Prolonged high-power endocardial ablation of epicardial microreentrant VT from the LV summit in a patient with nonischemic cardiomyopathy

Introduction Epicardial mapping and ablation have emerged in the last decade as a strategy to increase the success rate for the eradication of arrhythmogenic circuits in complex scar substrates. It has been established that epicardial mapping and ablation are generally required for some arrhythmic substrates such as in arrhythmogenic right ventricular dysplasia, Brugada syndrome, Chagas cardiomyopathy, nonischemic cardiomyopathy (NICM), and to a lesser extent in ischemic cardiomyopathy (ICM). Ablation in patients with NICM has been shown to be inferior to that in patients with ICM, as scar patterns are more variable with epicardial and intramural locations. In addition, the arrhythmic mechanism of ventricular tachycardia (VT) in patients with NICM is not always macroreentrant, as focal and automatic sites of origin have been reported in up to 20% of patients. Furthermore, delivering radiofrequency (RF) lesions in the epicardial space might be limited because of significant epicardial fat as well as close proximity to phrenic nerves and coronary vasculature. In this report, we present a case of a patient with NICM and VT, in whom (1) a microreentrant mechanism was demonstrated by activation and entrainment mapping and (2) successful elimination of an epicardial circuit was achieved with ablation through normal endocardial tissue because of proximity of the epicardial site of origin to a coronary artery.