Which side are you on? – Deducing the chamber of origin of atrial tachycardia

Abstract Atrial arrhythmias rising from the regions of the atria that are in close proximity to each other may pose a challenge in identifying the chamber to map and ablate in. In this report, we discuss a patient with left atrial tachycardia which initially mimicked right atrial tachycardia. We discuss the origins of the abnormal electrograms in the right atrium and how this provides a general understanding of the mechanism of double potentials.