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IBHRE® > Algorithms > Flashcards

Algorithms Flashcards

Provides an understanding of the software programming that allows appropriate therapy delivery in a number of different cardiac scenarios. Currently weighted 8% in the CCDS exam.

1
Q

List two major purposes of algorithms that search for intrinsic conduction.

A
  1. Minimize RV pacing
  2. Extend battery life
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2
Q

List 5 algorithms that encourage intrinsic conduction and may account for observed rates lower than the programmed LRL.

A
  1. Search Hysteresis
  2. Sinus preference
  3. Rate Hysteresis
  4. Scan Hysteresis
  5. Sleep rate
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3
Q

List 2 algorithms specifically designed to treat neurocardiogenic syncope.

A
  1. Rate drop response (Medtronic)
  2. Sudden brady response (BSC)
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4
Q

The following statement best describes what algorithm?

‘Monitors 8 consecutive AA intervals that are less than twice the total atrial blanking period. Extends PVARP to uncover P-waves.’

A

Blanked Flutter Search (Medtronic).

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5
Q

List 6 algorithms designed to prevent AF.

A
  1. Pace conditioning
  2. Rate Smoothing
  3. PAC suppression
  4. Post PAC response
  5. Post AF response
  6. Atrial preference pacing
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6
Q

True / False

Pace conditioning and PAC suppression both decrease HR following a PAC.

A

False.

Both Algorithms increase HR following a PAC.

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7
Q

The following best describes what algorithm?

‘Atrial overdrive pacing just above pacing rate (3bpm)’.

A

Rate Smoothing.

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8
Q

The following best describes what algorithm?

‘Prevents pauses following a PAC’.

A

Post PAC response.

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9
Q

Which is the only algorithm to distinguish SVT vs VT using farfield IEGM shape?

A

Morphology.

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10
Q

What is the nominal probabilistic counter setting for morphology match?

A

5/8 or 7/12.

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11
Q

Specificity / Sensitivity

True negatives correctly identified as such describes _____?

A

Specificity.

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12
Q

Specificity / Sensitivity

True positives correctly identified as such describes ______?

A

Sensitivity.

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13
Q

List two weaknesses of morphology match.

A
  1. Inaccurate template
  2. EGM truncation (amplified signal clipped)
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14
Q

What algorithm unique to Bostons S-ICD complements wavelet discrimination?

A

QRS width.

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15
Q

Which algorithm continually assesses R-R intervals to decide whether rhythm is VT or AF with RVR?

A

Stability.

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16
Q

The following describes which tachycardia detection algorithm?

'Continually assess R-R intervals for either fixed or continually variable variance of a pre-determined amount to confirm/deny tachycardia’.

A

Stability.

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17
Q

The following describes which tachycardia detection algorithm?

‘Discriminates between tachycardia that initiates spontaneously vs. that in which HR gradually increases to tachycardia rate’.

A

Sudden Onset.

VT has sudden and spontaneous HR increase profile. Sinus Tachycardia has a more gradual HR increase profile.

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18
Q

Should onset be used as a sole discriminator?

A

No.

If not stability, morphology should always be programmed on too.

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19
Q

What is the cornerstone dual chamber building block for discriminating SVT vs VT?

A

A vs. V rate.

Are there more A’s than V’s or vice versa?

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20
Q

What is a major weakness of Atrial vs Ventricular rate discrimination?

A

Accurate atrial sensing during high ventricular rates.

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21
Q

What are two major causes of atrial undersensing?

A
  1. Low amplitude EGMs
  2. Functional interactions with PVAB
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22
Q

How does sudden onset in DDD sensing work?

A

SVT = Atrial event occurs between last V-event in sinus zone and V-event in VT zone.

VT = No intrinsic atrial event in these two zones.

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23
Q

What is a major cause of atrial oversensing and best way to prevent it?

A

FFRWS.

Reposition lead to site where large A-EGM is seen without FFRW.

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24
Q

How does Abbott differ from all manufacturers with regards to A vs V rate?

A

Atrial lead senses V signals constantly.

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25
Q

How does AV association work?

A

Distance from A event to V event intervals calculated across 12 beats. Second shortest subtracted from second longest.

If more than 40ms = VT Unstable association indicates VT.

26
Q

How does PR logic identify FFRW?

A

Successive sequences of short long AA intervals with >30ms differences.

27
Q

What percentage of RR interval regularity defines regular or irregular rhythms?

A

>75% = Regular rhythm

<50% = Irregular rhythm

28
Q

True / False

Primary prevention patients typically don’t benefit from dual chamber SVT discrimination.

A

True.

Primary patients are largely implanted with single chamber ICDs for this reason.

29
Q

Dual chamber ICDs are better than SR ICDs because of which 3 things.

A
  1. Algorithms that reduce RV pacing in patients with SND
  2. AF diagnostics
  3. Atrial channel EGMS available
30
Q

Single chamber ICDs are better than DR ICDs because of which 3 things.

