Validation of a novel mapping system and utility for mapping complex atrial tachycardias

ECGI targeted ablation for persistent AF not responding to pulmonary vein isolation: Results of a two-staged strategy (TARGET AF2)

Background

Mechanisms sustaining persistent atrial fibrillation (AF) remain unclear.

Objectives

The study sought to evaluate both the clinical outcomes and response to ablation of potential drivers in patients with recurrent persistent AF recurrence following pulmonary vein isolation (PVI).

Methods

A total of 100 patients with persistent AF of <2 years' duration underwent cryoballoon PVI (ECGI phenotyping of persistent AF based on driver burden and distribution to predict response to pulmonary vein isolation). Patients with documented recurrence of atrial arrhythmia within 12 months were recruited and underwent repeat PVI (if needed) followed by ablation of potential drivers (PDs) identified by electrocardiographic imaging (ECGI). PDs were defined as rotational activity >1.5 revolutions or focal activations. Cycle lengths were measured pre- and postablation. The primary outcome was freedom from atrial arrhythmia off antiarrhythmic drugs at 1 year as per guidelines.

Results

Of 37 patients recruited, 26 had recurrent AF and underwent ECGI-guided ablation of PDs. An average of 6.4 ± 2.7 PDs were targeted per patient. The mean ablation time targeting PDs was 15.5 ± 6.9 minutes. An ablation response occurred in 20 patients (AF termination in 6, cycle length prolongation ≥10% in 14). At 1 year, 14 (54%) of 26 patients were free from arrhythmia, and 12 (46%) of 26 were off antiarrhythmic drugs. Considering the 96 patients who completed follow-up out of the original cohort of 100 patients undergoing cryoablation in this staged strategy, freedom from arrhythmia at 1 year following the last procedure was 72 (75%) of 96, or 70 (73%) of 96 off antiarrhythmic drugs.

Conclusions

In patients with recurrent AF despite PVI, ECGI-guided ablation caused an acute response in a majority with reasonable long-term outcomes.

ECG-I Phenotyping of Persistent AF Based on Driver Burden and Distribution to Predict Response to Pulmonary Vein Isolation (PHENOTYPE-AF)

BACKGROUND

This prospective trial sought to phenotype persistent AF based on AF mechanisms using ECGI mapping to determine whether this would predict long term freedom from arrhythmia after pulmonary vein isolation (PVI).

METHODS

Patients with persistent AF of < 2 years duration underwent cryoballoon PVI. ECGI mapping was performed prior to PVI to determine potential drivers (PDs) defined as rotational activations completing ≥ 1.5 revolutions or focal activations. The co-primary end point was the association between (1) PD burden (defined as the number of PD occurrences) and (2) PD distribution (defined as the number of segments on an 18 segment model of the atria harbouring PDs) with freedom from arrhythmia at 1 year follow up.

RESULTS

Of 100 patients, 97 completed follow up and 52 (53.6%) remained in sinus rhythm off antiarrhythmic drugs. Neither PD burden nor PD distribution predicted freedom from arrhythmia (HR 1.01, 95% CI 0.99 - 1.03, p = 0.164; and HR 1.04, 95% CI 0.91 - 1.17, p = 0.591 respectively). Otherwise, the burden of rotational PDs, rotational stability, and the burden of PDs occurring at the pulmonary veins and posterior wall all failed to predict arrhythmia recurrence (all p > 0.10).

CONCLUSIONS

AF mechanisms as determined using ECGI mapping do not predict outcome after PVI for persistent AF. Further studies using different methodologies to characterise AF mechanisms are warranted. (NCT03394404) This article is protected by copyright. All rights reserved.

Comparison of the empirical linear ablation and low voltage area-guided ablation in addition to pulmonary vein isolation in patients with persistent atrial fibrillation: a propensity score-matched analysis

Background

The efficacy of pulmonary vein isolation (PVI) alone is not guaranteed for persistent atrial fibrillation (PeAF), and it is unclear which type of ablation approach should be applied in addition to PVI. This study aimed to compare outcomes and prognosis between empirical linear ablation and low-voltage area (LVA) ablation after PVI for PeAF.

