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When Tickers Start to Flicker: Pacemaker Malfunction
Kevin C Reed, MD, FACEP
Assistant Professor of Emergency Medicine
Georgetown University and Washington Hospital Center
Case #1.
A 67 year old woman was admitted due to dizziness. Because of complete AV block, she had
permanent pacemaker insertion 2 years ago. An ECG is performed. What is the diagnosis?
Case#2: A 70 year-old male with a history of hypertension and congestive heart failure status
post pacemaker placement for 3rd degree heart block presents to the emergency department with
fatigue for 1 week. He had a syncopal event today while out playing with his grandchildren. On
exam he appears in mild distress with a blood pressure of 108/58, irregular pulse of 36-70,
respirations of 20 and oxygen saturation of 100% on 4 liters nasal cannula. This ECG is obtained.
What is going on in these cases?
Introduction:
The first implantable electronic pacemakers were introduced in the 1950s to
prevent Stokes-Adam attacks. Today, an estimated 112,000 to 121,000 new pacemakers
are implanted annually with an additional 25,000 replacement procedures (majority due
to batteries) performed annually.
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Current models are usually reliable, but malfunctions may arise. Patients with
pacemaker malfunction often have vague and nonspecific symptoms including
palpitations, irregular heart beats, syncope, presyncope, dizziness, chest pain, dyspnea,
orthopnea, paroxysmal nocturnal dyspnea or fatigue. A 12-lead electrocardiogram (ECG)
is an essential part of the evaluation for pacemaker malfunction.
Goals of this lecture:
1. Review basic components of pacers and typical ECG findings of normal pacer function.
2. Understand the different types of pacer malfunction and their associated ECG findings.
3. Develop a game plan for dealing with pacer complications.
***Important caveat: Only discussing permanent not temporary pacemakers.
I. Outline:
a) Indications
b) Anatomy of a pacemaker
c) Pacemaker nomenclature
d) Normal paced ECG findings
e) Pacemaker appearance on CXR
f) Pacemaker malfunctions
II. Indications:
a) Too slow: Pacemaker
i) symptomatic bradyarrythmias: bradycardia and various types of heart blocks.
****A complete list of guidelines for implanting pacemakers is available online at
http://circ.ahajournals.org/cgi/content/full/112/16/2555.
b) Too fast: AICD
i) Atrial fibrillation/flutter, Vtach, Brugada, WPW, Prolonged QT
http://www.odec.ca/projects/2007/torr7m2/images/pacemaker.gif
III. Anatomy
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a)
b)
c)
d)
Box: pulse generator, lithium battery, electric circuit
Pacing leads (1, 2, or 3)
Batteries are lithium based and have life-spans approaching 10 years.
Manufacturers: Medtronic, St. Jude and Guidant
IV. Pacemaker Nomenclature
Table 1. NASPE/BPEG Codes for classification of pacing modes.7
NASPE=North American Society of Pacing and Electrophysiology
BPEG= British Pacing and Electrophysiology Group
Position
I
Chamber(s)
Paced
O = None
A = Atrium
V = Ventricle
D = Dual
Chamber
II
Chamber(s)
Sensed
O = None
A = Atrium
V = Ventricle
D = Dual Chamber
III
Response to
Sensing
O = None
A = Atrium
V = Ventricle
D = Dual Chamber
IV
Programmability Rate
Modulation
O = None
P = Simple
M = Multiprogrammable
C = Communicating
R = Rate Responsive
VI
Antitachycardia
(AICDs)
O = None
P= Pacing
(antidysrhythmia)
S= Shock
D= Dual (P + S)
Most common seen in the ED:
1) DDD = Paces, senses and responds to sensing in both the right atrium & ventricle
2) VVI – Paces and senses the ventricle only and inhibits ventricular pacing
V. How does a normal pacemaker function?
a) Paces or stimulates the heart
i) Asynchronous (fixed)
ii) Synchronous (demand)
b) Sense intrinsic electrical activity
VI. Normal paced ECG
http://library.med.utah.edu/kw/ecg/mml/ecg_12lead066.gif
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a)
b)
c)
d)
Heart rate: 600-100bpm
Pacer spikes (most of the time)
Left axis deviation
Wide QRS with LBBB appearance
i) Pattern occurs due to initiation of electrical activity in the right ventricle that
spreads slowly to the left ventricle, similar to a right ventricular ectopic beat.
