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Pacemakers
Outline
• Basic Function and Types
• Associated Morbidity
• Specific Indications for Use
• Follow Up
Basics
Pulse Generator
Purpose
• Symptomatic bradyarrhythmia
o
o
Bradycardia
Block
Pacemaker Codes
1
2
3
4
Chambers Paced Chambers Response to
Rate
Sensed
Sensed
Modulation?
Stimulus
5
Multisite
Pacing
(ICD)
O (none)
O
O
O (non-rate
responsive)
O
A (atrium)
A
T (triggered)
R (rate
responsive)
A
V (ventricle)
V
I (inhibited)
D (both atrium &
ventricle)
V
D
Paced Rhythm
• Stimulated P wave nearly normal in
appearance
• Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and
from apex to base
o Resembles complete LBBB
o
o
• Broad T wave and may include sharp
inversions that mimic ischemia
Paced Rhythm
• Stimulated P wave nearly normal in
appearance
• Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and
from apex to base
o Resembles complete LBBB
o
o
• Broad T wave and may include sharp
inversions that mimic ischemia
Paced Rhythm
• Stimulated P wave nearly normal in
appearance
• Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and
from apex to base
o Resembles complete LBBB
o
o
• Broad T wave and may include sharp
inversions that mimic ischemia
AAI Pacing
• Underlying sinus note dysfunction but intact
cardiac conduction
• Sense atrial activity
• Inhibit pacing if the patient’s heart rate remains
above prevent target
• At lower rates, pacer stimulates atria
Pacemaker Configurations
AAI
Indications
Sick sinus syndrome in the absence of AV node
disease or atrial fibrillation.
VVI Pacing
• No useful atrial function eg Afib
• Tracks ventricular activity
• Paces ventricle only if a QRS complex is not
sensed within a predefined interval
Pacemaker Configurations
VVI
Indications
The combination of AV block and chronic atrial
arrhythmias (particularly atrial fibrillation).
DDD Pacing
• Most common form of dual chamber pacing
• Atrial impulse generated if native atrial activity
fails to occur within a preset time period after the
last atrial impulse
• If a QRS complex does not occur during a preset
interval after the atrial impulse, a ventricular
impulse occurs
Pacemaker Configurations
DDD
Indications
1. The combination of AV block and SSS.
2. Patients with LV dysfunction and LV hypertrophy
who need coordination of atrial and ventricular
contractions to maintain adequate CO.
Pacemaker Configurations
VOO
Indications
Temporary mode some-times used during surgery to
prevent interference from electrocautery
Pacemaker Configurations
VDD
Indications
AV block with intact sinus node function (particularly
useful in congenital AV block).
• Basic Function and Types
• Associated Morbidity
• Specific Indications for Use
• Follow Up
Associated Morbidity
- Pacemaker Syndrome
o
o
o
o
Dizziness, weakness, dyspnea, presyncope, syncope,
exertional-fatigue
AV dyssynchrony usu d/t VVI pacing with intact sino-atrial
activity
Tx: Dual-chamber pacers which restore atrial kick
Complications: Afib, stroke
Associated Morbidity
- Pacemaker-mediated Tachycardia
o Rapid ventricular pacing at max programmed rate
caused by an endless loop
 PVC conducted retrograde via AV node to atrium
 Retrograde signal sensed by atrial channel
 Pacing of ventricle
 Retrograde conduction to atria
o Most pacemakers can recognize and terminate PMT
• Basic Function and Types
• Associated Morbidity
• Specific Indications for Use
• Follow Up
Indications
•
•
•
•
Sinus Node Disease
AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure
• Class I: Conditions for which there is evidence
and/or general agreement that a given procedure
or treatment is useful and effective.
• Class II: Conditions for which there is conflicting
evidence and/or a divergence of opinion about
the usefulness/efficacy of a procedure or
treatment.
• Class III: Conditions for which there is evidence
and/or general agreement that the
procedure/treatment is not useful/ /effective and
in some cases may be harmful.
Indications
• Sinus Node Disease
o
In general, pacemaker therapy is
recommended only when symptoms are
present
Class I
1. Sinus node dysfunction with documented symptomatic
bradycardia
2. Symptomatic chronotropic incompetence (failure to
increase HR with exercise or increased metabolic demand)
Indications
• Sinus Node Disease
Class II
- Heart rate <40 beats/min spontaneously or in the
presence of essential medical therapy when clinically
important symptoms are not correlated with bradycardia
- Syncope and abnormal sinus node function documented
in electrophysiologic study
- Heart rate <40 beats/min and minimal symptoms
Class III
- Asymptomatic sinus node disease
- Clear documentation that symptoms are unrelated to
bradycardia
- Sinus node disease due to nonessential drug therapy
Pacemaker mode selection in sinus node disease may markedly affect patient outcomes
Indications
•
•
•
•
Sinus Node Disease
AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure
Common Causes of Acquired Atrioventricular Block
• Degenerative disease
o Lev disease
o Lenègre disease
o Secondary
degeneration/calcification
• Medications
o β-Receptor blockers
o Calcium channel
antagonists
o Digoxin
o Other antiarrhythmic agents
• Atherosclerotic heart disease
o Myocardial ischemia
o Myocardial infarction
• Dilated cardiomyopathy
• Infiltrative disease
o Sarcoidosis
o Amyloidosis
o Metastasis
• Infections
o Endocarditis
o Lyme disease
o Chagas disease
• Iatrogenic causes
o After atrioventricular nodal
ablation
o After cardiac surgery
o After radiation therapy
• Enhanced parasympathetic activity
Indications
• Acquired AVB in adults
Class I
• Third-degree AVB
o Asystole >3 s or escape rate <40 beats/min
o Associated neuromuscular disease (eg, KearnsSayre, Erb dystrophy)
o After atrioventricular node ablation
o After cardiac surgery
• Symptomatic second-degree AVB
• Alternating bundle branch block type II second-degree
AVB with underlying bifascicular block
Indications
• Acquired AVB in adults
Class II
• Third-degree AVB with LV dysfunction
• Type II second-degree AVB
• Syncope with underlying bifascicular block when VT
excluded
• Neuromuscular diseases with any AVB or fascicular
block
Class III
- Asymptomatic first-degree or type I second-degree AVB
• AVB expected to resolve
• Fascicular block with first-degree AVB or no AVB
Indications
•
•
•
•
Sinus Node Disease
AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure
Neurocardiogenic Syndrome
• transient imbalance in the cardiovascular
autonomic regulation that results in
vasodilation with or without inappropriate
bradycardia.
