General Pacing Flashcards
(36 cards)
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
