Background: A reentrant mechanism explains most post-infarct ventricular tachycardias (VT). The socalled ‘protected isthmus’ of the reentrant circuit is the critical element for the maintenance of these VTs and,therefore, the target for ablation. Several authors have proposed an anatomical based approach relying on sinusrhythm (SR) scar definition and/or pace mapping within the infarct area to determine the appropriate ablationzone. As far as pace mapping during SR is concerned, this technique has not yet been correlated with the actualdefinition of isthmuses boundaries as identified by an electro-anatomical mapping system (EAMS). Such was theaim of the present study. We studied 10 patients (8 men, mean age = 70.7±10.8 years) all had a remote(19.2±5.6 years) myocardial infarction. Infarct locations were anterior (n=4), inferior (n=5) or anterior andinferior (n=1) with mean left ventricular ejection fraction (EF) of 36.8± 13.5%. Four patients were equipped withan implantable cardioverter defibrillator (ICD) at the moment of the ablation procedure and another fourunderwent ICD implantation after the ablation procedure. All patients underwent 1: Ventricular ProgrammedElectrical Stimulation; 2: Left Ventricular Electroanatomic Mapping & Pace Mapping(PM) during SinusRhythm;3: Left Ventricular Electroanatomic Mapping during VT. After the identification of each VT isthmuscharacteristics (boundaries definition, length and width), isthmuses as well as their peri-isthmian zone werecompartmentalized into 7 separate segments. Both PM-map and VT activation map were then superimposed onthe main screen of the CARTO™ system; allowing the allocation of any point on any PM-map at a givencompartment on the superimposed VT segmented isthmus/peri-isthmus zone. The correlation between PM-mapand VT map could then be analyzed. We reported 43 points of pace maps in the isthmus zone, 92 points at theexit area, 85 points at the entrance area, 51 points at the side zones, 81 points at the peripheral zone of exit and53 points at the peripheral zone of entry. A total number of 405 points of pace maps were collected. In thisstudy, the best mean average percentage of correlation of pace mapping was found at the level of the exit zone(89±8%), whereas the worst average mean percentages of correlation were found at the level of the outerentrance zone (23±28%) and at the level of the entrance zone of the isthmus (39±34%). While at the level of theisthmic zone, the mean average percentage of correlation was 59±32%.Conclusions : This study is the first toevaluate the utility of the pace mapping combined with 3D electro-anatomical mapping system for theidentification and the localization of VT isthmus; we believe that our study represents an important step for theidentification of the reentry circuits in sinus rate/rhythm using pace mapping for slow VT and hence fast VT.