Ultra-high Density Mapping Research Articles

Ppulsed field ablation and ultra-high-density mapping for PVI: use of machine learning and data augmentation to guide procedure and identify recurrent tachycardia mechanisms at one-year follow-up

Abstract Background In managing atrial fibrillation (AF), radiofrequency and cryoablation have been cornerstone techniques for achieving pulmonary vein isolation (PVI). Recently, pulsed-field ablation (PFA) has introduced a novel method for PVI. There remains a gap in knowledge regarding the permanent efficacy of ablation, related explicitly to acute lesion characteristics following PVI. Purpose Our study delves into an in-depth examination of acute lesion characteristics following PFA-PVI through ultra-high-density mapping (UHDM). We aim to identify specific clinical, anatomical, and periprocedural lesion features independently related to 1) intraoperative identification of UHDM non-isolated gaps with electrical conduction after first isolation and 2) three months follow-up recurrency of specific arrhythmias. Methods Results The present study includes 204 patients submitted to PFA-PVI for AF. UHDM guided all procedures to identify non-isolated gaps with electrical conduction. Perioperative and 3-month follow-up data were collected prospectively and analyzed. To build our prediction model, avoiding biases related to the unbalanced nature of the data, data augmentation was performed with SMOTE (Synthetic Minority Over-sampling Technique). Two machine learning (ML) models have been built, using logistic regression as learner, to predict the presence of isolation gaps identified by UHDM and follow-up recurrence of arrhythmias. A 20-fold cross-validation has been performed to train and test the models. The non-isolated gap was detected and immediately corrected in 14 (6.9%) patients and was present more often in patients with larger left atria (LA) (p<0.0001) and those with persistent AF (p=0.02). The ML model achieved an AUC of 0.88 in the prediction of the non-isolated gap after PFA (Precision: 0.65; Sens.: 0.90; F1: 0.76; Spec.: 0.83; NPV: 0.96). At three months follow-up, no patient experienced recurrent AF; recurrent roof-dependent atrial tachycardia was present in 10 (4.9%). Patients with recurrent atrial tachycardia had a significantly narrower remaining atrial-roof conduction bridge (p=0.01) identified intra-procedurally by UHDM, significantly larger LA (p=0.03), and non-significant trend for older age (p=0.07). The ML model achieved an AUC of 0.86, predicting recurrent tachycardia after PFA (Precision: 0.63; Sens.: 0.86; F1: 0.72; Spec.: 0.82; NPV: 0.94). Conclusions Consistent use of UHDM can help identify non-isolated gaps with electrical conduction that may occur even after PVI with updated technologies, such as PFA. Non-isolated gaps should be expected, particularly in patients with larger LA, where UHDM could be of particular use. Moreover, UHDM can help predict the eventual recurrence of arrhythmias. Again, LA size plays an essential role in such recurrencies, together with the size of the remaining conducting tissue "bridges" within the LA roof, measure by UHDM.

Sinoatrial node function and the role of sinoatrial conduction in the typical atrial flutter substrate

BackgroundSinoatrial node (SAN) activation and sinoatrial conduction pathways (SACPs) have been assessed in animals but not in humans. ObjectivesWe used ultrahigh-density mapping and simulated models to characterize the SAN and to investigate whether slowed SAN conduction may contribute to the atrial flutter (AFL) substrate. MethodsTwenty-seven patients undergoing electrophysiologic procedures had right atrial mapping. SAN activation patterns and conduction block were analyzed. The interaction between the SAN and the intercaval line of block (LOB) was analyzed, and right atrial simulations with different degrees of block were created to investigate arrhythmia mechanisms. ResultsFifteen AFL patients and 12 reference patients were enrolled. SACPs were identified in all patients with sinus rhythm maps. An SAN-adjacent LOB was observed in AFL patients. SAN conduction velocity was slower in AFL vs reference (0.60 m/s [0.56–0.78 m/s] vs 1.13 m/s [1.00–1.21 m/s]; P = .0021). Coronary sinus paced maps displayed an intercaval LOB in AFL patients but not in reference patients, which was completed superiorly by the SAN-adjacent LOB. Corrected sinus node recovery time was longer in AFL patients (552.3 ± 182.9 ms vs 325.4 ± 138.3 ms; P < .006) and correlated with degree of intercaval block (r = 0.7236; P = .0003). Computer modeling supported an important role of SAN-associated block in the flutter substrate. ConclusionUltrahigh-density mapping accurately identifies SAN activation and SACPs. The LOB important for typical AFL was longer in AFL patients, and when partial, it was always present inferiorly and completed superiorly because of slowed conduction across the SAN. Corrected sinus node recovery time correlated with intercaval block, suggesting a role for SAN disease in the genesis of the typical AFL substrate.

