Pacemaker troubleshootingsingle chamber pacemakers
Reasons for evaluation
• Patient symptomatic
– Palpitation
– Syncope
– presyncope
• Pacemaker malfunction suspected
– ECG
– Telemetry
– Ambulatory ECG
• Routine pacemaker follow up
Patient details
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Indication for pacing
Implant operative note
Diagnosis
Medication –can alter pacing tresholds
DC ,MRI,electrocautery
Trauma,electrical current exposure
Concurrent medical problems-CRF,hyperkalemia
Prior ECG,CXR
Pacemaker system
– manufacturer
– Model
– current programming
– date of implant
– special features
– Sensing and pacing tresholds
– impedance
Lead system
– manufacturer
– model
– polarity
– Fixation
– insulation and date
Causes of pacemaker malfunction
• Pacing stimuli present with failure to capture
• Pacing stimuli present with failure to sense
• Pacing stimuli absent
– Oversensing
– No output
• Pseudomalfunction
Failure to capture
• No evidence of depolarization after pacing
artifact
Loss of capture
Early post device implantation
• CXR abnormal
– Lead dislodgement
• Downward migration of PG
• Failure to secure anchoring sleeves properly
• Too little or too much slack
– Lead perforation
• Elevated impedance
– Loose set screw
– failure to seat lead pin properly in header
• Normal CXR,normal impedance
– Micro lead dislodgement
– Inflammatory response
Late post device implantation
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Battery depletion
Twiddler s syndrome
Abnormal myocardium
Insulation failure
Conductor failure
– Mechanical stress on lead
• Anchoring sleeve
• Interaction with generator in pocket
• b/w clavicle and first rib
• Increase the energy in the output pulse
– Run a capture threshold test
– Adjust the output parameters, if necessary
• Pulse amplitude (V)
• Pulse width or duration (ms)
– It is generally more efficient to increase the pulse
amplitude
• Investigate possible lead problems
• Reprogram device polarity
Undersensing
• An intrinsic depolarization that is
present, yet not seen or sensed by the
pacemaker
P-wave
not sensed
Atrial Undersensing
• Undersensing occurs when the pacemaker does not
detect intrinsic activity that really is there
• Undersensing causes the pacemaker to pace more
than it should
Undersensing May Be Caused By:
• Inappropriately programmed sensitivity
• Lead dislodgment
• Lead failure:
– Insulation break; conductor fracture
• Lead maturation
• Change in the native signal
• Functional
– Magnet
– Noise reversion
• Adjust the sensitivity setting
– Run a sensing threshold test
– Measure the intrinsic signals
– Adjust the sensitivity appropriately
• To increase sensitivity, decrease the mV setting
– Make all changes to sensitivity settings in small
steps since large changes may only introduce new
sensing problems
Oversensing
Marker channel shows
intrinsic activity...
...Though no
activity is present
Ventricular Oversensing
• The sensing of an inappropriate signal
– Can be physiologic or nonphysiologic
• Oversensing occurs when the pacemaker
inappropriately “thinks” that it sees intrinsic
activity that is not there
• Oversensing causes the pacemaker to inhibit
the pacing output pulse, even though the
device should be pacing
• Myopotentials
– Pectoralis,rectus abdominis,diaphragm
– Bipolar leads are less susceptible
• Oversensing of normal intracardiac signals
– Reduce sensitivity of affected lead to eliminate
oversensing
• EMI
• Provocative maneuvers may be needed if
intermittent symptoms
• Magnet eliminates pauses-oversensing
• Reprogram the sensitivity
– Conduct a sensing threshold test
– Adjust the sensitivity by making the device less
sensitive (increase the mV setting)
– Make only small changes
• Extend the refractory period
No Output
• Pacemaker artifacts do not appear on the
ECG; rate is less than the lower rate
Pacing output delivered; no
evidence of pacing spike is seen
No Output May Be Caused By:
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Poor connection at connector block
Lead failure
Battery depletion
Circuit failure
• Steps to take for possible loss of output
– Verify all lead connections
– Check lead integrity
– Evaluate battery status
– Contact the device manufacturer
• Loss of output may require the replacement of
all or part of the pacing system
Pseudomalfunctions
Pseudomalfunctions are defined as:
Unusual,Unexpected ECG findings that appear
to result from pacemaker malfunction but that
represent normal pacemaker function
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Hysteresis
Magnet rate
rate responsive pacing
Noise reversion
Rate drop response
Sleep rate algorithm
Hysteresis
• Allows a lower rate between sensed events to
occur; paced rate is higher
Lower Rate 70 ppm
Hysteresis Rate 50 ppm
Magnet Operation
• Magnet application causes asynchronous
pacing at a designated “magnet” rate
• Threshold Margin Test (TMT)
• Three beats at 100 bpm, followed by a magnet rate of 85
• Third beat has an automatic pulse width decrement of 25%
• Elective replacement indicators-change the rate from 85 to
65
• Extended TMT.