ii) ?RBBB seen: Think lead in LV (left ventricular epicardial placement) or lead
dislodged from myocardium/perforation
e) Appropriate discordance of ST segments
Figure 3. Schematic and tracings showing rule of appropriate discordance in pacemakers. From Mattu A and
Brady W. ECGs for the Emergency Physician BMJ Publishing Group, London, 2003.
VII. CXR findings
a) Make sure leads cross the midline.
b) Pacer wires should point toward sternum (PA/lateral) not the spine!!!
c) Radiopaque logo of pacemaker to identify manufacturer/type (if no card)
d) Check for complications of recently placed pacemaker:
i) Pneumo/hemothorax, pleural effusion
ii) Pericardial effusion/tamponade (rupture through myocardium)
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a) Reed switch
i) activated by an externally placed magnet
ii) Applying magnet turns off sensing function
(1) Horseshoe or ring/donut shape
(2) Place directly on pacemaker
iii) Asynchronous pacing at set rate (VOO/AOO/DOO if dual chamber)
iv) Allows for testing of the pacemaker’s pacing capacity.
***Will not harm the patient!!!!
v) When to use?
(1) Heart rate too slow
(2) Heart rate too fast
(3) AICD going wild (repeated shocks)
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Figure 7. Placement of magnet inhibits sensing and reverts the pacemaker to asynchronous pacing. The magnet allows
for assessment of capture (but not sensing). The first 4 beats show native atrial activity inhibiting atrial pacing and
triggering ventricular pacing. When the magnet is placed (m), atrial sensing is halted and asynchronous atrial and
ventricular pacing occurs. This represents DOO pacing. From Chan TC, Cardall TY. Electronic Pacemakers. Emerg
Med Clin N Am 2006;24:179-194.
VIII. Evaluation for suspected pacemaker malfunction
a) Usually present with recurrent symptomatic brady-arrhythmias.
b) Most dangerous failures result from pacemaker induced tachycardias.
c) Common conditions predisposing to pacemaker complication
i) hyperkalemia, hypokalemia, hypoxemia
ii) acute myocardial infarction
iii) cardioactive drugs
b) Approach to patient with suspected pacemaker malfunction
(1) Manufacturer/type of pacemaker, ?Card with patient
(2) Date of implantation?
(3) Indication for pacemaker placement?
(4) Cardiac related meds
(5) Presenting symptoms
(6) Physical exam
(a) Vital signs, cardiopulmonary
(b) Pacemaker pocket
(7) ECG and rhythm strip (EMS)
(8) CXR
(9) Electrolytes (CA++, Mg, Phos)
(10) Magnet application?
(11) Interrogation
***Caveat: Technician/Rep performing interrogation is not a “licensed”
professional to give accurate reading. Should be reviewed by EP/Cardiologist. If
unavailable and patient with concerning symptoms (chest pain, syncope)
recommend admit for observation even if “normal” per tech as malfunction
may still exist.
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Rhythm strip
P=paced beat
B. Interrogation strip: from top to bottom: surface ECG, electrogram markers, and near-field ventricular
electrograms. Key: AS = atrial sense; VS = ventricular sense; VP = ventricular pace.
Available at www.medscape.com/viewarticle/524834_4
IX. Types of pacemaker malfunction
a) Failure to sense
i) Causes: fibrosis at the tip of the electrode, lead dislodgement, impending
battery failure, as well as severe electrolyte abnormalities that widen the QRS
and delay its upstroke
ii) Undersensing: pacemaker fails to sense or detect native cardiac activity
(1) 1.3% of pacemaker replacements.
