Homework Flashcards
Define Threshold
the minimum amplitude and duration required to generate the self-propagation wave
Where are the anode and cathode located in a bipolar system?
inside the heart
Where are the cathode and anode in a unipolar system?
cathode in the heart
anode outside the heart
Which stimulation has the larger spike?
unipolar
What is the equation for Ohm’s law?
V = IR
Define stimulation threshold
Minimum stimulus and duration necessary to initiate depolarization wavefront
What two conditions must be met for a pacing stimulus to “capture”?
threshold: proper amplitude and duration
What is the programmed margin of safety for voltage?
2x voltage threshold
What is the programmed margin of safety for pulse duration?
3x duration threshold
What do low impedance measurements reflect?
failure in lead conductor insulation
what do high impedance values suggest?
conduction fracture or loose set-screw at connector
What steroid is used in pacemaker leads?
DSP, to reduce inflammation
What is the largest single entity inside the pulse generator?
battery
What is “crosstalk”?
atrial channel thinks that far-field ventricle activity is intrinsic atrial activity
Name the two output parameters
Voltage
time
How much high can chronic thresholds be compared to acute thresholds?
2-5 times higher
What should the sensitivity margin be at implant?
2
Explain noise reversion
A change in pacing mode, typically to async pacing at the programmed rate
What is the most advanced form of pacing system currently available?
DDDRD
What are the five components of pacing leads?
electrodes conductors insulation connector pin fixation mechanism
What type of lead is more difficult to extract?
passive fixation - tends to be more scar
What is IS-1?
Industry Standard
What is the power source of all present generators?
Lithium powered battery
What does a magnet do to the reed switch?
closes the reed switch, which puts the pacemaker into OO mode
Which two sensors are “blended”?
Minute-ventilation and activity sensor
Define AAI mode
no intrinsic A is sensed the pacemaker will pace in the A; when A is sensed the pacemaker inhibits
What three names might the “pacing rate” also be called?
automatic interval
basic interval
pacing rate
demand interval
How is the pacing interval’s time defined?
time period in milliseconds between two consecutive paced event in the same chamber
why would a RV paced beat have a LBBB morphology?
it goes from RV to LV like in LBBB
Define pseudofusion beat
pacemaker output falls simultaneously on an intrinsic event but the intrinsic comes slightly before
Define fusion beat
output pulse which contributes to an intrinsic beat
