EP2: EP Diagnostics Part 2 and Ablation

Question 1

Surface ECG vs electrogram

Answer 1

-RV apex is as early as His due to how ventricles depolarise

Question 2

What arrhythmias are shown?

Answer 2

a) AVNRT
b) AVRT
c) Atrial flutter

Question 3

Rates of atrial rhythms

Answer 3

300/anticlockwise/macro re-entry - atrial flutter

Question 4

Where is His electrogram recorded from?

Answer 4

-Catheter that lies across the posterior aspect of the tricuspid valve

Question 5

What does this represent?

Answer 5

-V pacing with V to A conduction
-Going through AV node (earliest CS 9,10)

Question 6

Why in retrograde conduction is A signal earliest in His channels?

Answer 6

-That is where the depolarisation has travelled through the AV node
-First part of the atria that is depolarised
-CS9-10 is also early because catheter is placed next to AV node

Question 7

What does this represent?

Answer 7

-V pacing with V to A conduction
-Going through accessory pathway (earliest in CS 1,2)

Question 8

What does no retrograde conduction look like?

Answer 8

-A signals are not related to V signals
-No VA conduction through AV node or accessory pathway

Question 9

Could you have AVRT with no retrograde conduction?

Answer 9

-No because there is no retrograde conduction
-Accessory pathway can’t conduct retrograde (orthodromic)
-AV node can’t conduct retrograde (antidromic)

Question 10

If someone has a concealed accessory pathway (no delta wave or short PR) what type of AVRT will one never see?

Answer 10

-Pathway can’t conduct antegradely because no delta wave, so no orthodromic
-Early V to A on left or right side
-Left or right atrium will be stimulated first

Question 11

Does VA conduction matter if patient has atrial flutter/fibrillation?

Answer 11

Yes
-Accessory pathway can still conduct antegrade
-Doesn’t have decremental properties
-Can conduct into ventricle and degenerate into VF

Question 12

Explain AVNRT

Answer 12

-Dual AV nodal pathways
-Fast conduction speed, long refractory
-Slow conduction speed, short refractory

Question 13

Perpetual AVNRT explanation

Answer 13

Question 14

AVNRT ablation

Answer 14

-EP study can reveal dual AV node physiology
-Normal AV node will show decremental properties
-In dual AV physiology, decrement is seen up to fast pathway blocking
-Then a jump is seen as conduction switches to slow pathway

Question 15

Define AH jump

Answer 15

-With a 10ms decrease in the extrastimulus (A-A) coupling interval, there is a >50ms increase in the AH interval

Question 16

Example of AH jump

Answer 16

-If we pace heart 10ms faster (480 after 500), increase in AH interval >50ms = AH jump
-Different from decrement which is slow lengthening of conduction time through AV node

Question 17

What can happen after AH jump?

Answer 17

-Single atrial stimuli at faster rate
-Results in AH jump and tachycardia initiation

Question 18

How to ablate AVNRT

Answer 18

-Mapping catheter advanced to Triangle of Koch
-RF energy applied to slow pathway, without involving AV node
-You might see junctional rhythm
-Do Jump testing

Question 19

AVRT ablation (WPW)

Answer 19

-Overt accessory pathway causes short PR interval and delta wave
-Destroy abnormal pathway with radio-frequency (RF)
-By mapping around valve ring until earliest activation of ventricle is found (shortest AV signal)
-Ablating gives normal ECG and AH increase due to only AV nodal conduction

Question 20

Ablation strategy for typical atrial flutter

Answer 20

-Radiofrequency catheter ablation of the Cavotricuspid isthmus
-Full thickness of CTI is ablated from tricuspid ring to IVC
-RF applied point to point (45-60s at each site) or continuously from TR to IVC
-Bidirectional CTI block checked by recording along the ablation line/differential pacing manoeuvres

Question 21

Pathogenesis of AF

Answer 21

Initiating trigger: Rapidly firing ectopic foci from pulmonary vein
Substrate: Abnormal atrial tissue (mitral valve disease)

Question 22

Pathogenesis of Atrial flutter

Answer 22

-Abnormal macro re-entry
-Counter clockwise
-Right atrium

Question 23

Ablation strategy for atrial fibrillation

Answer 23

-Complete isolation of pulmonary veins by linear lesions around their antrum
-Using point to point RF ablation or single-shot ablation
-3D mapping system based on magnetic or impedance field
-Confirmation of electrical isolation by circular mapping catheter

Question 24

How to see whether you’ve isolated pulmonary veins in PVI ablation?

Answer 24

-Pace and record
-If no signal received, you have isolated