Ablation Targets of Scar-related Ventricular Tachycardia Identified by Dynamic Functional Substrate Mapping
Phase: NA
Conditions: Tachycardia, Ventricular
Sponsor: Ain Shams University

Ablation 
Targets 
of 
Scar-related 
Ventricular Tachycardia Identified by 
Dynamic 
Functional 
Substrate 
Mapping 
Registration number: NCT05086510 
Date: 28th Seprember 2021 
 
 
 
 
 
 
 
 
 

Methods 
Patients 
Consecutive patients presenting to Ain Shams University hospitals for ablation 
of ventricular tachycardia were evaluated for participation in the study. Patient 
recruitment period was from October 2021 till January 2023. Approval was 
obtained from the ethical committee at Ain shams University before starting the 
research.  
 Inclusion criteria  
o Patients with structural heart disease including previous myocardial 
infarction, left ventricular (LV) dilatation and/or systolic dysfunction, or 
normal LV diameters and systolic function with evidence of ventricular scar 
on 
contrast 
enhanced-cardiac 
magnetic 
resonance 
(ce-CMR) 
or 
electroanatomic map (EAM). 
o Sustained monomorphic VT documented by 12-lead electrocardiogram 
(ECG) or implantable cardioverter defibrillator (ICD) electrograms resistant 
to antiarrhythmic drug treatment or requiring ICD therapies. 
 Exclusion criteria 
 Patients with ventricular arrhythmias attributed to reversible causes. 
 
Methods: 
On admission, patients were subjected to the following after a written 
informed consent: 
A.  History taking: 
1. Age & sex.  
2. Smoking status. 
3. Medical history including hypertension (HTN), diabetes mellitus (DM), renal 

impairment, etc. 
4. Previous history of coronary artery disease, myocardial infarctions (MI), 
revascularization procedures 
5. Previous episodes of ventricular tachycardia, requirement for external  shock, ICD 
shocks. 
6. Medical treatment with special emphasis on antiarrhythmic drugs. 
B. Physical examination: with special emphasis on vital data including general & 
local examination. 
C. 12 lead surface ECG:  during sinus rhythm and of VT(s); if available. 
D. Laboratory investigations: Including serum electrolytes, kidney function 
E. Echocardiography will be done routinely for all patients with special emphasis 
on ejection fraction (to be assessed by Simpson’s method), left ventricular 
dimensions, resting segmental wall motion abnormalities (RSWMAs). 
F. Coronary angiography according to the patient’s clinical characteristics; if there 
is doubt about coronary artery disease as contributor to VT or LV dysfunction. 
G. Randomization: 
Patients were randomly allocated to either DEEP group or non-DEEP group 
before the procedure. Patients were informed of the group to which they have 
been randomized. 
H. Procedure: 
The electrophysiological study and ablation was conducted under general 
anesthesia under supervision of an anesthesiologist.  Continuous Non-invasive or 
intra-arterial blood pressure monitoring and digital pulse oximetry were 
performed. ICD therapies were inactivated.   
Vascular sheaths were inserted into the right femoral vein (2 to 3), right femoral 
artery and/or subxiphoid area under local anesthesia (bupivacaine). A steerable 
quadripolar or decapolar catheter was positioned in the right ventricular apex or 
coronary sinus. The access was via endocardial retroaortic approach, trans-septal 
approach, epicardial approach or endocardial retroaortic with ad-hoc epicardial 
approach. Epicardial mapping and ablation was performed when preprocedural ce-

CMR showed epicardial scar, endocardial mapping did not identify subendocardial 
scars, unipolar LV mapping suggested the presence of epicardial scar, ECG of clinical 
or induced VT suggests epicardial origin (Berruezo et al., 2004) (Vallès, Bazan and 
Marchlinski, 2010). The right ventricle (RV) was mapped when right ventricular 
origin of VT was supected e.g. in arrhythmogenic right ventricular cardiomyopathy 
(ARVC). Surface electrocardiograms (ECGs) and bipolar intracardiac electrograms 
were continuously monitored. 
 