A
  1. Lower cost
  2. Lower risk of complications
  3. Increased longevity
31
Q

How successful is 1st round ATP for VT (%)?

A

72-89%.

32
Q

How successful is 2nd round ATP for VT (%)?

A

35%.

33
Q

How successful is ATP for FVT >250bpm (%)?

A

6x ATP = 30% successful.

34
Q

True / False

Burst (with/without scan) is more successful than ramp and also has less acceleration risk.

A

True.

35
Q

Define Burst.

A

ATP pulses (nominally 8) are delivered at same cycle length.

36
Q

Define Scan.

A

Same as burst however ATP (8 beats) is delivered at a set cycle length, then next 8 beat train is at a programmed shorter cycle length, then shorter again and so on.

37
Q

Define Ramp.

A

Of an 8 pulse train, each pulse is delivered at a shorter cycle length than previous.

38
Q

Is there a significant advantage to programming more than 8 pulses of ATP?

A

No - ADVANCE-D 2010.

Unless in HF with EF <40%.

39
Q

True / False

ATP should not be programmed in patients with Polymorphic VT .

A

True.

May induce rhythms less likely to respond to therapy.

40
Q

Yes / No

Should ATP be used for slow VT?

A

Yes.

However consider a less aggressive coupling interval (91% opposed to 81% CL).

41
Q

What is a type 1 response pattern to Ventricular ATP?

A

Atrial cycle length remains stable.

Therefore the V is disassociated to the A. This is more likely an A-Tach / AVNRT.

42
Q

What is a type 2 response pattern to V ATP?

A

Atrial cycle length varies.

Potential association of the chambers. Likely AVRT or VT.

43
Q

What is a type 3 response pattern to V ATP?

A

Atrial cycle length accelerates to V rate (Entrainment).

VAAV response = AT

VVA response = VT

44
Q

Define PPI.

A

Post pacing interval.

Time required for last stim wavefront to reach circuit, travel around and return to pacing site.

45
Q

A PPI which varies <50ms is likely to be what?

A

VT.

46
Q

Define fallback.

A

Prevents a sudden rate drop when the atrial rate exceeds the URL of the device.

Occurs automatically after mode switch, gradually decreasing pacing rate to ATR/VTR fallback LRL.

47
Q

Define rate smoothing.

A

Used to minimise variations in RR intervals / regularise ventricular rhythm.

Uses the most recent RR interval (whether intrinsic or paced) to calculate an allowable increase or decrease in cycle length based on programmable rate smoothing percentage.

48
Q

Yes / No

Is rate smoothing the same as Atrial and Ventricular Rate Stabilization?

A

Yes.

However rate stabilisation runs exclusively off PVCs.

49
Q

What is the purpose of Atrial and Ventricular rate stabilization?

A

Intended to eliminate long pauses after PAC or PVC respectively.

50
Q

Describe how the Medtronic Non-Competitive-Atrial-Pacing algorithm works.

A

A sensed atrial event in the PVARP starts a NCAP period during which no atrial pacing can be delivered.

51
Q

What range is the Medtronic Non-Competitive-Atrial-Pacing algorithm programmable to?

A

200-400ms.

52
Q

Which algorithm is shown to treat neurocardiogenic syncope patients, yet isn’t specifically designed to do so?

A

CLS - Biotronik’s Rate Response algorithm.

53
Q

List 3 major benefits of automatic capture verification algorithms.

A
  1. Improves safety (reduces risk of Loss of capture)
  2. Decreases current drain
  3. Increases device longevity
54
Q

What signal does the ventricular automatic capture algorithm look for to determine capture?

A

Evoked response.

55
Q

What 3 factors can effect a devices ability to sense an evoked response?

A
  1. Lead tissue interface (Chronic/Acute)
  2. Polarisation effect
  3. Tip-ring spacing
56
Q

Commonly, what signal does the atrial automatic capture algorithm look for to determine capture?

A

Measured P-P interval.

The device determines whether the atrial pace resets the sinus node and thus changes the P-P interval.

57
Q

What does MVP stand for and what is its purpose?

A

Managed Ventricular Pacing (Medtronic).

To uncouple Ap from Vp and allow intrinsic conduction when present.

58
Q

How does MVP work?

A

AAI when intrinsic conduction is present with Vp backup if block is detected. If block is detected device will switch to DDD.

59
Q

List 3 considerations before programming MVP on.

A
  1. Contraindicated for patients with CHB
  2. Patients with 1st degree AVB may experience PPM syndrome
  3. Ventricular proarrhythmia respondent to pause dependent VT (Hypokalaemia / Long QT)
60
Q

List 3 benefits of MVP.

A
  1. Reduced RV pacing increases battery life
  2. Reduced RV pacing reduces risk of PPM syndrome
  3. Reduced RV pacing reduces risk of Atrial Fibrillation
61
Q

True / False

ATP converts and accelerates FVT by 75% and 10% respectively.

A

True.

Review PainFreeRX study.

IBHRE® (24 decks)

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