Activation patterns and electrophysiologic characteristics of Marshall bundle–related left atrial tachycardias after atrial fibrillation ablation

BackgroundEpicardial Marshall bundles (MBs) are frequently used in left atrial tachycardias (LATs) after atrial fibrillation (AF) ablation with pulmonary vein isolation and substrate modification. ObjectiveThis study sought to classify different activation patterns of MB-mediated LATs and the corresponding electrophysiologic characteristics. MethodsFrom 2019 to 2021, 28 cases of atrial tachycardias after AF ablation were diagnosed as MB-mediated LATs by ultrahigh-density mapping and entrainment. Cannulation and mapping in the vein of Marshall (VOM) and epicardial mapping in the MB region were also performed in selected cases to further prove the mechanism. ResultsThree activation patterns were identified with a critical isthmus through the MB: perimitral macroreentry (perimitral LAT; n = 20 [71.4%]); left atrial appendage–related reentry (n = 5 [17.9%]); and left pulmonary vein–related reentry (n = 3 [10.7%]). In 18 patients, a characteristic triple potential observed along the previously endocardial left atrial ridge block line was composed of near-field double potentials and far-field MB potential. These findings were further delineated in 24 patients with either cannulation in the VOM (19 patients) or epicardial mapping (5 patients). Ethanol infusion of the VOM resulted in atrial tachycardia termination in 20 of 28 patients. ConclusionDifferent types of MB-mediated LATs after AF ablation could be identified by ultrahigh-density mapping. Ethanol infusion within the VOM was effective in eliminating these tachycardias.

Ultra-high density mapping for the evaluation of the antral scar extension after ablation with a radiofrequency balloon catheter in atrial fibrillation patients

Abstract Background The Heliostar radiofrequency (RF) balloon ablation catheter enables one-shot pulmonary veins isolation (PVI). The RF balloon by occluding the PV ostia creates an antral scar. Purpose We sought to investigate the extension of the antral scar by mean of ultra-high density mapping. Methods Paroxysmal and persistent atrial fibrillation (AF) patients undergoing first PVI ablation with the Heliostar catheter across 4 European centers were enrolled. Ultra-high density mapping of left atrium was performed with the Octaray catheter, a octa-spline mapping catheter before and after the ablation. All maps were acquired in sinus rhythm, patients in AF underwent electrical cardioversion before mapping. The bipolar voltage maps from each patients were analysed: the left atrial area &amp;lt; 0.2 mV was considered scar and was calculated before and after the ablation and the distance between left and right antral lesions at upper and inferior posterior wall were also calculated. Results Overall, 49 patients were enrolled, 82% were male, the mean age was 60±9 years, 66% had paroxysmal AF. PVI was achieved in 100% patients. The mean left atrial area was 209±44 cm2, the scar after the ablation was 9±4.6 %, with 49±11% of the posterior wall still viable (bipolar voltage &amp;gt; 0.5mV). The distance between left and right antral lesions at the upper posterior wall was 26.57 mm whereas at the inferior aspect was 29.59 mm. Conclusions The RF balloon catheter creates a wide antral scar during AF ablation although without compromising the integrity of the posterior wall.

Ultra-high density mapping and ablation of localized microreentrant tachycardias: insight from the CHARISMA registry

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 &amp;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 (&amp;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.

Local impedance drop as a predictor of sucessful pulmonary vein isolation

Abstract 1. Introduction Pulmonary vein isolation (PVI) is the cornerstone of AF treatment. An accurate estimation of the lesion size and a optimal evaluation of the catheter-myocardium coupling is crucial for achieving an effective and safe radiofrequency (RF) ablation. A few studies have suggested that local impedance (LI) drop is a better predictor than general impedance drop in terms of lesion size, electrical coupling and therefore acute PVI success. An open-irrigated ablation catheter designed to measure contact force (CF) and LI drop while applying RF has been recently developed. 2. Purpose The aim of this study is to evaluate if conduction GAPS are located in certain areas and if LI drop can predict the presence of conduction gaps in each of these segments. 3. Methods Observational prospective study including 55 consecutive patients who underwent PVI. The RF lesions were delivered with 30 W (posterior wall) or 35 W (anterior wall) for a maximum of 30 seg with a CF &amp;gt; 5 g. The applications were stopped if a LI of 35 Ohm was reached on the posterior wall or 40 Ohm on the anterior wall. PVs were divided into seven segments and ablation tags were assigned to a segment according to their anatomical position (figure 1) We categorized the tags included in each segment as successful or not according to the presence of conduction gaps detected with an Ultrahigh density mapping catheter once the WACA was completed. At the same time lesion by lesion were studied regardless of the segment where it was located. 4. Results We analyzed 4002 lesion tags of 55 patients who underwent PVI. 53 Gaps were found in 19/55 (34.5%) left WACA and 16/54 (29,6%) right WACA and were localized predominantly in three PVI segments (L1, L6 and R3) 34(54.85%) vs 19 (35,8%) (L2-L5, L7, R1-R2, R4-R7) (p&amp;lt;0.001) (figure 1). They were mainly circumscribed to anterior segments in left PVs and posterior-superior segment in right PVs (figure1). When examining lesions independently of their location we found a significant difference in LI drop among successful and unsuccessful lesions (24.22±8.31 vs 15.67±7.85) Ohm, p&amp;lt;0.001). In the same line when studying lesions in those segments with &amp;gt; 10% of GAPS (L1, L6 R1 and R3) LI drop was greater in successful lesion tags: L1 25.2 ± 5.35 vs 16.8 ± 5.17 (p&amp;lt;0.001), L6 25.2±5.7 vs 16±5.48 (p&amp;lt;0.001), R1 27.9±4.78 vs 17.1±5.73 (p=0.03) and R3 18.5±5.4 vs 10.7±2.49 (p&amp;lt;0.001). 5. Conclusions Gaps were located predominantly in anterior segments in left PVs and posterior-superior segment in right PVs. A low LI drop was an excellent predictor of conduction gaps, and it performs well regardless of the segment where it was analyzedFig. 1

