ECG VT ABLATION2

Report
ECG DIAGNOSIS OF
ISCHEMIC VT
BY
SAID FAWZY
ASSISSTENT LECTURER OF
CARDIOLOGY
BENHA UNIVERSITY
Disclosures
None
Do you think that it is important to
have a 12 lead ECG recording of VT
before starting VT ablation procedure ?

YES

NO

IT DEPENDS
ECG is very specific tool for localizing
VT foci or reentry circuit exit sites ?

AGREE

DO NOT AGREE

IT DEPENDS
Clinical or inducible non clinical VT ?!
Possible VT mechanisms in ischemic
patients

Scar related reentrant VTs (most common).

Focal VTs (including those originating from
the papillary muscles).

Fascicular VTs (inter-fascicular)

BBR VT
What do we expect from the ECG ?

Localize or at least Regionalize the focus or
the exit site.

The possible mechanism of the tachycardia.

Is it endocardial or Epicardial
Limitations of the ECG as a mapping tool

The presence and the extent of infarction.

The degree of intra-myocardial fibrosis.

The shape of the heart and its position in
the chest .

Influence of non-uniform anisotropy in
affecting propagation from tachy site.
Continue…Limitations

Effect of acute ischemia,drugs,and
metabolic abnormalities on conduction.

Integrity of the His-Purkinje system.

Presence of increased myocardial mass
What we are searching for ?

QRS initial forces

QRS amplitude

QRS width

QRS frontal plane axis

BBB pattern

Concordance

The presnece of QR complexes.
QRS initial forces

Rapid initial forces>>> More likely arising from
normal myocardium

Slurred initial forces (pseudodelta wave )>>>
More likely from a scar or from epicardium
QRS amplitude

Usually VTs arising from diseased
myocardium have lower QRS amplitudes
from those arising from normal myocardium
QRS width
>

Free wall VTs
Septal VTs ( assuming
conduction in all directions is equal )

Epicardial VTs
>
Endocardial VTs
QRS frontal plane axis

Superior axis >>> apical site (septal or
lateral ) or inferior wall VTs

Inferior axis>>> basal , outflow tract,high
septal or latral wall of LV.
Concordance

Positive concordance>>> Basal sites

Negative concordance>>> Apical (
mainly apical septum and most commonly
seen with anteroseptal infarctions )
BBB pattern

RBBBR pattern>>> VT certainly from LV

LBBB pattern>>> VT from LV septum or
the right side of the septum
Presence of QS complexes

QS complexes in the inferior leads>>>
Activation start at the inferior wall !

QS complexes in precordial leads>>>
Activation is going away from the anterior
wall.
Just to rememeber
Basic roles in post MI VTs

Almost all VTs arise in the LV or IVS

ECG looses a lot of its ability to precisely
localize VT origin or exit sites

Accuracy of the ECG in anterior MI
(greater myocardial damage)patients is
much less than in inferior MI.
Continue…Basic roles

It is extremely rare for an inferior MI dependent VT to
have an exit site at the higher septum close to the aortic
valve

QS complexes in the lateral leads (V4-V6) reflect origin
near the apex ( septal or lateral )

Almost impossible to distinguish VTs coming from apical
septum and apical free wall based on ECG alone
Inferior infarction VT

Activation goes from back to front>> large R
wave in the precordial leads starting from V2

LBBB VT in inferior MI >> mainly basal septum
(inferobasal septum with left axis and higher
septal with normal axis).
Anterior infarction VT

The situation becomes more complicated with less
accuracy of the ECG (more myocardial damage).

LBBB VT or RBBB VT can occur

LBBB VT and LAD is associated usually with
inferoapical septal region.It can present with negative
concordance and always associated with Q wave in I
and aVL

R wave in V1 and Q in aVL indicates more
posterior position on the septum

RBBB VT usually shows superior axis. V1
can show monophasic R or qR pattern
with QS from V2-V4 or up to V6
Endocadial or Epicardial VT ?
Can the ECG alone answer this Q ?
The answer is simply
NO
What is epicardial VT ?

VTs in which the origin or the critical sites of the
reentrant circuit are located in the subepicardial
tissue as suggested by entrainment maneuvers
and/or termination withen 10 seconds of standard
RF pulses.

Critical epicardial sites may be entained or
interrupted from both the epicardial and
endocardial surfaces making it difficult to
demonstrate the presence of a truly epicardial
circuit in a given case
Limitations

Most of the adopted ECG criteria to predict
Epicardial foci or exit sites have been described
in patients with NICM and idiopathic VTs .

Even VTs with presumed epicardial exit sites
can be still ablated from the endocardial
approach (The entrance or the central isthmus).

No ECG features distinguished outflow tract
epicardial exit sites.

Poor sensitivity and specificty.
Suggested ECG criteria
1-Total QRS duration

QRS more than 198
ms has 86%
specificity and 69%
sensitivity for
epicardial origin of
VT.
2-Pseudo delta wave

Earliest ventricular
actiavation to the
fastest delection an
any precordial lead

Pdw >34 ms has
80% sensitivity and
specificty
3-Intrinscoid deflection time

ID from the earlist
ventricular activation to the
nadir of the first S wave in
any precordial lead .

ID more than 97 ms has
80% specificity and 50%
sensitivity for epicardial VT
origin.
4-RS duration

RS from the earliest ventricular activation
to the peak of R wave in lead V2

RS >121 ms is 82% specific and 57%
sensitive for epicardial VT
5-Maximum Deflection Index
( MDI)

It is defined as the shortest time to maximum
positive or negative deflection in any precordial
lead divided by the QRS duration.

A cut-off value of 0.55 has high sensitivity
(100%) and specificity (98%) for epicardial VT.

This was mainly adopted for epicardial VTs
arising from sinuses of Valsalva.
6-Precordial pattern break (R wave
regression progression)

This was mainly described by Marchilinski group
in Pheladelphia and was in the context of
idiopathic VTs (but may still work).

There is a brupt loss of R wave in V2 followed
by a resumption in R waves from V3 to V6.

Unkown predictive value.
7-Regional Q waves
Again….Remember

Even with the presence of all of the above
mentioned criteria, the ECG is not predictive for
epicardial access and mapping .

Endocardial mapping should be commenced at
first for all cases

The role of the above mentioned criteria in post
MI patients has no strong evidence.
Post MI VTs from papillary
muscles
When to suspect ?
ECG…nothing specific
Gadolinium enhanced MRI
BBR VT

More common in patients with NIDCM.

Its incidence is propably underestimated.

Should be considered in DD specially if there is
ECG evidence of His Purkinje disease
Typical and Atypical BBR VT.
VT involving the left purkinje
system
When to suspect ?
Conclusion

Different VT mechanisms are involved in patients with IHD

ECG, inspite of limitations, is a useful tool in localizing or at least
regionalizing the exit sites of VTs in post MI patients.

ECG has poorer predictive value in patients with anterior infarction
than those with inferior MI

Different ECG criteria can support epicarial focus or exit site but this
does not necessarily indicate the successful ablation site.

Finally,it is mapping and not the ECG that determine where you
have to ablate
THANK YOU

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