Pacemakers and ICDs
Chris McCrossin
Thanks to: Margriet Greidanus, Gord
McNeil, Nadim Lalani, Juliette Sacks
Outline
• Pacemakers




Function
Malfunction
General complications and ED management
Rhythm recognition
• ICDs
 Function
 Malfunction
 ED management of common ICD presentations
• TV Pacemaker Insertion




When to do it
When not to do it
How to do it
Settings
Class I indications for
Permanent Pacing in Adults
1.
2.
3.
4.
5.
6.
Third-degree AV block at any anatomic level*
Symptomatic bradycardia resulting from 2nd degree AV block
Chronic bifascicular or trifascicular block with intermittent 3rd
degree AV bock or type II 2nd degree AV block
Chronic bifascicular or trifascicular block with intermittent 3rd
degree AV block or type II 2nd degree AV block
Sinus node dysfunction with symptomatic bradycardia or
chronotropic incompetence
Recurrent syncope caused by carotid sinus stimulation
Pacemaker Functions
1. Stimulate cardiac depolarization
2. Sense intrinsic cardiac function
3. Respond to increased metabolic demand
by providing rate responsive pacing
4. Provide diagnostic information stored by
the pacemaker
Pacemaker Components
• Pulse Generator:
battery
• Leads
• Cathode
• Anode
Lead
IPG
Anode
Cathode
Lead System
• Bipolar
 Lead has both negative
(cathode) and anode
(positive) electrodes
 Separated by 1 cm
 Larger diameter: more
prone to fracture
 Compatible with ICD
• Unipolar
 Negative (cathode)
electrode in contact
with the heart
 Positive (anode)
electrode: metal casing
of pulse generator
 Prone to oversensing
 Not compatible with
ICD
Bipolar
• Current travels short
distance
• Small pacing spike (<
5 mm)
Anode
Cathode
Unipolar
• Current travels a
longer distance
between electrodes
• Larger pacing spike (>
20 mm)
Anode
Cathode
Pacemaker Code
Chamber
Paced
0 = None
A = Atrium
V = Ventricle
D = Dual
Chamber
*
Table 1. Codes for Classification of Pacing Modes
Chamber
Response to
Rate
Antitachycardia
Sensed
Sensing
Modulation*
(AICDs)
0 = None
0 = None
0 = None
0 = None
A = Atrium
T = Triggered
R = Rate
P = Pacing
Responsive
V = Ventricle
I = Inhibited
S = Shock
D = Dual
D = Dual (T+I)
D = Dual (P+S)
Chamber
This position may also be used to indicate the degree of programmability through the
codes P, M, and C.
Pacemaker Code
• Five letter code
 First 3 letters refer to anti-bradycardic function
 Fourth letter refers to programmability
 Fifth refers to anti-tachycardic function
• Last two letters may be left off the code if no
programmable features or anti-tachycardic features
exist
Pacemaker Code
• First letter
 Chamber of the heart that is paced
• A = Atrium
• V = Ventricle
• D = Dual
Pacemaker Code
• Second Letter
 Chamber sensed
• Third Letter
 Response to sensing of an electrical impulse
 I = inhibited by a sensed event
 T = triggered by a sensed event
Pacemaker Code
• Fourth letter
 Many pacemakers have rate modulating
features
 Allows the HR to rise in response to
physiologic demand
 Designated by an “R”
Pacemaker Code: Examples
• VVI
 Ventricles paced, ventricles sensed, when it senses it stops from triggering
a beat
• DDD
 Both Chambers paced, both chambers sensed, inhibits if ventricular
depolarization is sensed, triggers if only atrial depolarization is sensed
• VDD
 Capable of pacing only the ventricle, senses both atrial and ventricular
activity, responds by inhibition of ventricular pacing if ventricular
depolarization is sensed, triggers a beat if only atrial depolarization is
sensed
Pacemaker Complications
1.
Pocket Complications
a)
b)
2.
3.