Catheter ablation of premature ventricle complex from multiples site of origin guided by an ultra-high density mapping system in a single-center

Abstract Background Frequent premature ventricle complex (PVC) could induce cardiomyopathy in some patient. PVC ablation by radiofrequency (RF) is a well-stablished procedure in high density PVC patients and results are consistent and robust in literature, with somewhat differing success rates reported. Catheter ablation of radiofrequency guided by ultra-high density mapping systems (UHDMS), enable a much more accurate reconstruction of the site of origin (SOO). Furthermore, we obtained this anatomic recreation with the analysis of a few number of beats. The UHDMS have demonstrated to be feasible and safe in a wide range / large spectrum of arrhythmic substrates, however, there is lack of evidence of its usefulness in the ablation of PVC. Purpose To determine the safety and utility, both in the acute phase and in the short-medium term, of employing a UHDMS in PVC catheter ablation in a retrospective cohort of patients treated at a single centre. Methods Catheter ablation procedures guided by an UHDMS carried out from July 2015 to January 2021 in a single-center of Spain were retrospectively included. The primary outcomes analyzed were: acute success rate, short-medium success rate (6-month efficacy after ablation), and complication rate related to the procedure. Results One hundred and two procedures, corresponding to 92 patients (mean age 59 ± 14 years, 63% male, 74% without cardiomyopathy, mean LVEF of 60%), were analyzed. The acute success rate was 93%. According the SOO, the lowest acute success rate was PVC from epicardial level (LV Summit) (75%). At 6-month follow-up after the first procedure, the short-medium success rate was up to 84% (no recurrence of the PVC ablated). There were three acute complications related to the procedure (complication rate 2,94%). In 19% (21 out 102) of the procedures, at least two arrhythmic substrates were successfully ablated in a single intervention. Conclusion Catheter ablation guided by an UHDMS showed an excellent safety profile in PVC ablation procedures. Beyond this minor complication rate, this type of technique has improved acute and short-term success rates. This allows us to assert that this type of technique grants a very high success rate and improves previously results. Last but not least, this new approach was useful and accurate in complex patients, providing good results in ablation procedures of two or more arrhythmic substrates without altering the safety profile.

Electrophysiologic mechanism and ablation strategy for macroreentrant biatrial tachycardias after Cox-maze procedures

BackgroundDifferent types of recurrent atrial tachycardia (AT) after Cox-maze procedures have been reported, whereas biatrial tachycardia (BiAT) has not been systematically analyzed. ObjectiveIn this study, we retrospectively investigated the electrophysiologic characteristics of BiAT after Cox-maze procedures by use of an ultrahigh-density mapping system. MethodsOf a consecutive 76 patients who underwent catheter ablation of AT after Cox-maze procedures, 12 BiATs were identified. High-density activation mapping was performed in both the left atrium and right atrium in combination with entrainment pacing to confirm the circuit. ResultsWe classified these BiATs into 2 groups. In group 1 (7 patients), the bidirectional block of maze linear lesions to prevent the macroreentrant AT was achieved; the posterior interatrial connections were involved in the circuit. In group 2 (5 patients), the bidirectional block of maze linear lesions was not blocked, and the most common gap was located at the end of the linear lesion near the annulus. In group 1, all the ATs were terminated by targeting the corresponding left atrium end of the posterior interatrial connections. In group 2, the ATs were terminated by targeting the gap near the annulus. ConclusionThe optimal ablation strategy for BiATs after the maze procedure should be based on detailed demonstration of the circuit by high-density mapping.

Left atrial low-voltage areas, but not volume, predict the recurrence of atrial fibrillation in repeat ablation procedures.

