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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3651_Библиотеки_им_академика_М_И_Перельмана
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Fig. 20.24 CARTO image in LAO 95°, caudal 0° showing the activation map of the VT (left panel) in relationship with the VT substrate depicted by the epicardial
Fig. 20.25 A 12-lead ECG at the end of the ablation procedure showing sinus rhythm with a heart rate of 80bpm, QRS
axis at +30°, absence of LV hypertrophy, and absence of ischemia
bipolar voltage map (right panel), with superposed RF
ablation lesions (pink and red dots) at the level of the VT
isthmus
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B. Bakouboula et al.
Commentary
The present case illustrates a combined approach
(endocardial and epicardial) catheter ablation
procedure for a fast sustained monomorphic ventricular tachycardia in a 69-year-old male patient
with ischemic cardiomyopathy and prior
infero- lateral myocardial infarction. Several
observations can be made about the present case.
The 12-lead ECG recorded during VT is a
very useful tool that can help the physician identify the site of origin of the VT. Several criteria
have been published up to date that suggest an
epicardial origin of VT. According to the group
of Marchlinski [3], in patients with nonischemic
cardiomyopathy, elements in favor of an epicardial origin are 1. the presence of q wave in lead I
and the absence of q waves in inferior leads, 2. a
pseudo-delta wave ≥34ms, 3. intrinsicoid deection time ≥ 85 ms, 4. the shortest RS complex
≥121ms, and 5. the maximum deection index
(dened as the ratio between the QRS onset and
the peak of the QRS and the total length of the
QRS complex)≥0.55. The presence of q wave in
lead I has a sensitivity of 88% and a specicity of
88% in identifying the epicardial origin of
VT.The same working group proposed an algorithm composed of four criteria: 1. the presence
of q waves in inferior leads, 2. the presence of a
pseudo-delta wave >75 ms, 3. A maximum
deection index >0.59, and 4. the presence of q
waves in lead I, algorithm that has >95% specicity and>20% sensitivity in identifying epicardial origins of VTs. According to Berruezo etal.
and their study on patients with coronary artery
disease and idiopathic dilated cardiomyopathy
(72% and 28%, respectively) [4], elements on the
12-lead ECG in favor of an epicardial origin of
VTs are 1. pseudo-delta wave ≥34ms and 2. an
intrinsicoid deection in lead V2≥85ms and the
shortest RS complex in any lead ≥121 ms.
According to Daniels et al. [5], a maximum
deection index in the precordial leads of ≥0.55
is in favor of an epicardial origin of the VT.Bazan
etal. [6] suggested that the presence of q waves
in lead I is indicative of epicardial VT originating
from the anterolateral left ventricle. These criteria were developed in a study on patients with
nonischemic cardiomyopathy. Several of these
criteria could be identied in the above-presented
patient (see Fig. 20.5 explained), suggesting an
epicardial origin of the VT.
The VT origin in patients with ischemic cardiomyopathy and prior myocardial infarction is
most of the times endocardial. However, epicardial ablation is potentially needed in a minority
of patients [7]. In the experience of Sarkozy etal.
[8], this is the case in at least 6% of patients. In
their study on 444 patients with VT related to
prior myocardial infarction, epicardial access
was considered appropriate in 56 patients (13%).
Of these 56 patients, 38 (68%) had epicardial VT
targets, and epicardial ablation terminated at least
one VT in 27 patients (6% of the total population). Major complications occurred in eight
patients with epicardial access. According to
Hayashi et al. [9], an important epicardial substrate involved in the VT mechanism is present in
up to 14% of patients with ischemic cardiomyopathy. Most of the epicardial critical ablation
sites are situated opposite to the endocardial scar
area demonstrated by the bipolar voltage map.
Catheter ablation was effective in eliminating
VTs in their study. Romero etal. [10, 11] recently
showed that a combined endocardial-epicardial
approach for VT ablation was associated with a
lower risk of VT recurrence and a lower mortality
compared to an endocardial approach in patients
with structural heart disease and scar-related
VT.However, this was at a cost of a higher complication rate with the combined endocardialepicardial approach. In the above-presented
patient, the combined epicardial-endocardial
approach was justied by the prior failed
endocardial- only approach and by the patient’s
history of aborted SCD due to fast VT.