Pacemaker syndrome
Abnormal Pacemaker function
a)
b)
c)
d)
4.
5.
Infection
Thrombophlebitis
Failure to Pace
Failure to Sense
Failure to Capture
Oversensing
Pacemaker Mediated Tachycardia
Psychiatric (ICD’s) - Not covered
Case
• 67 y/o M
• Pacemaker placed 2 weeks ago
• Presents with pain & redness over site
(looks infected)
• Afebrile, vitals normal, looks well
• Pain easily controlled with PO analgesics
Pocket Complications
• Infection
 25% with local infection have positive blood
cultures
 Can have bacteremia without evidence of local
infection
 Bacteriology
• Staph aureus and Staph epidermidis
 Vancomycin empirically until cultures are back
Pocket Complications
• Thrombophlebitis
 30-50% incidence of venous obstruction
 Thrombosis may include
• Axilla, subclavian, innominate veins, SVC
 Chronic thrombosis of the upper limb is usually
asymptomatic b/c of collaterals
 Sequelae
• Edema, SVC syndrome, ? PE
Case A: Mrs Non Specific
• 55 yo F
• Had a dual chamber PM placed two weeks
ago
• Presents complaining of feeling “not quite
right”
• Lightheaded, fatigued
• Indication for pacemaker?: “…well it’s for
my heart”
Case B: Mrs Still Ticking
• 86 yo F presents with 24 hours of chest pain
• Had dual chamber pacemaker inserted 5
weeks ago for SSS
• No complications
• PMHx: non-contributory
Abnormal Pacemaker
Function
• Clinical Features
 In general symptoms are non-specific
 May present with palpitations, syncope,
dizziness, chest pain, dyspnea, orthopnea,
paroxysmal nocturnal dyspnea, or fatigue
Abnormal Pacemaker
Function
• Investigations
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Electrolytes (incl Ca, Mg, PO4)
Troponin (as indicated)
ECG
CXR
Application of magnet*
Having the pacemaker nurse interrogate the
pacemaker
Case
Failure to Pace
(AKA failure to generate output)
• Diagnosis
 Pacemaker does not fire when expected
 There should be a pacemaker spike between two native complexes
occuring at an interval longer than the LRLI
 A complete absence of pacer spikes immediately after an exceeded
LRLI indicates failure to generate output
 Application of magnet yields no pacing spikes
 What do you think is happening if you see intermittent pacemaker
spikes on the ECG?
• Suggests that pacemaker is oversensing and NOT failing to generate
output
Failure to Pace
• Etiology
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Lead fracture
Loose connection
Insulation defect
Battery depletion
Oversensing
Case
Oversensing
• Diagnosis
 Resulting rhythm is a bradycardia
 May see intermittent or an absence of spikes
 In absence of spikes it is difficult to tell
between failure to generate output
 Suspect if time b/w two native beats is longer
than the LRLI without an intervening
pacemaker spike
Oversensing
• Etiology
 Extracardiac
• Myopotentials (pectoralis)
• Electrocautery
 Intracardiac
• Large T or U waves
• Crosstalk (dual chamber pacemakers)
Case
Failure to Capture
• Fusion Beat
• Pseudofusion Beat
 Indicates failure to
capture
Failure to Capture
• Diagnosis
 Pacing spike is seen on the tracing; but there is
no evidence of depolarization
 Must differentiate between fusion and pseudofusion beats
Failure to Capture
• Etiology
 Lead Issues
• Lead dislodgment (most common)
• Twiddler’s syndrome
• Perforation (rare)
 Increased threshold for capture
•
•
•
•
•
Electrolytes (especially hyperK)
Ischemia
Scar tissue
Metabolic disturbances (acidosis, hypothyroidism, hypoxemia)
Drugs (antiarrhythmics)
Mrs Non Specific cont…
• Labs Normal
• I don’t have a copy of the ECG; but here is
her CXR…
Case cont.