(2) ECG Pacer ignores any intrinsic rhythm and paces at a fixed rate
(3) competitive with the intrinsic rhythm
Ventricular undersensing. In this patient with a DDD pacemaker, intrinsic ventricular events are not sensed. A native,
upright, narrow QRS complex (narrow arrow) occurs soon after each atrial stimulus, but these complexes are not
sensed, and before ventricular repolarization has a chance to get started, ventricular pacing occurs, triggering the wider
QRS complexes (wide arrow). From Chan TC, Cardall TY. Electronic Pacemakers. Emerg Med Clin N Am
2006;24:179-194.
iii) Oversensing: pacemaker unexpectedly senses a signal as a proper atrial or
ventricular signal ventricular and does not fire
(1) 10% of pacemaker replacements
(2) Common: skeletal muscle myopotentials/tremors
(a) pectoralis, rectus abdominal. diaphragm muscles
(3) Lead fracture, dislodgement, or loose connections (Check CXR!)
(4) Electrocautery, MRI, and extracorporeal shock wave lithotripsy.
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(5) Crosstalk: only in dual chamber pacemakers.
(a) pacing stimulus in one chamber is sensed by other chamber’s sensors
as that second chamber’s own impulse
(6) ? I-Pod/music players: interference BUT NO functional compromise
(7) Airport screening: not significant effects
b) Failure to capture
i) Pacemaker output is generated but fails to depolarize myocardium
ii) ECGtypically shows a pacing spike without capture and depolarization
iii) Causes:
(1) Exit Block: Most common
(a) First few weeks following implantation
(b) Maturation of tissues at the electrode-myocardium interface
(c) External cardiac defibrillation
(2) Battery failure or faulty programming
(3) Lead fracture or dislodgement
(4) Electrolyte abnormalities
(5) Myocardial ischemia or MI(Right sided)
(6) Insulation break, faulty connection of a lead to the pacemaker
(7) Cardiac perforation by pacer leads (rare)
(a) Chest radiograph showing the lead tip out of the heart
(b) ECG paced complex with a new RBBB
(8) Twiddler’s syndrome
(a) Patient fidgeting with the pulse generator
(b) resulting in the lead tip being pulled away from the myocardium
Failure of ventricular capture. This patient has underlying sick sinus syndrome and complete heart block. There is
intermittent native atrial activity (a) and atrial pacing and capture (p) when no native activity is present. There is
failure of ventricular capture, however, because no QRS complexes following the ventricular pacing spikes (arrow).
The QRS complexes on this tracing are slow ventricular escape beats (v). In the fourth QRS complex, the pacemaker
generates a stimulus at the same time a ventricular escape beat occurs, yielding a type of fusion beat (f). From Chan
TC, Cardall TY. Electronic Pacemakers. Emerg Med Clin N Am 2006;24:179-194
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DDD pacing with intermittent loss of ventricular capture (arrow). After the third loss of capture event there is a
junctional escape beat (J). In the next to last beat, a junctional escape beat is bracketed by two pacing spikes as a
form of safety pacing. Rather than inhibiting ventricular pacing (and risk having no ventricular output if the sensed
event were not truly a native ventricular depolarization), the AV interval is shortened and a paced output (S) occurs.
From Chan TC, Cardall TY. Electronic Pacemakers. Emerg Med Clin N Am 2006;24:179-194.
c) Failure to pace or generate output
i) pacemaker fails to deliver a stimulus
http://library.med.utah.edu/kw/ecg/mml/ecg_out_fail.gif
ii) Causes: oversensing (most common)
(1) pacing lead problems (lead fracture or dislodgement)
(2) battery or pacemaker generator failure (rare)
(3) electromagnetic interference (MRI scanning or cellular telephones)
(4) blunt trauma
iii) ECG  absence of pacemaker spikes at a point at which the pacemaker
spikes would be expected
iv) Consider application of magnet
(1) evaluating appropriate pacemaker function
(2) may correct the problem
X. Pacemaker mediated dysrhythmias
a) Pacemaker mediated tachycardia (PMT) (aka: endless-loop tachycardia)
i) Due to interactions between native cardiac activity and the pacemaker
ii) Re-entry dysrhythmia
(1) Initiation usually occurs by a PVC with retrograde atrial conduction
(2) Pacemaker senses this as a native atrial stimulus
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(3) Leads to generation of a ventricular stimulus and another retrograde P
wave is produced
(4) Pacemaker acts as the antegrade conductor for the reentrant rhythm
(5) Persistent retrograde conduction occurs through the intact AV node
Pacemaker-mediated tachycardia. The third QRS complex is a paced beat (narrow arrow), and causes a retrograde P
wave that triggers a run of PMT. In this case the pacemaker detects the PMT and in the penultimate beat (wide arrow)
temporarily lengthens the PVARP, preventing atrial sensing of the retrograde P wave and breaking the re-entrant loop.
