Ablation of the epicardial substrate in ventricular tachycardia associated with structural heart disease: outside in or inside out?

Percutaneous epicardial access, introduced by Sosa et al. (1) in the mid-1990s, provided an important diagnostic and therapeutic approach to the recognition and management of scar-related epicardial ventricular tachycardia (VT). Since that time, the need for epicardial ablation has been reported in 10% to 15% of patients with ischemic cardiomyopathy (ICM) (2–4), 25% to 50% of patients with nonischemic cardiomyopathy (NICM) (4–8), and 30% to 40% of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) (4,9–12). Controversy persists with regard to the timing of epicardial intervention (initial procedure or only after unsuccessful endocardial approaches) and the extent of epicardial ablation required (focused regional ablation targeting specific VT morphologies or elimination of all epicardial late or abnormal potentials [13,14]). These con-