Transcript Loss of capture

HK-IN-PACE
Heart Rhythm Refresher Course 2013
Module 3: ECG Interpretation
Pacemaker ECGs
Dr. K Chan
Ruttonjee and Tang Shiu Kin Hospitals
Outline
• PPM ECG – Morphology
• PPM ECG - Troubleshooting
PPM ECG - Morphology
CM Yu et al. Cardiac Resynchronisation Therapy
RV Apical vs Septal Pacing
RV Septum
RV Apical
CM Yu et al. Cardiac Resynchronisation Therapy
Biventricular pacing
CM Yu et al. Cardiac Resynchronisation Therapy
ECG morphology in BiV pacing
Loss of LV capture  Lead I : Loss of negativity
Loss of RV(A) capture  Lead III: Loss of negativity
CM Yu et al. Cardiac Resynchronisation Therapy
RV Apical Pacing ECG – Any problem?
RV Lead inside LV
BiV Pacing ECG
BiV Pacing ECG – Any problem?
PPM ECG Troubleshooting
Common PPM ECG Problems:
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Oversensing
Undersensing
Oversensing
Noncapture
No output
Pseudomalfunction
Is there any pacing spike?
No pacing spike – No output
True malfunction
• Over-sensing ( of T, P, R waves; myopotential,
EMI, crosstalk…)
– New implant: Open circuit (conductor #, loose set-screw,
pin/header mismatch, air in pocket)
– Old implant: Insulation or component failure, battery
depletion
Pseudo-malfunction (Functional over-sensing)
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•
•
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Sleep rate
Rate hysteresis
Mode switching
PMT intervention
MVP (Managed ventricular pacing – Medtronic)
Oversensing
Marker channel shows
intrinsic activity...
...Though no
activity is present
Ventricular Oversensing
• The sensing of an inappropriate signal
– Can be physiologic or nonphysiologic
Absent pacing spike –
Ventricular Oversensing
Senstivity @ 1mV
Oversensing of noise  Inhibition of pacing
Senstivity @ 2mV
Decreasing sensitivity  No more noise oversensing
 Normal pacemaker output
Senstivity @ 4mV
Ventricular Over-sensing
Cross-talk : Ventricular inhibition due
to far-field sensing of atrial output
Over-sensing – What to do?
• Ask history:
– Use of electronic equipments – oversensing of EMI
– Arm movements – oversensing of myopotentials
• Check CXR:
– Lead dislodgement (e.g. Dislodged A lead sensing V)
– Lead fracture/ insulation break
– Loose set screws
• Check PPM
– Lead impedance
• High  Lead #
• Low  Lead insulation break
–
–
–
–
Battery depletion/Circuit failure
Real time EGM – any oversensing of T waves/ Cross talk
Programming – Rate hysteresis/ sleep rate/ PMT/
Blanking/Refractory period – long enough to prevent cross-talk /
oversensing
Is there any pacing spike?
Too many pacing spikes
• True malfunction
– Undersensing:
• Patient factor: MI/ CMP/ Electrolytes/ Drugs / Arrhythmias AF, VF, VT
• Lead factor: Lead dislodgement; loose set screw (New implant) ; Lead
maturation / insulation break or fracture (Old implant); Suboptimal lead
position  Small EGM
• Pacemaker factor: Low sensitivity; battery depletion; circuit failure; stuck
reed switch  magnet mode operation
• Pseudo-malfunction: Functional undersensing
– Mode related: Magnet mode, Noise mode, PMT intervention, mode
switching, DVI Mode
– Timing cycle related: pacemaker Wenckebach
– Refractory/blanking period related: Long blanking/refractory period;
pseudofusion & safety pacing; post PVC PVARP extension
Undersensing – What to do?
• Ask history:
– Symptoms of MI/ CHF
– Antiarrhythmics/ diuretics
• Check CXR:
– Lead dislodgement (e.g. Dislodged A lead sensing
V)
– Lead fracture/ insulation break
– Loose set screws
• Check PPM
– Battery status/ sensitivity/ mode/
blanking/refractory periods
Undersensing
• An intrinsic depolarization that is present,
yet not seen or sensed by the pacemaker
P-wave
not sensed
Atrial Undersensing
Is there any caputre?
