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Multiple groups have reported on the usefulness of ablating in atrial regions exhibiting abnormal electrograms during atrial fibrillation (AF). Still, previous studies have suggested that ablation outcomes are highly operator- and center-dependent. This study sought to evaluate a novel machine learning software algorithm named VX1 (Volta Medical), trained to adjudicate multipolar electrogram dispersion.This study was a prospective, multicentric, nonrandomized study conducted to assess the feasibility of generating VX1 dispersion maps. In 85 patients, 8 centers, and 17 operators, we compared the acute and long-term outcomes after ablation in regions exhibiting dispersion between primary and satellite centers. We also compared outcomes to a control group in which dispersion-guided ablation was performed visually by trained operators.The study population included 29% of long-standing persistent AF. AF termination occurred in 92% and 83% of the patients in primary and satellite centers, respectively, p = 0.31. The average rate of freedom from documented AF, with or without antiarrhythmic drugs (AADs), was 86% after a single procedure, and 89% after an average of 1.3 procedures per patient (p = 0.4). The rate of freedom from any documented atrial arrhythmia, with or without AADs, was 54% and 73% after a single or an average of 1.3 procedures per patient, respectively (p 0.001). No statistically significant differences between outcomes of the primary versus satellite centers were observed for one (p = 0.8) or multiple procedures (p = 0.4), or between outcomes of the entire study population versus the control group (p 0.2). Interestingly, intraprocedural AF termination and type of recurrent arrhythmia (i.e., AF vs. AT) appear to be predictors of the subsequent clinical course.VX1, an expertise-based artificial intelligence software solution, allowed for robust center-to-center standardization of acute and long-term ablation outcomes after electrogram-based ablation.

Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Volta Medical Saint Joseph Hospital Marseille, France Background Spatiotemporal dispersion is an electrical footprint of atrial fibrillation (AF) drivers that has been successfully implemented to target extra-pulmonary veins (PVs) regions during persistent AF ablation. Purpose The aim of the study is to characterize spatiotemporal dispersion extent and location and to compare dispersion atrial localization and extent between pacing-induced AF and spontaneous AF. Methods Spatiotemporal dispersion maps were built with an artificial intelligence software (VX1, Volta Medical) and analyzed in 71 consecutives persistent (66%) and long-standing persistent (34%) AF patients admitted for a first ablation procedure. Fifty-two patients were in spontaneous AF (73%) at the outset of the procedure while AF was induced in 19 patients (27%) by burst pacing ± isoproterenol infusion. A semi-quantitative visual quantification of dispersion extent was conducted by implementing an atrial segmentation into 22 regions and a region-centered score from 0 (no dispersion) to 3 (high dispersion). Also, an automated quantification was performed as follows: (i) a gradient filter designed to extract atrial shapes from background was applied, (ii) dispersion areas were segmented using a color thresholding method, and (iii) a structuring element was used to connect segmented dispersion areas. Results The regional characterization of dispersion shows that dispersion distribution follows a similar pattern and is present in similar atrial regions, regardless of whether AF is spontaneous or induced (Figure 1). Global dispersion extent, however, is significantly higher in the left atrium of patients in spontaneous AF compared to patients with induced AF (15.43% ± 9.04 versus 9.86% ± 6.41, P=0.0025, Figure 2). Accordingly, the regional dispersion score tends to be lower when AF is induced. Dispersion hotspots are: LSPV anterior antrum -ridge (R1), RSPV anterior antrum (R5), anterior wall (R9), roof (R10), posterior wall (R11), and low left atrial septum (R15) in the left atrium. In the right atrium: low right atrial septum (R15) and posterior right atrium (R20) (Figure 1). Conclusions Artificial intelligence-enabled dispersion persistent AF mapping indicates that dispersion is reduced in induced vs. spontaneous-AF but that its distribution follows a similar pattern.

