CRM 6 - TARP and PVARP and Functions Flashcards
What does PVARP stand for?
Post Ventricular Atrial Refractory Period
What does TARP stand for?
Total Atrial Refractory Period
What is the VA interval?
LRL - AV delay
VA interval is not programmable
Goes from beginning of V to beginning of following P
What 2 things are generated after paced V?
-Lower rate limit
-Maximum tracking rate
What is decrement?
-As rate gets faster, PR interval gets longer, then blocks (Wenckebach)
-Protective mechanism so beats don’t get through to ventricles
What 2 things can normal conduction system modulate?
-Sinus rate
-PR interval (AV node - decremental and refractory properties)
AV node decrement with block
-Pacing the atrium
-Completely normal at faster rates
-Seen at slower rates in diseased AV nodes
What happens during PVARP?
-Refractory period where p waves are sensed but not acted on
What are the 3 types of tracking of atrial sensed beats (p waves)?
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)
What happens to p waves that fall into PVARP?
No AV delay
Why was PVARP invented?
-To stop pacemaker mediated tachycardia
-Avoid retrograde P waves, farfield R waves, atrial ectopics starting an AV interval
What is the TARP?
-The whole atrial refractory period
-AV delay + PVARP
How does pacemaker mediated tachycardia occur?
-Ventricle is paced
-Atrium is not refractory and AV node conducts retrograde
-Atrium contracts, generates AV delay, V paces
-PVARP covers retrograde p wave
How can you prevent PMTs?
-Extend the PVARP so retrograde P wave is blanked
What happens to P wave that falls into MTR?
-Wait until after MTR and extend AV delay
What happens to P wave that falls into TARP
-Does not generate AV delay
What rhythm does P wave falling in TARP create?
-2:1 block
What rhythm does P wave falling into MTR create?
-Wenckebach
How to calculate atrial rate behaviour?
60000/interval
-2:1 block rate for TARP interval
-Wenckeback block rate for MTR interval
-1:1, 2:1, Wenckebach
What is chronotropic incompetence?
-the inability to increase the heart rate adequately during exercise to match CO to metabolic demands
What are the types of sensors in rate response?
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
How are sensors used?
Dual sensor
-one metabolic, one non
-sensor ‘blending’ and ‘cross-checking’
Considerations when optimising
-IHD?
-Inactive patients
-Lung disease
-Cello players
What happens when magnet is put over pacemaker?
-Asynchronous pacing
-Paces at a faster magnet rate
-Shortens A-V interval
-Confirm battery status
-Identify mode
-Terminate PMT
DDD -> DDO
