Timing cycles

Question 1

What does the 1st column in the NGB code dictate?

Answer 1

Chamber Paced.

Question 2

What does the 2nd column in the NGB code dictate?

Answer 2

Chamber Sensed.

Question 3

What does the 3rd column in the NGB code dictate?

Answer 3

Action (Inhibit or trigger).

Question 4

When do we use asynchronous pacing?

Answer 4

Used only transiently for pacing-dependent patients.

This avoids inappropriate pacing inhibition during interventions or surgeries associated with noise.

Question 5

Why use a triggered mode?

Answer 5

Excellent marker for the site and time of sensing within a complex in an ECG tracing.

Question 6

What are the 4 modes of DDD pacing?

Answer 6

1. As Vs
2. As Vp
3. Ap Vs
4. Ap Vp

Question 7

What are the 4 States of DDD pacing?

Answer 7

1. AV
2. PV
3. PR
4. AR

Question 8

AV delay + PVARP =

Answer 8

TARP - Total Atrial Refractory Period.

Question 9

True / False

‘In DDD pacing generally a V output can be delivered in absence of an Atrial event’.

Answer 9

False

An atrial event is required in order to start the AV delay interval.

Question 10

When Rate Response is programmed off, what will the atrial pacing rate be?

Answer 10

Pacing rate will always be at base rate.

Question 11

True / False

PV delay = SAV (Sensed AV delay).

Answer 11

True.

Also known as the P-wave Tracking Interval, PV Interval.

Question 12

The following statement best describes what phenomena?

‘Occurs when the sensed atrial rate is faster than the maximum tracking rate’.

Answer 12

Pacemaker wenckebach.

This can lead to 2:1 block if the atrial rates are fast enough.

Question 13

True / False

Ventricular pacing below the base rate is normal in VDD pacing.

Answer 13

True.

In VDD mode, if the atrial rate drops below the LRL, the mode will appear VVI.There is no atrial LRL as it is a sensed channel only.

Question 14

The following statement best describes what type of timing?

‘The sensed R wave causes the AEI/VAI timer to start’.

Answer 14

Ventricular Based Timing.

Question 15

True / False

Ventricular based timing can cause the atrial rate to be above the base rate.

Answer 15

True.

The next atrial output will occur at a rate that is faster than the programmed base rate.

Question 16

The following statement best describes what type of timing?

‘The AEI timer begins with the P-wave’.

Answer 16

Atrial Based Timing.

AEI = Atrial Escape Interval

Question 17

True / False

PR state can be defined as an inhibited pacing state.

Answer 17

True.

No outputs are delivered in this state of DDD pacing as intrinsic events are ‘inhibiting’ output.

Question 18

What mode is use to prevent tracking of Atrial Arrhythmias?

Answer 18

DDI / DDIR.

Question 19

True / False

In DDI the ventricular paced rate will never be greater than the programmed LRL regardless of the atrial rate.

Answer 19

True.

In DDIR it may be higher but only if sensor driven.

Question 20

Which two pacing states cant be provided by VDI when compared to the four pacing states possible in DDD.

Answer 20

1. AS-VP (inhibition mode)
2. AP-VP (no A pace function)

Question 21

What is the major difference between DDI and DVI modes?

Answer 21

DVI senses only in the ventricle and ignores atrial events.

Question 22

When would one programme DVI in preference to DDI?

Answer 22

Patients with SSS and atrial sensing malfunction (oversensing) in which AV synchrony is desired.

Question 23

The following statement best describes a lead most commonly associated with what pacing mode?

‘Single-pass lead which integrates an atrial-sensing electrode with a ventricular-pace/sense electrode’

Answer 23

VDD.

Question 24

If DDD device senses well however has an abnormally high atrial threshold, what mode can be used?

Answer 24

VDD.

Maximise battery life + Maintains atrial diagnostics. Only for patients who require no atrial pacing!

Question 25

In VDD mode, if the atrial rate drops below the LRL - what mode will it resemble?

Answer 25

VVI. ## Footnote *Atrial is sensed only, thus there is no atrial LRL. If the atrial rate drops below the ventricular LRL, the ventricular clock will time out and will VP at the base rate, asynchronous with the slower atrial intrinsic rate.*

Question 26

What are the 6 types of VDD floating leads?

Answer 26

1. Unipolar 2. Bipolar (Narrow spacing) 3. Bipolar (Wide spacing) 4. Orthogonal 5. Diagonal 6. Bipolar half ring

Question 27

What is the single main purpose of blanking periods?

