Ultra-high density mapping and ablation of localized microreentrant tachycardias: insight from the CHARISMA registry
Authors: Bulian F , Rossi P , Pelargonio G , Solimene F , Del Giorno G , Marinigh R , Bisignani A , Bencardino G , Di Cori A , Russo M , Bianco D , Giomi A , Sartari U , Malacrida M , Mantovan R 
Published: May 2024

Abstract

Background
The optimal criteria for distinguishing microreentrant atrial tachycardias (mAT) from macroreentrant atrial arrhythmias (MAT) in clinical practice have not been definitively established. Recent advancements in ultra-high-density mapping featuring automated functionalities, has enhanced our understanding of mAT circuits and the precise localization of foci.

Purpose
Our intent was to observe the diagnostic support provided by high density mapping and Lumipoint algorithm in mAT as well as the ablation outcomes.

Methods
Consecutive patients eligible for atrial tachycardia (AT) ablation in 22 Italian centres were prospectively enrolled. all ATs were comprehensively mapped in either the left or right atrium utilizing the Rhythmia mapping system and the 64-pole Orion basket catheter. A mAT was defined as an AT characterized by slow, continuous, low fragmented potentials covering a minimum of 50% of the tachycardia cycle length (CL) within a confined area (defined as a circuit within &lt; 1 cm2), enclosed by a couple of closed splines of the Orion catheter, and exhibiting a centrifugal activation pattern to the rest of the atria. The Lumipoint tool was systematically employed to confirm electrogram fragmentation within this defined area.

Results
Among 159 ATs analysed, 97 (61.0%) were identified as MAT, 50 (31.4%) as focal atrial tachycardias and 12 (7.5%) as mAT. Of these latter, 6 patients (50%) had a previous history of atrial ablation procedure. Concerning the mAT group, the predominant origin site was the left atrium (10 mAT, 83,3%); the targeted activity was localized in the anterior wall in 4 cases (33.3%), in proximity to PVs in 3 cases (25%), along the left ridge in 2 cases (16.6%) and at the roof in 1 case (8,3%). In the remaining right mAT, the foci were found in the free wall and along the CTI in 1 case (8.3% each). The electrical activity spanning the whole CL was detected by 2.7±1.8 pairs of close bipoles of the Orion catheter, was confined to a region of 0.36±0.3cm2 with the longest component of fractionated EGM per spline equal to 64.7±17% of the CL. Low voltage areas (&lt;0.1 mV) were detected in all mAT cases and colocalized with the origin site. Voltage level was 0.2±0.1mV at the site of longest duration of the fragmented potential. A single shot RF delivery terminated each arrhythmia at targeted location. Consolidative RF ablations were then delivered in the adjacent area. Over a median of 288 [248-349] days of follow-up, 5 (3.1%) patients suffered from an AT/AF arrhythmia recurrence and of these, 3 (3.1%) were in the MAT group, 1 (2%) in the focal AT and 1 (8.3%) in the mAT group. No complications were observed.

Conclusions
A novel automated algorithm for microreentrant atrial tachycardia identification, coupled with the identification of matched areas of electrogram fractionation by the Orion catheter, may restrict the extent of required ablation and result in a low arrhythmia recurrence.