Fogoros Homework Flashcards
What does Mobitz II AV block indicate?
distal AV block
What does Phase 2 of the AP correlate to on the surface EKG?
ST segment
Where is the site of Wenckebach AV block usually located?
localized to the AV node
What does HV interval measure?
conduction through the His - Purkinje system
Name evaluations done in an EP study
- Assess function of the SA node, Av node and purkinje system
- Mapping the locaiton of arrhythmogenic foci
- Evaluation efficacy of antyiarrhythmic drugs or devices
How do you calculate Cycle Length to Heart rate?
60 000 divided by cycle length
Where can AV block originate from?
- within the AV node
- distal to the AV node in the His Bundle
What is the inward moving depolarization ion in the Cardiac Muscle?
Sodium
Which interval is prolonged if the block is within the AV node?
AH interval
In the extrastimulus technique, what is S2?
After the drive train S1 a single premature beat is initiated called S2
What is the equation for Corrected Sinus Node Recovery Time?
cSNRT = SNRT - BCL
What is the couplign interval?
the time between the lst normal impulse and premature impulse
S1 - S2
What are 2 uses for an electrode catheter?
- recoding
- pacing
How is the refractory period of cardiac tissue defined in the EP lab?
terms of the tissue’s response to premature paced impulses
Define overdrive suppression of the SA node
When an automatic foci (SA node) can be overdriven by a more rapidly firing pacemaker
What measurement is used to asses the automaticity of the SA node?
SNRT
Sinus Node Recovery Time
What does the coupling interval (S1 - S2) that produces block in the AV node represent?
AVNERP
AH lengthens until S2 is blocked
What does Phase 0 of the AP correlate to on a surface EKG?
QRS
Name the two pacing methods used to evaluate the AV conduction system
- Extrastimulus pacing
- Incremental pacing
What phase of the AP is generally recorded on the electrogram?
Phase 0
What is the outward moving repolarizing ion in a cardiac muscle cell?
Potassium
What are the three basic components of the PR interval?
- PA interval / intraatrial conduction
- AH interval
- HV interval
What ion mediates the rapid upstroke of the AP?
Sodium
Which interval is prolonged if the block is below the AV node?
HV interval
In most EP labs, what measurement of the SNRT is considered abnormal ?
> 1500 ms
Which type of AV block is a normal phenomenon with rapid atrial pacing?
Wenchebach
What is the most common mechanism for tachyarrhythmias?
Reentry
Define extrastimulus pacing.
PES - introducing one or more premature impulses at preprogrammed intervals
Which intracardiac electrogram is most valuable in assessing ht evarious types of AV nodal block?
His Bundle Electrogram
What are the three mechanisms for tachyarrhythmias ?
- Automaticity
- Triggered
- Re entry
What is the EP equivalent of heart rate?
cycle length
What ion accounts for the plateau phase of the AP?
Calcium
What part of the action Potential curve determines the speed of conduction?
Phase 0
What does the AH interval measure?
Conduction time through the AV node
Define incremental pacing.
introducing a train of paced impulses at a fixed cycle length
What type of block is potentially lethal?
AV block occuring distally to the AV node
True or False:
Each membrane channel is selective for its particular ion.
True
What causes phase 0 depolarization in a cardiac muscle cell?
rapid influx of Sodium into the cell
At what mV do the m gates open allowing Na+ ions to rush into the cell? What do we call this level?
-60 mV
Threshold membrane potential
What is the basic unit of time in EP?
Milliseconds (ms)
What is the primary benefit for slowing of the impulse through the AV node?
Allows for complete atrial emptying before the electrical impulse reaches the ventricles
What is the resting potential of a cardiac muscle cell?
-80 to -90 mV
What electrode distance provides very focused view of tissue?
2mm
What should the EGM be recording?
Depolarization
What does high bandpass filter do?
Allows for higher frequencies to be displayed by rejecting filters below
What is the typical high bandpass filter cutoff?
30 Hz
What does a low bandpass filter do?
everything below 30 Hz is cut out
What is often the low bandpass filter cutoff frequency?
500Hz
What is the typical range for high-low bandpass filtering?
30 - 500Hz
What is the nomenclature that refers to an 8 beat pacing train?
S1
What does S4 represent ?
Indicates the third premature response
Describe unipolar
- one electrode within the heart recording
- more information
- not as specific
Describe bipolar recording
- voltage difference between 2 electrodes within the heart
- more specific
What happens when a wave of depolarization goes toward a positive electrode?
positive deflection
What does the maximum negative slope in a unipolar recording coincide with?
the arrival of the depolarization wavefront directly beneath the electrode
What other electrogram finding helps the ablation to be more precise?
point of earliest activation on a unipolar matching with bipolar
How are low-frequency oscillations removed?
by high pass filtering that attenuates the frequencies that are slower than the specified cut off
What does low pass filtering reduce?
attenuate frequencies that are slower than the specified corner frequency (200 - 500Hz)
What can a notch filter eliminate?
reduce electrical noise introduced by the frequency of common AC current (50 or 60 Hz)
How do most antiarrhythmic drugs work?
by affecting the shape of the action potential
Which class of drugs affects the rapid sodium channel?
Class 1
What percentage of the population has Torsades de Pointes?
3-4%
