Left atrial roof-dependent atrial tachycardia via the Marshall bundle

Left atrial (LA) roof–dependent atrial tachycardias (ATs) are one of the common forms of iatrogenic ATs after a percutaneous or surgical LA ablation of atrial fibrillation (AF). The reentrant circuits of LA roof–dependent ATs generally rotate around either or both of the right and left pulmonary veins (RPVs and LPVs). We present an unusual case of an LA roof–dependent AT with dual reentrant circuits: one rotating around the RPVs and the other around the LPVs, passing through the vein of Marshall (VOM). Key Teaching Points • The present case exhibited an unusual form of a left atrial (LA) roof–dependent atrial tachycardia (AT) with dual reentrant circuits: one rotating around the right pulmonary veins (PVs) and the other around the left PVs, passing through the vein of Marshall (VOM). • High-resolution activation mapping combined with entrainment pacing from not only the LA endocardium but also the VOM could be helpful to establish an accurate diagnosis of the LA roof–dependent AT mechanism. • An ethanol infusion into the VOM can be one of the therapeutic options for treating LA roof–dependent ATs via the Marshall bundle.