High-density Mapping System Research Articles

Novel cryoballoon technology for atrial fibrillation ablation: Impact of pulmonary vein variant anatomy, cooling characteristics, and 1-year outcome from the CHARISMA registry

BackgroundNo data have been reported on cooling characteristics and the impact of variant pulmonary vein (PV) anatomy on atrial fibrillation (AF) recurrences after POLARx cryoballoon (CB) ablation. ObjectiveThe purpose of this study was to analyze the impact of PV anatomy variants and cooling characteristics after CB ablation from a large multicenter prospective registry. MethodsThe primary end point was defined as 1-year absence of any atrial tachyarrhythmias (ATAs: AF/atrial flutter/atrial tachycardia). Correlation between ATA recurrences and anatomy variants/cooling characteristics were evaluated. The secondary outcome was the rate of major periprocedural complications. ResultsA total of 429 consecutive patients diagnosed with paroxysmal AF (83.4%) or persistent AF (peAF; 16.6%) were enrolled. Twenty-eight patients (6.6%) exhibited an anatomical variant (common ostium: 4.0%; adjunctive PV: 2.6%). Nadir temperature, thaw time, and total deflation time were different between standard PVs and PV variants. After the blanking period, over a mean of 431 ± 99 days of follow-up, 63 patients (14.7%) suffered an ATA recurrence. Patients with recurrences had both a shorter thaw time (18.5 ± 7 seconds vs 19.8 ± 7 seconds; P = .0012) and a shorter total deflation time, whereas time to isolation was longer (57.4 ± 42 seconds vs 49.1 ± 33 seconds; P = .04). Patients with anatomy variants showed a similar ATA recurrence rate (5 of 28 [17.9%]) to the standard PV anatomy group (58 of 401 [14.5%]) (P = .584), with a hazard ratio (HR) of 1.43 (95% confidence interval [CI] 0.49–4.13; log-rank, P = .4384). After adjusting for confounders, heart failure (HR 4.12; 95% CI 1.75–9.73; P = .0013) and peAF (HR 1.81; 95% CI 1.03–3.18; P = .0433) remained associated with ATA recurrence during follow-up. ConclusionThe POLARx CB system demonstrated long-term efficacy, along with a safe profile, in both patients with paroxysmal AF and those with peAF, regardless of the presence PV variants. Time to isolation was longer in patients with ATA recurrences during follow-up. Clinical Trial RegistrationCatheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice (CHARISMA). ClinicalTrials.gov identifier: NCT03793998. Registration date: January 4, 2019.

Contact-force local impedance algorithm to guide effective pulmonary vein isolation in AF patients: 1-year outcome from an international multicenter clinical setting.

The combination of highly localized impedance (LI) and contact force (CF) may improve tissue characterization and lesion prediction during radiofrequency (RF) pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF). We report the outcomes of our acute and long-term clinical evaluation of CF-LI-guided PVI in consecutive AF ablation cases from an international multicenter clinical setting. Three hundred twenty-four consecutive patients from 20 European centers undergoing RF catheter ablation with the Stablepoint™ catheter were enrolled in the CHARISMA registry. Of these, 275 had a minimum follow-up of 1year and were included in the primary analysis. The mean procedure duration was 115 ± 47min, and the mean fluoroscopy time was 9.9 ± 6min. At the end of the procedures, all PVs had been successfully isolated in all study patients. Minor complications were reported in 12 patients (4.4%). At 1year, 36 (13.1%) patients had had an AF recurrence, and freedom from antiarrhythmic drugs and AF recurrence was achieved in 228 (82.9%) patients. The recurrence rate was higher in patients with persistent AF (21/116, 18.1%) than in those with paroxysmal AF (15/159, 9.4%; p = 0.0459). On multivariate logistic analysis adjusted for baseline confounders, only time > 6months from first diagnosis of AF to ablation (HR = 2.93, 95%CI 1.03 to 8.36, p = 0.0459) was independently associated with recurrences. An ablation strategy for PVI guided by CF-LI technology proved safe and effective and resulted in a low recurrence rate of AF over 1-year follow-up, irrespective of the underlying AF type. Catheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice. (CHARISMA). URL: http://clinicaltrials.gov/ Identifier: NCT03793998.