Answer 27

To prevent crosstalk.

Question 28

What two refractory cycles are present in AAI?

Answer 28

1. ABP - Atrial Blanking Period 2. ARP - Atrial Refractory Period

Question 29

# True / False Far Field R-Wave Sensing can reset an AAI timing cycle, giving a longer R-R interval than expected

Answer 29

True. ## Footnote *A sensed far field signal can prolong duration between outputs.*

Question 30

What two refractory cycles are present in VVI?

Answer 30

1. VBP - Ventricular Blanking Period 2. VRP - Ventricular Refractory Period

Question 31

With respect to Dual Chamber timing, what is the main purpose of the PVARP?

Answer 31

Prevent tracking of retrograde P-waves. ## Footnote *Retrograde P-waves (alongside other things) can initiate a PMT.*

Question 32

PVARP is present in which 3 Device Modes?

Answer 32

1. DDD 2. VDD 3. DDI

Question 33

Generally what is the programmable range of PVAB?

Answer 33

12-125ms.

Question 34

The following statement best describes what? 'Ventricular-sensing amplifier during the AVI immediately after the PAVB'.

Answer 34

The crosstalk window.

Question 35

# Inhibit / Triggered Impulses sensed within the crosstalk window will cause what output response?

Answer 35

Device will Trigger pace.

Question 36

Generally what is the range of ventricular safety pacing?

Answer 36

AVI of 100-120ms. ## Footnote *Programmable 50-150ms in some devices.*

Question 37

What should one suspect if the observed AVI is shorter than what is programmed?

Answer 37

Suspect crosstalk.

Question 38

List 4 programmable ways to eliminate crosstalk.

Answer 38

1. Turn on any anti-cross talk algorithms 2. Increase/extend the PAVB (best answer) 3. Decrease the atrial output (unlikely answer) 4. Reduce the ventricular sensitivity (also unlikely answer)

Question 39

The following statement best describes what? 'Triggering of an A-Tach by an atrial pacing stimulus that falls within the atrium’s vulnerable period'

Answer 39

Competitive Atrial Pacing.

Question 40

The following statement best describes what window? 'Portion of the RR cycle that is not part of the PVARP or AVI'.

Answer 40

The ASW - Atrial Sensing Window.

Question 41

# True / False LRL is never violated in V-based timing.

Answer 41

True. ## Footnote *With V-based timing its impossible to violate LRL.*

Question 42

# True / False LRL is never violated in A-based timing.

Answer 42

False. ## Footnote *A-A LRL will be reset by a sensed ventricular event within the VAI. This function mimics the compensatory pause commonly seen in normal sinus rhythm with ventricular ectopy.*

Question 43

# True / False Max Sensor Rate is never violated in V-based timing.

Answer 43

False. ## Footnote *Effective atrial-paced rate may theoretically be considerably higher than the programmed max sensor rate if AV conduction is present.*

Question 44

Hybrid based timing is a combination of what?

Answer 44

Atrial and Ventricular based timing.

Question 45

Hybrid based timing uses predominantly what style of timing?

Answer 45

Atrial based timing. ## Footnote *Once a loss of AV conduction occurs it then switches to ventricular based timing.*

Question 46

# Yes / No If the MTR interval has not yet been completed at the end of the AVI will an output be delivered?

Answer 46

No. ## Footnote *Ventricular pacing is withheld until the Max Track Rate interval completes.*

Question 47

The following statement best describes what? 'A PV interval greater than the programmed sensed AV delay'.

Answer 47

Pseudo 1st degree AVB.

Question 48

How does one calculate the Atrial Escape Interval?

Answer 48

LRL minus AV interval. ## Footnote *60bpm = 1000ms / PAV = 150ms* *1000 - 150 = AEI of 850ms = 70bpm*

Question 49

What does the 4th column in the NGB code dictate?

Answer 49

Whether rate responsive pacing is on/off.

Question 50

What does the 5th column in the NBG code dictate?

Answer 50

Whether there is multisite pacing in one anatomical location. ## Footnote *IS4 lead with multiple active pacing electrodes stimulating the LV.*

Question 51

To determine the exact moment a device senses an impulse, what action (NGB 3) can I employ?

Answer 51

Triggered pacing will show exact moment of impulse detection.

Question 52

A V event without a preceding sensed/paced A event will be labeled as a \_\_\_\_\_\_.