• triggered by vasovagal syncope or by
compression of the carotid sinus (carotid
sinus hypersensitivity)
Neurocardiogenic Syndrome
• Substantial bradycardia during tilt-table
(not always needed for dx)
• If vasodilation cause for hypotension =
NOT a candidate for pacing
• Ventricular pacing – frequent AV block
Indications
•
•
•
•
Sinus Node Disease
AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure
Indications
• Chronic Heart Failure
Interventricular conduction delay common •
poor coordination of ventricular contraction
o 3 leads
o
 Right ventricle
 Coronary sinus to pace left ventricle
 Right atrium to sense intrinsic rhythm to ensure
appropriate AV timing interval
Indications
• NYHA III – IV on medical therapy
• QRS duration > 130 msec (LBBB)
• LV enlargement (end-diastolic dimension
> 55 mm)
• LV Ejection Fraction <35%
Indications
• Basic Function and Types
• Associated Morbidity
• Specific Indications for Use
• Follow Up
Follow Up
• Routine visits
o Hx:
palpitations, light-headedness, syncope,
or change in exercise tolerance
o 12-lead EKG
o Overpenetrated PA and lat CXR (to check
placement of pulse generator and leads)
Pacemaker Failure
• Failure to sense
• Failure to pace
• Internal malfunction of the pacer
generator
Failure to Sense
• Undersensing
Lead related changes (dislodgement, lead
fracture)
o Change in lead-myocardium interface (change
in activation sequence as in new BBB or
PVCs, electrolyte abnormality, new med, lead
maturation and fibrosis, infarction at lead tip)
o
Failure to Sense
• Oversensing – sensing of inappropriate
signals
Other parts of the normal ECG
Electromagnetic interference when subjected
to strong electrical field
o Lead or pulse generator malfunction
o
o
 Lead fracture
 Loose set screw
Problems with Pacemakers
Failure to Sense
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
• Undersensing
• Oversensing
Failure to Capture or Pace
• Pacer lead (lead dislodgement, fracture)
• Pulse generator (battery depletion, loose
screw)
• Change in interface (fibrosis, electrolyte,
meds, infarctions)
• Pacemaker-mediated tachycardia
Problems with Pacemakers
Failure to Capture
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
•
•
•
•
Threshold rise (electrolytes, drugs)
Lead dislodgement
Lead fracture
RV infarct
Problems with Pacemakers
Failure to Pace
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
•
•
•
•
Oversensing
Battery failure
Internal insulation failure
Conductor coil fracture
Problems with Pacemakers
Failure to Pace
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
• Crosstalk
Paced Rhythm
• Stimulated P wave nearly normal in
appearance
• Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and
from apex to base
o Resembles complete LBBB
o
o
• Broad T wave and may include sharp
inversions that mimic ischemia
Acute MI – how to tell?
discordant - in the opposite direction of the QRS vector
Perioperative Mgmt
• Applicable to neck and chest surgeries
o
Obtain pacemaker programming info
Magnet may be placed over device to inhibit sensing or the
pacemaker may be programmed to asynchronous mode
before surgery
Ensure availability of temporary pacing in case of
emergency
Use low energy and short bursts of electrocautery
Avoid electrocautery near device and place grounding pads
away from device
Turn off program rate modulation during surgery
o
Interrogate and reprogram pacemaker after surgery
o
o
o
o
o
Example 1
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/
Ventricular paced, Ventricular sensed,
Consistent with VVI
Example 2
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/
Ventricular paced, Atrial sensed,
Consistent with DDD or VDD
Example 3
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/
Atrial paced
Consistent with AAI or DDD
Example 4
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/
Failure to Pace
Example 5
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/
Failure to Sense
Key points
• Find out pacemaker model, date of
implantation, date of last pacemaker
check, indication for pacemaker
• Modes
o
o
o
VVI: permanent afib
AAI: SSS and normal AV conduction
DDD: Most common Sinus and AV nodal
disease
Key points
• Modes
o
o
o
VVI: permanent afib
AAI: SSS and normal AV conduction
DDD: Most common Sinus and AV nodal
disease
Key points
• Permanent pacing for
o
o
symptomatic bradycardia and complete heart block
Heart Failure on optimal medical tx for ≥ 3 mo
Key points
• Problems
o
o
o
o
Pacemaker-mediated tachycardia
Pacemaker syndrome
Failure to sense
Failure to pace
Sources
• “Contemporary Pacemakers: What the Primary Care
Physician Needs to Know” Mayo Clinic Proceedings
2008
• “The Paced Electrocardiogram: Issues for the
Emergency Physician” American J of Emergency Med
• Dr. Huang’s Cardiology Handout
• medresidents.stanford.edu/TeachingMaterials/Pacemak
ers/Pacemakers.ppt