Ep Flashcards
Pa interval?
Earliest activation in sinus node region and region of av node
What does a prolonged PA interval indicate?
Delay in intra-atrial conduction(usually do to atrial dx or drugs)
Pa interval in ms?
25-55ms
What does AH interval duration time measure?
Time taken for cardiac impulse to travel over av node
Normal AH interval?
45-150ms
Normal PR interval time?
80-140ms
What causes conduction in AV node to vary?
Cycle length because of decremental properties
Total conduction time over His bundle should be <
<30ms
Hv interval is?
Conduction over specialized fibers of purkinje system
How is HV measured?
His bundle electrogram to earliest recorded ventricular activation
HV interval in ms?
35-55ms
QT measured in?
QTc
Bazette formula
QTc=QT/ square root RR
What is a normal QRS
< or = 100ms
Normal QTc for men and women
440ms for men
460ms for women
2 test sinus node function tests for bradycardia
SNRT
SACT
CSNRT
SNRT-SCL
Reasonable values
SNRT<1500ms max CSNRT <550ms and TRT <5s
Why causes the av node to decrement?
Slow inward calcium channels
What specialized conducting fibers of His-Purkinje system make it less decremental
Fast sodium channels
What V extra stim used for?
Determine retrograde conduction, detect accessory pathways, and arrhythmia induction
Venoatrial conduction over the node
Either baseline or with Isuprel or atropine
What V stim concentric atrial activation
CS activation proximal to distal, HRA at least 30ms after atrial electrogram registered by His bundle catheter
Eccentric retrograde atrial or VA conduction that is non-decremental or shows discontinuity may indicate
Accessory path or dual av nodal pathway
What rate do you do incremental ventricular pacing
Slightly faster than sinus rate down to VA wcl or minimum cl of 300 ms
What is unlikely if VA conduction is completely absent
AV reentry
AVNRT
Programmed V stim using multiple exrastimuli (short-long-short) may facilitate
BBB reentry
How can you differentiate between aflutter and Atach
P wave cycle length on surface ekg
Atach cl
250-500ms (120-140 beats/min)
Cycle length <220ms and rate >270 beats/min
Aflutter