Electroanatomic Mapping - An Introduction

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04-04-2020

Raja Selvaraj. Professor of Cardiology, JIPMER

Introduction

What is electroanatomic mapping ?

  • Anatomical information collected with electrical information
  • In the same system

What does it do

Memory aid

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3d_all.png

Visualization tool for electrical information

  • Any aspect of electrical information that can be quantified
  • Display over the anatomical map

Quantification of electrical information

  • Bipolar voltage
  • Activation time in relation to a fixed time reference
  • Unipolar voltage

Catheter visualization

  • Continuous
  • Non-fluoroscopic

Visualize geometry of chamber

  • Collect only intermittently
  • Or collect continuously (FAM)
  • But how does the system know where the walls (shell) are ?

Image integration from other modalities

  • CT / MRI
  • Rotational angio
  • Ultrasound

What it does not do

  • Automatically identify the mechanism of tachycardia
  • Automatically identify the site of ablation
  • Free operator from need to exercise judgement

The "self driving" car

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When allowed to drive by itself

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Why ? - or why not just conventional mapping ?

Ablate arrhythmias that we (almost) cannot otherwise

  • Scar based VT
  • Atypical atrial flutter

Reduce fluoroscopy significantly

  • Atrial fibrillation
  • Typical atrial flutter

Reduce fluoroscopy marginally (balance with costs)

  • AVNRT
  • AVRT
  • Idiopathic ventricular tachycardia
  • Focal atrial tachycardia

Record ablation points

  • Helpful for linear ablation
  • new technologies incorporating various parameters to color code ablation points

Other benefits

  • Improved success ?
  • Reduce complications ?

Evidence

  • RCT - 102 patients undergoing ablation for various arrhythmias in 2004
  • CARTO vs conventional
  • Success and duration same
  • Reduced radiation
  • Increased cost
  • similar results in other studies (2,3)

  1. Sporton S … Schilling R. Electroanatomic Versus Fluoroscopic Mapping for Catheter Ablation Procedures: A Prospective Randomized Study. JCE 2004;15:310-315
  2. Khongphatthanayothin … Nademanee. Nonfluoroscopic Three‐Dimensional Mapping for Arrhythmia Ablation: Tool or Toy? JCE 2000;11:239-243
  3. Ealey M et al. Radiofrequency ablation of arrhythmias guided by non-fluoroscopic catheter location: a prospective randomized trial. EHJ 2006;27:1223–1229,

Technology

Magnet based

carto_principle.png

Magnet based

  • pros
    • Accurate
  • cons
    • Needs special catheter with magnetic sensor at tip

Impedance based

  • Low amplitude, high frequency current
  • Six patches in three orthogonal directions

Impedance based

  • pros
    • Can be used with any catheter / any electrode / anything like an electrode
  • cons
    • Impedance less reliable, especially over time

Systems

  • CARTO
  • NavX
  • Rhythmia

Point by point

  • pros
    • Every point validated
    • Ablation catheter itself
  • cons
    • Takes time
    • False annotations may affect more

Multi point

  • pros
    • faster
    • more points
  • cons
    • Cannot check each point
    • Need separate catheter for ablation
    • Few false annotations may have less weight

Technical aspects in practice

Types of maps

  • Anatomical
  • Voltage
  • Activation / propagation
  • Others

Anatomical maps

  • Only geometry acquired
  • Atrial fibrillation
  • AVNRT

Voltage maps

  • Iso-voltage maps - EGM amplitude
  • Cut-offs derived from small set of patients
  • Varies based on catheter
  • Normal > 1.5 mV, abnormal < 1.5, scar < 0.5, dense scar ?

Voltage map

iwmi_isthmus.jpg

voltage map in epicardium

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Activation map

  • Isochronal map
  • Activation time in relation to fixed reference
  • Similar activation times marked with same colour

schematic_activation.png

focal_at.jpg

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example - reentry

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Kumar S, Subramanian A, Selvaraj RJ. Peritricuspid reentrant ventricular tachycardia in Ebstein's anomaly. Europace. 2014 Nov;16(11):1633

Assess conduction velocity

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Combining information

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Other maps

  • Non contact mapping
  • Manual tags
  • Impedance maps
  • Contact force
  • Ripple maps

Substrate - Late potentials

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Practical sequence

Choosing a reference

  • Atrium
    • fixed egm
    • avoid multi-component signal
    • screw in lead
  • Ventricle
    • Surface ECG QRS
    • Intracardiac EGM

schematic_reference.png

Setting the window

schematic_window.png

<n> focal = clear reentry = couple of choices

Window in reentry

  • How big ? - 90% / 95% / 100%
  • 10% of CL may be a large part of the circuit !

Two maps in trial flutter

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Munoz F .. Asirvatham SJ. Three-dimensional mapping of cardiac arrhythmias: what do the colors really mean? Circ Arrhythm Electrophysiol. 2010 Dec;3(6):e6-11

Setting window in reentry

  • Start in systole / diastole
  • Window starting mid-diastole
    • Early meets late at mid-diastole
    • Identification of mid-diastolic activation
  • De Ponti method

De Ponti R et al. Treatment of macro-re-entrant atrial tachycardia based on electroanatomic mapping: identification and ablation of the mid-diastolic isthmus. Europace. 2007 Jul;9(7):449-57

Identifying reentry

  • Activation throughout the CL = LATs cover CL (example)
  • Activation path as a circuit = Head meets tail

Setting window

tof_vt_1.jpg

Selvaraj RJ et al. Chasing red herrings: making sense of the colors while mapping. Circ Arrhythm Electrophysiol. 2014 Jun;7(3):553-6.

Setting window

tof_vt_2.jpg

Selvaraj RJ et al. Chasing red herrings: making sense of the colors while mapping. Circ Arrhythm Electrophysiol. 2014 Jun;7(3):553-6.

Setting window for substrate mapping

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Manually collecting a point

  • Catheter stability
  • Contact
  • See few beats
  • Confirm beat taken

Beat buffer

Annotating activation

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Annotating activation

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Annotating activation - single potentials (needs image)

  • Earliest activation - may record far field
  • Peak - May miss early activation
  • Peak of first near field (Sam)
  • Peak negative deflection (Nakagawa)
  • Onset of first rapid deflection
  • Have to correlate with neighbouring areas

Annotating double potentials

  • Attempt to identify the near field component
  • Annotate consistently
  • Tag as dp with location only when unsure or both appear near

Double potentials - near field

ra_la_at.jpg

Selvaraj RJ et al. Which side are you on? - Deducing the chamber of origin of atrial tachycardia. Indian Pacing Electrophysiol J. 2017 Mar

  • Apr;17(2):54-57.

Double potentials - near field

ra_la_at2.jpg

Selvaraj RJ et al. Which side are you on? - Deducing the chamber of origin of atrial tachycardia. Indian Pacing Electrophysiol J. 2017 Mar

  • Apr;17(2):54-57.

Double potentials = pace to identify

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Double potentials - tag

atriotomy_flutter.jpg

Annotating fragmented signals

  • Consistent approach based on neighbours
  • Adding single timing misleading
  • Location only and add to CL later
  • Multiple annotations with different times

Annotating fragmented signals

schematic_frag_early.png

Annotating fragmented signals

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Annotating fragmented signals

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Pitfalls

You only see what you have mapped

sam_early_endo_vs_epi1.png

Samuel Asirvatham

You only see what you have mapped

sam_early_endo_vs_epi2.png

Samuel Asirvatham

Interpolation

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Summary

  • Basics of 3D mapping
  • Simplified some concepts
  • Not covered recent advances