Interpretation of Unipolar Electrograms for

Noncontact Mapping

Yenn-Jiang Lin, MD; Shih-Ann Chen, MD.

Taiwan HRS Meeting and St. Jude Medical

Taipei, 10/16, 2011 Division of Cardiology, Taipei Veterans General Hospital

and National Yang-Ming University, Taipei, Taiwan

Non-contact Mapping System

The differences between unipolar and

bipolar electrograms

Unipolar electrogram voltage

Unipolar electrogram morphology

Electronic filtering of unipolar recordings

Topics

Differences Between Unipolar and Bipolar Electrograms

Differences Between Unipolar and Bipolar Electrograms

Unipolar

Electrogram

Bipolar

Electrogram

AAB

B

A

B

A

B

IndifferentElectrode

A

B

Unipolar Bipolar

•Subtract Far-field signal

•Morphology indicates direction of WF

•WF direction affects amplitude

Differences Between Unipolar and Bipolar Electrograms

1Uniformly Isotropic Substrate

(HRA epicardial stimulation – RL view of RA)

A

C

B

A

B

C

1Uniformly Isotropic Substrate

(HRA epicardial stimulation – RL view of RA)

A

C

B

A

B

C

QS

1Uniformly Isotropic Substrate

(HRA epicardial stimulation – RL view of RA)

A

C

B

A

B

C

QS

RS

1Uniformly Isotropic Substrate

(HRA epicardial stimulation – RL view of RA)

A

C

B

A

B

C

QS

RS

R

A

B

C

Smaller R wave

Smaller S wave

A

B

C

QS

RS

R

A

B

C

A

B

C

Amplitude ofUnipolar Vol.

Less negative deflection indicated abnormal substratePNV of unipolar Eg for the dynamic substrate mapping

Peak Negative Unipolar Voltage

P = 0.01 P = 0.004

Fig 5

Voltage and conduction velocity Voltage and conduction velocity within the conduction isthmuswithin the conduction isthmus

Huang JL and Lin YJ et al JACC 2006

Conduction Velocity Along the Circuit

0 20 40 60 80 100

100-Specificity (%)

100

80

60

40

20

0

Se

nsi

tivity

(%

)

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Inside isthmus

<=0.38Sens: 92.3

Spec: 85.7

A: ROC Curve Analysis

B: Ratiometric voltage

Ra

tiom

etr

ic V

olg

ate

Outside isthmus

Prediction of slow conduction Prediction of slow conduction using ratiometric PNV unipolar Egusing ratiometric PNV unipolar Eg

38% of the maximal PNV predicted slow conductionAreas (less than 37% of PNV indicated slow

conduction area) and could be arrhythmogenic

Huang JL and Lin YJ et al JACC 2006

Appropriate Orientation of the Anatomic model and Unipolar Eg

Right

Right atrial septum

From LA?

Unipolar electrograms at the earliest sites were associated with substrate property

and wavefront dynamics

R wave morphologiesClinical Implications

QS MorphologiesClinical Implications

Slow QS Concealed R Wave

1. Subendocardial or epicardial focus 2. Anisotropic conduction3. Poor contact of catheter

Isotropic conduction

Anisotropic conduction

Non-uniformed anisotropic conduction

Slow conduction in reentry circuits

Conduction block

Specific Unipolar Eg

1. Isotropic ConductionSingle Compact Site

• Activation typically proceeds concentrically away from a single “spot” of early activation

20

½ vel

norm vel

AB

C

A

B

C

2. Uniformed Anisotropic Substrate

21

7

½ vel

norm vel

AB

C

A

B

C

Uniformed Anisotropic Substrate

Seidl, Munger, Binder, Guzman

1

2

3

1

1: Initial onset of depolarization

2

2: Breakout

3

3: Wrap around effect

3. Non-Uniformed Anisotropic conductionOrigin, preferential pathway, and exit site

Earliest Activation from Bipolar mapping

Single-morphology from channel

Ventricular Channel

++

**

EndocardiumEndocardium

EpicardiumEpicardium

4. Epicardial in Origin

5. Reentry Circuits5. Reentry Circuits

6. Slow Conduction6. Slow Conduction

Lin YJ and Chen SA et al Heart Rhythm 2009

4

Line of Block

B

C

D

B

C

D

A

A

7. Lines of Conduction Block7. Lines of Conduction Block

Low Amplitude <30-37% of maxim

< 1.0 mV (PNV)

Fibrosis, marked anisotropic property, far away from array

Fractionated, continuous Eg

> 70 ms, multiple baseline crossing

Slow conduction, anisotropic conduction, noise

Split potentials > 50 ms, seperated by isoelectric line

Local conduction block

Low frequency Low dV/dt Preferential conduction,

far-field (not near field)

Late component

After QRS or P wave

Delay activation, lines of block, slow conduction, bystander

Summery of Unipolar Eg InterpretationSummery of Unipolar Eg Interpretation

Combined = Bandpass Filter (passes depolarization)

V

f

Baseline noise

depol

physiologic environmental

Highpasscutoff freq

(0.5 - 32 Hz)

Lowpasscutoff freq

(250 - 500 Hz)

Low pass and High pass filtering of Low pass and High pass filtering of Unipolar ElectrogramsUnipolar Electrograms

V

f~16 Hz ~64 Hz

approximates the derivative

High-pass unipole: d(Vol)/d(time) vs.

Bipole: d(Dis)/d(time)

depol

High pass filtered unipolar Eg was compatible to conventional bipolar recordings (without far-fields)

Biophysics of Unipolar EgBiophysics of Unipolar Eg

Soejima, et al., JCE 2005

High pass filtered Eg eliminates the far-field unipolar signal; however, limits the Eg Morphology

Earliest activation site of VT

SLOW & FAST FAST ONLY

WAVEFRONT POSITION-VELOCITY WAVEFRONT “POSITION” BLEND “VELOCITY”

Scar

Flutter

AF

EAT

VT exit Ischm Circuit Idio Circuit

WPW & AVNRT

H P F R E Q U E N C Y (Hz)

Equivalent CL (ms) – and – HR (bpm)

0.5 1 2 4 8 12 16 32 2000 1000 500 250 125 83.3 62.5 31.3 30 60 120 240 480 720 960 1920

Application of High Pass Filtering in Unipolar Electrograms

Take home message: What Take home message: What information could be obtained from information could be obtained from

single site unipolar recordingsingle site unipolar recording

PNV: for the substrate mapping, <30-38% to the maximal PNV indicates abnormal

Accurate timing for very wide-band activation (0.5-300), with onset negative voltage

Approaching wavefronts (mass, speed)

Local activation (dV/dt)

High-pass filtering (4-16 Hz)

1. X slow conduction

2. X far-field signals

3. X morphology

THANK YOU