Answer 52

PVC. ## Footnote *This rule is always true. If a device is incorrectly labeling PVCs, look to see if it undersensed the previous atrial event.*

Question 53

List the major difference between device blanking and refractory periods.

Answer 53

* Blanking = Device will see nothing * Refractory = Device will see event & log in counters, however won't necessarly act upon it

Question 54

# True / False The Atrial Escape Interval can be violated in Atrial Based timing.

Answer 54

False. ## Footnote *Its impossible to violate the AEI in Atrial Based Timing.*

Question 55

# True / False The Atrial Escape Interval can be violated in Ventricular Based timing.

Answer 55

True. ## Footnote *LRL will be reset by a sensed ventricular event within the AEI.*

Question 56

# True / False Shortening the PVAB will increase sensitivity to atrial arrhythmias.

Answer 56

True. ## Footnote *Shorter blanking periods decrease the time the device is 'blind'. Thus quicker atrial rates will be seen.*

Question 57

# True / False Lengthening the PVAB will increase specificity to atrial arrhythmias.

Answer 57

True. ## Footnote *Reducing sensitivity increases specificity. Thus a longer PVAB will reduce risk of inappropriate mode switch.*

Question 58

List the only 2 P-synchronous ventricular modes in which a PMT can occur.

Answer 58

1. DDD 2. VDD

Question 59

List 5 ways a PMT can be initiated.

Answer 59

1. Ventricular extrasystole 2. Loss of Atrial Capture 3. Atrial Oversensing 4. Atrial extrasystole 5. Intermittent loss of Atrial Sensing

Question 60

During PMT is a higher programmed Max Track Rate **more** or **less** likely to induce symptoms?

Answer 60

More likely. ## Footnote *PMTs typically run at the MTR - Thus higher MTR = Faster PMT which is more likely to induce symptoms.*

Question 61

# True / False Most contemporary CRT devices use LV sensing.

Answer 61

False. ## Footnote *Most devices sense of the RV only.*

Question 62

Which two PVAB cycles exist in CRT?

Answer 62

1. PAVBRV = similar purpose to dual chamber devices 2. PAVBLV = To prevent inappropriate inhibition of LV pacing due to far-field atrial pace oversensing

Question 63

The following statement best describes what CRT timing cycle? 'LV-sensed event post an LV event (paced or sensed) that won't reset timing cycles'.

Answer 63

LVRP.

Question 64

What is the purpose of LVRP?

Answer 64

Prevents oversensing of QRS or T waves following a ventricular event (paced or sensed). ## Footnote *This prevents inappropriate loss of CRT (seen more commonly with unipolar LV leads).*

Question 65

The following statement best describes what CRT timing cycle? 'Prevents device from inadvertently delivering an LV output during the LV vulnerable period after an LV-sensed event, such as when an LV PVC occurs'.

Answer 65

LVPP. ## Footnote *RV pacing is not inhibited however.*

Question 66

# True / False LVPP maximises CRT delivery while reducing the risk of inducing a ventricular tachyarrhythmia.

Answer 66

True.

Question 67

# True / False Extending the LVPP interval will reduce the MTR and inhibit biventricular pacing at higher rates.

Answer 67

True.

Question 68

Which CRT timing cycle is best described below? 'Timing between the RV and LV-paced events'.

Answer 68

VV delay / LV Offset.

Question 69

List the 3 possible programming options of VV delay / LV Offset.

Answer 69

1. Positive (RV first) 2. Negative (LV first) 3. Zero (simultaneous RV/LV)

Question 70

List 5 events that inhibit BiV pacing.

Answer 70

1. Rapid atrial or sinus rates above MTR 2. Short and dynamic PR intervals 3. PACs 4. Frequent PVCs 5. AF with ventricular response \> LRL +/- SIR

Question 71

Define negative hysteresis.

Answer 71

Shortens AV delay to promote pacing.

Question 72

Define positive hysteresis.

Answer 72

Extends AV delay to promote intrinsic conduction.

Question 73

With respect to CRT, the statement below best describes what timing cycle? 'LV pacing immediately after intrinsic conduction / sensed event'.

Answer 73

Ventricular Sensed Response / BiV trigger.

Question 74

# True / False Ventricular Sensed Response / BiV trigger must function between the LRL and MTR.

Answer 74

True.

Question 75

# True / False BiV pacing will cease above MTR (TARP).

Answer 75

True. ## Footnote *The vast majority of CRT timing problems can be erased by programming higher MTR, irrespective of whether you believe the patient will achieve those rates.*

Question 76

With respect to CRT, what timing cycle could further reduce BiV pacing due to PVC's?

