Sustained ventricular tachycardia (VT) in patients with nonischemic cardiomyopathy (NICM) often involves midmyocardial and epicardial structures. Delayed-enhancement magnetic resonance imaging (DE-MRI) of scar and fibrosis is the method of choice to define the substrate of monomorphic VT.

The aim of the study was to compare the outcome of endocardial vs. epicardial VT ablation in patients with epicardial DE-MRI substrates in NICM.

Among 44 patients with NICM referred for VT ablation who underwent DE-MRI, 12 patients had an epicardial-only (n = 4) or predominantly epicardial DE-MRI substrate (n = 8). 9 of the 12 patients had a prior myocarditis. Endocardial-only VT ablation was successful in two patients with epicardial DE-MRI substrate. A pericardial access for epicardial mapping and ablation was attempted in 8 patients and could be accomplished in seven. Epicardial low voltage (<1.5 mV) and very low voltage (<0.5 mV) areas were in good qualitative correlation to the epicardial DE-MRI substrates. Epicardial abnormal electrograms in combination with a good pace map QRS match were found in epicardial very low voltage areas in five patients and in low voltage areas in two patients. 2 patients with endocardial-only ablation, five patients with endo-epicardial ablation and two patients with primary epicardial ablation had a favorable post-ablation outcome (follow-up 32 ± 26 months) but one patient had to undergo heart transplantation for heart failure deterioration.

Endo-epicardial ablation or primary epicardial ablation should early be considered in patients after myocarditis or with other forms of nonischemic cardiomyopathy with epicardial DE-MRI substrates.