Methods

We enrolled 128 patients with PeAF who were assigned to the linear ablation group (n = 64) and the LVA ablation group (n = 64) using a propensity score-matched model. After PVI and cardioversion, the patients underwent either empirical linear ablation or LVA ablation during sinus rhythm. All patients in the linear ablation group underwent both roof line and mitral valve isthmus (MVI) ablations. An electrical-guided ablation targeting LVA (< 0.5 mV) was performed in the LVA group. When there was no LVA in the LVA group, only PVI was applied. We compared the procedural outcomes and recurrence after ablation between the two groups.

Results

The baseline characteristics were well-balanced between the two groups. Fifty patients had LVA (22 and 28 patients in the linear and LVA groups). The roof and MVI lines were completed in 100% and 96.9% of the patients. During the mean follow-up of 279.5 ± 161.3 days, the LVA group had significantly lower recurrence than the linear group (15 patients [23%] vs. 29 patients [45%], p = 0.014). Thirty-five patients were prescribed antiarrhythmic drugs during the follow-up period (linear group, n = 17; LVA group, n = 18); amiodarone and bepridil were administered to most of the patients (15 and 17 patients, respectively). The difference in the prognosis was relevant among the patients with LVA, while this trend was not observed in those without LVA. The LVA ablation group demonstrated significantly lower radiofrequency energy and shorter procedural time compared to the linear ablation group. The recurrence of atrial flutter was more likely to occur in the linear group than in the LVA group (14 [22%] vs. 6 [9.4%], p = 0.052).

Conclusion

The electrophysiological-guided LVA ablation is more effective than empirical linear ablation in PeAF patients with LVA. Unnecessary empirical linear ablation might have a risk of iatrogenic gap and atrial flutter recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02460-9.

Beyond pulmonary vein isolation for persistent atrial fibrillation: sequential high-resolution mapping to guide ablation

Purpose

We aimed to evaluate whether outcomes with ablation in persistent (PsAF) and long-standing persistent (LsPsAF) AF can be improved beyond what can be achieved with pulmonary vein isolation (PVI) alone, using individualized mapping to guide ablation.

Methods

We studied 20 pts (15 M, 68 ± 11y) with PsAF (14) or LsPsAF (6) referred for first-time AF ablation. Following antral PVI, individualized mapping (IM) was performed using a high-density mapping catheter stably and fully deployed for 30 s at each of 23 ± 9 sites per patient. Activation data were reviewed, and an ablation strategy designed to intersect areas of focal and rotational activity. Mean follow-up was 429 ± 131 days. The study population was compared to a matched contemporary control cohort (CC) of 20 consecutive patients undergoing conventional ablation.

Results

Despite the IM group having a higher median comorbidities score, 3.5 vs. 2.5 in the CC group, indicating potentially more complex patients and more advanced substrate, cumulative freedom from AF after a single procedure was achieved in 94% of patients in the IM group vs. 75% in the CC group at 1 year and remained the same in both groups at the conclusion of the study (p = 0.02). There was a similar trend in atrial arrhythmia-free survival between both groups (84% vs. 67% at 1 year) that did not reach statistical significance. The procedure duration was longer in the IM group by a median of 31.5 min (p = 0.004).

Conclusions

Individualized mapping to guide AF ablation appears to achieve significantly greater AF-free survival compared to conventional PVI when applied as a primary ablation treatment. The results of this pilot study need to be confirmed in a larger, randomized trial.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10840-021-01115-7.

RETRO-MAPPING: A New Approach to Activation Mapping in Persistent Atrial Fibrillation Reveals Evidence of Spatiotemporal Stability

[Figure: see text].

Cardiac Mapping Systems: Rhythmia, Topera, EnSite Precision, and CARTO

Novel cardiac mapping systems allow a safe and highly accurate 3-D reconstruction of cardiac structures as well as fast and accurate visualization of cardiac arrhythmias. In addition, they are increasingly reducing the need for fluoroscopy in these procedures. The current state of the art, as well as the presentation of possible uses of individual systems and their limitations, is presented in this article. Cardiac mapping systems can significantly contribute to an optimal therapeutic decision making in invasive electrophysiology. This article introduces new developments of Rhythmia, Topera, EnSite Precision, and CARTO systems and provides a look ahead to the future.