Answer 76

PVC response. ## Footnote *Remember PVC response will cause an abnormally long PVARP extension.*

Question 77

List 5 things that can be done to improve BiV pacing in AF patients.

Answer 77

1. Increase LRL 2. Enable ventricular sense response 3. Aggressive Medical therapy 4. AF Ablation 5. AVN Ablation

Question 78

List 4 signals that the Ventricular Refractory Period (VRP) is designed to blank.

Answer 78

1. Its own output stimulus 2. T-wave 3. Excessive Afterpotential 4. Paced QRS complex

Question 79

# True / False All refractory periods start with a blanking period.

Answer 79

True. ## Footnote *Blanking periods can be standalone and don't necessarily need refractory periods following them.*

Question 80

What are the 4 fundamental timing cycles associated with the ventricular channel in DDD mode?

Answer 80

1. Lower rate interval (LRI) 2. Ventricular refractory period (VRP) 3. Atrioventricular interval (AVI) 4. Post Atrial Ventricular Blanking (PAVB)

Question 81

What are the 3 fundamental timing cycles associated with the atrial channel in DDD mode?

Answer 81

1. Atrial escape interval (AEI) 2. Postventricular atrial refractory period (PVARP) 3. Total atrial refractory period (TARP)

Question 82

The following statement best describes what timing cycle? 'The longest interval possible following a sensed or paced ventricular event and the following ventricular paced event without and intervening sensed events'.

Answer 82

Lower rate interval.

Question 83

The following statement best describes what timing cycle? 'Initiated by a ventricular event during which a new LRI cannot be initiated'.

Answer 83

Ventricular Refractory Period (VRP).

Question 84

The following statement best describes what timing cycle? 'Interval between an atrial event and a scheduled V paced event'.

Answer 84

Atrioventricular interval (AVI).

Question 85

The following statement best describes what timing cycle? 'Interval between a ventricular event and the following atrial paced event'.

Answer 85

Atrial escape interval (AEI). ## Footnote *Most manufacturers use V-Based timing, which ensures the AEI is always a constant interval.*

Question 86

The following statement best describes what timing cycle? 'Interval following a ventricular event during which an atrial event cannot initiate the Atrioventricular interval (AVI)'

Answer 86

Postventricular atrial refractory period (PVARP). ## Footnote *Avoids inappropriate atrial sensing of ventricular events and also retrograde P-waves.*

Question 87

The following statement best describes what timing cycle. 'Is a derived value from AVI + PVARP'.

Answer 87

Total atrial refractory period (TARP). ## Footnote *A p-wave which falls within the TARP will not be tracked, thus functional 2:1 block can occur.*

Question 88

The following statement best describes what timing cycle? 'Interval is initiated by an Atrial Paced event and disables all sensing of the ventricular channel'

Answer 88

Post Atrial Ventricular Blanking (PAVB). ## Footnote *Prevents crosstalk of ventricular channel sensing atrial events and respondent pacing inhibition. Programmable, short duration ~10-50ms.*

Question 89

What is the purpose of ventricular safety pacing?

Answer 89

To prevent ventricular pacing inhibition respondent to crosstalk. ## Footnote *While also ensuring pacing in a non-vulnerable section of the cardiac cycle.*

Question 90

# Yes / No Does VSP prevent crosstalk?

Answer 90

No. ## Footnote *It only prevents the deleterious consequences of crosstalk. E.g. V-pacing inhibition.*

Question 91

What is the typical AV delay seen during VSP?

Answer 91

100-110ms. ## Footnote *Far shorter than a normal AV delay!*

Question 92

Why is the VSP stimulus delivered in a far shorter time than a normal physiologic AV delay?

Answer 92

To pace within a refractory period of the cardiac cycle. ## Footnote *This prevents pacing on the vulnerable T-wave if there's a competitive instrinsic impulse present.*

Question 93

# True / False The VSP window is initiated by a Ventricular event.

Answer 93

False. ## Footnote *The VSP window is typically started by an atrial event.*

Question 94

# Yes / No If an atrial event falls within the PVAB, will it be detected and a VSP delivered?

Answer 94

No. ## Footnote *Although both are started at the same time, the PVAB must expire before detection in the VSP window can occur and a respondent VSP be delivered.*

Question 95

# Yes / No PAVB programmed to 60ms / VSP programmed to 100ms Would a ventricular detection and subsequent VSP occur 70ms after the initial atrial event?

