For Internal Use Only How to Select a Reference Channel, Set a WOI and Annotate EGMs of the Mapping Catheter with

For Internal Use Only

How to Select a Reference Channel, Set a WOI and Annotate EGMs of

the Mapping Catheter with


Selecting a Reference Channel


What is the Reference Channel

• The Reference channel (REF) is a signal which is the fiduciary point in which all EA points are measured against

• Window of Interest (WOI) will be built around the REF channel

• Used as the Zero point for LAT maps

• Used to visually Gate Map Catheter location

• Generally speaking the REF channel should reflect the chamber being mapped

• Atrium should reference an Atrial signal

• Ventricle should reference a Ventricular signal



• In the Map Setup, select a REF channel from the drop down

• Select a REF channel that is appropriate to the chamber you are mapping

• Atrium = CS Atrial electrogram

• Ventricle = BS QRS



Atrial Reference (CS A)• Maps of Atria

– Atrial Tach, Atrial Flutter, PV Tach, Sinus Tach, Normal Sinus Rhythm

Ventricular Reference (QRS)• Maps of Ventricles

– LAT, Bipolar Maps– Anatomical Maps– Afib, AVNRT, Isthmus lines– AVRT may use the QRS as a REF channel,

because the ventricle is part of the circuit and there is a fixed AV or VA ratio


Atrial Reference

Atrial Reference Options• Coronary Sinus Catheter• Best choice as CS is stable, unlikely

to be dislodged• Choose a Reference that is physically

close to the chamber being mapped– CS 7-8 or 9-10 for Right Atrium– CS 1-2 for Left Atrium– Choose an REF channel in which the

A waves are larger that the V waves• High RA Quad Catheter

– Use only if CS not accessible• Stability is an issue – position in RAA• Snapshot location

• Lasso® Catheter pair occasionally used, positioned in LAA

VA


Ventricular Reference

• A body surface QRS will provide the most stable reference for any Ventricular Rhythm

• You may consider BS QRS for:• Anatomical Maps in which EA

information is not acquired • Anatomical Maps of Afib• AV Nodal Reentry Tachycardia (AVNRT)• Anatomical ablations such as Caval

Tricuspid Isthmus lines• Atrial Ventricular Reentry

Tachycardia(AVRT), as there is constant 1:1 AV or VA ratio


REF Channel Criterion

• Once you have selected a REF channel, you will have to determine where you would like the system to annotate the waveform

• Choices are: – Maximum Value– Minimum Value– Up Slope– Down Slope

MAXIMUM VALUE


Maximum Value

• Annotation on the highest amplitude of the ECG

Animate: 1 of 4. See original for timing of the waveform.


Minimum Value

• Annotation on the lowest amplitude of the ECG



Up Slope

• Annotation on the most positive slope of the ECG


• Slope is an option only if choosing pacing artifact as the reference


Down Slope

• Annotation on the most negative slope of the ECG


• Slope is an option only if choosing pacing artifact as the reference


REF Annotation Criterion

• When selecting an annotation

criterion, it is important to visualize

the EGM of the REF channel on the

Carto® 3 System to determine the

annotation criterion

• In this tracing, there are two positive

deflections of equal amplitude and

one large negative deflection on the

REF 9-10Maximum Value good choice

Maximum Value poor choice


REF Annotation Criterion

• If we were to select REF 9-10,

maximum value, the system may

have difficulty in determining which

positive deflection to annotate from

beat to beat. Minimum value would

be a better choice for CS 9-10

• But in this example, we decide to

choose another electrogram, REF

3-4, Maximum value as the REF

channel, as there is only 1 positive

component to the electrogram

Maximum Value good choice

Maximum Value poor choice


Verify REF in Monitor Window

• After selecting a Reference channel, visually verify in the monitor window that

your reference annotation is consistent and reproducible

• Notice that the REF annotation is marking each and every Atrial signal at it’s

maximum peak, but ignoring all Ventricular signals. This is a reliable choice.


Verify REF in Monitor Window

• This is an example of a

poor choice for a REF

channel selection

• Notice that the REF

annotation is identifying

both atrial and

ventricular signals on the

CS catheter

• Another pair of

electrodes should be

selected


Beware of Wandering Reference

• Pick your reference carefully

Surface ECG Reference Designation


Pacing Artifact as Reference

• Pacing artifact can be used as a reference

• It is reliable, reproducible, stable

• Identify a QRS or EGM that has a prominent pacing spike (Ld II in the example)

• Select Up/Down Slope for REF Criterion - or - Minimum/Maximum Value

• Set WOI From: +10 ms to exclude pace spike

Pacing Spike (Select a REF channel with a prominent spike)

.