Case
Failure to Sense
(AKA Undersensing)
• Diagnosis
 Occurs when a previous electrical potential is not detected by the
pacemaker
 Detected by finding a pacemaker beat that is immediately followed
by a native beat at an interval less than the LRLI*
 Pacemaker output competes with the intrinsic rhythm of the heart
 Responsible for 1.3% of pacemaker replacements
 Example
• Pacemaker spike occurs between the QRS and the T wave
Failure to Sense
• Etiology (anything that changes amplitude, vector, or frequency of
electrical signals)
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All causes of failure to capture
New BBBs
PVCs
Atrial or ventricular tachydysrhythmias
Functional undersensing*
• Complexes occur during the pacemaker’s refractory period
 Electrolyte abnormalities severe enough to widen the QRS
Failure to Sense
• Management
 You don’t need a magnet
 Call EPS
Pacemaker Syndrome
• Pathophysiology
 Occurs in pacemakers that
pace only the ventricle (e.g.
VVI)
 AV sychrony is lost 
retrograde VA conduction 
atrial contraction against
closed MV + TV valve 
jugular venous distension +
atrial dilation  sx of CHF
and reflex vasodepressor
effects
• Symptoms
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Pre/syncope
Orthostatic dizziness
Fatigue
Exercise intolerance
Weakness
Lethargy
Chest fullness or pain
Cough
Uncomfortable pulsations in
neck or abdomen
 RUQ pain
Pacemaker Syndrome
• Diagnosis
 Difficult diagnosis
 Suggested by lack of AV synchrony
 Retrograde P waves suggest ventriculoatrial conduction which in
the context of AV dyssynchrony may cause atrial overload
 May also see SBP drop of > 20 mmHg when a native rhythm
converts to a paced rhythm
Case
Pacemaker Syndrome
• Management
 1/3 of patients adapt and symptoms resolve
 1/3 require placement of a dual chamber pacer
 Caution: Symptoms of pacemaker syndrome
are non-specific and the same as patients
presenting with pacemaker malfunction
Pacemaker Syndrome
• 20% of patients present with
new complaints or worsening
of initial symptoms that led to
pacemaker insertion
• More commonly with single
chamber pacer
• AV synchrony is lost 
retrograde VA conduction
atrial contraction against a
closed MV + TV  jugular
venous distention + atrial
dilation sx of CHF and
reflex vasodepressor effects
• Symptoms
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Pre/syncope
Orthostasis
Fatigue
Exercise intolerance
Weakness
Lethargy
Chest fullness/pain
Cough
RUQ pain
Pacemaker Mediated
Tachycardia
• Pathophysiology
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

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
Similar to AVNRT
Occurs in patients with dual lead pacemakers
Retrograde conduction from ventricle to atria
Sensed by atria pacer as atria
Ventricular lead fires sooner than expected
thinking that an atrial depolarization has just
occurred
Pacemaker Mediated
Tachycardia
• Management
 Rarely dangerous
 Doesn’t exceed rate maximum set by
pacemaker (~140)
 Magnet can work to temporarily slow rate
 Pacemaker reprogramming
Mrs Still Ticking cont…
Myocardial Perforation
• Can happen early or late (days to weeks)
post implantation
• Need high index of suspicion because:
 Often well tolerated due to small puncture size
 May auto-tamponade
 May be asymptomatic
• May have increased pacing threshold
• CXR, Echo (if cxr negative and highly
suspicious)
Myocardial Perforation
• Symptoms
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Pericardial chest pain
Shoulder pain
Diaphragmatic pacin
Skeletal muscle pacing
Dyspnea
Hypotension
Hiccups
• Signs
 Pericardial rub
 Intercostal or
diaphragmatic pacing
 Failure to pace or sense
 New pericardial
effusion (or
tamponade!)