Endocardial contact mapping of the left atrial appendage in persistent atrial fibrillation

INTRODUCTION

Isolation of the left atrial appendage (LAA) is often performed in persistent atrial fibrillation (AF). Propagation patterns in the LAA during AF remain to be elucidated. We sought to characterize propagation patterns in the LAA during AF in persistent AF.

METHODS

Persistent AF patients undergoing catheter ablation were studied. Pulmonary vein isolation (PVI) was performed during continuous AF. If AF was not terminated by PVI, bi-atrial mapping was performed using a multi-electrode catheter during AF. Maps were collected at each site for 30 seconds and analyzed offline with a novel software, CARTOFINDER. This software made automatic determinations of whether activation was focal or rotational. The left atrium (LA) was divided into five regions, of which the LAA was one, and the right atrium (RA) into three.

RESULTS

Eighty patients were studied (62 ± 10 years, 65 males). On average, 9.6 ± 2.2 and 4.1 ± 1.2 maps were created in the LA and RA, respectively. The LAA was mapped in 70 patients, resulting in 85 maps. In the LAA, activation was identified as focal more often than rotational (64 [91%] vs 10 [14%] patients, P < .001), seven patients displayed both. The number of focal activation events was greatest in the LAA (28.5 events/30 seconds [interquartile range, 15-54]) of the eight atrial regions. During focal activation, sites designated as earliest activation frequently covered a wide area, rather than being localized to a discrete site (5.4 ± 3.1 electrodes).

CONCLUSIONS

The results of this study suggest that focal activation is a major mechanism underlying the arrhythmogenicity of the LAA in persistent AF.

Online webinar training to analyse complex atrial fibrillation maps: A randomized trial

BACKGROUND

Specific tools have been recently developed to map atrial fibrillation (AF) and help guide ablation. However, when used in clinical practice, panoramic AF maps generated from multipolar intracardiac electrograms have yielded conflicting results between centers, likely due to their complexity and steep learning curve, thus limiting the proper assessment of its clinical impact.

OBJECTIVES

The main purpose of this trial was to assess the impact of online training on the identification of AF driver sites where ablation terminated persistent AF, through a standardized training program. Extending this concept to mobile health was defined as a secondary objective.

METHODS

An online database of panoramic AF movies was generated from a multicenter registry of patients in whom targeted ablation terminated non-paroxysmal AF, using a freely available method (Kuklik et al-method A) and a commercial one (RhythmView-method B). Cardiology Fellows naive to AF mapping were enrolled and randomized to training vs no training (control). All participants evaluated an initial set of movies to identify sites of AF termination. Participants randomized to training evaluated a second set of movies in which they received feedback on their answers. Both groups re-evaluated the initial set to assess the impact of training. This concept was then migrated to a smartphone application (App).

RESULTS

12 individuals (median age of 30 years (IQR 28-32), 6 females) read 480 AF maps. Baseline identification of AF termination sites by ablation was poor (40%±12% vs 42%±11%, P = 0.78), but similar for both mapping methods (P = 0.68). Training improved accuracy for both methods A (P = 0.001) and B (p = 0.012); whereas controls showed no change in accuracy (P = NS). The Smartphone App accessed AF maps from multiple systems on the cloud to recreate this training environment.

CONCLUSION

Digital online training improved interpretation of panoramic AF maps in previously inexperienced clinicians. Combining online clinical data, smartphone apps and other digital resources provides a powerful, scalable approach for training in novel techniques in electrophysiology.

Evaluation of a new algorithm for tracking activation during atrial fibrillation using multipolar catheters in humans

BACKGROUND

Conventional mapping techniques during atrial fibrillation (AF) are difficult to apply because of cycle length irregularity. Mapping studies are usually restricted to short durations of AF in limited regions because of the laborious manual annotation of local activation time (LAT). The purpose of this study was to test an automated algorithm to map activation during AF, with comparable accuracy to manual annotation.

METHODS

Left atrial (LA) mapping was performed using a 20-pole double loop catheter (AFocusII) in 30-second data segments from 16 patients. The new algorithm (RETRO-Mapping) was designed to detect wavefront propagation between electrodes, and display activating wavefronts on a two-dimensional representation of the catheter. Activation patterns were validated against their bipolar electrograms and with isochronal maps. The mapping protocol was approved by the research ethics committee (13/LO1169 and 14/LO1367).