Answer 95

Yes. ## Footnote *The PAVB window has expired and the VSP window is still active, thus ventricular events will be detected and a VSP delivered.*

Question 96

# Yes / No PAVB programmed to 60ms / VSP programmed to 100ms Would a ventricular detection and subsequent VSP occur 110ms after the initial atrial event?

Answer 96

No. ## Footnote *Although the ventricular even will be counted, the VSP window expired 10ms prior - thus no VSP delivered.*

Question 97

# True / False PVARP should never be programmed shorter than VRP.

Answer 97

True. ## Footnote *Short PVARP programming increases risk of far field atrial sensing of the terminal portion of the QRS complex.*

Question 98

Give the equation to calculate 2:1 block rate.

Answer 98

60,000 / TARP (Total Atrial Refractory Period)

Question 99

# True / False Wenckebach upper rate response will only occur if the URI is longer than the TARP.

Answer 99

True. ## Footnote *If the Upper Rate Interval is equal to the Total Atrial Refractory Period the upper rate response will instantly be 2:1 block.*

Question 100

If the URI is equal to the TARP, what will my upper rate behaviour be?

Answer 100

2:1 block. ## Footnote *No upper rate wenckebach behaviour will occur.*

Question 101

# True / False A shorter TARP will equate to a lower 2:1 block rate.

Answer 101

False. ## Footnote *A shorter TARP interval will result in a higher 2:1 block rate.*

Question 102

# Yes / No If a patients spontaneous atrial interval exceeds the TARP but is shorter than the URI, will Wenckebach behaviour be permitted?

Answer 102

Yes.

Question 103

# True / False Sensed AVI is typically longer than Paced AVI.

Answer 103

False. ## Footnote *sAVI is shorter than the pAVI as it is assumed the device only detects the p-wave after a portion of the p-wave is already completed. Typically sAVI is shorter by 30-50msec.*

Question 104

# True / False Rate adaptive AVI aims to mimic the physiological lengthening of the AVI during exercise.

Answer 104

False. ## Footnote *Rate adaptive AVI will shorten, not lengthen, the AVI in response to exercise. Shorter intervals = Faster rates.*

Question 105

# True / False Pacemaker mediated tachycardia or Endless loop tachycardia typically occurs at the URI.

Answer 105

True.

Question 106

Which 3 programmable parameters can be changed to test for likelihood of PMT?

Answer 106

1. Program lowest possible Atrial Output 2. Program shortest possible PVARP 3. Program highest possible Atrial Sensitivity

Question 107

What are the 4 predisposing factors for RNRVAS?

Answer 107

1. Long VA conduction time 2. Long PVARP 3. Short LRI 4. Long AVI

Question 108

# True / False DVI results in competitive atrial pacing, shown to lower risk of Atrial Fibrillation.

Answer 108

False. ## Footnote *Competitive Atrial pacing has been shown to increase risk of Atrial Fibrillation.*

Question 109

# True / False DDI = Non Triggered / Tracking mode.

Answer 109

True. ## Footnote *Both chambers are sensed, however an Atrial sensed event will not start an AVI and a respondent V-pace. This prevents tracking of Atrial Arrhythmia.*

Question 110

What dual chamber mode does not have timing cycles of PAVBP or VSP?

Answer 110

VDD. ## Footnote *As there is no risk of AV crosstalk due to lack of Atrial output.*

Question 111

# True / False A VDD system is suitable for patients with SND, SSS or Chronotropic incompetence.

Answer 111

False. ## Footnote *Dedicated atrial lead is required. These patients will require atrial stimulus which a single pass lead does not provide.*

Question 112

# True / False With Atrial Based timing, the A-A is constant and equal to the LRI.

Answer 112

True. ## Footnote *A-A = As-Ap & Ap-Ap*

Question 113

# True / False With Atrial Based timing, the AEI is constant in order to maintain a constant A-A interval.

Answer 113

False. ## Footnote *The AEI varies to maintain a constant A-A interval. AEI = Vp-Ap & Vs-AP*

Question 114

Which type of lower rate timing is best described by the following statement? 'The AEI remains constant at all times'.

Answer 114

Ventricular based timing. ## Footnote *AEI = Vp-Ap & Vs-AP.*

Question 115

Which type of lower rate timing is best described by the following statement? 'Can cause AV delays longer than the programmed value'.

Answer 115

Ventricular based timing.