Improved procedural workflow for catheter ablation of paroxysmal AF with high density mapping system and advanced technology: insights from a multicenter, international study

Abstract Background A high incidence of pulmonary vein (PV) reconnection has been reported in patients with clinical recurrences of AF. Low-voltage activity beyond PVs (e.g. antral activity potentials, RAP) likely represent vulnerabilities in antral lesion sets and they may contribute to ablation failures. Purpose The aim of this study is to validate a structured application of an approach that includes the complete abolition of any antral potential achieving electrical quiescence in antral regions. Methods DELETE AF is a prospective, single-arm, international post-market cohort study. Consecutive patients from 10 centers who were undergoing radiofrequency ablation of paroxysmal AF were included. The Lumipoint map-analysis tool was used sequentially on each PV component. Post-ablation, all patients were monitored with ambulatory event monitoring, starting within 30 days post-ablation to proactively detect and manage any recurrences within the 90-day blanking period, as well as Holter monitoring at 3, 6, 9, and 12 months post-ablation. Additional ECG monitoring were performed as indicated by patient symptoms. The ablation endpoint was PV isolation (PVI). Long-term outcome was the recurrence of AF over follow-up. Data are reported as median [IQ range]. Results One-hundred ten cases of AF ablation were analyzed: 28 (25.5%) females, age=63[56-69] years, 24 (21.8%) patients with a history of AT/AFL. The procedure duration was 58[24-76] min (RF delivery time=18[12-28] min, number of ablation spots=77[44-101]) and the fluoroscopy time was 13[9-19] min. Thirty-eight (34.5%) were repeat ablation: in these patients after initial mapping a total of 114 PV gaps (PVGs) in 29 (76.3%) patients and 69 RAPs in 15 patients (39.5%) were found. After ablation, a total of 5 early PVGs in 2 (1.8%) patients (all in de novo procedures) and a total of 10 RAPs in 7 (6.3%) patients (3 out 38 -7.9%- of repeat ablations vs 4 out 72 -5.6%- of de novo cases, p=0.690) were detected after first remapping. Each residual PVG was first targeted and additional focal ablations were performed at any low-voltage propagation suspected within the region of previous antral ablation. Acute procedural success was 100%, with all PVs successfully isolated and RAPs completely abolished in all study patients except for one that still exhibited a residual low-voltage antral signal after adenosine infusion with no PV conduction. Eighty-six (78.2%) patients had complete follow-up information. During the 90-day blanking period, 8 (9.2%) patients experienced an early recurrence. After the blanking period, over a follow-up of 357[190-380] days, 13 patients (15.1%) suffered an AF recurrence (time to recurrence: 207[144-300] days). No major complications or adverse events occurred. Conclusion A structured ablation workflow for catheter ablation, with consistent high-density mapping and improved diagnostic tools to guide the ablation, proved to be safe and effective in paroxysmal AF.

Comparison of voltages between atria: differences in sinus rhythm and atrial fibrillation

BackgroundUltra high-density mapping systems allow for comparison of atrial electroanatomical maps in unprecedented detail. Atrial scar determined by voltages and surface area between atria, rhythm and atrial fibrillation (AF) types was assessed.MethodsLeft (LA) and right atrial (RA) maps were created using Rhythmia HDx in patients listed for ablation for paroxysmal (PAF, sinus rhythm (SR) maps only) or persistent AF (PeAF, AF and SR maps). Electrograms on corresponding SR/AF maps were paired for direct comparison. Percentage surface area of scar was assigned low- (LVM, ≤ 0.05 mV), intermediate- (IVM, 0.05–0.5 mV) or normal voltage myocardium, (NVM, > 0.5 mV).ResultsThirty-eight patients were recruited generating 96 maps using 913,480 electrograms. Paired SR-AF bipolar electrograms showed fair correlation in LA (Spearman’s ρ = 0.32) and weak correlation in RA (ρ = 0.19) and were significantly higher in SR in both (LA: 0.61 mV (0.20–1.67) vs 0.31 mV (0.10–0.74), RA: 0.68 mV (0.19–1.88) vs 0.47 mV (0.14–1.07), p < 0.0005 both). Voltages were significantly higher in patients with PAF over PeAF, (LA: 1.13 mV (0.39–2.93) vs 0.52 mV (0.16–1.49); RA: 0.93 mV (0.24–2.46) vs 0.57 mV (0.17–1.69)). Minimal differences were seen in electrogram voltages between atria.Significantly more IVM/LVM surface areas were seen in AF over SR (LA only, p < 0005), and PeAF over PAF (LA: p = 0.01, RA: p = 0.04). There was minimal difference between atria within patients.ConclusionsUltra high-density mapping shows paired electrograms correlate poorly between SR and AF. SR electrograms are typically (but not always) larger than those in AF. Patients with PeAF have a lower global electrogram voltage than those with PAF. Electrogram voltages are similar between atria within individual patients.

