High‐resolution 3D mapping of epicardial conduction during Marshall bundle‐related atrial tachycardia

A 73‐year‐old woman was admitted for atrial tachycardia (AT) ablation. The activation map and pacing study indicated that the AT propagated around the left pulmonary vein and that the Marshall bundle (MB) bypassed the scar area of the left pulmonary vein ridge and mitral isthmus. The Rhythmia Mapping System revealed double potentials propagated along the assumed position of the MB. The mapping system includes a confidence mask that can be used to visually identify low‐confidence areas of the map based upon extremely low‐voltage signals. Given the low‐voltage area in the endocardial side, the epicardial conduction was emphasized.