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Validation of Scar EP Substrate (Cuculich, JACC 2011; 58:893) .
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24 subjects with infarct – related myocardial scar participated in the study. Based on ECGI
reconstructed epicardial electrograms that displayed the characteristics of scar-related electro-
grams (low voltage and fractionation) the epicardial EP scar was reconstructed. The ECGI imaged

scar matched the anatomical scar (imaged with gadolinium delayed-contrast MRI) in location, size
and morphology. This is an important validation, because it is done with a completely independent
and well established method (MRI).

Validation in Clinical Applications

1. Focal LV Tachycardia (Intini, Heart Rhythm 2005;2:1250) 282 . ECGI was applied in a young
athlete with focal VT. The ECGI- reconstructed isochrones localized the site of origin to the LV

apex, in an area of a diverticulum. QS morphology of a reconstructed EGM from this site
indicated epicardial origin. These ECGI determinations and the reconstructed activation
map correlated precisely with invasive endocardial and epicardial catheter mapping using
standard EP mapping techniques.

2. WPW Syndrome (Ghosh, Circulation 2008; 118:907 283 and Ghosh, Annals of Biomedical
Engineering 2009; 37:902 272 ). 14 WPW pediatric patients undergoing ablation participated in
the study. ECGI-localized pre-excitation sites were consistent with the successful ablation

site with high accuracy, much better than the conventional Arruda algorithm. ECGI
distinguished between epicardial and endocardial accessory pathways based on electro
gram morphology. ECGI also determined the presence and locations of dual pathways, not
detectable from the ECG, that were confirmed by invasive EP study and subsequent

ablation at the two predicted sites.

3. Ventricular Arrhythmias Study (Wang, Science Translational Medicine, August 2011:
Vol 3 Issue 98: 98ra84) 284 . 25 patients participated in the study. Compared to invasive

EP study, ECGI correctly identified the LV or RV site of origin 100% of the time. Specific
locations within each ventricle were in agreement with invasive EP study in 10 of 11 RV sites
(91%) and in 11 of 12 LV sites (92%). ECGI reconstructed reentrant VT patterns were always
related to areas of ventricular scar. Entrainment maneuvers confirmed a reentrant

mechanism and when ablation was performed in this region it terminated the VT. Through
comparison with invasive EP studies, ECGI was also evaluated for its ability to determine
epicardial or intramural locations (depth) of VT based on electrogram morphology. The
EP study determined the site of origin to be epicardial in 5 patients, endocardial in 6 patients

and mid-myocardial in 2 patients. All 5 patients with epicardial origin had a reconstructed
pure Q wave EGM (100%) at the site of earliest activation, indicative of epicardial origin.
In seven of the eight patients with non-epicardial origin, the EGM had a small r wave (88%)
indicative of intramural origin.