General Pacing Flashcards
Rheobase is
Minimum voltage that will depolarize at longest possible pulse width
Chronaxie is
Shortest pulse width that depolarizes at 2x Rheobase voltage
Can hysteresis be initiated by a paced event
No - always a sensed event
what are the normal sensing values for A and V
A = 0.5mv V = 2.5mv
What does positive hysteresis mean
Promote intrinsic conduction and minimise RV pacing
What does negative hysteresis mean
Promotes pacing
Why would we want to promote pacing and how to do it
To ensure maximum benefit from CRT/ BiV devices - Shorten AV delay
What is an evoked response
Small cardiac signal that occurs at contraction - Used by devices to determine capture
What are the two different ways rate drop response detects
Drop Detect
Low Rate detect
How does drop detect work
A programmed drop size with final rate below accepted rate for a programmed period of time
Low rate detect
Gradual decline in rate below the LRL - pacing kicks in
Is the cathode negative or positive
Negative
Is the anode negative or positive
Positive
How can you reduce polarization effect
Reduce tip size
Reduce pulse width
What does the polarization effect do
Reduces flow of charge to myocardium
Low drain and long battery life are assoicated with what
higher impedance
Low impedance could mean what
Decreased battery life and higher drain
What could cause high drain / low impedance
Insulation fracture
What would a conductor break look like
High impedance >3000 ohms
What must A and V slew rates be above
A >0.5v/s
V >0.75v/s
doubling voltage will do what to stim energy
Four fold increase in stim energy
doubling pulse width will do what to stim energy
Two fold increase in stim energy
Which lead is best to determine anodal capture
Lead 3
How does RV pacing look in lead 3
Positive
How does LV pacing look in lead 3
Negative
Anodal capture is RV pacing, why does it occur
RV threshold is much higher, therefore too high stim energy is programmed
Why is Anodal capture bad
Loss of VV synchrony, reduced EF and CRT effectiveness - plus higher battery usage
Also increases onset of HF due to RV pacing
What mode and rate will a device change to at ERI
AAI / VVI @ 65bpm
What is the magnet rate
85bpm
How long from does RRT last before hitting ERI
3 months
What gives a 54% relative reduction in risk for HF hospitalization
A 10% VP reduction below 40% of total VP
What drug can increase pacing threshold
Flecanide
What % change in impedance warrants investigation
30%
Which study determined 40% pacing is high
MOFSET
Is there a change in HF onset between 40-100%
NO - once above 40% likelihood of HF remains same
Which study found out anything below 40% RV pacing is associated with better HF outcome
BLOCKHF study