Use of the advisor™ HD Grid mapping catheter in transcatheter ablation of atrial arrhythmias in palliated CHD and children without CHD.

In this study, we describe our experience utilising Advisor™ High Density (HD) Grid mapping catheter in transcatheter ablation of intraatrial re-entrant and focal atrial tachycardias with or without CHD. Forty-five consecutive patients with intraatrial re-entrant and focal atrial tachycardia who underwent a transcatheter ablation procedure by using Advisor™ HD Grid mapping catheter and high-density mapping system in our hospital from January 2017 to January 2023 were included into the study. The mean age of the patients was 14.2 ± 7.3 years (6-32 years), and the mean weight was 48.3 ± 16.2 kg (22-83 kg). Of the total 45 patients, 21 were intraatrial re-entrant tachycardia and 25 were focal atrial tachycardia. Of the 21 re-entrant circuits, 15 were classified as cavotricuspid isthmus-dependent and 5 were non-cavotricuspid isthmus-dependent. In one patient, two re-entrant circuits were identified. A transbaffle ablation was successfully performed from the left atrium in one patient. Of the 25 focal atrial tachycardia, 19 were from right atrium and 6 were from left atrium. A cryoablation was performed in only one patient and radiofrequency ablation in others. The mean procedure time was 180 ± 64 minutes. The mean follow-up period was 69.3 ± 35.3 months. Acute success was 95.5%. Recurrence was noted in two patients (4.4%). Advisor™ HD Grid mapping catheter was found to be safe and achieved an acceptable success in transcatheter ablation of patients with intraatrial re-entrant tachycardia and focal atrial tachycardias.

Delineation of conduction gaps of linear lesions during atrial fibrillation ablation using ultra-high-density mapping.

Linear lesions are routinely created by radiofrequency catheter ablation. Unwanted electrical conduction gaps can be produced and are often difficult to ablate. This study aimed to clarify the characteristics of conduction gaps during atrial fibrillation ablation by analysing bidirectional activation maps using a high-density mapping system (RHYTHMIA). This retrospective study included 31 patients who had conduction gaps along pulmonary vein (PV) isolation or box ablation lesions. Activation maps were sequentially created during pacing from the coronary sinus and PV to reveal the earliest activation site, defined by the entrance and exit. The locations, length between the entrance and exit (gap length), and direction were analysed. Thirty-four bidirectional activation maps were drawn: 21 were box isolation lesions (box group), and 13 were PV isolation lesions (PVI group). Among the box group, nine conduction gaps were present in the roof region and 12 in the bottom region, while nine in right PV and four in left PV among the PVI group. Gap lengths in the roof region were longer than those in the bottom region (26.8 ± 11.8 vs. 14.5 ± 9.8 mm; P = 0.022), while those in right PV tended to longer than those in left PV (28.0 ± 15.3 vs. 16.8 ± 8.0 mm, P = 0.201). The entrances and exits of electrical conduction gaps were separated, especially in the roof region, indicating that epicardial conduction might contribute to gap formation. Identifying the bidirectional conduction gap might indicate the location and direction of epicardial conduction.