From Chan TC, Cardall TY. Electronic Pacemakers. Emerg Med Clin N Am 2006;24:179-194.
iii) Additional triggers:
(1) Oversensing of skeletal muscle myopotentials
iv) ECG regular, ventricular paced tachycardia
(1) max 160-180bpm
(2) Hemodynamic instability uncommon
Tachycardia induced ischemia a concern
v) ED Treatment
(1) Applying magnet to break the reentry circuit
(2) Turns off all sensing  asynchronous mode of pacing
(3) Alternatives:
(a) Initiating VA conduction block
(b) Adenosine or judicious use of vagal maneuvers
b) Runaway pacemaker
iii) Older-generation pacemakers?? STILL EXISTS??
iv) Modern pacemakers preprogrammed upper rate limit preventing this problem
v) ECG paced ventricular tachycardia RATES UP TO 400BPM
vi) Placement of a magnet may induce a slower pacing rate temporarily
vii) Magnet fails?  emergent surgery to disconnect or sever pacemaker leads
Figure 2. "'Runaway pacemaker" from Harper RJ, Brady WJ, Perron AD, et al. The paced electrocardiogram: issues
for the emergency physician. Am J Emer Med 2001;19:551-560.
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In general, the type of pacemaker malfunction will be related to the patient’s heart rate
at presentation:
1) Slow heart rate
a. Failure to pace
b. Failure to capture
2) Elevated heart rate
a. Failure to sense
b. Dysrythmia
c. Pacemaker mediated tachycardia or runaway pacemaker (rare)
3) ED Disposition
a. Magnet useOK!!! Can be used to make diagnosis/treatment.
b. If you apply a magnet and see the following:
i. No spikes  failure to output/pace from component failure
ii. Spikes without corresponding QRS/p wave failure to capture
iii. No pacing baseline with long pauses or profound bradycardia
then apply a magnet and pacing occurs oversensing
c. Interrogation key
d. Consultation with EP/cardiologist
e. Admit high risk history (chest pain, syncope) even if interrogation
“normal” per technician
Case answers and resolutions:
Case 1: A 67 year old woman was admitted due to dizziness. Because of complete AV block,
she had permanent pacemaker insertion 2 years ago. An ECG and CXR are performed. What is
the diagnosis?
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Answer Failure to capture ECG spikes due to lead fracture (arrows). Patient had new pacemaker placed.
Case#2: A 70 year-old male with a history of hypertension and congestive heart failure status
post pacemaker placement for 3rd degree heart block presents to the emergency department with
fatigue for 1 week and syncopal event today.
AnswerFailure to pace: Complete heart block with wide QRS escape rhythm and a few paced
complexes with pacing artifact immediately preceding the QRS (2nd and 4th QRS complexes in the rhythm
strip) are seen. In this case the failure to routinely pace is due to battery failure of the pulse generator and a
replacement was needed.
Conclusions: Practioners with a basic understanding of pacemaker modes and function
can use the ECG to assist with diagnosis of pacemaker malfunction and complications. In
addition to a through history, physical exam and chest radiograph, the ECG is a valuable
tool in evaluating and treating patients with symptoms concerning for pacemaker
malfunction in the emergency room, on the hospital floor or in the ICU setting.
Thanks for your time and attention!!!
Please email any questions or comments to:
kreedmd1@hotmail.com
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Bibliography
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