RESULTS

During AF, uniform wavefront activation direction (mean ± SD, degrees) from manually constructed isochronal maps was comparable to RETRO-Propagation Map (RETRO-PM) and RETRO-Automated Direction (RETRO-AD): 1 ± 6.9 for RETRO-PM; and 2 ± 6.6 for RETRO-AD. There was no significant difference in activation direction assigned to 1373 uniform wavefronts during AF when comparing RETRO-PM with RETRO-AD (Bland-Altman mean difference: -0.1 degrees; limits of agreement: -8.0 to 8.3; 95% CI -0.4 to 0.2; (r = 0.01) R2 = < 0.005; P = .77).

CONCLUSION

We have developed and validated a new technique to map activation during AF. This technique shows comparable accuracy to that of conventional isochronal mapping with careful manual adjustment of LAT.

Left atrial scarring and conduction velocity dynamics: Rate dependent conduction slowing predicts sites of localized reentrant atrial tachycardias

BACKGROUND

Low voltage zones (LVZs) are associated with conduction velocity (CV) slowing. Rate-dependent CV slowing may play a role in reentry mechanisms.

METHODS

Patients undergoing catheter ablation for AT were enrolled. Aim was to assess the relationship between rate-dependent CV slowing and sites of localized reentrant atrial tachycardias (AT). On a bipolar voltage map regions were defined as non-LVZs [≥0.5 mV], LVZs [0.2-0.5 mV] and very-LVZs [<0.2 mV]. Unipolar electrograms were recorded with a 64-pole basket catheter during uninterrupted atrial pacing at four pacing intervals (PIs) during sinus rhythm. CVs were measured between pole pairs along the wavefront path. Sites of rate-dependent CV slowing were defined as exhibiting a reduction in CV between PI = 600 ms and 250 ms of ≥20% more than the mean CV reduction seen between these PIs for that voltage zone. Rate-dependent CV slowing sites were correlated to sites of localized reentrant ATs as confirmed with conventional mapping, entrainment and response to ablation.

RESULTS

Eighteen patients were included (63 ± 10 years). Mean CV at 600 ms was 1.53 ± 0.19 m/s in non-LVZs, 1.14 ± 0.15 m/s in LVZs, and 0.73 ± 0.13 m/s in very-LVZs respectively (p < 0.001). Rate-dependent CV slowing sites were predominantly in LVZs [0.2-0.5 mV] (74.4 ± 10.3%; p < 0.001). Localized reentrant ATs were mapped to these sites in 81.8% of cases (sensitivity 81.8%, 95% CI 48.2-97.9% and specificity 83.9%, 95% CI 81.8-86.0%). Macro-reentrant or focal ATs were not mapped to sites of rate-dependent CV slowing.

CONCLUSIONS

Rate-dependent CV slowing sites are predominantly confined to LVZs [0.2-0.5 mV] and the resultant CV heterogeneity may promote reentry mechanisms. These may represent a novel adjunctive target for AT ablation.

Automated detection of repetitive focal activations in persistent atrial fibrillation: Validation of a novel detection algorithm and application through panoramic and sequential mapping

INTRODUCTION

Identifying drivers in persistent atrial fibrillation (AF) remains challenging. We sought to validate an automated system for detection of focal activation using basket and PentaRay catheters in AF.

METHODS

Patients having ablation for atrial tachycardia (AT) and persistent AF were mapped. Thirty-second unipolar basket and PentaRay recordings were analyzed using CARTOFINDER. Focal activation or "region of interest" (ROI) was defined as more than or equal to 2 consecutive focal activations with one electrode leading relative to its neighbors with QS morphology on the unipolar electrogram. ROI was validated in AT. AF patients were mapped to (1) look for evidence of focal activations on wavefront maps, (2) evaluate whether these were detected as ROI on basket recordings, and (3) whether these sites could be identified on sequential PentaRay recordings.

RESULTS

ROIs were identified in five focal ATs but none of 16 reentrant ATs. Twenty-eight AF patients had 35 focal drivers identified from basket wavefront maps with an ablation response in all (16 cycle length slowing and 19 AF termination). Thirty focal activations were detected on basket ROI maps (86%). Twenty-three of 28 patients had sequential PentaRay mapping and 22 of 30 focal drivers in these patients (73%) were identified as ROI. These drivers had greater temporal stability (3.6 ± 0.6 vs 2.7 ± 0.6; P < 0.001), higher recurrence rate (12.4 ± 2.7 vs 7.2 ± 0.9; P < 0.001), and more frequently were associated with AF termination ( P < 0.001) compared with those not identified as ROI.