Clinical outcomes of high-density mapping for atypical atrial flutter ablation

Abstract Background High-density mapping is increasingly used in catheter ablation of complex arrhythmias. In atypical atrial flutters (AAFl), high-density mapping can provide a more accurate delineation of the arrhythmic circuit. This promotes acute procedural success, but follow-up data on clinical outcomes are scarce. Purpose To study procedural characteristics and arrhythmia recurrence of high-density mapping-guided AAFl ablation. Methods In this monocenter prospective observational cohort study, we included patients that were treated for AAFl using a high-density mapping system with a grid-patterned mapping catheter. We evaluated acute procedural success and atrial flutter recurrence at follow-up. Acute success was defined as non-inducibility of atrial flutters. Arrhythmia recurrence was defined by electrocardiographic documentation of atrial flutter. Results Between April 2018 and July 2020, 65 patients (69% male; age 65±8yr; 69% prior PVI; 60% prior cardiac surgery) were included in this study. A total of 100 AAFl were observed during the procedures. The flutter circuit was unmappable for 14 flutters in 11 patients (17%). Critical isthmuses were identified and ablated in 32 patients (49%). Other ablation strategies included linear ablation lesions (i.e., roof in 25% of patients, box in 9%, anterior in 35%, left lateral mitral in 17%), re-PVI (11%), septal (8%) and right atrial (8%) ablation. Acute procedural success was achieved in 86% of the cohort. During a follow up of 1.5±0.7 years, 38% of the cohort had recurrence of an atypical atrial flutter for which 23% had a re-intervention (repeat flutter ablation in 11% patients and his ablation with pacemaker implantation in 14%). Atypical atrial flutter recurrence was associated with presence of an unmappable flutter (HR: 2.7, 95% CI [1.1–6.4], p=0.03) and critical isthmus ablation (HR: 0.40, 95% CI [0.17–0.93], p=0.03). Conclusions Despite high-density mapping, 38% of patients had recurrence of an AAFl at follow-up. Presence of an unmappable flutter was associated with atrial flutter recurrence while critical isthmus ablation was associated with freedom from atrial flutter recurrence. Funding Acknowledgement Type of funding sources: None.

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.

UK multi-centre retrospective study of the learning curve and relative performance of the rhythmia high density mapping system for atrial ablation

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): University Hospital Southampton Background Rhythmia HDx® is a novel ultra-high density electroanatomical mapping system using an innovative 64 electrode basket catheter. A learning curve is a recognised phenomenon for any new technology and was examined in this study. Purpose Comparison of performance, long-term success, and complications using Rhythmia for atrial ablation in the UK. Methods Retrospective data collection from three centres across the UK from the introduction of Rhythmia. Patients were matched with controls who had undergone ablation using the well-established Carto3 mapping system. Assessed were: fluoroscopy, radiofrequency ablation and procedure times; acute and long term success, and complications. Results 253 study patients with 253 controls were included. Significant correlations existed between procedural efficiency metrics and centre experience for de novo atrial fibrillation (AF) ablation (procedure time, Spearman’s ρ = -0.624; ablation time, ρ = -0.795), and de novo atrial flutter (AFlut) ablation (ablation time, ρ = -0.566; fluoroscopy time, ρ = -0.520). No such correlations existed for redo AF, redo AFlut, de novo atrial tachycardia (AT), or redo AT cases. For de novo AF and AFlut, procedural efficiency metrics were significantly improved after 10 procedures in each centre, (procedure time [AF only, p = 0.001], ablation time [AF, p &amp;lt; 0.0005; AFlut p &amp;lt; 0.0005] and fluoroscopy time [AFlut only, p = 0.0022]), and became comparable to controls (Figures 1 and 2). Acute success and long-term success did not see significant improvement with experience but were comparable to the control group. There was no relationship between experience and complications, which were comparable to Carto3 (3.6% in both groups). Conclusion A short learning curve exists with the use of Rhythmia HDx for standardised procedures (de novo AF / AFlut). Procedural performance improves and becomes comparable to Carto3 following 10 cases at each centre. Clinical outcomes at 6 and 12 months, and complications are not affected by this learning curve and remain comparable with controls.

Optimized radiofrequency lesions through local impedance guidance for effective CTI ablation in right atrial flutter.

Although radiofrequency (RF) catheter ablation of cavo-tricuspid isthmus (CTI) is an established treatment for typical right atrial flutter (RAFL), it remains to be established whether local tissue impedance (LI) is able to predict effective CTI ablation and what LI drop values during ablation should be used to judge a lesion as effective. We aimed to investigate the ability of LI to predict ablation efficacy in patients with RAFL. RF delivery was guided by the DirectSense™ algorithm. Successful single RF application was defined according to a defragmentation of atrial potentials (DAP), reduction of voltage (RedV) by at least 80% or changes on unipolar electrogram (UPC). The ablation endpoint was the creation of bidirectional conduction block (BDB) across the isthmus. 392 point-by-point RF applications were analyzed in 48 consecutive RAFL patients. The mean baseline LI was 105.4±12Ω prior to ablation and 92.0±11Ω after ablation (p<0.0001). According to validation criteria, absolute drops in impedance were larger at successful ablation sites than at ineffective ablation sites (DAP: 17.8±6Ω vs. 8.7±4Ω; RedV: 17.2±6Ω vs. 7.8±5Ω; UPC: 19.6±6Ω vs. 10.1±5Ω, all p<0.0001). LI drop values significantly increased according to the number of criteria satisfied (ranging from 7.5Ω to 19.9). BDB was obtained in all cases. No procedure-related adverse events were reported. A LI-guided approach to CTI ablation was safe and effective in treating RAFL. The magnitude of LI drop was associated with effective lesion formation and BDB and could be used as a marker of ablation efficacy. Catheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice (CHARISMA). URL: http://clinicaltrials.gov/ Identifier: NCT03793998.

