Catheter ablation of scar related VT significant challenges for operators and role of 3d electroanatomic mapping

Catheter Ablation of scar related
VT: significant challenges for
operators and role of 3D
electroanatomic mapping
Dr TEO Wee Siong
MBBS (S’pore), M Med (Int Med), FAMS, MRCP (UK), FRCP (Edin), FACC, FHRS
President, APHRS

Mt Elizabeth Hospital, Singapore
Senior Advisor, Electrophysiology & Pacing
Department of Cardiology
National Heart Centre, Singapore


Size and site of scar
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Compared to ischemic cardiomyopathy, pts with nonischemic
cardiomyopathy have smaller endocardial scar areas (often with
a patchy distribution and preferential localization adjacent to
the mitral valve) and fewer fractionated electrograms and
isolated diastolic potentials.
However there appears to be more extensive epicardial scarring
An epicardial origin is seen in > 25% of pts idiopathic
nonischemic cardiomyopathy and < 10% in pts with remote
MI and ARVC

Potential scar related VT circuits


Scar related VT - etiology

Stevenson, WG et al. Circulation 2007:2750-2760


Indications for ablation in the scar related VT pts
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Pts with recurrent symptomatic VT not well controlled
with drug therapy or failed drug therapy
Pts with tachycardia cardiomyopathy
Pts with recurrent ICD discharges


Clinical considerations before VT ablation
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Documented VT – stable or unstable
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Ischemic vs nonischemic etiology – need for epicardial
Pre-procedure assessment
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12 lead ECG, ICD EGM

LVEF, LV thrombus
Artificial valves
Scar imaging

Tolerance for procedure
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Sedation risks
Potential for hemodynamic instability
Risk of fluid overload and heart faioure
Potential ischemia
Potential for incessant VT
Need for hemodynamic support

Identification of scar prior to EP study
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ECG
MRI
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Delayed enhance MRI Circ AE 2013 Zeppenfeld

CT
Echo
Intracardiac echo


ECG localization
• RBBB vs LBBB VT
– RBBB suggests LV free wall
– LBBB suggest RV or septum

• Superior vs Inferior axis
– II, III and AVF negative suggest inferior site

• Precordial transition
– Apex actually is anteriorly located in the
coronal section of the heart and is thus at V4-5

• V3-4 Q or qS –Apical site
• V4-6 R – Basal site
• Lead I - distinguish Left vs right
• Narrow vs wide QRS
• Notching of QRS


ECG suggesting Epicardial origin
VTs that originate in the subepicardium generally produces a longer
QRS duration and slower QRS upstrokes in the precordial leads
compared to those with an endocardial exit
May be less reliable in pts with heart disease

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Widen QRS duration
Broad pseudo delta wave> 34ms
Broad RS complex
Intrinsicoid deflection > 85 ms
Maximum deflection index > 0.55

QS in I and aVL

Berruezo A, Mont L, Nava S et al.
Electrocardiiograqphic recognition of the epicardial origin of ventricular tachycardias.
Circulation 2004;109:1842-1847


Mapping technique and systems
• Endocardial
– Retrograde aortic
– Transeptal

• Epicardial
• Navigation systems
• Remote magnetic - Stereotaxis
• Advance mapping systems
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CARTO
Navx
Noncontact balloon
Rhythmia



Catheter ablation of recurrent scar-related ventricular tachycardia using electroanatomical mapping and irrigated ablation technology:
results of the prospective multicenter Euro-VT-study.

Tanner H et al. J Cardiovasc Electrophysiol 2010;21(1):47-53.


Techniques for VT scar Mapping and ablation
• Begin by Substrate mapping during sinus rhythm
– Voltage and scar mapping, electrical unexcitable scar
– Electrogram mapping
– Pre-systolic, mid-diastolic, late potentials
– Low amplitude fragmented potentials, continuous electrical activity

• Induce VT
• Stable or unstable


Techniques for VT scar Mapping and ablation
Stable VT
 Activation mapping
– Endocardial localization
for earliest activation
 Electrogram mapping
– Pre-systolic, mid-diastolic,
fragmented potentials,
continuous electrical
activity
 Entrainment mapping
 Pace mapping

Unstable VT
 Pace map for possible isthmus
 Map for Late potentials

Substrate Mapping
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Done in Sinus rhythm or with pacing
Use CARTO, Navx or ESI
Voltage map – vary voltage threshold to identify
channels
Scar map – electrical unexcitable scars
Electrogram mapping – Tag sites of:
Widened, fractionated
 Late potentials
 Double potentials
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Mapping of substrate – during sinus rhythm or pacing
Identification of scars
Voltage defined scar
• defined by voltage mapping
– Scar < 0.5 mv
– Border zone 0.5-1.5
– Normal > 1.5

Electrical unexcitable scar
• defined by pacing threshold
• Unipolar pace from standard 4 mm tip ablation catheter
threshold > 10 mA (pulse width 2 ms)


Late abnormal ventricular activation
(LAVA) mapping and ablation
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Look at suspected areas based on ECG of VT or MRI
suggested areas of scar
Usually after the QRS
Often fragmented and multiple
Often low amplitude
Later than local V electrogram
Often sharp
May be seen only on epicardial and not endocardial



Late potentials

Induce VT before ablation


Further mapping and ablation strategy
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Depends on type of inducible VT - Stable vs unstable VT/VF


Mapping of stable scar related VT
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Mapping of substrate
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Voltage mapping
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Electrogram mapping
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looking for scars, channels/isthmus

low amplitude, fragmented, diastolic, double potentials, late potentials

Mapping of VT circuit substrate
Map to identify exit, entry, central isthmus/channel, inner loop, outer
loop, bystander sites by:
 Activation mapping
 Entrainment mapping
 Pacemapping


EGM mapping during stable VT
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EGM timing
Presystolic
 Mid diastolic potentials
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Double potentials
EGM voltage
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Usually low voltage within “scar” area

EGM morphology
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Prolong low amplitude fragmented potentials spanning a
large portion of the CL of the tachycardia


Electrogram
mapping in sinus
rhythm and VT
Sinus rhythm
- Delayed fragmented continuous potentials

VT
-Presystolic low amplitude fragemented potentials
-Late abnormal ventricular activation (LAVA)