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Year 3 Cardiac physiology > CRM9,10: Device clinic, Troubleshooting > Flashcards

CRM9,10: Device clinic, Troubleshooting Flashcards

1
Q

What class and level of evidence for permanent pacemaker implant in complete AV block post acute MI

A

Class 3, Level C
-Reversible cause so don’t implant
-Use temporary pacing instead

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2
Q

Why do you look at lead impedance?

A

To check lead integrity:
-Conduction
-Insulation
-Fixation

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3
Q

What would indicate that CRT device is not working?

A

-BBB
-Heart failure symptoms:
-ankle swelling, coughing, SOB

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4
Q

Systematic approach to troubleshooting

A

-Does problem involve atrium or ventricle?
-Sensing malfunction? undersensing or oversensing?
-Pacing malfunction? loss/failure to capture, loss/failure to output pacing spike?
-Pseudo-malfunction? poor programming, reset, battery depletion, pseudo-fusion/fusion?

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5
Q

What is undersensing?

A

-When intrinsic P or R wave is not sensed
-Red arrows = R waves not sensed
-First 2 pacing spikes don’t capture because they fall in refractory periods

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6
Q

Causes of undersensing

A

-Poorly programmed sensitivity
-Change in intrinsic electrogram (sinus rhythm P waves to atrial fibrillation F waves)
-Lead failure (conduction or insulation) - reduction or loss of sensed electrogram

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7
Q

How to manage undersensing?

A

-Review patient history/ECG/drugs/ electrograms
-Measure intrinsic signals, thresholds and impedance
-Check that programming of sensing is appropriate
-Chest x ray if impedance and other lead integrity tests indicate a lead/connector issue
-Re-intervention if system failure

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8
Q

What is oversensing?

A

-Sensing of inappropriate signal causing ‘loss’ of output
-Something other P wave or R wave is sensed
-Pacemaker does not emit pacing output to atrium or ventricle
-Oversensing leads to underpacing

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9
Q

Causes of oversensing

A

-Oversensing of myopotentials, intracardiac signals (T waves and farfield P/R waves), or electromagnetic interference

Lead failure:
-insulation break (myopotentials sensed near the break)
-conductor fracture (causing electrical artefact)
-Connector/connector block issues causing electrical artefact

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10
Q

What can cause lead voltage to change?

A

-Movement of lead
-Fibrosis due to MI

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11
Q

What causes impedance to increase and decrease?

A

-Fracture of conductor causes increase
-Fracture of insulation causes decrease

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12
Q

How to assess oversensing?

A

-Does oversensing occur during activity?
-Provocative manoeuvres - arm moving, stretching, pushing
-Have telemetry while patient uses equipment that might cause oversensing
-Measure pacing threshold and lead impedance

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13
Q

How to manage oversensing?

A

If oversensing is due to programming of sensitivity:
-Reprogram sensitivity, PVARP, polarity

If oversensing is due to lead/connector issue:
-Chest x ray to inspect leads
-Consider re-intervention

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14
Q

Why do ICDs have sensing that degrades?

A

-Helps to pick up VF
-Picks up big and small complexes

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15
Q

What is failure to capture?

A

-Output pulse is not enough to capture the myocardium
-Threshold has not been programmed high enough
-No evidence of depolarisation after pacing artefact

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16
Q

What can fix failure to capture?

A

-Autocapture

17
Q

Causes of failure to capture

A

-Battery depletion
-Low output caused by incorrect programming
-Poor connection to connector block/connector issues
-Lead dislodgement
-Lead maturation causing threshold rise
-Effects of drug causing threshold rise
-Rare causes - electrolyte imbalance/MI

18
Q

How to manage loss of capture?

A

-Measure intrinsic signals, impedance and thresholds
-Increase pacing output if you can - consider battery life and stimulation of diaphragm/phrenic nerve
-Chest x ray if needed
-Consider re-intervention

19
Q

What is failure to output?

A

-Impulses are generated but not transferred to myocardium
-Impulses are not generated
-Pacemaker artefacts not seen on ECG
-No spike and no depolarisation

20
Q

Causes of failure to output?

A

-Battery depletion
-Poor connector at connector block
-Lead failure
-Pacemaker malfunction - rare

21
Q

How to manage failure to output?

A

-Interrogate to show battery life - magnet rate
-Measure impedance
-Measure stimulation threshold
-Failure to output - verify all lead connections
-Chest x ray may help
-Consider re-intervention to look at connections/to replace lead or device

22
Q

What does this image show?

A

Failure to output

23
Q

What does this image show?

A

Loss of capture

24
Q

What is pseudo-malfunction?

A

-When something looks abnormal but isn’t
-Normal pacemaker function

25
Q

What is pseudo-fusion?

A

-Pacemaker output falls on an intrinsic event
-Refractory so no depolarisation due to paced output
-All depolarisation is intrinsic

26
Q

What is true fusion?

A

-Pacemaker output falls at the start of intrinsic event
-Myocardial depolarisation wave from paced chamber combines and fuses with intrinsic beat

27
Q

What does this image show?

A

Normal upper rate behaviour
-Wenckebach upper rate behaviour sensed AV delay extends until TARP is reached
-Then sensed P wave falls into TARP and is counted as ‘retrograde P wave’
-Not tracked so no V pacing spike generated

28
Q

What can cause electrical reset? (device reverts to back up or factory settings)

A

-Electromagnetic interference
-Cold
-Electrocautery
-Defibrillation

29
Q

What is battery depletion?

A

-When battery reverts to an end of life mode (e.g. VVI unipolar)

30
Q

Symptoms due to malfunctions

A

-Dyspnoea
-Fatigue
-Dizziness
-Syncope
-Palpitations

31
Q

What causes symptoms in device malfunction?

A

-Lack of AV synchrony
-Loss of capture/sensing
-Absence of rate modulation
-Biventricular pacing fails - patient can go back into heart failure
-Inappropriate shocks/withheld therapy

32
Q

What is this an example of?

A

-Lead has moved and causes diaphragmatic stimulation

33
Q

What does this image show?

A

Functional undersensing
-Atrial flutter
-Classing A waves as retrograde as they are falling in the TARP
-If falls in post-ventricular blanking period, wouldn’t see them at all

34
Q

Patient history to consider in CRM

A

-Surgery, sport, traumatic injury
-New hobby/employment (deep sea diving, arc welding)
-New medication (flecainide)

35
Q

High ventricular ectopic burden without ventricular ectopics?

A

-Device not sensing P waves
-2 R waves with no P wave in between - labelled as ectopic

36
Q

What does this image show?

A

Hysteresis
-after sensed beat, pacing interval is increased

37
Q

What does this image show?

A

Device is working fine
-Normal upper rate behaviour

Year 3 Cardiac physiology (30 decks)

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