Loss of capture
• True Noncapture:
– Lead factor:
• New implant: Lead dislodgement, inflammation, loose set screw
• Old implant: lead maturation/ fibrosis ; Lead insulation failure/
fracture
– Pacemaker factor:
• Battery depletion, recording system artefact
– Patient factor:
• MI/ CMP/ Metabolic/ Electrolytes abnormalities/ Drugs
• Functional noncapture (pseudomalfunction)
– Mode related: Atrial asynchronous mode: DDI / DVI Mode ; Magnet
mode/ Noise reversion mode/ Mode switch
– Blanking / referactory period related: Long refractory /blanking period;
PVARP extension post PVC
– True undersensing  pacing at absolute refractory period
– Others: Saftey pacing; ectopic activation (PVC,BBB)
Loss of capture
Loss of capture:
No evidence of depolarization after pacing
artifact
Loss of capture
Pseudomalfunctions
Pseudomalfunctions are defined as:
 Unusual
 Unexpected
 Eccentric
ECG findings that appear to result from
pacemaker malfunction but that represent
normal pacemaker function
Pseudomalfunctions:
• Rate related
• AV interval/refractory periods related
• PPM Mode related
Rate Changes related to normal
PPM operation:
• Magnet operation
• Timing variations
– A-A versus V-V timing
• Upper rate behavior
– Pseudo-Wenckebach; 2:1 block
• Electrical reset
• Battery depletion
• PMT intervention
• Rate response
Magnet Operation
• Magnet application causes asynchronous
pacing at a designated “magnet” rate
A to A vs. V to V Timing
A to A = 1000 ms
A-A
Timing
AV = 200
V-A = 800
A to A = 1000 ms
AV = 150
V-A = 850
Atrial rate is held constant at 60 ppm
A to A = 1000 ms
V-V
Timing
AV = 200
V-A = 800
A to A = 950 ms
AV = 150
V-A = 800
Atrial rate varies with intrinsic ventricular conduction
Upper Rate Behavior
• Pseudo-Wenckebach operation will cause a
fluctuation in rate
Upper Rate Behavior
• 2:1 block operation will cause a drastic
drop in rate
Electrical Reset and Battery Depletion
• Reset may occur due to exposure to electromagnetic
interference (EMI) – e.g., electrocautery,
defibrillation, causing reversion to a “back-up” 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”)
PMT Intervention
• Designed to interrupt a Pacemaker-Mediated
Tachycardia
Rate Responsive Pacing
• An accelerating or decelerating rate may be
perceived as anomalous pacemaker behavior
VVIR / 60 / 120
Rate Changes May Occur Due to
Therapy-Specific Device Operation
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•
•
•
Hysteresis
Rate drop response
Mode switching
Sleep function
Hysteresis
• Allows a lower rate between sensed events to
occur; paced rate is higher
Lower Rate 70 ppm
Hysteresis Rate 50 ppm
Rate Drop Response
• Delivers pacing at high rate when episodic
drop in rate occurs
– Pacing therapy indicated for patients with
neurocardiogenic syncope
Mode Switching
• Device switches from tracking (DDDR) to
nontracking (DDIR) mode
Sleep Function
30
mins.
30
mins.
Rate
Lower
Rate
Sleep
Rate
Wake Time
Bed Time
Time
AV Intervals/Refractory Periods May
Appear Anomalous Due to:
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•
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Safety pacing
Blanking
Rate-adaptive AV delay
Sensor-varied PVARP
PVC response
Noncompetitive atrial pace (NCAP)
Safety Pacing
• Designed to prevent inhibition due to
“crosstalk”
– Delivers a ventricular pace 110 ms after an atrial
paced event
Ventricular Safety Pace
Blanking
DDDR / 60 / 125 / 200 / 225
Rate-Adaptive AV Delay
• AV interval shortens as rate increases
PAV delay with no activity: 150 ms
PAV with activity: 120 ms
Sensor-Varied PVARP
• PVARP will shorten as rate increases
Long PVARP with little activity
Shorter PVARP with increased activity
PVC Response
• PVARP will extend to 400 ms
DDD / 60 / 120 PVARP 310 ms
Noncompetitive Atrial Pace (NCAP)
• Prevents atrial pacing from occurring too
close to relative refractory period, which
may trigger atrial arrhythmias
A Change in Pacing Modes
May Be Caused By:
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•
•
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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
Pacemaker-Mediated Tachycardia (PMT)
• A rapid paced rhythm that can occur with
atrial tracking pacemakers
PMT is the Result of:
• Retrograde conduction
• Tracking fast atrial rates (physiologic or
non-physiologic)
Retrograde Conduction
Retrograde Conduction May Be Caused By:
• Loss of A-V synchrony due to:
– Loss of sensing/capture
– Myopotential sensing
– Premature ventricular contraction (PVC)
– Magnet application
High Rate Atrial Tracking is Caused By:
• Supra-ventricular tachyarrhythmias
• Atrial over-sensing
Suspected Pacemaker malfunction
Pacing stimuli present
Capture
Yes
No
YES
Threshold increased
Lead impedance changed
No
Yes
No
appropriate timing of
pacing stimuli
Impedence increased:
(conductor fracture, loose setscrew)
Impedence decreased:
(insulation defect)
lead maturation, drugs, metabolic
dislodgement,
programming error
functional noncapture, recording artefact
Yes
No
Normal
undersensing
insulation failure
low amplitude, functional
lead maturation/dislodgement
program error, drugs, metabolic
Suspected PM malfunction
Pacing stimuli absent
Intrinsic rhythm absent
Intrinsic rhythm present
Timing appropriate to inhibit pacer
No
Yes
Pacing restored with magnet
Normal function
No
Yes
conductor fracture,
loos setscre, battery depletion
OVO,ODO mode
pacemaker component failure
Oversensing
myopotentials,
P,R,T wave
EMI,crosstalk
insulation or conductor defect
PPM ECG Workshop