I. Mapping and Ablation Strategy: 
All patients underwent bipolar voltage mapping during sinus rhythm. Mapping 
was performed by either an irrigated tip ablation catheter (ThermoCool SF™ 
catheter; Biosense Webster, Diamond Bar, CA, USA), (ThermoCool ST™ catheter; 
Biosense Webster, Diamond Bar, CA, USA), (FlexAbility ™; Abbott, St. Paul, MN, 
USA), (TactiCath™; Abbott, St. Paul, MN, USA) or a multi-electrode mapping 
catheter (Pentaray™, Biosense Webster, Diamond Bar, CA, USA).  Late potentials 
(LPs) (defined as sharp high frequency or fractionated potentials at or after the 
terminal portion of QRS (Arenal et al., 2003)) were pinpointed and tagged. 
Patients allocated to the DEEP group were subjected to further analysis of their 
LPs by RV extrastimulus pacing. This constituted an S1 drive train at 600 ms or 500 
ms (according to the sinus rhythm cycle length) followed by a single S2 
extrastimulus at 20 ms longer than the ventricular effective refractory period. 
Thereafter, the time interval from the surface ventricular far-field signal to the local 
bipolar LP electrogram was measured both during the RV drive train and with S2 
extrastimualtion. If the difference between the 2 measured values was > 10 ms, the 
analyzed LP was annotated as a DEEP. The same applied for multicomponent 
signals where DEEP was annotated if there was a more than 10 ms splitting of 
components in response to S2 (Figure 1) (Porta-Sánchez et al., 2018).  The 
percentage of points with LPs and DEEPs was calculated in relation to the total 
number of mapped points. 
Figure (1): Intracardiac electrogram demonstrating DEEP 

 
Figure (1): Intracardiac electrogram of a patient with arrhythmogenic right 
ventricular cardiomyopathy during right ventricular S1-S2 pacing. The late 
component of the paced QRS on the distal pole of ablation catheter shows significant 
delay with extrastimulation denoting a DEEP 
Ablation was performed by ThermoCool SF™ catheter (Biosense Webster), 
ThermoCool ST™ catheter (Biosense Webster), FlexAbility ™ (Abbott) or 
TactiCath™ (Abbott). Concerning the DEEP group, ablation was initially restricted 
to points with DEEPs, while in the non-DEEP group, ablation aimed at elimination 
of all LPs. Acute success was defined as VT non-inducibility, including both clinical 
and non-clinical tachycardias. If VT was still inducible after ablation, activation and 
entrainment mapping were performed for hemodynamically-tolerated tachycardias, 
aiming at identification of the critical components of the re-entrant circuit -according 
to previously defined criteria (Brunckhorst et al., 2004)(Stevenson et al., 1997), 

followed by ablation at such locations. If the VT was untolerated, pacemapping was 
performed aiming at a > 96% match (Bogun et al., 2006). 
J. Follow up: 
The study population was followed up for a mean duration of 12 months for 
the occurrence of the study endpoints. The primary endpoint was VT recurrence 
rates. Secondary endpoints were all-cause mortality and cardiovascular mortality. 
For patients with implanted defibrillators, follow up was done by interrogation of 
device recordings, while when defibrillators were not implanted, follow up was by 
history taking for the occurrence of symptoms or need for emergency department 
admission attributed to recurrence of VT. 
K. Statistical analysis: 
Continuous variables with normal distribution are presented as mean ± 
standard deviation and range whilst those with non-normal distribution are 
reported as median and interquartile range (IQR). Continuous variables were 
compared by Student’s t-test, while categorical variables were compared by chi-
square tests, or Fisher’s exact tests as appropriate. Statistical analysis were 
performed using SPSS 25 for Windows (SPSS Inc, Chicago, Illinois, USA).