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Paediatric pacemakers > Pacemakers (edit) > Flashcards

Pacemakers (edit) Flashcards

1
Q

In DDDR mode explain tracking of intrinsic rate Vs sensor indicated rate

A

Intrinsic atrial - AsVp
Sensor indicated - ApVp

Note* Whatever is faster is in control

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2
Q

Purpose of Upper tracking rate and Upper sensor rate

A

Rate limits for atrial tracking that are programmable.

Prevents tracking of atrial tachycardias

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3
Q

True or false

In DDI mode An atrial event INSIDE the PVARP inhibits scheduled atrial stimulus but will not start AV interval

A

False

An atrial event sensed OUTSIDE the PVARP will INHIBIT a scheduled Ap (I.e. sensed) but will not start a AV interval

Note* basically As doesn’t not start AV delays is DDI mode

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4
Q

At what rate do Vp events occur following As events during DDIR mode pacing?

A

At the sensor indicated rate

Note* Vp after As is at sensor indicated rate not base rate (paced at base rate in DDI mode only)

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5
Q

Pacing mode with continuous Ap regardless of intrinsic atrial activity

A

DVI/R

Note* sensing only occurs in the ventricles

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6
Q

True or false

Programming rate response on in a chrontropically competent patient is beneficial

A

False

It would unnecessarily increase Ap with possible competition between the intrinsic and pacing rates

  • in the long run this would be unnecessary battery depletion
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7
Q

True or False

Triggered mode pacing occurs at the LRL

A

True

But a As/Vs event also triggers an immediate pacing output (rather than inhibiting)

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8
Q

Blanking periods in ODO, OAO and OVO are…

A

automatically minimised to maximise sensing windows

Note* marker channel May display FFRWOS that otherwise would not appear if blanked as usual

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9
Q

Decremental Device testing in clinic unmasks twitching at high pacing rates. What should be done?

A

Test twitching from high to low voltage and see where it stops. There should be a 2V safety margin if possible.

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10
Q

CRT post implant optimisation includes

A
  1. Checking morphology is narrow with optimal VV and AV delays
  2. Checking for change in morphology during threshold testing (confirms true RV and LV capture)
  3. ECHO optimisation of AV delays if necessary
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11
Q

Identify the appropriate steps for device check

A
  1. Read all previous reports
  2. Take snapshot presenting rhythm
  3. VHR/AHR episodes
  4. Sensing test - underlying rhythm
  5. Threshold test - look for change in morphology/EGM to confirm capture
  6. Parameters - adjust as appropriate according to testing results
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12
Q

Clinical significance of pseudofusion

A

Battery depletion

*occurs when intrinsic heart rate is very close to the lower rate of the pacemaker - Pseudofusion is not dangerous to the patient.

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13
Q

What is important to look for during device threshold checks?

A

Loss of capture
Change in EGM/ ECG morphology to confirm capture.

*no change but pacing spike = pseudofusion or true pacing
* Change and pacing = fusion or true capture

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14
Q

In what inherited arrhythmia can a dual chamber ICD be indicated?

A

LQTS where AP is required to maintain regular rhythm and prevent long short intervals
extra lead for discrimination is not indicated

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15
Q

Bipolar sensing WITH unipolar pacing suggests…?

A

Issue with lead impedance/integrity or high thresholds

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16
Q

Unipolar sensing WITH Bipolar pacing suggests…?

A

Noise on Bipolar channel unable to be blanked by changing sensitivity settings

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17
Q

Are epicardial device MRI compatible?

A

No!

*Epicardial leads have not been MRI tested and thus not licensed to have MRI performed with patients implanted with such devices.

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18
Q

How is it determined if a signal is seen by a/the device?

A

Marker channel annotations indicate sensed and paced events as well as detection and therapies delivered

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19
Q

How does FFRWOS occur

A

Tip of atrial lead is close enough to ventricle to sense ventricular depolarisation

*i.e. if in right atrial appendage which sits right over RV then oversensing can occur

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20
Q

Surgical Vs congenital escape/Junctional rhythm - which is more reliable?

A

A surgical escape rhythm is less reliable than a congenital escape rhythm

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21
Q

Noise always results from…?

A

A
Conductor fracture or insulation breach
EMI
TENS

*noise on a lead is not normal

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22
Q

What do conductor and insulation failure affect?

A

Thresholds (trending or sharp increase)
Impedances

*these done always change dramatically particularly if there is a micro fracture/micro dislodgement

*Occasionally, pacing thresholds and impedance rise, typically gradually over months, without any detectable fracture from development of scar tissue at electrode myocardial interface (exit block) or the deposition of calcium hydroxyapatite crystals at the lead-tissue interface

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23
Q

What is exit block?

A

development of scar tissue at the electrode myocardial interface (exit block)

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24
Q

How has exit block been resolved?

A

Steroid elution in current-generation pacing leads has virtually eliminated the risk of exit block

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25
Q

Predictors of good lead fixation

A

EGM widening and ST segment elevation and good sensing

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26
Q

Define battery end of life

A

Battery has depleted to point of unpredictable function

27
Q

Define battery elective replacement indicator

A

90 days of reliable function remain

28
Q

Sensing safety margin preferred is…?

A

2x

29
Q

In the instance of elevated bipolar thresholds or sensing, what can be used instead?