Mapping of Scar-Related VTBackground Substrate-based VT ablation is mostly based on maps acquired with ablation catheters. We hypothesized that multipolar mapping catheters are more effective for identification of scar and local abnormal ventricular activity (LAVA). Methods and results Phase1: In a sheep infarction model (2 months postinfarction), substrate mapping and LAVA tagging (CARTO®3) was performed, using a Navistar (NAV) versus a PentaRay (PR) catheter (Biosense Webster). Phase2: Consecutive VT ablation patients from a single center underwent NAV versus PR mapping. Point pairs were defined as a PR and a NAV point located within a 3D-distance of ≤3 mm. Agreement was defined as both points in a pair being manually tagged as normal or LAVA. Four sheep (4 years, 50 ± 4.8 kg) and 9 patients were included (53 ± 14 years, 8 male, 6 ischemic cardiomyopathy). Mapping density was higher within the scar with PR versus NAV (3.2 vs. 0.7 points/cm2, P = 0.001) with larger bipolar scar area (68 ± 55 cm2 vs. 58 ± 48 cm2, P = 0.001). In total, 818 point pairs were analyzed. Using PR, far-field voltages were smaller (PR vs. NAV; bipolar: 1.43 ± 1.84 mV vs. 1.64 ± 2.04 mV, P = 0.001; unipolar; 4.28 ± 3.02 mV vs. 4.59 ± 3.67 mV, P < 0.001). More LAVA were also detected with PR (PR vs. NAV; 126 ± 113 vs. 36 ± 29, P = 0.001). When agreement on LAVA was reached (overall: 72%; both LAVA, 40%; both normal, 82%) higher LAVA voltages were recorded on PR (0.48 ± 0.33 mV vs. 0.31 ± 0.21 mV, P = 0.0001). Conclusion Multipolar mapping catheters with small electrodes provide more accurate and higher density maps, with a higher sensitivity to near-field signals. Agreement between PR and NAV is low.

Unipolar Signal and Atrial Flutter AblationIntroduction Complete elimination of the negative component of the unipolar atrial electrogram recently proved predictive of lesions transmurality. We prospectively assessed its relevance as a real-time local ablative endpoint for each individual lesion created across the cavotricuspid isthmus (CTI) in order to constitute a line of bidirectionnal block during common atrial flutter (AFL) ablation. Methods and Results Sixty-two consecutive patients underwent common AFL ablation following an electrophysiological approach guided by real-time electrogram modification analysis. In 31 patients (unipolar group), the local ablative endpoint was complete elimination of the negative component of the unipolar atrial electrogram, while the other 31 patients (control group) were treated following our standard approach based on the currently used local ablative endpoint defined by a ≥50% amplitude decrease of the bipolar atrial electrogram. Bidirectional block was achieved in all patients (mean age 67.9 ± 11.5 with 80.6% of men). Mean ablation time (164.3 ± 88.3 seconds vs 332.8 ± 151.5 seconds; P < 0.001) and mean energy delivery (7.5 ± 4.1 kJ vs 14.2 ± 6 kJ; P < 0.001) were significantly shorter in the unipolar group compared to the control group. No statistical differences were seen in procedure time (68.5 ± 22.6 min vs 77.5 ± 20.2 min; P = 0.10). Conclusion Real-time unipolar electrogram modification is a relevant local endpoint during common AFL ablation and leads to a substantial reduction of ablation time and energy delivery compared to a standard ablative approach while displaying a similar short- and long-term success rate.