Left atrial (LA) low voltage areas (LVA) are a controversial target in atrial fibrillation ablation procedures. However, LVA and LA volume are good predictors of arrhythmia recurrence in ablation-naïve patients. Their predictive value in progressively diseased pre-ablated atria is uncertain. Consecutive patients with recurrent atrial fibrillation (AF) or atrial tachycardia (AT), who were scheduled for repeat LA ablation, were enrolled in the prospective Bernau ablation registry between 2016 and 2020. All patients received a complete LA ultrahigh-density map before ablation. Maps were analyzed for LA size, LVA percentage and distribution. The predictive value of demographic, anatomic, and mapping variables on AF recurrence was analyzed. 160 patients (50.6% male, 1.3 pre-ablations, 60% persistent AF) with complete LA voltage maps were included. Mean follow-up time was 16 ± 11 months. Mean recorded electrograms (EGMs) per map were 9754 ± 5808, mean LA volume was 176.1 ± 35.9 ml and mean rate of LVAs <0.5 mV was 30.6% ± 23.1%. During follow-up recurrence rate of AF or AT>30 s was 55.6%. Patients with recurrence had a significant higher percentage of LVAs (40.0% vs. 18.8%, p < .001) but no relevant difference in LA volume (172 vs. 178 mL, p = .299). ROC curves revealed LVA as a good predictor for recurrence (AUC = 0.79, p < .001) and a cut-off of 22% LVAs with highest sensitivity (73.0%) and specificity (71.8%). Based on this cut off, event free survival was significantly higher in the Low LVA group (p < .01). Total LVA percentage has a good predictive power on arrhythmia recurrence in a cohort of advanced scarred left atria in repeat procedures independent of the applied ablation strategy. Left atrial volume seems to have minor impact on the rhythm outcome in our study cohort.

Ultrahigh-density mapping for evaluation of antral scar extension after ablation with radiofrequency balloon catheter in atrial fibrillation patients

Ultrahigh-density mapping for evaluation of antral scar extension after ablation with radiofrequency balloon catheter in atrial fibrillation patients

Pulsed field ablation technology for pulmonary vein and left atrial posterior wall isolation in patients with persistent atrial fibrillation.

Limited data exist on pulsed-field ablation (PFA) in patients with persistent atrial fibrillation (PeAF) undergoing left atrial posterior wall isolation (LAPWI). The Advanced TecHnologies For SuccEssful AblatioN of AF in Clinical Practice (ATHENA) prospective registry included consecutive patients referred for PeAF catheter ablation at 9 Italian centers, treated with the FARAPULSETM-PFA system. The primary efficacy and safety study endpoints were the acute LAPWI rate, freedom from arrhythmic recurrences and the incidence of major periprocedural complications. Patients undergoing pulmonary vein isolation (PVI) alone, PWI + LAPWI and redo procedures were compared. Among 249 patients, 21.7% had long-standing PeAF, 79.5% were male; mean age was 63 ± 9 years. LAPWI was performed in 57.6% of cases, with 15.3% being redo procedures. Median skin-to-skin times (PVI-only 68 [60-90] vs. PVI + LAPWI 70 [59-88] mins) did not differ between groups. 45.8% LAPWI cases were approached with a 3D-mapping system, and 37.3% with intracardiac echocardiography. LAPWI was achieved in all patients by means of PFA alone, in 88.8% cases at first pass. LAPWI was validated either by an Ultrahigh-density mapping system or by recording electrical activity + pacing maneuvers. No major complications occurred, while 2.4% minor complications were detected. During a median follow-up of 273 [191-379] days, 41 patients (16.5%) experienced an arrhythmic recurrence after the 90-day blanking period, with a mean time to recurrence of 223 ± 100 days and no differences among ablation strategies. LAPWI with PFA demonstrates feasibility, rapidity, and safety in real-world practice, offering a viable alternative for PeAF patients. LAPWI is achievable even with a fluoroscopy-only method and does not significantly extend overall procedural times.

High-density mapping of Koch's triangle during sinus rhythm and typical atrioventricular nodal re-entrant tachycardia, integrated with direct recording of atrio-ventricular node structure potential.

The mechanism of typical slow-fast atrioventricular nodal re-entrant tachycardia (AVNRT) and its anatomical and electrophysiological circuit inside the right atrium (RA) and Koch's Triangle (KT) are not well known. To identify the potentials of the compact AV node and inferior extensions and to perform accurate mapping of the RA and KT in sinus rhythm (SR) and during AVNRT, to define the tachycardia circuit. Consecutive patients with typical AVNRT were enrolled in 12 Italian centers and underwent mapping and ablation by means of a basket catheter with small electrode spacing for ultrahigh-density mapping and a modified signal-filtering toolset to record the potentials of the AV nodal structures. Forty-five consecutive cases of successful ablation of typical slow-fast AVNRT were included. The mean SR cycle length (CL) was 784.1 ± 6 ms and the mean tachycardia CL was 361.2 ± 54 ms. The AV node potential had a significantly shorter duration and higher amplitude in sinus rhythm than during tachycardia (60 ± 40 ms vs. 160 ± 40 ms, p < .001 and 0.3 ± 0.2 mV vs. 0.09 ± 0.12 mV, p < .001, respectively). The nodal potential duration extension was 169.4 ± 31 ms, resulting in a time-window coverage of 47.6 ± 9%. The recording of AV nodal structure potentials enabled us to obtain 100% coverage of the tachycardia CL during slow-fast AVNRT. Detailed recording of the potentials of nodal structures is possible by means of multipolar catheters for ultrahigh-density mapping, allowing 100% of the AVNRT CL to be covered. These results also have clinical implications for the ablation of right-septal and para-septal arrhythmias.