Improved procedural workflow for catheter ablation of paroxysmal AF with high-density mapping system and advanced technology: Rationale and study design of a multicenter international study.

BackgroundThe antral region of pulmonary veins (PV)s seems to play a key role in a strategy aimed at preventing atrial fibrillation (AF) recurrence. Particularly, low‐voltage activity in tissue such as the PV antra and residual potential within the antral scar likely represent vulnerabilities in antral lesion sets, and ablation of these targets seems to improve freedom from AF. The aim of this study is to validate a structured application of an approach that includes the complete abolition of any antral potential achieving electrical quiescence in antral regions.MethodsThe improveD procEdural workfLow for cathETEr ablation of paroxysmal AF with high density mapping system and advanced technology (DELETE AF) study is a prospective, single‐arm, international post‐market cohort study designed to demonstrate a low rate of clinical atrial arrhythmias recurrence with an improved procedural workflow for catheter ablation of paroxysmal AF, using the most advanced point‐by‐point RF ablation technology in a multicenter setting. About 300 consecutive patients with standard indications for AF ablation will be enrolled in this study. Post‐ablation, all patients will be monitored with ambulatory event monitoring, starting within 30 days post‐ablation to proactively detect and manage any recurrences within the 90‐day blanking period, as well as Holter monitoring at 3, 6, 9, and 12 months post‐ablation. Healthcare resource utilization, clinical data, complications, patients' medical complaints related to the ablation procedure and patient's reported outcome measures will be prospectively traced and evaluated.DiscussionThe DELETE AF trial will provide additional knowledge on long‐term outcome following a structured ablation workflow, with high density mapping, advanced algorithms and local impedance technology, in an international multicentric fashion. DELETE AF is registered at ClinicalTrials.gov (NCT05005143).

Initial Experience in Ablation of Non-coronary Cusp PVCs by using High-density Mapping System (Rhythmia)

Initial Experience in Ablation of Non-coronary Cusp PVCs by using High-density Mapping System (Rhythmia)

High density mapping guided partial antral ablation for a pulmonary vein isolation

The muscular discontinuities at the pulmonary vein (PV)–left atrial (LA) junction are known. The high-density mapping may help to find the muscular discontinuity. This study evaluated the efficacy of a partial antral ablation for a pulmonary vein (PV) isolation using high density (HD) mapping. A total of 60 drug-refractory atrial fibrillation (AF) patients undergoing catheter ablation were enrolled. The detailed activation mapping of each PV and LA junction was performed using an HD mapping system, and each PV segment’s activation pattern was classified into a “directly-activated from the LA” or “passively-activated from an adjacent PV segment” pattern. The antral ablations were performed at the directly-activated PV segments only when the PV had “passively-activated segments”. If the PV did not contain passively-activated segments, a circumferential antral ablation was performed on those PVs. A “successful partial antral ablation” was designated if the electrical isolation of targeted PV was achieved by ablation at the directly-activated segments only. If the isolation was not achieved even though all directly-activated segments were ablated, a “failed partial antral ablation” was designated, and then a circumferential ablation was performed. Among 240 PVs, passively-activated segments were observed in 140 (58.3%) PVs. Both inferior PVs had more passively-activated segments than superior PVs, and the posteroinferior segments had the highest proportion of passive activation. The overall rate of successful partial antral ablation was 85%. The atrial tachyarrhythmia recurrence was observed in 10 patients (16.7%) at 1-year. HD mapping allowed the evaluation of the detailed activation patterns of the PVs, and passively-activated segments may represent muscular discontinuity. Partial antral ablation of directly-activated antral segments only was feasible and effective for a PVI.

