LAUSR

A 48-year-old male endurance athlete was referred for ablation of incessant atrial tachycardia (AT). He had undergone ablation for persistent atrial fibrillation 1 year earlier consisting of pulmonary vein isolation plus substrate modification. 3D activation map (CARTO software, Biosense Webster, Diamond Bar, USA) confirmed lasting large circumferential PV isolation and demonstrated the earliest activation during AT at the rightsided fossa ovalis Fig. 1. Sinus rhythm was briefly restored during catheter manipulation at the earliest LAT spot (while inserting the ablation catheter within the 2 layers of the interatrial septum) and endocardial tracings evidenced a rapid and dissociated activity with a cycle length of around 282 ms only recorded within the fossa ovalis (anterior to the previous transseptal puncture site). Consecutive radiofrequency ablation (6 RF applications at 45 W to reach an ablation index > 500) resulted in elimination of the dissociated potentials and definitive sinus rhythm restoration. We consider this concealed AT a highly probable trigger of the clinical AF recurrence after the first procedure. In an 8-month follow-up, the patient stayed free of symptoms.