pacing concepts

Question 1

Voltage is…

Answer 1

the force that causes electrons to move through a circuit

Question 2

voltage is often referred to as the

Answer 2

amplitude

Question 3

current is measured in

Answer 3

Milliamps

Question 4

is current programmable?

Answer 4

no

Question 5

impedance is

Answer 5

the opposition to current flow from the electrode to the myocardium

Question 6

current is

Answer 6

the actual continuing volume of flow of electricity

Question 7

ohms law is

Answer 7

current x resistance (V=IxR)

Question 8

if impedance remains constant and the voltage decreases….

Answer 8

the current decreases

Question 9

if the voltage is constant and the impedance decreases….

Answer 9

the current increases

Question 10

1.5v as output divided by 397 ohms for resistance equals

Answer 10

0.00378 A or 3.78 milliAmps

Question 11

Which of these are true of current in a pacing system?

Answer 11

-Determined by the amount of electrons that move through the circuit
-Represented by the letter “i”
-Measured in mA

Question 12

typical impedance range

Answer 12

200-1000 ohms

Question 13

low resistance in impedance can be caused by….

Answer 13

Leaks in the hose (insulation leak)- which results in low resistance, high current drain, and early battery depletion

Question 14

high resistance can be caused by…

Answer 14

a lead conductor break or

Question 15

if a fracture is not complete, what can happen?

Answer 15

you can see both high and low impedance values

Question 16

another result of an insulation break

Answer 16

oversensing- the EGM can often pick up abnormal electrical signals

Question 17

What would you expect to happen with a lead fracture?

Answer 17

Current would decrease while impedance would increase

Question 18

What would you expect to happen if there’s an insulation break?

Answer 18

Impedance drop, increased current, potential loss of capture

Question 19

two stages of the lead maturation process

Answer 19

inflammation and fibrosis

Question 20

lead maturation may eventually…

Answer 20

raise capture threshold

Question 20

do steroid eluting leads have an effect on threshold?

Answer 20

no

Question 21

pulse width

Answer 21

duration of the current flow

Question 22

safety margin

Answer 22

2x amplitude or 3x pulse width threshold

Question 23

acceptable sensing values

Answer 23

A >/=1 mV, V= >/= 3 mV

Question 24

how do pacemakers sense?

Answer 24

electrical activity of myocardial cells between the cathode and the anode