A Novel Annotation Technique During Mapping to Facilitate the Termination of Atrial Tachycardia Following Ablation for Atrial Fibrillation

Timing of critical isthmus from end of P wave and usefulness of activation mapping with window of interest from end to end of P wave in reentrant atrial tachycardia

In activation mapping of reentrant atrial tachycardia (AT), there was no reference for window of interest (WOI). We examined the timing of a successful termination site from end of the P wave and attempted to determine whether the critical isthmus can be identified using activation mapping when WOI was set as end to end of the P wave. Forty patients with 54 reentrant AT who underwent 3D electroanatomic mapping and radiofrequency catheter ablation were evaluated retrospectively. The critical isthmus was defined as a successful termination site. We evaluate critical isthmus timing from end of the P wave and percentage of critical isthmus timing from end of the P wave to tachycardia cycle length. In 54 reentrant AT, Macro-reentry was identified in 46 (85.2%) and micro-reentry was identified in eight (14.8%). The timing of the critical isthmus site from end of the P wave was - 4.0 ± 31.1 ms (Macro-reentry vs. Micro-reentry; - 8.9 ± 29.4 ms vs. 24.0 ± 26.7 ms; P = 0.005). The percentage of critical isthmus timing from end of the P wave/tachycardia cycle length was - 1.4 ± 10.5% (Macro-reentry vs. Micro-reentry; - 3.1 ± 9.8% vs. 8.3 ± 9.3%, P = 0.004) The critical isthmus of reentrant AT is located within 10% backward and forward from end of the P wave to tachycardia cycle length. Setting the WOI from end to end of the P wave is useful for identification of the critical isthmus through activation mapping.

Open Window Mapping of Accessory Pathways: A Literature Review and Practical Guide

Catheter ablation is the treatment of choice for patients with symptomatic accessory pathways (APs) causing recurrent atrioventricular reciprocating tachycardia or in situations where APs conduct rapidly, posing a risk of sudden cardiac death. Conventional AP mapping relies on point-by-point assessment of local electrograms looking closely for pathway electrograms or early atrial or ventricular electrograms, which may be challenging and time consuming. Recently, open window mapping (OWM) using 3D navigational systems has emerged as a novel technique to help localise and ablate APs. OWM has significant advantages over conventional point-by-point mapping techniques. The purpose of this review is to summarise the currently available literature on the OWM technique and to highlight the technical aspects and mapping considerations for OWM, including specific cases demonstrating its utility.

Left Atrial Anterior Wall Scar-Related Atrial Tachycardia in Patients after Catheter Ablation or Cardiac Surgery: Electrophysiological Characteristics and Ablation Strategy

Background: The mechanisms of atrial tachycardia (AT) related to the left atrial anterior wall (LAAW) are complex and can be challenging to map in patients after catheter ablation for atrial fibrillation (AF) or cardiac surgery. We aimed to investigate the electrophysiological characteristics AT and to devise an ablation strategy. Methods and Results: We identified 31 scar-related LAAW reentrant ATs in 22 patients after catheter ablation for AF or cardiac surgery. Activation maps of the left atrium (LA) or both atria were obtained using a high-density mapping system, and the precise mechanism and critical area for each AT were analyzed. Patients were followed up regularly in a clinic. After analyzing the activation and propagation of each AT, the scar-related LAAW ATs were classified into three types, based on mechanisms related to: (1) LAAW conduction gap(s) in 19 LA macro-reentrant ATs; (2) LAAW epicardial connection(s) in 11 LA or bi-atrial ATs; and (3) LAAW local micro-reentry in 1 LAAW AT. Multiple ATs were identified in seven patients. Effective ablation (termination or circuit change of AT) was obtained in 30 ATs by targeting the critical area identified by the mapping system. During 16.0 ± 7.6 months follow-up, recurrent AT occurred in two patients. Conclusions: Three mechanisms of scar-related AT of LAAW were identified, most of which were related to LAAW conduction gaps. Notably, epicardial AT or bi-atrial AT comprised a nonnegligible proportion. A high-density mapping system could make it possible to determine the accurate mechanism of AT and serve as a guide following ablation.

Ripple mapping-guided atrial tachycardia ablation following open-heart surgery

Ripple mapping can make the visualization of activation conduction on a 3-dimensional voltage map and is useful tool for scar-related organized atrial tachycardia (AT). This study sought to assess the efficacy of ripple mapping for interpreting reentrant circuits and critical isthmus in postoperative ATs. 34 consecutive patients with a history of mitral valve surgery (mean age, 54.5 ± 12.4 years) underwent high density (HD) RM during ATs with CARTO3v4 CONFIDENSE system. The voltage activation threshold was determined by RM over a bipolar voltage map. The identification of underlying mechanisms and ablation setting was based on RM without reviewing activation mapping. A total of 41 ATs (35 spontaneous, 6 induced) were characterized. 39 reentry circuits were successfully mapped (cycle length, 256 ± 43 ms). Of the 41 ATs, 28 were confirmed by ripple mapping alone (68%), and 12 (29%) by ripple mapping and entrainment mapping. Of 12 ATs in the left atrium, 9 (75%) needed entrainment to confirm, compared with 5 (17.8%) in the right atrium. Primary endpoint after initial ablation set was achieved in 32 of the 34 patients (94.1%). Freedom from atrial arrhythmias was 79.4% after the follow-up of 12 ± 5 months. Of the seven patients with recurrence, three underwent the repeated catheter ablation. Ripple mapping precisely delineated reentrant circuits in post-cardiac surgery AT resulting in a high success rate of ablation. Entrainment maneuvers remain useful for elucidation of complex AT circuits.

An improved window of interest for electroanatomical mapping of atrial tachycardia

PURPOSE

Diagnosis of atrial tachycardia (AT) with 3D mapping system remains challenging due to fibrosis or previous ablation. This study aims to evaluate a new electroanatomical mapping annotation setting using a window of interest adjusted at the end of the P wave (WOI_{p wave}) to identify the AT mechanism more accurately.

METHODS

Twenty patients with successful ablation of left AT using navigation system CARTO3 were evaluated. Two maps for each patient were generated offline using either conventional settings of WOI (WOI_conv.) or WOI_{p wave}. Three investigators from two centres analysed the maps blindly.

RESULTS

Mechanisms of AT were macroreentrant in 14/20 patients (70%) and focal in 6/20 (30%). WOI_{p wave} resulted in a significant increase in the percentage of correct identification of the mechanism based on mapping alone (93.3 ± 13.7% vs 58.3 ± 33.9%; p = 0.0003) compared with WOI_conv.. Diagnoses based on mapping were arrived at faster (27.8 ± 16.4 s vs 38.97 ± 13.64 s, respectively; p = 0.0231) and with a greater confidence in the diagnosis (confidence index 2.57 ± 0.45 vs 2.12 ± 0.45, respectively; p = 0.0024). With perimitral re-entry specifically "early meets late" was closer to the anatomical region of the mitral isthmus (15.9 ± 20.9 mm vs 48.77 ± 23.23 mm, respectively; p = 0.0028).

CONCLUSIONS

This study found that electroanatomical mapping acquisition with a window of interest set at the end of the P wave improves the ability to diagnose the arrhythmia mechanism based on the initial map. It is particularly beneficial in identifying area of interest for ablation in perimitral AT.