Algorithms

Question 1

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

Answer 1

1. Minimize RV pacing
2. Extend battery life

Question 2

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

Answer 2

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

Question 3

List 2 algorithms specifically designed to treat neurocardiogenic syncope.

Answer 3

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

Question 4

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.’

Answer 4

Blanked Flutter Search (Medtronic).

Question 5

List 6 algorithms designed to prevent AF.

Answer 5

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

Question 6

True / False

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

Answer 6

False.

Both Algorithms increase HR following a PAC.

Question 7

The following best describes what algorithm?

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

Answer 7

Rate Smoothing.

Question 8

The following best describes what algorithm?

‘Prevents pauses following a PAC’.

Answer 8

Post PAC response.

Question 9

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

Answer 9

Morphology.

Question 10

What is the nominal probabilistic counter setting for morphology match?

Answer 10

5/8 or 7/12.

Question 11

Specificity / Sensitivity

True negatives correctly identified as such describes _____?

Answer 11

Specificity.

Question 12

Specificity / Sensitivity

True positives correctly identified as such describes ______?

Answer 12

Sensitivity.

Question 13

List two weaknesses of morphology match.

Answer 13

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

Question 14

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

Answer 14

QRS width.

Question 15

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

Answer 15

Stability.

Question 16

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’.

Answer 16

Stability.

Question 17

The following describes which tachycardia detection algorithm?

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

Answer 17

Sudden Onset.

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

Question 18

Should onset be used as a sole discriminator?

Answer 18

No.

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

Question 19

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

Answer 19

A vs. V rate.

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

Question 20

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

Answer 20

Accurate atrial sensing during high ventricular rates.

Question 21

What are two major causes of atrial undersensing?

Answer 21

1. Low amplitude EGMs
2. Functional interactions with PVAB

Question 22

How does sudden onset in DDD sensing work?

Answer 22

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.

Question 23

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

Answer 23

FFRWS.

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

Question 24

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

Answer 24

Atrial lead senses V signals constantly.

Question 25

How does AV association work?

Answer 25

Distance from A event to V event intervals calculated across 12 beats. Second shortest subtracted from second longest. ## Footnote *If more than 40ms = VT Unstable association indicates VT.*

Question 26

How does PR logic identify FFRW?

Answer 26

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

Question 27

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

Answer 27

\>75% = Regular rhythm \<50% = Irregular rhythm

Question 28

# True / False Primary prevention patients typically don't benefit from dual chamber SVT discrimination.

Answer 28

True. ## Footnote *Primary patients are largely implanted with single chamber ICDs for this reason.*

Question 29

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

Answer 29

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

Question 30

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

Answer 30

1. Lower cost 2. Lower risk of complications 3. Increased longevity

Question 31

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

Answer 31

72-89%.

Question 32

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

Answer 32

35%.

Question 33

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

Answer 33

6x ATP = 30% successful.

Question 34

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

Answer 34

True.

Question 35

Define Burst.

Answer 35

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

Question 36

Define Scan.

Answer 36

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.

Question 37

Define Ramp.

Answer 37

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

Question 38

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

Answer 38

No - ADVANCE-D 2010. ## Footnote *Unless in HF with EF \<40%.*

Question 39

# True / False ATP should not be programmed in patients with Polymorphic VT .

Answer 39

True. ## Footnote *May induce rhythms less likely to respond to therapy.*

Question 40

# Yes / No Should ATP be used for slow VT?

Answer 40

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

Question 41

What is a type 1 response pattern to Ventricular ATP?

Answer 41

Atrial cycle length remains stable. ## Footnote *Therefore the V is disassociated to the A. This is more likely an A-Tach / AVNRT.*

Question 42

What is a type 2 response pattern to V ATP?

Answer 42

Atrial cycle length varies. ## Footnote *Potential association of the chambers. Likely AVRT or VT.*

Question 43

What is a type 3 response pattern to V ATP?

Answer 43

Atrial cycle length accelerates to V rate (Entrainment). ## Footnote *VAAV response = AT* *VVA response = VT*

Question 44

Define PPI.

Answer 44

Post pacing interval. ## Footnote *Time required for last stim wavefront to reach circuit, travel around and return to pacing site.*

Question 45

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

Answer 45

VT.

Question 46

Define fallback.

Answer 46

Prevents a sudden rate drop when the atrial rate exceeds the URL of the device. ## Footnote *Occurs automatically after mode switch, gradually decreasing pacing rate to ATR/VTR fallback LRL.*

Question 47

Define rate smoothing.

Answer 47

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

Question 48

# Yes / No Is rate smoothing the same as Atrial and Ventricular Rate Stabilization?

Answer 48

Yes. ## Footnote *However rate stabilisation runs exclusively off PVCs.*

Question 49

What is the purpose of Atrial and Ventricular rate stabilization?

Answer 49

Intended to eliminate long pauses after PAC or PVC respectively.

Question 50

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

Answer 50

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

Question 51

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

Answer 51

200-400ms.

Question 52

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

Answer 52

CLS - Biotronik's Rate Response algorithm.

Question 53

List 3 major benefits of automatic capture verification algorithms.

Answer 53

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

Question 54

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

Answer 54

Evoked response.

Question 55

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

Answer 55

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

Question 56

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

Answer 56

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

Question 57

What does MVP stand for and what is its purpose?

Answer 57

Managed Ventricular Pacing (Medtronic). ## Footnote *To uncouple Ap from Vp and allow intrinsic conduction when present.*

Question 58

How does MVP work?

Answer 58

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

Question 59

List 3 considerations before programming MVP on.

Answer 59

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)

Question 60

List 3 benefits of MVP.

Answer 60

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

Question 61

# True / False ATP converts and accelerates FVT by 75% and 10% respectively.

Answer 61

True. ## Footnote *Review PainFreeRX study.*