Pacemaker Malfunction
Failure to Sense
Undersensing
Lead dislodgment
Lead fracture
Myocardial fibrosis
MI
electrolyte disturbances
Failure to Capture
Lead dislogment
Twiddler's syndrome
Lead fracture
Improperly programmed
voltage
Change in required
voltage
MI
Electrolyte changes
Drugs
Battery failure
Failure to Pace
Lead fracture
Loose connection
Insulation defect
Battery depletion
Oversensing
Intracardiac
Extracardiac
Crosstalk
Pacemaker
Syndrome
Pacemaker Magnet
•
•
Does not inhibit/turn off pacemaker
Closes a reed switch in the circuit

•
Converts to asynchronous pacing
Indications for magnet
1. Pacemaker Mediated Tachycardia
2. Oversensing
3. Repeated firing of ICD (will turn off defib
function, not pacing function)
4. Suspected failure to capture
5. Suspected failure to generate output
Disposition
• Who needs admission?
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
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
Failure to capture
Failure to generate output
Failure to sense
Lead perforation
Lead dislodgment
ICDs
ICD’s
•
4 Major Functions
1. Sensing
2. Detection
3. Provision of therapy
to terminate VF/VT
A. Shock
B. Antitachycardia
pacing
4. Pacing for
bradycardia
Defibrillation Threshold
• Minimum amount of energy that will
reliably terminate the arrhythmia
• Measured by electrocardiologist in the lab
• Threshold may be altered by
 Ischemia
 CHF
 Drugs
Drug Interactions
• Can slow VT to the point that sustained VT
isn’t within the threshold for defibrillation
• Drugs may have a pro-arrhythmic effect
• Drugs can alter the defibrillation threshold
ICDs
• Indications
 Syncope with unstable VT
 Ventricular dysfunction
 Long QT
 Brugada
 HOCM
(anyone at risk of sudden cardiac death)
ICD’s
• Patients reporting shock - three possibilities
 Appropriate Shock
 Inappropriate Shock
 Phantom Shock
Case
• 64 y/o M
• Presents to the ED after having sustained 4
shocks from his ICD
• How should we begin?
… more history
• HPI
 Had 4 shocks, all within a matter of 30 minutes
 Was sitting at the computer, no syncope or pre-syncope
 Feeling unwell for ~ 1 week; nausea, vomiting, diarrhea
• PMHx
 Had ICD put in 1 year ago following MI
 Had prob with ICD in 1st month (multiple shocks) but resolved
with setting adjustments
 DM II, 2 PPD smoker, CHF
Causes of ICD Shocks
• Appropriate Shocks
 Ventricular fibrillation
 Monomorphic ventricular
tachycardia
 Polymorphic ventricular
tachycardia
 Torsades de pointes
• Inappropriate Shocks

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A fib
A flutter
A tachycardia
SVT
Junctional tach
Sinus tach
Multiple PVC’s
Oversensing of T waves
Electromagnetic
interference
 Oversensing due to lead
failure or insulation break
Case
• O/E
 HR 105, BP 122/80,
SaO2 95% R/A
 Chest clear
 Sysolic mumur, reg
rhythm, min edema,
JVP 1 cm ASA
ICDs
• ED presentations of patients with ICDs

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Isolated shock
Multiple isolated shocks
Multiple shocks within short sequence
Electrical Storm
• Patient may symptomatic (e.g.
CP/SOB/Syncope) or asymptomatic for any
of the above
ICDs
• Approach
 Single or multiple shocks?
• If multiple: how far apart?
 Symptomatic or asymptomatic?
 Interrogation of ICD
• Determines appropriate vs inappropriate shock
ICDs
• Management
 Single asymptomatic shock
• F/U with electrophysiologist within 1 week (don’t
need to come to ED)
 Single symptomatic shock (CP, Syncope, CHF,
SOB)
• Rule out ACS, suboptimal CHF tx, electrolyte
imbalance
• Interrogate ICD to see if appropriate shock
• If appropriate and no cause found may be referred to
electrophysiologist as an outpatient
ICDs
• Management
 Multiple shocks
• History/Interrogate ICD
 Inappropriate therapy?
 Adjustment of ICD detection zones (ICD nurse or
electrophysiologist can do this)
 Rule out mechanical malfunction (lead malfunction, lead fracture)
 If still receiving multiple shocks in ED can disarm with magnet
 Appropriate therapy?