The efficacy of ultra-high-density mapping guided partial antral ablation for pulmonary vein isolation in atrial fibrillation patients

BackgroundThe muscular discontinuities or lack of myocardial extensions around the pulmonary veins (PVs) antrum were previously reported. The objective of our study was to compare the efficacy of a partial antral ablation for PV isolation (PVI) using ultra-high density (UHD) mapping with a conventional wide antral circumferential ablation (WACA) in atrial fibrillation (AF) patients.MethodsA total of 119 patients medical records who received catheter ablation for AF in our hospital were analyzed. In one group of patients, detailed activation mapping of each PV was performed using a UHD mapping system. Each PV antral segment’s activation pattern was classified into “directly-activated from the LA” or “passively-activated from an adjacent PV segment” patterns. The ablation applications were performed at the directly-activated PV antral segment only for the PVI when the PV had “passively-activated segments” (partial antral ablation; PA-UHD group). Another patient group received a conventional WACA for the PVI (WACA group).ResultsSixty patients received partial antral ablation (PA-UHD), and age/sex-matched 59 patients received WACA. In the PA-UHD group, passively-activated segments were observed in 58.3% of all PV segments. The success rate of a partial antral ablation for the PVI in PVs with passively-activated segments was 85%. The 1-year atrial tachyarrhythmia recurrence did not differ between the PA-UHD and WACA groups.ConclusionsOur study revealed the presence of passively-activated PV segments, which could potentially indicate muscular discontinuity at the PV-LA junction. In most PVs with passively-activated segments, PVI was successfully achieved by ablation with only directly-activated segments. The 1-year recurrence rate of atrial tachyarrhythmia in PA-UHD group was comparable to that observed in the WACA group.

Focal pulsed field ablation and ultrahigh-density mapping — versatile tools for all atrial arrhythmias? Initial procedural experiences

BackgroundFocal pulsed field ablation (FPFA) is a novel and promising method of cardiac ablation. The aim of this study was to report the feasibility, short-term safety, and procedural findings for a broad spectrum of ablated atrial arrhythmias.MethodsPatients (n = 51) scheduled for ablation of atrial arrhythmias were prospectively included and underwent FPFA using the Galvanize CENTAURI generator with energy delivery through commercially available ablation catheters with ultrahigh-density (UHDx) 3D electroanatomic voltage/local activation time map evaluations. Workflow, procedural data, and peri-procedural technical errors and complications are described.ResultsPlanned ablation strategy was achieved with FPFA-only in 48/51 (94%) of the cases. Ablation strategy was first-time pulmonary vein isolation (PVI) in 17/51 (36%), repeat ablation in 18/51 (38%), PVI + in 13/51 (28%), and cavotricuspid isthmus block (CTI)-only in 3/51 (6%). The mean procedure time was 104 ± 31 min (first-time PVI), 114 ± 26 min (repeat procedure), 152 ± 36 min (PVI +), and 62 ± 17 min (CTI). Mean UHDx mapping time to assess lesion formation and block after ablation was 7 ± 4 min with 5485 ± 4809 points. First pass acute (linear) isolation with bidirectional block for anatomical lesion sets was 120/124 (97%) for all PVs, 17/17 (100%) for (any) isthmus, and 14/17 (82%) for left atrium posterior wall (LAPW). We observed several time-consuming integration errors with the used ablation system (mean 3.4 ± 3.7 errors/procedure), one transient inferior ST elevation when ablating CTI resolved by intravenous nitroglycerine and one transient AV block requiring temporary pacing for > 24 h.ConclusionsFPFA was a highly versatile method to treat atrial arrhythmias with high first-pass efficiency. UHDx revealed acute homogenous low-voltage lesions in ablated areas. More data is needed to establish lesion durability and limitations of FPFA.

Assessment of scar between atria, rhythms and atrial fibrillation types: does ultra high density mapping offer new insights?