Electrophysiologic evidence of epicardial connections between low right atrium and remote right atrial region or coronary sinus musculature: Relevance for catheter ablation of typical atrial flutter

The coronary sinus (CS) is surrounded by a myocardial coat with extensive connections to the left and right atria that contributes to the interatrial electrical connection. Whereas epicardial connections between CS musculature and the left atrium have largely been demonstrated, clinically relevant epicardial connections from the CS musculature toward the low right atrium (LRA) and epicardial connections between two regions of the right atrium remain questionable ( Fig. 1 ). Five patients underwent electrophysiology (EP) study for typical atrial flutter (AFl) using either conventional multipolar catheters (four patients) or three-dimensional high-density mapping system (one patient). All five patients had a similar sequence of events during the EP studies. After several cavotricuspid isthmus (CTI) radiofrequency (RF) applications, double potentials were recorded along the ablation line while tachycardia persisted. The right atrial activation pattern strongly suggested the presence of a complete endocardial CTI line of the block. Based on the detailed conventional atrial mapping, RF applications at the middle cardiac vein/CS ostium allowed sinus rhythm restoration in four patients. High-density mapping showed an early breakthrough site at the septal side of the ablation line, close to the CS ostium during counterclockwise AFl, in the fifth patient. RF applications at this site resulted in tachycardia termination. Our observations suggested the existence of epicardial fibers connecting the LRA with either the CS musculature or a remote right atrial region. When AFl ablation fails whereas evidence for the local endocardial block is observed, the operators should integrate this finding in the diagnosis and ablation strategy.

Mapping strategies for premature ventricular contractions-activation, voltage, and/or pace map.

Ahigh premature ventricular contraction (PVC) burden is associated with an increase in cardiovascular mortality and may become clinically apparent through palpitations, reduced physical capacity or PVC-induced cardiomyopathy. Catheter ablation has been shown to be amore effective tool to treat patients with ahigh PVC burden than medical therapy alone. Current recommendations list catheter ablation as aclassI option in patients with symptomatic idiopathic outflow tract PVCs as well as in patients with suspected PVC-induced cardiomyopathy. Careful planning is necessary to maximize efficiency and outcome of the ablation procedure. Prediction of the most likely PVC origin by studying the 12-lead electrocardiogram (ECG) is important. Ahigh burden of spontaneous PVCs is associated with abetter outcome during and after the procedure; pharmacological provocation can be performed. Developments in high density mapping systems have greatly advanced accuracy and efficiency of arrhythmia mapping in recent years. Different systems are now available that allow the simultaneous use and integration of different mapping information in an automated manner. Voltage mapping, activation mapping and pace mapping are used in clinical practice today. Activation mapping is used to visualize the area of earliest activation. While it is avery accurate tool, it relies on ahigh burden of spontaneous PVCs. Pace mapping aims to find the target area by means of stimulation and comparison of paced QRS complexes with the clinical PVC. Today, mostly acombination of both methods is used to maximize procedure outcome and efficiency. While voltage mapping plays aprimary role in the mapping of substrate-based sustained arrhythmias in patients with underlying structural heart disease, activation and pace mapping are the methods of choice for PVC mapping.

High-density mapping of Koch's triangle during sinus rhythm and typical AV nodal reentrant tachycardia: new insight.

Atrial activation during typical atrioventricular nodal reentrant tachycardia (AVNRT) exhibits anatomic variability and spatially heterogeneous propagation inside the Koch's triangle (KT). The mechanism of the reentrant circuit has not been elucidated yet. Aim of this study is to describe the distribution of Jackman and Haïssaguerre potentials within the KT and to explore the activation mode of the KT, in sinus rhythm and during the slow-fast AVNRT. Forty-five consecutive cases of successful slow pathway (SP) ablation of typical slow-fast AVNRT from the CHARISMA registry were included. The KT geometry was obtained on the basis of the electroanatomic information using the Rhythmia mapping system (Boston Scientific) (mean number of points acquired inside the KT = 277 ± 47, mean mapping time = 11.9 ± 4min). The postero-septal regions bounded anteriorly by the tricuspid annulus and posteriorly by the lateral wall toward the crista terminalis showed a higher prevalence of Jackman potentials than mid-postero-septal regions along the tendon of Todaro and coronary sinus (CS) (98% vs. 16%, p < 0.0001). Haïssaguerre potentials seemed to have a converse distribution across the KT (0% vs. 84%, p < 0.0001). Fast pathway insertion, as located during AVNRT, was mostly recorded in an antero-septal position (n = 36, 80%), rather than in a mid-septal (n = 6, 13.3%) or even postero-septal (n = 3, 7%) location. During typical slow-fast AVNRT, two types of propagation around the CS were discernible: anterior and posterior, n = 31 (69%), or only anterior, n = 14 (31%). During the first procedure, the SP was eliminated, and acute procedural success was achieved (median of 4 [3-5] RF ablations). High-density mapping of KT in AVNRT patients both during sinus rhythm and during tachycardia provides new electrophysiological insights. A better understanding and a more precise definition of the arrhythmogenic substrate in AVNRT patients may have prognostic value, especially in high-risk cases. Catheter Ablation of Arrhythmias With High Density Mapping System in the Real World Practice (CHARISMA) URL: http://clinicaltrials.gov/ Identifier: NCT03793998.