+10


Recap

Pick your reference correctly

• Correct reference – easy for system to recognize

– Reliable and Reproducible

– Clean, sharp signal that will remain stable

– No far-field signals from other chambers

• Incorrect reference – can distort map

– V signals annotated instead of A signals in CS

– Changing deflections of BS QRS in VT

– Changing deflections of CS A with respiration


Window Of Interest


What is Window of Interest?

• Time window is defined relative to the reference annotation - From and To Margins

• User determines values of WOI based on the chamber, mechanism and CL

• Time frame within the cardiac cycle during which the system is looking for the mapping annotation criterion

Reference ECG

-100 +250

LAT= +71

Time 0

From To

From To

Mapping Channel



• Annotation Viewer Window

• “From” Line – i.e., -250 (relative to REF channel)

• “To” Line– i.e., +100 (relative to REF channel)

• Reference Annotation– Zero Point

• Mapping Annotation– Local Activation Time (LAT) is relative time to

reference zero– Left of REF = negative number– Right of REF = positive number

























-250 102

--78









--78

-250 102









--78

-250 102


How to Set the WOI

Determine mechanism of tachycardia – Focal or Reentry?

• Rules of Thumb:

– If Reentry, set WOI to 95-100% of TCL – 3 formulas to choose from:

• Split WOI 50/50: i.e., TCL = 300 = 300/2 From: -150 To: +150

• 2/3-1/3 method: i.e., TCL = 300, 300/3=100 From: -200 To:+100

• DePonti Method: 95-100% of TCL, WOI adjusted so that P wave falls in middle of window

– Atrial Focus

• From: Pre P wave onset by 50-100 msec To: onset of QRS

• Ventricular Focus

– From: Pre QRS onset by 50-100 ms To: beyond end of QRS


Recap

Set the Window of Interest (WOI) correctly:

• Avoid erroneous data from signals outside window

• For focal arrhythmias, set window to 50-100 ms pre-P (AT) or QRS (VT) onset

• Helps exclude artifact, signals from wrong chamber

• For macroreentry, set window width to 95% of TCL

• All sites will appear only once within window of interest

• <90% of TCL: some sites will fall outside window

• >100% of TCL: some sites will be in window twice


Annotating the Mapping Signal


Selecting a Map Channel

• In the Map Setup, select a Mapping Channel from the drop down menu. Options are:– MAP 1-2 (Default) Recommended– MAP 3-4 – M1– M2

• Options to Select a Mapping Criterion– Maximum Value– Minimum Value– Up Slope– Down Slope

• As Map signals are collected from a roving catheter, it is important to annotate every time, thus default map criterion (maximum value) is acceptable

MAXIMUM


How to Annotate LAT Maps

• What chamber are we mapping?

• If it lines up with QRS, it is probably a V

• Beat Buffer to previous beat if unclear






• What signal should you annotate?







• What channel are we referencing?








CS



• What chamber are we mapping? Atrium





• What signal is this?

CS



• What chamber are we mapping? Atrium







CS


LAT Map Annotation

• The system will automatically assign an annotation based upon the Map Annotation Criterion

• Many physician will ask you to annotate the signal to the earliest deflection from baseline on the M1-M2 signal

Earliest Annotation


LAT Map Annotation



Earliest Annotation


LAT Map Annotation



• Others will prefer annotation to earliest sharp deflection on M1-M2 that correlates with the sharpest down slope of the unipolar (M1)

Earliest Sharp Annotation

Earliest Annotation



• Annotation is clear when you have sharp, distinctive electrograms







• Annotation is not so clear if there is slowed conduction in scar, double potentials or Early meets Late in the WOI. Be consistent













DP





DP


How to Annotate Signals Early Meets Late Signals

• Set WOI to 95-100% of TCL to avoid having 2 beats in window

• Take another point or use beat buffer if unsure

Copy of RA FINAL.CSZ-3rd map


How to Annotate Signals Early Meets Late Signals

• Set WOI to 95-100% of TCL to avoid having 2 beats in window

• Take another point or use beat buffer if unsure

• Be consistent as to where you mark

Copy of RA FINAL.CSZ-3rd map

Earliest deflection is inside window

Earliest deflection is outside window


• Earlys should be marked late

• Set WOI to 95%-100% of TCL

Annotate by Location

Images courtesy of Dr. Abrar Shah, University of Rochester Medical Center


Early Meets Late Annotation


How to Annotate by Location

Late based on neighboring

points

Late based upon distance from circuit

Counterclockwise Type I Flutter


Annotation

• Not clear if EGC on M1-M2 is A or V or both – use the Beat Buffer to scroll back to another beat for clarification


