Atypical left septal atrial flutter in a dog

Abstract A 6‐year‐old, male, entire Chesapeake Bay retriever was referred for electrophysiological mapping and radiofrequency ablation for clinical incessant supraventricular tachycardia. A baseline electrocardiogram showed frequent paroxysms of a narrow QRS complex, regular tachycardia with a ventricular rate of 200 beats per minute, with an atrial rate of 330 beats per minute, variable atrioventricular conduction ratio and negative atrial depolarisation in inferior leads (II, III, aVF). According to the electrocardiographic findings, a tentative diagnosis of left atrial flutter was made, and an electrophysiological study was recommended. Left atrial endocardial mapping confirmed the presence of a macro‐reentrant tachycardia consistent with an atypical atrial flutter with a new site of a critical isthmus within the left interatrial septum. Ablation of the isthmus was not performed due to a technical issue, which necessitated a power‐controlled irrigated catheter instead of a temperature‐controlled usual catheter, and the owner's concerns regarding risk assessment for left side radiofrequency delivery with this methodology.