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific Background 3D electroanatomical mapping systems demonstrate atrial scar by recording local tissue voltages as a surrogate. Increased scar has been shown with both progression of atrial fibrillation, (AF, paroxysmal (PAF) to persistent (PeAF)), and between sinus rhythm (SR) and AF on low density mapping systems. The introduction of ultra high density mapping allows a more detailed comparison. Objectives Assessment of atrial scar determined by voltages and surface area between atria, rhythm, and AF type. Methods Ultra high density 3D electroanatomical maps of left and right atria (LA, RA) were created. PeAF patients had maps created in AF and SR following DC cardioversion. PAF patients had maps created in SR only. Electrograms (EGMs) on corresponding AF and SR maps were paired using exported co-ordinates. Percentage surface area of scar was and assigned as low voltage myocardium (LVM, ≤ 0.05mV), intermediate, (IVM, 0.05 - 0.5mV), or normal, (NVM, &amp;gt; 0.5mV). Results 95 maps were produced using 913480 EGMs. Paired SR-AF EGM voltages had a moderate correlation in the LA (Bipolar: Pearson’s R = 0.32, unipolar: R = 0.36, both p &amp;lt;0.0005), and weak correlation in the RA, (Bipolar: R = 0.19, unipolar: R = 0.25, both p &amp;lt; 0.0005). Paired voltages were significantly higher in SR in both atria, LA/RA, bipolar/unipolar all p &amp;lt; 0.0005). There was significantly more LVM/IVM percentage surface area in AF over SR in the LA, (SR to AF - LVM: 6.4 ± 6.9 to 12.2 ± 9.5; IVM 41.0 ± 12.1 to 50.5 ± 10.0; NVM: 51.7 ±17.2 to 37.3 ± 16.1, p &amp;lt; 0.0005), but not in the RA (SR to AF – LVM: 6.5 ± 5.3 to 8.4 ± 8.3; IVM 42.0 ± 10.1 to 44.6 ± 6.9;NVM: 51.5 ± 13.6 to 47.0 ± 13.8, p = 0.62) Figure 1A. Global tissue voltages in SR were significantly higher in PAF over PeAF in both atria, (LA –bipolar: 1.13 vs 0.52mV, unipolar 1.96 vs 1.44mV, RA – bipolar 0.93 vs 0.57mV, unipolar: 1.68 vs 1.33mV all p &amp;lt; 0.0005). There was significantly more LVM/IVM surface area demonstrated in PeAF over PAF in the LA, (PAF to PeAF - LVM: 0.6 ± 0.7 to 6.6 ± 6.8; IVM 29.5 ± 12.3 to 43.1 ±11.4; NVM: 69.8 ± 12.8 to 50.3 ± 16.4, p = 0.01), but not in the RA, (PAF to PeAF - LVM: 4.6 ± 3.6 to 6.5 ± 5.3; IVM 32.7 ± 9.5 to 42.0 ±10.1; NVM: 62.7 ± 12.1 to 51.5 ± 13.6, p = 0.20). Figure 1B Comparing atria, the LA had a significantly lower voltage in SR, but this difference was small (LA/RA = 0.89, p &amp;lt; 0.0005). The percentage surface area of scar was comparable, (LA to RA - LVM: 4.0 ± 5.6 to 5.6 ± 4.5; IVM: 38.4 ± 37.6 to 37.6 ± 10.6; NVM: 57.5 ±18.4 to 56.8 ± 13.8). Figure 1C Conclusions Ultra high density mapping confirms atrial voltages are higher in SR over AF, and PAF over PeAF. The RA is comparable to the LA for tissue voltages but does not demonstrate a change in surface area of scar between AF and SR or PAF and PeAF. This may reflect the complexity of AF wavefronts in the LA compared to the RA leading to more bipole orientation related overestimation of scar in the fibrillating LA.

Insights into level of pulmonary vein isolation using pulsed-field ablation for atrial fibrillation and unexpected effects in the posterior wall

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Pulse field ablation (PFA) has emerged as an effective, safe and efficient tool for pulmonary vein isolation (PVI). Purpose We studied the extent of PVI, specifically the isolation of PV antrum, carina and left atria’s posterior wall after PFA with an ultrahigh density mapping (UHD). Methods We involved the first patients referred for atrial fibrillation (AF) ablation treated with a PFA multispline catheter. PFA-lesion extension was assessed with a voltage-map UHD mapping performed before and immediately after PVI. Results Sixty-one consecutive patients underwent PVI with PFA (62±10 year old, 23 women, 39 paroxysmal AF). Four out of 61 patients were excluded because their posterior wall was isolated with extra aplications on purpose. Acute results involved a 100% success of PVI and the only safety issue was a pericardial effusion in one patient managed conservatively. Mean procedure and fluoroscopy times were 59±39 min and 16±5 min, respectively. UHD immediately after PVI revealed early reconnection just in one vein (1/228 veins). PFA created wide antral circumferential lesions without electrical activity registered by UHD mapping inside the isolation area. There were no notch-like normal voltage areas at the anterior or posterior side of carinas. As a result of the PVI with this technology, it was observed the existence of a narrow corridor in the posterior wall in 8 patients (14%) and in another 8 cases right and left antral ablation converged at the posterior wall creating an unexpected isolation area. There was a significant relationship between LA posterior inter-carina distance and posterior wall´s level of isolation (77,1±7mm, no affectation; 68,8±7mm narrow corridor; 60,3±1mm posterior wall isolation (fig 1); p=0.036). Finally, it was a significant linear correlation between posterior inter-carina distance and the distance between the ipsilateral, antral levels of isolation at the posterior wall (fig 2, r=0.79, p=0.001) Conclusion(s) PFA creates wide antral circumferential PVI lesions involving the ipsilateral veins carina. Nevertheless, in small left atria it can create an undesired isolation or a narrow corridor in the posterior wall.