CONCLUSIONS

Focal activations can be detected in AF using sequential recordings. The ablation response at focal sources suggests they may be viable therapeutic targets.

Structural remodeling and conduction velocity dynamics in the human left atrium: Relationship with reentrant mechanisms sustaining atrial fibrillation

Background

Rate-dependent conduction velocity (CV) slowing is associated with atrial fibrillation (AF) initiation and reentrant mechanisms.

Objective

The purpose of this study was to assess the relationship between bipolar voltage, CV dynamics, and AF drivers.

Methods

Patients undergoing catheter ablation for persistent AF (<24 months) were enrolled. Unipolar electrograms were recorded with a 64-pole basket catheter during atrial pacing at 4 pacing intervals (PIs) during sinus rhythm. CVs were measured between pole pairs along the wavefront path and correlated with underlying bipolar voltage. CV dynamics within low-voltage zones (LVZs <0.5 mV) were compared to those of non-LVZs (≥0.5 mV) and were correlated to driver sites mapped using CARTOFINDER (Biosense Webster).

Results

Eighteen patients were included (age 62 ± 10 years). Mean CV at 600 ms was 1.59 ± 0.13 m/s in non-LVZs vs 0.98 ± 0.23 m/s in LVZs (P <.001). CV decreased incrementally over all 4 PIs in LVZs, whereas in non-LVZs a substantial decrease in CV was only seen between PIs 300–250 ms (0.59 ± 0.09 m/s; P <.001). Rate-dependent CV slowing sites measurements, defined as exhibiting CV reduction ≥20% more than the mean CV reduction seen between PIs 600–250 ms for that voltage zone, were predominantly in LVZs (0.2–0.5 mV; 75.6% ± 15.5%; P <.001). Confirmed rotational drivers were mapped to these sites in 94.1% of cases (sensitivity 94.1%, 95% CI 71.3%–99.9%; specificity 77.9%, 95% CI 74.9%–80.7%).

Conclusion

CV dynamics are determined largely by the extent of remodeling. Rate-dependent CV slowing sites are predominantly confined to LVZs (0.2–0.5 mV), and the resultant CV heterogeneity may promote driver formation in AF.

Characterization of drivers maintaining atrial fibrillation: Correlation with markers of rapidity and organization on spectral analysis

BACKGROUND

Better characterization of drivers in atrial fibrillation (AF) may facilitate their identification.

OBJECTIVE

The purpose of this study was to demonstrate that certain driver characteristics are associated with greater mechanistic importance in maintaining AF.

METHODS

Persistent AF was mapped in patients using the CARTOFINDER system with a 64-pole basket catheter to identify and ablate drivers with rotational or focal activity after pulmonary vein isolation. An ablation response was defined as cycle length (CL) slowing ≥30 ms or AF termination. Driver sites with an ablation response were correlated to sites of fastest CL, highest dominant frequency (DF), and greatest organization (lowest cycle length variability [CLV] and highest regularity index [RI]). Parameters predicting AF termination with driver ablation were evaluated.

RESULTS

All 29 patients had ≥1 driver identified. Forty-four potential drivers were identified. The predefined ablation response occurred with 39 drivers (89%): 23 rotational and 16 focal. During a 30-second recording, each driver occurred 8.7 ± 5.4 times and completed 3.1 ± 0.9 consecutive repetitions per occurrence. Driver sites correlated best with markers of organization, corresponding to the site of lowest CLV (29/39 [74%]) and highest RI (26/39 [67%]). Correlation with sites of fastest CL and highest DF was poor (17/39 and 15/39, respectively) and depended on driver temporal stability. Greater temporal stability (3.4 ± 0.9 vs 2.7 ± 0.6; P = .001) and driver correlation with sites of lowest CLV and highest RI (both P <.001) predicted AF termination with ablation.

CONCLUSION

Intermittent focal or rotational drivers were identified in all patients. Drivers consistently correlated to organization markers. Greater temporal stability and organization predicted AF termination with driver ablation.