Question 116

# Yes / No If a signal falls within the Blanking or Refractory period, will it initiate an LRI or AVI?

Answer 116

No. ## Footnote *Blanking is blind to all signals. Refractory counts signals but still won't initiate LRI or AVI.*

Question 117

In lieu of an atrial flutter algorithm, what programming changes can be made to prevent 2:1 lock-in.

Answer 117

Program AVI + PVAB shorter than Atrial Cycle length.

Question 118

During Automatic Mode Switch - in what mode does a DR device typically function?

Answer 118

DDI or DDIR. ## Footnote *This prevents tracking of the arrhythmia, which would lead to overpacing the ventricle.*

Question 119

Which timing cycle is best described below? 'Longer at lower rates to protect against PMT. Shortens at higher rates to elevate the 2:1 block point'

Answer 119

Rate Adaptive PVARP.

Question 120

Which timing cycle is best described below? 'Prevents atrial stimulus when atrial sensed event is detected within the PVARP'.

Answer 120

NCAP - Non Competitive Atrial Pacing. ## Footnote *NCAP overrides the AV delay, which may shorten in response.*

Question 121

What is the purpose of NCAP?

Answer 121

To prevent an Atrial Stimulus being delivered in the vulnerable period of the atrium. ## Footnote *Such a stimulus at this time may invoke an atrial arrhythmia.*

Question 122

What is the purpose of AMS (Automatic Mode Switch).

Answer 122

To prevent ventricular tracking of rapid atrial rates. ## Footnote *Most Dual Chamber systems will switch to DDI or DDIR mode.*

Question 123

# True / False The mode VOO is now obsolete and should never be programmed for fear of R on T pacing into VF.

Answer 123

False. ## Footnote *VOO is useful during testing, MRI and Electrocautery surgical procedures as a way to inhibit response to external noise. Outside of MI, Ischemia or electrolyte imbalances it is extremely rare for VOO pacing to induce VF.*

Question 124

VVT is a rarely used timing cycle - list 1 instance where its useful today.

Answer 124

To determine the exact moment when a device senses an event. ## Footnote *VVT is a triggered mode - thus the exact moment a device senses an event can be determined by observing when the respondent output is delivered.*

Question 125

# True / False AAI is functionally the same as VVI except it paces and senses in the Atrium.

Answer 125

True.

Question 126

DDD pacemaker programmed as follows will exhbit what when the atrial rate = 128bpm? 'LRL 50ppm, MTR 125ppm, AVD 175ms (reduced by 25ms above 100bpm), A refractory of 300ms' 1. 1:1 conduction 2. 2:1 conduction 3. 3:1 conduction 4. Mobitz II 5. Pseudo Wenckebach

Answer 126

5 - Pseudo Wenckeback. ## Footnote *TARP = AVD (175-25 = 150ms) + PVARP (300ms) / 60,000 = 133ppm.* *Atrial rates between 125 and 133 will show pseudo wenckebach behaviour. Above 133ppm device will exhibit 2:1 block.*

Question 127

DDD pacemaker programmed as follows will exhbit what when the atrial rate = 128bpm? 'LRL 50ppm, MTR 125ppm, AVD 175ms (reduced by 25ms above 100bpm), A refractory of 300ms' 1. CHB 2. Mobitz II 3. 3:1 block 4. 4:3 block

Answer 127

4 - 4:3 block. ## Footnote *As the atrial rate is just above the MTR most beats will be conducted, only the odd few will be dropped by falling within the TARP. Thus 4:3 is most likely - all other forms of block are too agressive.*

Question 128

At sensor indicated rates higher than the max track rate, which is most likely in a CHB patient? 1. 1:1 2. Mobitz I 3. Mobitz II 4. 2:1 5. 3:1

Answer 128

1 - 1:1. ## Footnote *The following describes normal function. The device effectively has complete control of the heartbeat in both chambers thus will sequentially pace A and V. Upper rate behaviour may arise when the intrinsic rhythm exceeds the programmed sensor / max track rate.*

Question 129

Which of the following is not a programmable timing cycle in both VVI and DDD pacemakers? 1. Output 2. AV Delay 3. Refractory periods 4. Sensitivity

Answer 129

2 - AV Delay. ## Footnote *VVI generators sense/pace the ventricle only, thus cannot initiate AV intervals.8

Question 130

# Yes / No Device is programmed VVI 60 - however you observe a rate of 50ppm. Is this an example of ventricular based timing?

Answer 130

No ## Footnote Venticular based timing allows rates above the LRL but never below