Novel mapping tool to identify drivers in persistent atrial fibrillation: first clinical experience

Abstract Funding Acknowledgements Type of funding sources: None. Background Developing ablation strategies beyond pulmonary vein isolation (PVI) in persistent atrial fibrillation (persAF) is still a challenge. To date, few diagnostic tools have allowed identification of potential drivers during AF, with questionable results. There is a need for a tool that allows to consistently display and detect EGMs and identify optimal ablations targets. A novel mapping tool can provide algorithmic detection of ablation targets based on EGM properties specific to relatively stable localized rotational activations. Objective Describing an initial series of patients (pts) where Ockham mapping was used during AF to identify ablation targets and treat PersAF. Methods PersAF pts presenting in AF for were mapped using an ultra-high density mapping system (RHYTHMIA). A novel PersAF mapping feature (Ockham) was used to detect ablation targets by calculating local cycle length (LCL) and local spread of activation time within that LCL (Duty Cycle) for consistent EGMs. A scatterplot tool (F1 A) was used to identify regions of consistent (relatively stable) local activation. Among these areas, those with fast CL and high DC (&amp;gt;90%) were used to guide the optimal PVI line placement. Additionally, during remapping the same approach was used to target ablation beyond PVI.RF was delivered at 40-45 W via a StablePointTM IntallaNav OI catheter aiming at the maximum impedance drop (30 ohms).Durable PVI was verified by EGM visualization. In case of ongoing AF at the end of the procedure patients were monitored for 48 h before eventual cardioversion. Follow-up was by Holter every 3 months (more if symptoms). Data are median [IQR]. Results The novel mapping tool was used on 31 PersAF pts (68±9.5 years, 71% male, 20 De Novo).A median of 41228 [32789-46512] EGMs was collected before PVI. After PVI, 3 de novo pts had AF terminate into AT. Additional targets were identified in the other ones from a second post-PVI map. 81% of the extra-venous potential drivers identified on the post-PVI maps were already present on the pre-PVI map, supporting the reproducibility of the tool. Pts had a median of 3 [1-4.25] extra-PV drivers targets. Across all pts, following PVI and targeted ablation, there was progressive AF organization demonstrated by global activation slowing (a rightward shift of CL; F1 B), which in approximately half of the patients formed bi-modal curves clustered around 2 discrete CL values. Acutely, 88% of patients had AF terminate to SR or AT. At 10 months [5.75-13] follow-up, 3 (15%) patients had recurrence of persAF, and 2 (10%) patients had AT recurrences. No complication occurred. Discussion This clinical experience demonstrates that this tool can identify limited, but highly selective, reproducible extra-PV AF drivers. Since PersAF pts have high variability in arrhythmogenic sites, this novel tool allows efficient identification of ablation targets based on EGM properties for an individualized approach to ablation beyond PVI.

PO-04-038 ULTRA HIGH DENSITY MAPPING TO IDENTIFY MICRO-REENTRANT LEFT ATRIAL FLUTTER CIRCUITS WITHIN LOW BIPOLAR VOLTAGE REGIONS: A CASE SERIES

Micro-reentrant (MR) atrial flutter (AFL) circuits may not be evident with standard bipolar or multipolar mapping. We report 3 cases of left atrial (LA) AFL where HD Grid + Omnipolar technology (Ensite X, Abbott) revealed MR circuits within an area of scar as noted by standard multipolar mapping. N/A Three patients with prior LA ablation presented with symptomatic AFL. LA mapping was done using the Ensite X system in Voxel mode. Bipolar voltage cutoff was set at 0.3 to 0.05 mV. A 65-year-old presented with AFL CL of 335 ms. Mapping with an Advisor spiral showed a large posterior wall scar and no AFL circuit in LA or RA. Remapping with HD Grid identified a 12 mm MR circuit with entire CL in the low LA posterior wall which showed dense scar by spiral mapping (Figure 1A). A 59-year-old male presented with AFL CL of 340 ms with proximal to distal CS activation. HD grid mapping identified a 21 mm MR circuit in the mid LA posterior with fractionated mid-diastolic electrograms (Figure 1B and 1C). Third patient was a 54-year-old male who had a MR circuit in the posterolateral mitral annulus, otherwise noted as scar by bipolar mapping. Successful ablation sites in all 3 cases did not have an identifiable bipolar electrogram on ablation catheter (<0.05 mV, Figure 1 D). Low voltage cut off during HD mapping was manually adjusted and had to be lowered to 0.04 to identify the circuit in all cases. This case series demonstrates that ultra high-density mapping with HD Grid + Omnipolar technology, with dynamic adjustment of low voltage threshold, enables identification of MR AFL circuits, leading to successful ablation, where critical isthmi were not identified by standard bipolar or multipolar mapping.