When performing epicardial ablation for ventricular tachycardia, the ablation strategy needs
to be well prepared before the beginning of the
procedure. Things to consider before starting the
procedure include 1. the type of approach, epicardial only vs. epicardial + endocardial; 2. for
the epicardial approach, percutaneous vs. surgical approach; 3. in case of a combined approach
(epicardial + endocardial) and the type endocardial approach (transseptal, retrograde aortic, or
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both); and 4. coronary angiography during the
procedure vs. CT angiography performed before
the ablation procedure and integrating the 3D
reconstructed images in the electro-anatomical
mapping system (this is necessary to avoid coronary artery injury during epicardial ablation). In
the above-presented patient, a combined epicardial and endocardial approach was used during
the second ablation procedure. For the epicardial
approach, a percutaneous technique was used,
and for the endocardial approach, a mixed antegrade (transseptal) and retrograde (transaortic)
technique was used. Coronary angiography was
performed during the procedure to avoid lesions
to the epicardial coronary arteries, and the CT
angiography images were integrated into the
CARTO working platform as well.
Potential complications related to the epicardial approach include acute hemopericardium
(6.3%), delayed tamponade (1.3%), hemothorax
(1.3%), and major pericardial reaction (1.3%).
Other potential complications include coronary
artery lesions with subsequent myocardial infarction and phrenic nerve injury. In the experience
of Lin etal. [12], these occur in 10% of patients.
Therefore, the risk-benet ratio of an epicardial
approach has to be well weighed before performing such a procedure. In the above-presented
patient, no complication occurred, and he was
discharged from the hospital 48hours later.
Concerning the mapping strategy used in this
case for the second ablation procedure, substrate
mapping in sinus rhythm was performed rst, in
order to localize a potential VT substrate. This
was found to be present at the level of the inferior
LV wall. Next, activation mapping was performed for a limited period of time, due to the
poor hemodynamic tolerance of the VT.However,
this was enough to identify the critical components of the VT circuit (the VT isthmus, the
entrance zone, and the exit zone) and to understand its mechanism: macro-reentry forming a
double-loop or a “gure of 8” circuit (see
Figs.20.19 and 20.20). Of note, the VT isthmus
was present in a borderline zone, at the junction
of an area of myocardial scar with healthy myocardial tissue. At this level, late potentials were
recorded during sinus rhythm and during diastole
in VT.The exit point of the VT was conrmed by
pacemapping during sinus rhythm: a correlation
of over 95% was present between the QRS morphology during VT and that produced during
local pacing (Fig.20.22). All these elements were
helpful in guiding the catheter ablation procedure. The use of an electro-anatomical mapping
system (the CARTO system in this case) was
extremely useful all throughout the ablation
procedure.
Ablation was subsequently performed, with
ablation lesions being deployed at the level of the
VT isthmus. Regarding the ablation settings used
in this case, the target power chosen was 30W.To
our knowledge, up to the present date, there is no
ablation index target derived from clinical trials
(neither observational nor randomized) for epicardial ablation of VTs. Therefore, no xed value
was used as a target value. RF applications were
carried out until disappearance of the local electrogram was seen.
Up to the present date, the patient remains
VT-free.
Learning Points
• The 12-lead ECG clues in favor of an
epicardial origin of VT include 1. the
presence of q wave in lead I and the
absence of q waves in inferior leads, 2. a
pseudo-delta wave ≥34ms, 3. intrinsicoid deection time ≥ 85 ms, 4. the
shortest RS complex ≥121 ms, and 5.
the maximum deection index ≥0.55.
• In the setting of ischemic cardiomyopathy and prior myocardial infarction, epicardial ablation may be needed in 6 to
14% of patients in order to achieve VT
elimination.
• A combined epicardial-endocardial
approach, after a failed endocardialonly approach, increases the success
rate of the procedure, but with the cost
of a higher complication rate.
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References
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