Annotation



Annotation


Annotate a signal

Beat buffered


Annotation


V signal aligns with QRS

Annotate a signal

Beat buffered


Annotation



Annotate a signal

Beat buffered


Annotation



Annotate a signal

Beat buffered


LAT Annotation in Slow/Scar Border

System automatic annotation User defined annotation


WOI and Annotation during Bipolar Map

• Bi (mv) is the average peak to peak voltage measure on M1-M2 in the WOI

• Avoid pacing artifact in WOI in voltage mapping as this artificially elevates voltages in map

Normal voltage

3.86mv


WOI and Annotation during Bipolar Map

• Bi (mv) is the average peak to peak voltage measure on M1-M2 in the WOI

• Avoid pacing artifact in WOI in voltage mapping as this artificially elevates voltages in map

• No need to annotate EGM in Bipolar maps

Normal voltage

3.86mv


Map Annotation in Bipolar Map

• Voltage is measured as the average peak to peak voltage on the M1-M2 signal that falls within the WOI

• With low voltages, it is important to confirm catheter contact

• Annotation not necessary in Voltage maps


Map Annotation in Bipolar Map

• Voltage is measured as the average peak to peak voltage on the M1-M2 signal that falls within the WOI

• With low voltages, it is important to confirm catheter contact

• Annotation not necessary in Voltage maps


Test Your Knowledge

Default WOI

CS 1-2

M1-M2

Which Chamber was intended to be mapped?

• Ref is CS, however only V electrogram is visible – select another channel that displays prominent A signal


Test Your Knowledge

Default WOI

CS 1-2

M1-M2



Which signal should be annotated on M1-M2 ? • Atrial


Test Your Knowledge



Which signal should be annotated on M1-M2 ? • Atrial

Was WOI set correctly?• No, this is the default WOI and

includes both A and V

Default WOI

CS 1-2

M1-M2


Annotating Accessory Pathways

Manifest (WPW) can map in:

• Sinus Rhythm

• A pacing

• V pacing

• Tachycardia (Orthodromic or Antidromic)

Concealed can map in:

• V pacing

• Tachycardia (Orthodromic)


Accessory Pathways with V Pacing

• REF – CS 5-6 Max Value

• WOI adjusted to exclude pacing artifact from WOI

• Mapping along annulus should result in a VA signal

• Move annotation to earliest A

Annotate to earliest AAnnotate to earliest A

REF CS 5-6, Maximum Value

V & A fusedV A

Early site -33 ms


Accessory Pathways with Atrial Pacing

Can only use with a Manifest pathway

• Atrial pacing slows AV node conduction with increasing paced rates, causing greater preexcitation though AP (Delta wave becomes more pronounced)

• Annotate to earliest V on M1-M2, correlate with M1 if unclear

A pacing spike

Delta wave

Antegrade A

Antegrade V

M1


Recap

Annotate Map activation times correctly

• The system will always pick an activation time

• All activation points acquired must have operator oversight

Problematic situations:

• Complex electrograms (scar-based AT or VT)

• Sites on annulus with both A and V signals

• It only takes 1 or 2 points with incorrect activation times to mangle a map


How to Build A Map

• Verify CL is consistent with TCL

A A V


How to Build A Map

• Verify CL is consistent with TCL

A A V


How to Build A Map

• Verify CL is consistent with TCL• Verify REF channel is annotating correctly

A A V


How to Build A Map

• Verify CL is consistent with TCL• Verify REF channel is annotating correctly• Verify WOI is set correctly

A A V


How to Build A Map

• Verify CL is consistent with TCL• Verify REF channel is annotating correctly• Verify WOI is set correctly• Identify the waveforms

A A V

QRS


How to Build A Map

• Verify CL is consistent with TCL• Verify REF channel is annotating correctly• Verify WOI is set correctly• Identify the waveforms• Verify or move annotation to correct

location

A A V

QRS


How to Build A Map


location• Visualize color progression on map –

It should make sense A A V

QRS


How to Build A Map


location• Visualize color progression on map –

It should make sense• Do these steps for every point acquired

A A V

QRS


Happy Mapping!

Authored by: [email protected]

Documents

For Internal Use Only How to Select a Reference Channel, Set a WOI and Annotate EGMs of the Mapping Catheter with