Background— It has been experimentally shown that elimination of the negative component of the unipolar atrial electrogram (R morphology completion) during radiofrequency applications reflects transmural lesions creation. Subsequently, it has been clinically suggested that such a transmurality can be either irreversible or reversible. The present study is aimed to determine, at the histological level, whether transmural lesions, assessed by R morphology completion, might indeed be reversible in some circumstances or not. Methods and Results— In 6 Mongrel hound dogs, superior and inferior vena cavae were isolated and individual lesions were created in the right atrium using radiofrequency energy (30 W/48°C/17 mL/min as presettings and 10 g of force in average) under CARTO guidance. Five types of lesions were created; R + 0: termination of ablation at the time of R morphology completion; R + 5, R + 10, or R + 20: extension of ablation for 5, 10, or 20 seconds, respectively, after R morphology achievement; and conventional: radiofrequency applications lasting 30 seconds irrespective of the atrial electrogram modification. All conventional, R + 5, R + 10, and R + 20 lesions were necrotic and transmural, whereas some R + 0 lesions were not (comprising a part of necrosis and a part of reversible cell damage). Interestingly, surrounding organ injuries were observed after conventional, R + 10, and R + 20 radiofrequency applications but were not observed after R + 0 and R + 5 applications. Conclusions— Elimination of the negative component of the unipolar atrial electrogram reflects, in general, irreversible transmural necrosis creation. In some cases, however, it translates transmural lesion only (with potential reversibility) likely related to transient cell damage creation.

Background— In patients treated for paroxysmal atrial fibrillation, the pulmonary vein (PV) reconnection rate is substantial and may be related to the lack of transmurality achievement while performing PV isolation (PVI). It has been experimentally demonstrated that positive unipolar atrial electrogram completion, when applying radiofrequency energy, was associated with transmural lesions. In this regard, we seek to determine whether the unipolar signal modification may be an appropriate end point for point-by-point radiofrequency application and find out whether it could improve the paroxysmal atrial fibrillation ablation results in humans. Methods and Results— Fifty consecutive patients (61±8 years old, 41 men) with paroxysmal atrial fibrillation underwent PVI using Carto and Lasso. Each radiofrequency application lasted until development of a completely positive unipolar electrogram. Fifty patients (63±9 years old, 40 men), who previously underwent PVI following the standard approach of our institution, corresponded to the control group. All PVs were isolated in all patients of both groups. However, the procedural and ablation times were significantly lower in the unipolar group compared with those of the control group, whereas the PV reconnection rate, after 30 minutes of waiting time, was not significantly different. Overall, 21±4 months after 1 PVI session, the sinus rhythm maintenance rate without antiarrhythmic drugs was significantly higher ( P =0.027) in the unipolar group (88%) compared with that of the control group (70%). Conclusions— Unipolar signal modification is a useful end point for radiofrequency energy delivery in patients with paroxysmal atrial fibrillation who undergo PVI and leads to a substantial midterm sinus rhythm maintenance rate.

Aims In the setting of congestive heart failure (CHF), atrial fibrillation (AF) ablation can improve clinical status and the left ventricular ejection fraction (LVEF) value. However, the impact of AF ablation on the implantable cardioverter defibrillator (ICD) indication has never been specifically addressed. Methods and results Study subject were six CHF (mean age 61.1 ± 6.9 years, mean LVEF 25.8 ± 7.3%) patients refractory to conventional medical treatment with long-lasting AF unresponsive to external cardioversion. Five patients had an idiopathic dilated cardiomyopathy (DCM) and one had an ischaemic cardiomyopathy (ICM). Their New York Heart Association (NYHA) class was III–IV. Two patients had renal insufficiency. No patient had left ventricular delay. All patients underwent AF ablation. LVEF and NYHA class were dramatically improved in the five DCM patients. New York Heart Association class, but not the LVEF, was improved in the ICM patient. A redo ablative procedure was undertaken in four of five DCM patients and in the ICM patient due to arrhythmia recurrence. Left ventricular ejection fraction and NYHA were improved again in the DCM patients (56 ± 4.4%, I–II, respectively) and led to ICD indication preclusion. The LVEF remained low in the ICM patient (30%) and led to ICD insertion. Sinus rhythm has been stable during the 18.1 ± 5.7 months follow-up period. Conclusion Atrial fibrillation ablation in CHF patients can improve both the clinical status of patients and their LVEF, especially among those affected by DCM. The LVEF improvement has the potential to preclude the indication for a primary prevention ICD insertion.