B-PO03-111 A NEW ELECTROPHYSIOLOGICAL TRIAD FOR ATRIAL FLUTTER CRITICAL ISTHMUS’ IDENTIFICATION AND LOCALIZATION

Abstract

Atypical atrial flutter (AFL) is a supraventricular arrhythmia that can be treated with catheter ablation. However, the best approach is still to be defined and this strategy has suboptimal results. The Carto® electroanatomical mapping (EAM) version 7 displays a histogram of the local activation times (LAT) of the tachycardia cycle length (TCL), in addition to the activation and voltage maps. The study aimed to assess the ability of an electrophysiological triad to identify and localize the AFL’s critical isthmus. Retrospective and prospective analysis of a multicentric registry of individuals who underwent left AFL ablation during a 1-year period with Carto® EAM. All patients with non-left AFL, lack of high-density EAM, less than 2000 collected points or lack of mapping in any of the left atrium walls or structures were excluded. Ablation sites of arrhythmia termination were compared to an electrophysiological triad constituted by: areas of low-voltage (0.05 to 0.3mV), sites of deep histogram valleys (LAT-Valleys) with less than 20% density points relative to the highest density zone and a prolonged LAT-Valley duration that included 10% or more of the TCL. The longest LAT-Valley was designated as the primary valley, while additional valleys were named as secondary. We assessed 21 patients (9 patients retrospectively and 12 patients prospectively), 14 men with a median age 74 IQR 67-76 years). All patients presented with left AFL and 66% had a previous atrial fibrillation and/or flutter ablation. The median TCL and number collected points were 252 (220290) milliseconds and 3250 (IQR 24103900) points, respectively. All AFL presented with at least 1 LAT-Valley in the analysed histograms, which corresponded to heterogeneous low-voltage areas (0.05 to 0.3mV) and encompassed more than 10% of TCL. Seventeen of the 21 patients presented with a secondary LAT-Valley. All arrhythmias were effectively terminated after undergoing radiofrequency ablation in the primary or the secondary LAT-Valley location. An electrophysiological triad was able to identify the AFL critical isthmus in all patients. Further studies are needed to assess the usefulness of this algorithm to improve catheter ablation outcomes.