A

sensing or pacing in unipolar configuration

30
Q

Surgical reprogramming for diathermy:
PPM dependant

A

Reprogram to asynchronous pacing mode or place magnet

*important for procedures about the hip

31
Q

Surgical reprogramming for diathermy:
NOT PPM dependant i.e. AsVs

A

No further device programming needed

32
Q

Causes of failure to capture (non capture)

A

Lead disconnection
break/failure
displacement
Exit block
Battery depletion
Pseudo-non capture (within refractory period)

33
Q

Causes of Undersensing

A

Lead displacement
Inadequate endocardia contact
Low voltage P or QRS
Lead fracture

34
Q

Causes of oversensing

A

Sensing extracardiac signals
T/R/P wave oversensing
Fracture
Displacement

35
Q

Causes of inappropriate rate

A

Battery depletion
PMT
1:1 response with atrial dysarrhythmia

36
Q

Evaluating pacemaker malfunction

A

Determine whether function is truly abnormal
Confirmed malfunction = detailed patient history
*Post implant Vs chronic

37
Q

Post implant complications

A

lead dislodgement, loose set screw, misalignment of lead within connector block, poor lead placement

38
Q

Chronic complications

A

Lead fracture or battery depletion

39
Q

Non capture corrective action

A
  1. Increase outputs
  2. Revise/replace lead
  3. Correct metabolic imbalances

*pseudo-non capture = more sensitive or revise lead if sensing is poor/ programme to unipolar

40
Q

what corrective measures can be taken to resolve undersensing in a device?

A

Increase sensitivity
Reprogram polarity
Revise lead or replace lead (if insulation or break)
Infrequent = observation

41
Q

What is the clinical significance of oversensing in a device?

A

Oversensing means underpacing

*in pacemaker dependant patient means necessary pacing is inhibited

*in Sinus or intermittent block patient = not completely at risk but should be resolved in case pacing is required at some point

42
Q

What steps can be used to resolve oversensing?

A
  1. Increase in thresholds or pacing? (No ? EMI)
    Identify the cause
  2. x-ray
  3. Provocations for replication
    (Sensing to 1mV - all checks and test)
  4. Increase sensitivity if margin to do so
    If no, unipolar and programme sensitivity with safety margin
    If still no, choose best configuration, monitor and replace lead.
43
Q

What steps can be used to resolve high threshold from autocapture?

A
  1. Check trend
  2. X-ray
  3. Bring in for manual threshold checks and auto capture test
  4. Perform provocation to rule out lead integrity issue
  5. If auto capture wrong - programme off
44
Q

What steps can be used to resolve high RV thresholds?

A

High RV thresholds = conductor fracture or macro dislodgement
*sometimes small R wave as sensing can be compromised too

  1. In for threshold check and provocations (run tests during these - R wave and threshold can change depending on position)
  2. X-ray
  3. Choose best sensing configuration, threshold measurements and sensitivity with safety margin.
45
Q

Steps for provocation testing

A
  1. In original sensing/pacing configuration - all checks
  2. Drop programmed sensitivity (1mV)
  3. With provocations
    - sensing issue - watch EGM for oversensing and check impedance
    - threshold issue - run threshold and impedance tests in different positions
  4. Programme appropriate threshold/sensitivity following results and plan next steps
46
Q

What do you expect to see sometimes occurring alongside increasing thresholds?

A

Decrease in R wave or P wave amplitude

*increase sensitivity = see more
But ultimately a change in sensing configuration or lead may be required at the end.

47
Q

Measured current is…?

A

The measured current in the pacing lead during delivery of a pacing pulse

48
Q

Measured impedance means…?

A

The measured impedance presented by the pacing lead and the electrode/tissue interface

49
Q

What is the direct result seen during the reduction of pulse width with programming?

A

More energy/ voltage required to depolarise the heart

50
Q

What is the direct result seen during the increase of pulse width with programming?

A

Less energy/voltage required to depolarise the heart

51
Q

Strength duration curve

Anything above the line =

A

Capture

52
Q

Strength duration curve:

Anything below the line =

A

LOC

53
Q

Define battery usage in a device

A

Current used during inhibition (sensed beat) Vs current used during pacing

*battery longevity is dependant on how much is available and how quickly it is used

54
Q

Purpose of cardiac pacing

A

Improve outcomes and treat symptoms (QOL, hospitilisations, symptoms) in AVB patients

55
Q

Why is DDDR better than VVIR

A

Maintains AV synchrony and reduces incidence of AF (caused by V only pacing leading to VA conduction)

*in paeds Dual chamber is not always possible due to size, age (will most likely require multiple leads in the future and a max of 4 are allowed to be left and capped thus prolonging PPM implant or number of initial leads will be helpful in the long run), vasculature access.

56
Q

PMT in defined as…

A

16 Vp beats following sensed atrial beats at the MTR with constant VA intervals

57
Q

Paced AV delay is…?

A

The interval between Ap and Vp

58
Q

Sensed AV delay is…?

A

The interval from As to Vp

59
Q

FFRWOS - true or false?

AR before Vs can be blanked

A

False

AR before the VS cannot be blanked because it is outside of the PVAB

60
Q

What are the major purposes of algorithms that search for intrinsic conduction?

A

Minimise RV pacing
Extend battery life

61
Q

What can cause sensing integrity counter counter to increase?

A

Lead noise
T wave Oversensing
Set screw noise
PVCs

62
Q

Relative refractory period

A

Device can see but not do

*cardiac events sensed but no trigger or reset of timing cycles

63
Q

Absolute refractory period (blanking period)

A

Sensing amplifier off or blind to cardiac events, thus cannot be detected

Paediatric pacemakers (9 decks)

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