– TMT is performed at 100 ppm
– Pulse width reduced by 25% on 3rd , 50% on 5th , and 75%
on 7th
Rate Responsive Pacing
• An accelerating or decelerating rate may be
perceived as anomalous pacemaker behavior
VVIR / 60 / 120
Electrical Reset and Battery Depletion
• Reset may occur due to exposure to EMI
electrocautery, defibrillation, causing reversion to a “backup” mode
– Rate and mode changes will occur
– Device can usually be reprogrammed to
former parameters
• Elective replacement indicators (ERI) can resemble back-up
mode
– Interrogating device will indicate ERI
(“Replace Pacer”)
A Change in Pacing Modes
May Be Caused By:
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Battery depletion indicators (ERI/EOL)
Electrical reset
Mode switching
Noise reversion
Noise Reversion
• Sensing occurring during atrial or ventricular
refractory periods will restart the refractory
period. Continuous refractory sensing is called
noise reversion and will:
– Cause pacing to occur at the sensor-indicated rate
for rate-responsive modes
– Cause pacing to occur at the lower rate for nonrate-responsive modes
Noise reversion
VT in a patient with VVI-pacing occurs at lower rate due to noise
reversion
Rate drop response
Delivers pacing at high rate when episodic drop in
rate occurs
Muscle Stimulation May Be Caused By:
• Inappropriate electrode placement near
diaphragm or nerve plexus
• Break in lead insulation
• Unipolar pacing
Flouro diagnosis
1.ECG shows
A.Failure to sense
B.Failure to capture
C.Hysteresis
D.Oversensing
2.ECG shows
A.Failure to sense
B.Failure to capture
C.Hysteresis
D.Oversensing
3.ECG shows
A.Failure to sense
B.Failure to capture
C.Hysteresis
D.Oversensing
• 4.ECG demonstrates
a.Failure to sense
b.Failure to capture
c.Functional non capture
d.fusion
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ECG shows
A.Failure to sense
B.Failure to capture
C.Hysteresis
D.Functional non capture
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ECG shows
A.Functional non capture
B.Failure to capture
C.Hysteresis
D.Oversensing
7.possibilities are
• A.VVI in VOO mode
• B.magnet kept
• C.persistent ventricular undersensing
• D.Noise reversion
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8.make and break potentials usually cause
A.undersensing
B.oversensing
C.functional non capture
D.failure to capture
• 9.elevated pacing threshold and elevated
impedance can be caused by
• A.lead fracture
• B.loose set screw
• C.insulation failure
• D.battery depletion
• 10.elevated threshold with decreased
impedance caused by
• A.lead fracture
• B.loose set screw
• C.insulation failure
• D.battery depletion
11.What are appropriate in this patient
A.sensitivity setting to be adjusted
B.lower the programmed rate
C.introduce hysteresis
D.check capture treshold
12.What is the next step in this patient
– A.adjust sensitivity-increase mV setting
– B.adjust sensitivity-decrease mV setting
– C.pacing treshold test-adjust output parameters
– D.activate hysteresis
13.What is appropriate in this patient
– A.adjust sensitivity-increase mV setting
– B.adjust sensitivity-decrease mV setting
– C.pacing treshold test-adjust output parameters
– D.activate hysteresis
14.What is appropriate in this patient
– A.adjust sensitivity-increase mV setting
– B.adjust sensitivity-decrease mV setting
– C.pacing treshold test-adjust output parameters
– D.activate hysteresis
15.What is appropriate in this patient
– A.adjust sensitivity-increase mV setting
– B.adjust sensitivity-decrease mV setting
– C.pacing treshold test-adjust output parameters
– D.activate hysteresis