PO-02-095 UTILITY OF LOCAL IMPEDANCE MONITORING TO GUIDE HIGH-POWER SHORT-DURATION RADIOFREQUENCY ABLATION FOR ATRIAL FIBRILLATION

Local impedance (LI) measurement can predict tissue heating during RF ablation. To evaluate the utility of prespecified target LI to prospectively guide high power, short-duration (HPSD) RF ablation for PV isolation. This is a single-center prospective study of 44 consecutive patients who underwent initial PV isolation for AF. Circumferential ablation around the antrum of each PV was performed using using a 4 mm tip open irrigation RF ablation catheter with an LI sensor. RF energy was applied at each site at power output of 50 W. Adequacy of each RF application was solely guided by LI measured from the ablation catheter. PV electrograms were not monitored during RF ablation. Annotation of RF ablation applications was based on predefined parameters: the: (1) catheter stability <3 mm; (2) LI drops by >5 Ω (regardless of baseline LI) within the first 5 seconds; and (3) RF application duration of >5 seconds. Each tagged RF application was continued for a total duration of 6-10 seconds for the LA posterior wall and 10-15 seconds for other LA regions. If the LI failed to drop quickly (>5-Ω decrease within the first 5 seconds energy delivery), RF application was interrupted and ablation catheter adjusted to achieve better tissue contact, and RF was reapplied. RF application was stopped if esophageal temperature rose to >40°C or LI dropped by >30 Ω. Ultrahigh-density mapping was performed after first pass encircling of all PVs with inter-lesion distance of 4 mm. First-pass PV isolation was achieved in 163 of 175 PVs (93.1%) in 34/44 patients (77.3%). In 5 PVs (in 5 patients), high-density mapping identified 11 LA-PV conduction gaps at sites where RF applications did not meet annotation criteria (due to catheter instability, esophageal heating, or lack of sufficient LI drop). In 7 other PVs (in 7 Patients), 10 conduction gaps were identified at sites where RF applications did satisfy our ablation protocol. Compared to sites with tagged ablation points with conduction gaps, sites without gaps (suggestive of acutely effective ablation lesions) exhibited significantly larger absolute LI drop (16.4 ± 6.7 Ω vs. 12.2 ± 4.6 Ω, p=0.01) and % change in LI (14.8% ± 5.1% vs. 10.9% ± 4%, p=0.013) during RF energy delivery. The anatomical distribution of conduction gaps is shown in Figure. No steam pops or major complications occurred during or after the procedures. Our prespecified LI target drop magnitude may be used prospectively to guide safe and successful HPSD ablation for AF.

Pulsed field ablation in patients with complex consecutive atrial tachycardia in conjunction with ultra-high density mapping: Proof of concept.

Catheter-ablation (CA) of consecutive left atrial tachycardias (LAT) can be challenging. Pulsed field ablation (PFA) yields a novel nonthermal CA technology for treatment of atrial fibrillation (AF). There is no data regarding PFA of LAT. This study sought to investigate PFA of consecutive LAT following prior CA of AF. Consecutive patients with LAT underwent ultrahigh-density (UHDx) mapping. Subsequent to identification of the AT mechanism, PFA was performed at the assumed critical sites for LAT maintenance. Continuous ablation lines were performed if required and evaluated with pre- and post-PFA HDx-mapping. Fifteen patients (age 70 ± 10, male 73%) who underwent 3.6 ± 2 prior AF-CA procedures were included. The total mean procedure and fluoroscopy times were 141 ± 43 and 18 ± 10 min, respectively. All 19 of 19 (100%) LAT were successfully ablated with PFA. Two AT located at the right atria required RF-ablation. LAT were identified as localized reentry (n = 1) and macro-reentry LAT (n = 18) and targeted with PFA. All LAT terminated with PFA either to sinus rhythm (9/15) or a secondary AT (6/15 and subsequently to SR); 63% (12/19) terminated with the first PFA-application. All lines (13 roof, 11 anterior, 1 mitral) were blocked. LA-posterior-wall isolation (LAPWI) was successfully achieved when performed (10/10). AF/AT free survival was 80% (12/15) after 153 [88-207] days of follow-up. No procedure-related complications occurred. PFA of consecutive LAT is feasible and safe. Successful creation of ablation lines and LAPWI can be achieved in a short time. PFA may offer the opportunity for effective ablation of atrial arrhythmias beyond AF.