CRM 6 - TARP and PVARP and Functions

Question 1

What does PVARP stand for?

Answer 1

Post Ventricular Atrial Refractory Period

Question 2

What does TARP stand for?

Answer 2

Total Atrial Refractory Period

Question 3

What is the VA interval?

Answer 3

LRL - AV delay
VA interval is not programmable
Goes from beginning of V to beginning of following P

Question 4

What 2 things are generated after paced V?

Answer 4

-Lower rate limit
-Maximum tracking rate

Question 5

What is decrement?

Answer 5

-As rate gets faster, PR interval gets longer, then blocks (Wenckebach)
-Protective mechanism so beats don’t get through to ventricles

Question 6

What 2 things can normal conduction system modulate?

Answer 6

-Sinus rate
-PR interval (AV node - decremental and refractory properties)

Question 7

AV node decrement with block

Answer 7

-Pacing the atrium
-Completely normal at faster rates
-Seen at slower rates in diseased AV nodes

Question 8

What happens during PVARP?

Answer 8

-Refractory period where p waves are sensed but not acted on

Question 9

What are the 3 types of tracking of atrial sensed beats (p waves)?

Answer 9

1:1 tracking
-A sense followed by sensed AV delay and pacing of RV
-Occurs up to MTR

Pacemaker Wenckebach
-A sense followed by extended AV delay until there is a dropped beat
-Occurs between MTR and PVARP

2:1 block
-Every other intrinsic P wave not tracked with a V pace as they fall into refractory blanking period (PVARP)

Question 10

What happens to p waves that fall into PVARP?

Answer 10

No AV delay

Question 11

Why was PVARP invented?

Answer 11

-To stop pacemaker mediated tachycardia
-Avoid retrograde P waves, farfield R waves, atrial ectopics starting an AV interval

Question 12

What is the TARP?

Answer 12

-The whole atrial refractory period
-AV delay + PVARP

Question 13

How does pacemaker mediated tachycardia occur?

Answer 13

-Ventricle is paced
-Atrium is not refractory and AV node conducts retrograde
-Atrium contracts, generates AV delay, V paces
-PVARP covers retrograde p wave

Question 14

How can you prevent PMTs?

Answer 14

-Extend the PVARP so retrograde P wave is blanked

Question 15

What happens to P wave that falls into MTR?

Answer 15

-Wait until after MTR and extend AV delay

Question 16

What happens to P wave that falls into TARP

Answer 16

-Does not generate AV delay

Question 17

What rhythm does P wave falling in TARP create?

Answer 17

-2:1 block

Question 18

What rhythm does P wave falling into MTR create?

Answer 18

-Wenckebach

Question 19

How to calculate atrial rate behaviour?

Answer 19

60000/interval
-2:1 block rate for TARP interval
-Wenckeback block rate for MTR interval
-1:1, 2:1, Wenckebach

Question 20

What is chronotropic incompetence?

Answer 20

-the inability to increase the heart rate adequately during exercise to match CO to metabolic demands

Question 21

What are the types of sensors in rate response?

Answer 21

Non metabolic:
-accelerometer - postural changes and body movements
-piezoelectric crystals - muscular pressure waves converted to electrical signal

Metabolic:
-QT intrval
-Minute ventilation
-Peak endocardial acceleration

Question 22

How are sensors used?

Answer 22

Dual sensor
-one metabolic, one non
-sensor ‘blending’ and ‘cross-checking’

Question 23

Considerations when optimising

Answer 23

-IHD?
-Inactive patients
-Lung disease
-Cello players

Question 24

What happens when magnet is put over pacemaker?

Answer 24

-Asynchronous pacing
-Paces at a faster magnet rate
-Shortens A-V interval
-Confirm battery status
-Identify mode
-Terminate PMT

DDD -> DDO

Question 25

What will magnet do in ICD?

Answer 25

-Temporarily stop therapy

Question 26

What is ERI battery status?

Answer 26

ERI - Elective Replacement Indicator

Question 27

Rhythms after magnet held to pacemaker. What are they?

Answer 27

AAI
VVI
DDO
-1 or 2 leads. Single or dual programmed to VVI/AAI?

Question 28

Pacemaker and ICD response to noise

Answer 28

Pacemaker:
-Switch to asyncronous pacing AOO, VOO, DOO

ICD:
-Categorise as VF
-Noise discrimination algorithm differentiates RV lead noise from VF
-Compares farfield EGM signal to near-field sensing

Question 29

What is sleep function?

Answer 29

-Most common in VVI modes
-Reduce pacing rate during sleep for comfort/battery life
-Suspends LRL and paces at programmed rate during programmed hours

Question 30

What is hysteresis?

Answer 30

-Allows more intrinsic rhythm before intervention
-Saves battery life
-Extend interval, inhibit pacing, no activity, pace at end of hysteresis interval

Question 31

What is rate adaptive AV delay?

Answer 31

-Mimics PR shortening on exercise
-Helps to prevent 2:1 block on exertion by having a longer atrial sensing window
-Automatic/programmable

Question 32

What is automatic PVARP?

Answer 32

-Protects against PMT by increasing PVARP at lower tracking rates
Provides higher 2:1 block rate by shortening PVARP and AV delay at higher tracking rates

Question 33

What is automatic sensing?

Answer 33

-Varies sensing
-Safety margin so that there is not under sensing
-Auto adjusts to 50% of measured wave

Question 34

What is automatic capture?

Answer 34

-Maintains safe pacing during acute, sub-acute and chronic phase by varying threshold
-Reduces hospital visits
-Adjusts to 2x pulse amplitude or 3x pulse width after taking a threshold

Question 35

How how lead technology tried to reduce a high threshold during the acute stage?

Answer 35

-Steroid-tipped lead

Question 36

What causes varying thresholds?

Answer 36

-Activity
-Posture
-Time of day
-Co-morbidities
-Drugs - flecainide
-Disease progression
-Lead position

Question 37

How does autocapture work?

Answer 37

-Decreases AV delay to force pacing
-Monitors each beat for evoked response
-Back-up safety pulse if there is no capture