Electrophysiologic evidence of epicardial connections between low right atrium and remote right atrial region or coronary sinus musculature: Relevance for catheter ablation of typical atrial flutter.

The coronary sinus (CS) is surrounded by a myocardial coat with extensive connections to the left and right atria that contributes to the interatrial electrical connection. Whereas epicardial connections between CS musculature and the left atrium have largely been demonstrated, clinically relevant epicardial connections from the CS musculature toward the low right atrium (LRA) and epicardial connections between two regions of the right atrium remain questionable. Five patients underwent electrophysiology (EP) study for typical atrial flutter (AFl) using either conventional multipolar catheters (four patients) or three-dimensional high-density mapping system (one patient). All five patients had a similar sequence of events during the EP studies. After several cavotricuspid isthmus (CTI) radiofrequency (RF) applications, double potentials were recorded along the ablation line while tachycardia persisted. The right atrial activation pattern strongly suggested the presence of a complete endocardial CTI line of the block. Based on the detailed conventional atrial mapping, RF applications at the middle cardiac vein/CS ostium allowed sinus rhythm restoration in four patients. High-density mapping showed an early breakthrough site at the septal side of the ablation line, close to the CS ostium during counterclockwise AFl, in the fifth patient. RF applications at this site resulted in tachycardia termination. Our observations suggested the existence of epicardial fibers connecting the LRA with either the CS musculature or a remote right atrial region. When AFl ablation fails whereas evidence for the local endocardial block is observed, the operators should integrate this finding in the diagnosis and ablation strategy.

P957Characteristics of atrial tachycardia after mitral surgey via biatrial trans-septal approach using high density mapping system

Abstract Background The biatrial trans-septal approach (BTSa) ameliorates mitral valve (MV) exposure in difficult cases when routine left atriotomy doesnt"t allow it. Main steps are an oblique incision on the right atrium (RA), reaching medially the right pulmonary veins (PV), a septal incision from the fossa ovalis, extended up to reach the first incision, then on the left atrium (LA). Purpose We aim to study the arrhythmic burden in this post-surgical context, focusing on atrial tachycardia (AT), to investigate the complexity of several possible circuits. Methods All patients (&amp;gt;18yo) with previous MV surgery via BTSa for MV repair or replacement, who underwent ablation of AT from January 2017 to September 2019, were enrolled. Patients ablated for persistent or paroxysmal AF, or with AF during the index procedure were excluded. Patients with associated surgery on other valves or congenital defects, coronary, surgical or percutaneous rhythm interventions weren’t excluded. Electroanatomical mapping was created using 2 different high-density mapping system. Substrate and activation map and radio-frequency (RF) ablation (25-50W, Ablation Index target 400) were realized. Cartographies were analysed to evaluate AT re-entry circuit, critical isthmus (CI) location and characterization, atrial vulnerability. Procedural outcomes (AT termination, sinus rhythm (SR) restoration, anti-arrhythmic drugs (AAD) withdrawal), and peri-procedural complications were also evaluated. Results We enrolled 49 patients (median age 57 ± 15), finding a maximum of 5 AT per procedure (2 ± 1). A total of 112 AT were mapped: the majority (72%) were persistent AT, 8,2% common atrial flutter. Cycle length was 314 ± 74 msec, with proximal-distal activation of coronary sinus (78%). A multiple re-entry circuit was observed in 70% of index AT. We identified 152 critical isthmus (maximum 5 per procedure). Only 27,9% of our patients had a single CI; CTI was the most frequent one (n = 37), envolved in 33% of all AT, while BTS scars altogether were envolved in 65% AT. A complete AT circuit was mapped in the RA, the LA and both atria in respectively 49%, 11,5% and 39%AT. The distribution of CIs is shown in figure 1. Biatrial and left AT leads to superior procedure, RF and fluoroscopy duration (p &amp;lt;0,05). SR was restored in 93,4%of patients, requiring a DC shock in 4 cases. Immediate AAD withdrawal was achieved after 41%procedures. No pericardial, oesophageal, vascular or phrenic complication occurred. 4 pace-maker implantations were realized because of 3 interatrial, 2 AV block and a sinus node dysfunction. Conclusions AT occurring after a BTSa have a high prevalence of multiple re-entry circuits with multiple critical isthmus. Ablation in this context is feasible and safe but often requires a left atrial access. Mapping of both atria should be considered to identify critical isthmus and tailored ablation strategy. Abstract Figure 1. Critical Isthmus Distribution

Impact of high-density mapping on outcome of the second ablation for atrial fibrillation.

