Electrophysiological Study and Endocardial Ablation Procedure
All patients underwent a transthoracic echocardiography study to
evaluate left ventricular ejection fraction (LVEF) and to look for
potential ventricular aneurysm or intracardiac thrombi. The
electrophysiological study was performed under general anesthesia.
Intracardiac electrograms were recorded using a digital
electrophysiological recording system (Prucka CardioLab, USA or
EP-WorkMate St. Jude Medical, St. Paul, MN, USA). Three-dimensional
electroanatomic mapping was guided by an EnSite NavX system (St. Jude
Inc., St. Paul, MN, USA) or CARTO 3 system (Biosense Webster, Diamond
Bar, CA, USA).
If the patient was in sinus rhythm (SR), an endocardial voltage map
during SR was acquired using an ablation catheter (ThermoCool NaviStar,
Biosense Webster, CA, USA or CoolFlex, St. Jude Inc., St. Paul, MN,
USA). Low voltage zones (LVZ) were defined as amplitude between 0.5 and
1.5 mV. Late potentials and/or local fragmented ventricular potentials
were also tagged. After voltage mapping, VT induction was attempted with
programmed stimulation. For hemodynamically well tolerated VTs, local
activation mapping was performed. In cases that were non-inducible or
with hemodynamically poorly tolerated VTs, substrate modification was
performed during SR. Low voltage areas, fragmented or late potentials
and areas with matching pace-maps were targeted. Radiofrequency (RF)
ablation was performed with a power of 30-45 W at a temperature limit of
45 °C. The acute procedural endpoint was defined as non-inducibility of
VTs.