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Where are catheters placed for a basic diagnostic EP study?
- Right atrial apendage
- Right ventricle apex
- Across the tricuspid annulus
- Coronary sinus
How can position of the His catheter be determined?
Relative size of the atrial and ventricular electrograms
- Atrial larger = proximal
- Ventricular larger = distal
What are the most important features of the catheters?
position, stability, and thresholds
When is the right bundle potential detected?
10-30 msec before ventricular electrogram in the HBE
What is the normal AH interval?
What is the HV interval?
Time between earliest His potential to the earliest ventricular deflection (on surface ECG or His tracing)
What is the normal HV interval?
35-55 msec (up to 60 with LBBB)
What does a split His indicate?
His bundle disease
What can procainamide do to the HV interval?
It specifically prolongs the HV interval
What are three causes of an abnormally short HV interval?
- 1. Accessory pathway
- 2. PVC
- 3. Incorrect measurement of RB-V rather than HV (if atrial signal too small)
What is the formula for pacing rate?
Pacing rate (BPM) = 60,000 / cycle length
What is the heart rate in the following?
Cycle length: 600, 500, 400, 300, 200
100, 120, 150, 200, 300
When performing incremental pacing, when does the operator stop bringing in S2?
when it fails to capture the myocardium
this is the tissue's refractory period
How are refractory periods determined?
Why are beats delivered in series during incremental pacing?
refractory periods are dependant on prior cycle lengths
What are the three types of refractory periods?
- Effective refractory period
- Functional refractory period
- Relative refractory period
What is the effective refractory period?
ERP is the shortest S1-S2 that fails to depolarize the stimulated tissue
FRP is the shortest interval between two conducted beats out of the tissue (the FRP of the His is the shortest V1-V2)
RRP is the longest coupling interval that results in prolonged conduction of S2
What channel likely results in nondecremental conduction?
IKs (delayed rectifier postassium slow channel)
What are the three repetitive ventricular responses to VES?
- 1. Bundle branch reentry beats (50% of healthy subjects)
- 2. AV nodal echo (15% of healthy subjects)
- 3. Intraventricular reentry (<15% of healthy sujects)
How does a bundle branch reentry beat happen?
RV stimulus blocks in the RB with transseptal conduction to the LB with retrograde HA activation with antegrade activation of the RB
How is intrinsic heart rate determined?
Give beta blockers and atropine
IHR = 117.2 - (0.52 x age)
How is sinus node recovery time determined?
What is normal?
Overdrive pace for > 1 minute then stop pacing
Corrected SNRT = SNRT - SCL
Normal is 500-600 msec
How is the sinoatrial conduction time determined?
8-10 beat train followed by PAC
SACT = [(A2-A3) - (A1-A1)] /2
In general, conduction below a cycle length of _______ means AV conduction is normal.
What percentage of the population has dual AV nodal pathways?
Which AV nodal pathway has the shorter refractory time?
What defines an AV jump?
> 50 msec increase in A2-H2 interval in response to a 10 msec decrease in A1-A2 coupling
What does concealed mean?
Unable to identify on the surface ECG
What is the gap phenomenon?
It occurs when a premature stimulus blocks or delays followed by conduction without delay of a more premature stimulus
What causes the gap phenomenon?
distal block and proximal conduction delay - longer coupling blocks in the distal segment; shorter coupling delays in the proximal segment and allows the distal segment to recover and conduct
What is supernormal conduction?
conduction that is better than would be expected
look for it with normalization of a wide qrs complex (when aberration resolves at a fast heart rate)
HV interval of ______ or longer is considered an indication for PPM.
What structure has the longest refractory period in the heart?
HPS at slow heart rates
Which bundle has longer refractory period at slow heart rates?
At fast heart rates?
What are the four common forms of aberration?
premature beat (phase 3), acceleration dependent, decceleration-dependent (phase 4), and retrograde invasion / concealment
What is phase 3 block?
Which bundle is more often affected?
stimulation during phase 3 resulting in decreased conduction of the next action potential (long-short)
What is Ashman phenomenon?
aberrant RBBB with a. fib; due to Phase 3 block
What is acceleration-dependent block?
aberration that occurs at a critical heart rate; not necessarily very rapid; occasionally with minimal (5 msec) increases in rate
What morphology does acceleration-dependent block have?
LBBB most often
(generally associated with underlying heart disease)
What is deceleration-dependent block?
Phase 4 block - bradycardia allows phase 4 depolarization in the Purkinje fibers which results in block or aberration
What is retrograde invasion or concealment?
retrograde conduction into a bundle branch which causes it to be refractory to the next impulse - the most common form of perpetuation of aberration
What are the 5 ways aberration normalizes?
- 1. "peeling back" - a VPD blocks retrograde invasion
- 2. Equal delay in both bundle branches (rare and must be accompanied by PR delay)
- 3. ipsilateral VPD to BBB
- 4. gap phenomenon
- 5. change in heart rate
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