Identification of a conduction gap between the left atrium and pulmonary vein (LA-PV gap) and the circuit of atrial tachycardia after pulmonary vein isolation (PVI) is an important process during the second ablation for atrial fibrillation (AF). The high-density mapping system RHYTHMIA® is useful for identification of an LA-PV gap and the circuit of atrial tachycardia. Therefore, this study was performed to investigate the effect of RHYTHMIA® in terms of the outcome of the second ablation for AF. One hundred patients underwent a second ablation for AF in our institute from April 2015 to December 2018. We retrospectively evaluated 49 patients using RHYTHMIA® (group 1) and 51 patients using the conventional method with additional anatomical guide by CARTO® system. In group 1, we performed redo PVI for 41 patients with 49 LA-PV countable gaps and ablation for other atrial arrhythmias in 7 patients. In group 2, we performed redo PVI in 40 patients with 33 LA-PV countable gaps and ablation for other atrial arrhythmias in 9 patients. Three and two unstable arrhythmias in each group were not ablated. The final recurrence of atrial arrhythmia was significantly lower in group 1 than 2 (8/49 (16%) vs. 17/51 (33%), respectively; P = 0.017). Atrial arrhythmias other than AF after the second ablation occurred in only one patient in group 1 but seven patients in group 2. Using high-density mapping for the second ablation of AF was found to be superior to the conventional ablation method in terms of the suppression of atrial events in this study. This technique warrants further investigation.

Epicardial ablation of ventricular tachycardia using a new high-density mapping system

We report the case of a 44-year-old woman who was referred for ablation of recurrent ventricular tachycardia (VT) in the setting of dilated cardiomyopathy secondary to myocarditis. The ECG displayed a right bundle branch block morphology and superior axis in the frontal plane, associated with a pseudo delta wave in the precordial leads that suggested an epicardial origin. Cardiac magnetic resonance performed prior to the procedure showed late gadolinium enhancement at the lateral wall of the left ventricle (LV) and excluded subendocardial fibrosis in either ventricle. This information was crucial and influenced the ablation strategy, identifying the target area as exclusively epicardial, thus avoiding unnecessary mapping of the endocardial surface of the LV. Epicardial activation mapping and ablation during VT were performed using the Orion® high-density catheter (Boston Scientific Inc.) and the Rhythmia® mapping system (Boston Scientific Inc.). Applications near the exit site immediately terminated the tachycardia, which was no longer inducible. One year after the procedure the patient was still in sinus rhythm with no episodes of VT or non-sustained VT recorded by continuous monitoring via an implanted cardioverter-defibrillator. Reportamos o caso de uma doente referenciada para ablação de taquicardia ventricular (TV) recorrente em contexto de miocardiopatia dilatada, secundária a miocardite. O ECG apresentava bloqueio de ramo direito e eixo superior no plano frontal, associado a uma pseudo onda delta nas derivações precordiais, sugerindo origem epicárdica. Previamente ao estudo eletrofisiológico, foi realizada ressonância magnética que revelou realce tardio (gadolínio) da parede lateral do ventrículo esquerdo (VE), permitindo também excluir fibrose subendocárdica em ambos os ventrículos. Esta informação foi crucial na decisão da melhor estratégia terapêutica, identificando a área alvo da ablação como exclusivamente epicárdica, evitando o mapeamento desnecessário da superfície endocárdica do VE. O mapa de ativação epicárdica e ablação em TV foram realizados utilizando o cateter de alta densidade Orion® (Boston Scientific® Inc) e o sistema de mapeamento Rhythmia® (Boston Scientific® Inc). Aplicações de energia de radiofrequência junto ao local de saída terminaram a taquicardia, que sob estimulação ventricular programada não voltou a ser induzida. Um ano após o procedimento, a doente mantém-se em ritmo sinusal, sem novos episódios de taquicardia ventricular mantida ou não (monitorização contínua através do cardioversor desfibrilhador implantado).