General Pacing

Question 1

Rheobase is

Answer 1

Minimum voltage that will depolarize at longest possible pulse width

Question 2

Chronaxie is

Answer 2

Shortest pulse width that depolarizes at 2x Rheobase voltage

Question 3

Can hysteresis be initiated by a paced event

Answer 3

No - always a sensed event

Question 4

what are the normal sensing values for A and V

Answer 4

A = 0.5mv
V = 2.5mv

Question 5

What does positive hysteresis mean

Answer 5

Promote intrinsic conduction and minimise RV pacing

Question 6

What does negative hysteresis mean

Answer 6

Promotes pacing

Question 7

Why would we want to promote pacing and how to do it

Answer 7

To ensure maximum benefit from CRT/ BiV devices - Shorten AV delay

Question 8

What is an evoked response

Answer 8

Small cardiac signal that occurs at contraction - Used by devices to determine capture

Question 9

What are the two different ways rate drop response detects

Answer 9

Drop Detect

Low Rate detect

Question 10

How does drop detect work

Answer 10

A programmed drop size with final rate below accepted rate for a programmed period of time

Question 11

Low rate detect

Answer 11

Gradual decline in rate below the LRL - pacing kicks in

Question 12

Is the cathode negative or positive

Answer 12

Negative

Question 13

Is the anode negative or positive

Answer 13

Positive

Question 14

How can you reduce polarization effect

Answer 14

Reduce tip size

Reduce pulse width

Question 15

What does the polarization effect do

Answer 15

Reduces flow of charge to myocardium

Question 16

Low drain and long battery life are assoicated with what

Answer 16

higher impedance

Question 17

Low impedance could mean what

Answer 17

Decreased battery life and higher drain

Question 18

What could cause high drain / low impedance

Answer 18

Insulation fracture

Question 19

What would a conductor break look like

Answer 19

High impedance >3000 ohms

Question 20

What must A and V slew rates be above

Answer 20

A >0.5v/s

V >0.75v/s

Question 21

doubling voltage will do what to stim energy

Answer 21

Four fold increase in stim energy

Question 22

doubling pulse width will do what to stim energy

Answer 22

Two fold increase in stim energy

Question 23

Which lead is best to determine anodal capture

Answer 23

Lead 3

Question 24

How does RV pacing look in lead 3

Answer 24

Positive

Question 25

How does LV pacing look in lead 3

Answer 25

Negative

Question 26

Anodal capture is RV pacing, why does it occur

Answer 26

RV threshold is much higher, therefore too high stim energy is programmed

Question 27

Why is Anodal capture bad

Answer 27

Loss of VV synchrony, reduced EF and CRT effectiveness - plus higher battery usage

Also increases onset of HF due to RV pacing

Question 28

What mode and rate will a device change to at ERI

Answer 28

AAI / VVI @ 65bpm

Question 29

What is the magnet rate

Answer 29

85bpm

Question 30

How long from does RRT last before hitting ERI

Answer 30

3 months

Question 31

What gives a 54% relative reduction in risk for HF hospitalization

Answer 31

A 10% VP reduction below 40% of total VP

Question 32

What drug can increase pacing threshold

Answer 32

Flecanide

Question 33

What % change in impedance warrants investigation

Answer 33

30%

Question 34

Which study determined 40% pacing is high

Answer 34

MOFSET

Question 35

Is there a change in HF onset between 40-100%

Answer 35

NO - once above 40% likelihood of HF remains same

Question 36

Which study found out anything below 40% RV pacing is associated with better HF outcome

Answer 36

BLOCKHF study