Comprehensive Cardiac Substrate Mapping Protocol

Endocardial (Endo) access to the left ventricle (LV) was obtained via the retrograde and transseptal approaches in all patients. Epicardial mapping was performed in all patients, as part of the clinical ablation study. Pericardial puncture was performed using the subxiphoid approach. Substrate maps were created during sinus rhythm, using CARTO 3D mapping system (Biosense Webster, Inc., Diamond Bar, CA, USA). Mapping was performed using a PentaRay (PentaRay, Biosense Webster, Inc.) or DecaNav mapping catheter (DecaNav, Biosense Webster, Inc.) with impedance parameters scaled to ensure tissue contact. Normal myocardium was defined as tissue with a bipolar voltage >1.5 mV, dense scar was defined as a bipolar voltage <0.5 mV, and scar borderzone was defined as a bipolar voltage 0.5–1.5 mV, consistent with previously published data.¹ (link)^,2 (link) Though debate exists regarding the optimal voltage cut-off to define Epi scar⁶ (link)^,7 (link) we sought to use a consistent value for both epicardium and endocardium as previously published,⁸ (link) in order to provide consistency to the APD measurements. Following this, activation mapping was performed if haemodynamically tolerated. Finally areas of late potentials and mid-diastolic potentials were identified.