 Electrical storm
 Embolic events
ICDs
• Multiple Shocks
 Management
• ICD inactivation
 Magnet application (2 types)
ICDs
• Electrical Storm
 Perspective
• Defined as 3 or more episodes of sustained
ventricular arrhythmia in a 24 hour period
• Patients with ICDs can present after receiving
repetitive shocks
• Incidence of ~15% of patients with ICDs
ICDs
• Electrical Storm
 Management
• Rule out reversible triggers (lytes, ischemia, drugs, new change in
settings)
• Amiodarone is considered 1st choice in the absence of reversible
triggers
• Second line
 Sympathetic blockade (BB’s*, stellate ganglionic blockade, Class I
antiarrhythmics),
 Sedation (propofol*)
 Overdrive pacing
 Emergent catheter ablation (last resort)
• Some patients may choose to discontinue ICD therapy
Approach to ICDs in ED
Contraindicated procedures
• Electrocautery
• Lithotripsy
• MRI
ICD in Cardiac Arrest
• Assume the ICD has
failed
• Check rhythm
• Standard ACLS
management
Emergency Pacing
Indications
•
•
•
•
•
Bradycardia
AV block
BBB
Tachycardias
Drug induced bradycardias
Contraindications
• Absolute Contraindications
 None
• Relative Contraindications





Hypothermia
Asystolic arrest
Traumatic cardiac arrest
Prosthetic tricuspid valve
Sepsis
Site Location
• All central venous access sites have been
described
• Things to consider
 RIJ & LSC have the most direct anatomical
access
 SC sites are where the pacemaker is the most
stable
 Jugular and femoral  risk of displacement
Procedure
• Obtain CV access
• Test balloon
• Turn pacer on
 Rate: b/w 60-80
 Sensing: lowest setting (asynchronous*)
 Output: Maximal setting (I.e. 20 mA)
•
•
•
•
Insert the pacer to the 15 cm mark
Inflate balloon once you are past the 15 cm mark
Advance until you get capture
Deflate the balloon
Procedure
• Verification of function
 Sensing threshold
• Set the rate ~ 10 bpm below the patient’s rate and
dial up the sensitivity (pacemaker will now be
inhibited)
• Next lower the sensing knob until the pacemaker
starts firing again (this is the sensing threshold)
• Pacemaker should be lowered to just below this
number
Procedure
• Verification of function
 Pacing threshold
• Minimum current needed to obtain capture
• Start at a high output (20mA) and dial down until
you lose capture
• Current should be set 2-2.5 times the threshold to
ensure capture
• Typical setting is 2-3 mA (if > 5mA then consider
repositioning)
TVP Placement under ECG
Guidance
• Tip of the TVP acts as an intracardiac ECG
lead
• The negative electrode from the end of the
TVP catheter is attached to any of the
precordial leads on the ecg machine using
an alligator clip
TVP under ECG Guidance
• High right atrium/
superior vena cava
• Negative/biphasic P
waves and negative
QRS complexes
• Low amplitude
TVP under ECG Guidance
• Mid to low right
atrium
• P wave become larger
• Inflate the balloon
TVP under ECG Guidance
• Low right atrium to
tricuspid annulus
• P wave starts to
become bipolar and
then positive
TVP under ECG Guidance
• Right ventricle
• Signaled by a small
positive P wave
followed by a deeply
negative QRS
• Deflate the balloon
TVP under ECG Guidance
• Contact with the right
ventricular cardium
• When the tip engages
the RV endocartium
the QRS complex will
show a current of
injury with STE
TVP under ECG Guidance
• Surface ECG
demonstrating capture
Summary
• Pacemakers




Pocket Complications
Failure to pace, failure to capture, failure to capture
PMT
Pacemaker syndrome
• ICDs
 Function
 Malfunction
• Pacemaker Placement
 Blind technique
 ECG guided technique
 Confirmation of placement and proper settings
The End