Transcript Pacemakers and AICD*s

Pacemakers
and
AICD’s
Emergency Medicine
Ryan Ngiam
Historical Perspective
1905 – Einthoven
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Published first two human AV block using string
galvanometer
1958 – Senning and Elmqvist
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Asynchronous (VVI) pacemaker implanted by
thoracostomy and functioned for 3 hours
Arne Larsson
First pacemaker patient
Used 23 pulse generators and 5 electrode systems
Died 2001 at age 86 of cancer
Historical Perspective
1960 – First atrial triggered pacemaker
1964 – First on demand pacemaker (DVI)
1977 – First atrial and ventricular demand
pacing (DDD)
1980 – Griffin published first successful
pacemaker intervention for
supraventricular tachycardias
Historical Perspective
1981 – Rate responsive pacing by QT
interval, respiration, and movement
1994 – Cardiac resynchronization pacing
1998 – Automatic capture detection
Now
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Approximately 3 million with pacemakers
Approximately 1 million with ICD device
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
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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
Pacemaker Nomenclature
1st letter – chamber paced
2nd letter – chamber sensed
3rd letter – Response to chamber sensed
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
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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
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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
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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
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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
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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
Impact on ALS protocols
Not many
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Can defibrillate
Sternal paddles should be placed a safe
distance (10 cm) from pulse generator
In case of MI
May require temporary transcutaneous pacing
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
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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
Case 1
CC: Chills, rigors
HPI:
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65 yom c/o fevers, chills, rigors x 1 day. Positive n/v
and anorexia. Pt states he had recent pacemaker
insertion 4 days ago for an arrhythmia.
PMH:
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HTN
Arrythmia
Hypercholesterolemia
PSHx:
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As stated above
Case 1
Physical exam
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Temp 101.2, HR 110, BP 90/55
EKG
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Diagnosis?
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Case 1
Pocket Infection
Pacemaker insertion is a surgical
procedure
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1% risk for bacteremia
2% risk for pocket infection
Usually occurs within 7 days of pacemaker
insertion
May have tenderness and redness over
pacemaker site
Case 2
CC: SOB
HPI:
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65 yom states he had onset of shortness of breath
and left sided pleuritic chest pain. Pt states he awoke
with pain and difficulty breathing. Had pacemaker
placed yesterday.
PMHx:
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HTN, Diabetes, Hypercholesterolemia, Arrythmia,
CAD
PSHx:
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Pacemaker, left knee surgery, b/l cataract
Case 2
Physical Exam
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BP 146/85, HR 80s, RR 30s, O2 Sat 88%
Lungs
Decreased breath sounds on left
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EKG
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Diagnosis?
Case 2
Pneumothorax
Occurs during cannulation of central veins
Incidence
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Cardiologist dependent
Treatment
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Small or asymptomatic – observation
Large or symptomatic – Chest tube
Case 3
CC: Cardiac arrest
HPI: 59 yom found on couch. Wife states
they were watching TV when patient let
out a moan and then became
unconscious. She states, he has a bad
heart and had “something” put in a few
years ago.
PMHx: unknown
Meds: bottles in bathroom
Case 3
Physical Exam
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Airway patent, no visible chest rise, no pulses
Generally: cool, clammy, diaphoretic
EKG:
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Diagnosis?
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Case 3
Cardiac Arrest with ICD (V-fib)
2% annual incidence with ICD
Etiology
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ICD delivered predetermined shocks for
identified event and patient failed to respond
ICD failed to recognize event and failed to
shock appropriately
Failure to sense, lead fracture, EMI, inadvertent
ICD deactivation
Case 3
Cardiac Arrest with ICD
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Treat using ACLS protocols
Secure airway
CPR
Defibrillate/shock as warranted
Keep sternal pad 10 cm away from pulse
generator
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Meds
Questions
References
Emedicine
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http://www.emedicine.com/emerg/topic805.htm
Minish, Travis. Pacemaker Emergencies.
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http://www.cgi.ualberta.ca/emergency/rounds/files/pacers3.ppt
The Implantable Pacemaker, a short historical overview.
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http://igitur-archive.library.uu.nl/dissertations/2006-0426-200006/c1.pdf
Healthy Hearts
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http://www.healthyhearts.com/pacemaker.htm
Medtronic
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http://www.medtronic.com/patients/heart.html
Shelton State University
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http://www.sheltonstate.edu/userfiles/File/faculty/s%20warren/NUR%20202%20
EKG%20Dysrrhythmias-Sinus,%20Atrial,%20Junctional,%20Vent%20.pdf
Google Images
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http://images.google.com