heart block
Chronotropic incompetence
Inability to increase heart rate to match exercise

Prolonged QT syndrome
Pacemaker Indications
3rd Degree heart block
Pacemaker Indications
Relative indications
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Cardiomyopathy
Dilated
Hypertrophic
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Severe refractory neurocardiogenic syncope
Paroxysmal atrial fibrillation
ICD Indications
Generally
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Used in cases where there was a previous
cardiac arrest
Or, patients with undetermined origin or
continued VT or VF despite medical
interventions
Pacemaker Complications
EKG abnormalities due to
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Failure to output
Failure to capture
Sensing abnormalities
Operative failures
Pacemaker Failure to Output
Definition

No pacing spike present despite indication to
pace
Etiology
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Battery failure, lead fracture, break in lead
insulation, oversensing, poor lead connection,
“cross-talk”
Atrial output is sensed by ventricular lead
Pacemaker Failure to Capture
Definition

Pacing spike is not followed by either an atrial
or ventricular complex
Etiology
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Lead fracture or dislodgement, break in lead
insulation, elevated pacing threshold, MI at
lead tip, drugs, metabolic abnormalities,
cardiac perforation, poor lead connection
Pacemaker Sensing
Abnormalities
Oversensing
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Senses noncardiac electrical activity and is
inhibited from correctly pacing
Etiology
Muscular activity (diaphragm or pecs), EMI, cell
phone held within 10cm of pulse generator
Undersensing
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Incorrectly misses intrinsic depolarization and
paces
Etiology
Poor lead positioning, lead dislodgement, magnet
application, low battery states, MI
Pacemaker Operative Failures
Due to pacemaker placement
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Pneumothorax
Pericarditis
Perforated atrium or ventricle
Dislodgement of leads
Infection or erosion of pacemaker pocket
Infective endocarditis (rare)
Venous thrombosis
Pacemaker Complications
Pacemaker syndrome
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Patient feels worse after pacemaker
placement
Presents with progressive worsening of CHF
symptoms
Due to loss of atrioventricular synchrony,
pathway now reversed and ventricular origin
of beat
ICD Complications
Similar to pacemaker complications
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Operative failures
Same as pacemakers
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Sensing and pacing failures
Inappropriate cardioversion
Ineffective cardioversion/defibrillation
Device deactivation
ICD Sensing failures
Similar to pacmakers
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Oversensing
Undersensing
Appropriate failure to treat
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Programmed cut off at 180 bpm
If V Tach occurs at 160 bpms, appropriately
fails to cardiovert
ICD Inappropriate Cardioversion
Most frequent complications
Provokes pain and anxiety in pts
Consider when
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Pt is in afib
With ventricular response > programmed cut off
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Received multiple shocks in rapid succession
Etiology
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Afib, T-wave oversensing, lead fracture, insulation
breakage, MRI, EMI
ICD Inappropriate Cardioversion
Treatment
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Magnet over ICD inhibits further shocks
Does NOT inhibit bradycardiac pacing
Note
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Some older devices produce beep with each QRS
If left on for >30 seconds, ICD disabled and continous
beep
To reactivate, lift off magnet and then replace for > 30
seconds, beep will return with each QRS
ICD Failure to Deliver
Cardioversion
Etiology

Failure to sense, lead fracture, EMI,
inadvertent ICD deactivation
Management
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External defibrillation and cardioversion
Do not withhold therapy for fear of damaging ICD
If pt’s internal defibrillator activates during chest
compressions, you may feel a mild shock (no
reports of deaths related to this)
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Antidysrhymthic medications
ICD Ineffective Cardioversion
Etiology
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Inadequate energy output
Rise in the defibrillation threshold
MI at the lead site
Lead fracture
Insulation breakage
Pre-programmed set of therapies per dysrythmia
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Manufacturer specific
Once number of attempts reached, will not deliver further
shocks until new episode is declared
Electromagnetic Interference
Can interfere with function of pacemaker
or ICD
Device misinterprets the EMI causing
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Rate alteration
Sensing abnormalities
Asynchronous pacing
Noise reversion
Reprogramming
Electromagnetic Interference
Examples
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Metal detectors
Cell phones
High voltage power lines
Some home appliances (microwave)
Electromagnetic Interference
Intensity of electromagnetic field
decreases inversely with the square of the
distance from the source
Newer pacemakers and ICDs are being
built with increased internal shielding