Identifying the origin of atrial tachycardia in the epicardial region by analyzing two separate roving activation intervals using a novel three-dimensional mapping system: A case study

Key Teaching Points•Marshall bundle–related atrial tachycardias (AT) are common after atrial fibrillation ablation, but their identification with conventional 3-dimensional mapping techniques may be difficult.•In analyzing the tachycardia mechanism, omnipolar technology, grid mapping catheter, and the improvement of noise filtering contributed to the observation of epicardial potentials.•In addition to the high-resolution performance of the EnSite X EP System (Abbott, St. Paul, MN), it was useful in assessing tachycardia through the evaluation of propagation with an annotation-dependent activation map and annotation-independent omnipolar vectors, and changing the roving activation intervals as needed for circuit identification.•Vein of Marshall (VOM) ethanol infusion is a feasible and safe treatment for VOM-related AT. •Marshall bundle–related atrial tachycardias (AT) are common after atrial fibrillation ablation, but their identification with conventional 3-dimensional mapping techniques may be difficult.•In analyzing the tachycardia mechanism, omnipolar technology, grid mapping catheter, and the improvement of noise filtering contributed to the observation of epicardial potentials.•In addition to the high-resolution performance of the EnSite X EP System (Abbott, St. Paul, MN), it was useful in assessing tachycardia through the evaluation of propagation with an annotation-dependent activation map and annotation-independent omnipolar vectors, and changing the roving activation intervals as needed for circuit identification.•Vein of Marshall (VOM) ethanol infusion is a feasible and safe treatment for VOM-related AT.