Biatrial tachycardia (BiAT) is a rare arrhythmia, and identification of the re-entry circuit is often complicated. ¹ By creating an activation map of the right atrium, left atrium, and coronary sinus as a single chamber, the Lumipoint module of the Rhythmia mapping system can be used in real time to make an accurate diagnosis. ² Ablation of the Bachmann bundle is a feasible way to terminate BiAT, but might cause interatrial conduction delay and electrical isolation of the left atrial appendage. Chemical ablation into the vein of Marshall might be the more beneficial treatment, avoiding any potential interatrial conduction delay.