Spatial and transmural properties of the reentrant ventricular tachycardia circuit in arrhythmogenic right ventricular cardiomyopathy: Simultaneous epicardial and endocardial recordings

Background: While advances in the characterization of the structural substrate in arrhythmogenic right ventricular cardiomyopathy (ARVC) have been made, the ventricular tachycardia (VT) circuit remains incompletely described. Objective: The purpose of this study was to delineate the reentrant VT circuit with simultaneous epicardial and endocardial mapping (SEEM) in ARVC. Methods: Twenty-three consecutive patients with ARVC and VT underwent SEEM at 4 centers between 2014 and 2020. Retrospective analysis was performed on combined isochronal activation maps. Results: Of the 30 VT circuits, 24 were delineated with SEEM (956 [341–1843] endocardial points and 1763 [882–3054] epicardial points). The apex and outflow tract rarely harbored VT circuits, with 50% distributed in the inferior wall and 43% in the free wall. The entire tachycardia cycle length was recorded from the epicardium in 71% of circuits. In all circuits, a large proportion of the tachycardia cycle length was recorded from the epicardium relative to the endocardium. Localized epicardial reentry was observed in 35% of patients (14 mm × 15 mm), which was associated with smaller endocardial low voltage area (39 cm² vs 104 cm²; P =.002) and preserved right ventricular ejection fraction (35% vs 25%; P =.046) compared with those with larger circuit dimensions. Seventy percent of termination sites were achieved from the epicardium. Conclusion: High-resolution recordings from both myocardial surfaces confirm a consistent predominance of epicardial participation during reentry in ARVC. Only the perivalvular inflow region of the “triangle of dysplasia” had a strong propensity to harbor VT circuits, with the greatest proportion located in the inferior wall. Localized epicardial reentry may be a manifestation of earlier stage disease with a relative paucity of endocardial substrate.