Basic EP

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Basic EP
2012-11-29 12:56:34
EP study

From Josephson
Show Answers:

  1. Where are catheters placed for a basic diagnostic EP study?
    • Right atrial apendage
    • Right ventricle apex
    • Across the tricuspid annulus
    • Coronary sinus
  2. How can position of the His catheter be determined?
    Relative size of the atrial and ventricular electrograms

    • Atrial larger = proximal
    • Ventricular larger = distal
  3. What are the most important features of the catheters?
    position, stability, and thresholds
  4. When is the right bundle potential detected?
    10-30 msec before ventricular electrogram in the HBE
  5. What is the normal AH interval?
    60-125 msec
  6. What is the HV interval?
    Time between earliest His potential to the earliest ventricular deflection (on surface ECG or His tracing)
  7. What is the normal HV interval?
    35-55 msec (up to 60 with LBBB)
  8. What does a split His indicate?
    His bundle disease
  9. What can procainamide do to the HV interval?
    It specifically prolongs the HV interval
  10. 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)
  11. What is the formula for pacing rate?
    Pacing rate (BPM) = 60,000 / cycle length
  12. What is the heart rate in the following?
    Cycle length: 600, 500, 400, 300, 200
    100, 120, 150, 200, 300
  13. 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
  14. How are refractory periods determined?
    incremental pacing
  15. Why are beats delivered in series during incremental pacing?
    refractory periods are dependant on prior cycle lengths
  16. What are the three types of refractory periods?
    • Effective refractory period
    • Functional refractory period
    • Relative refractory period
  17. What is the effective refractory period?

    The functional?

    The relative?
    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
  18. What channel likely results in nondecremental conduction?
    IKs (delayed rectifier postassium slow channel)
  19. 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)
  20. 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
  21. How is intrinsic heart rate determined?
    Give beta blockers and atropine

    IHR = 117.2 - (0.52 x age)
  22. 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
  23. How is the sinoatrial conduction time determined?
    8-10 beat train followed by PAC

    SACT = [(A2-A3) - (A1-A1)] /2
  24. In general, conduction below a cycle length of _______ means AV conduction is normal.
    500 msec
  25. What percentage of the population has dual AV nodal pathways?
  26. Which AV nodal pathway has the shorter refractory time?
    slow pathway
  27. What defines an AV jump?
    > 50 msec increase in A2-H2 interval in response to a 10 msec decrease in A1-A2 coupling
  28. What does concealed mean?
    Unable to identify on the surface ECG
  29. What is the gap phenomenon?
    It occurs when a premature stimulus blocks or delays followed by conduction without delay of a more premature stimulus
  30. 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
  31. 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)
  32. HV interval of ______ or longer is considered an indication for PPM.
    100 msec
  33. What structure has the longest refractory period in the heart?
    HPS at slow heart rates
  34. Which bundle has longer refractory period at slow heart rates?

    At fast heart rates?

  35. What are the four common forms of aberration?
    premature beat (phase 3), acceleration dependent, decceleration-dependent (phase 4), and retrograde invasion / concealment
  36. 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)

    right bundle
  37. What is Ashman phenomenon?
    aberrant RBBB with a. fib; due to Phase 3 block
  38. 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
  39. What morphology does acceleration-dependent block have?
    LBBB most often

    (generally associated with underlying heart disease)
  40. What is deceleration-dependent block?
    Phase 4 block - bradycardia allows phase 4 depolarization in the Purkinje fibers which results in block or aberration
  41. 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
  42. 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