Multielectrode Mapping Research Articles

FIRST-IN-HUMAN EXPERIENCE OF HIGH ENERGY ELECTROPULSE PULSED FIELD ABLATION: ACUTE RESULTS FOR PULMONARY VEINS AND POSTERIOR WALL ISOLATION

Different iterations of catheter and energy delivery system configurations are evolving for pulsed field ablation (PFA); however, some have used large and complex catheters, required large sheaths and had a recognised risk of haemolysis. To evaluate the acute safety and efficacy of a custom designed 8F variable loop multielectrode mapping and PFA catheter with contact sensing. This acute feasibility study recruited 30 patients undergoing de novo ablation of paroxysmal or persistent atrial fibrillation (AF). The ElectroPulse Study is a first-in-human, non-randomised, prospective study of a novel PFA system that utilizes an 8F 10-electrode variable loop steerable mapping and ablation catheter with 2800V biphasic bipolar waveform. All patients had pulmonary vein (PV) and posterior wall isolation (PWI) using the PFA system. The main outcomes were the acute success of PV/PWI and peri-procedural serious adverse events. Complete PV/PWI was successfully achieved in all 30 patients with 59.7±7.2 applications. Total procedural time was 113.6±26.3 mins with fluoroscopy time of 8.0±5.5 mins and LA dwell time of 78.7±18.6 mins. There was no esophageal injury, phrenic nerve palsy, clinical stroke or death. Brain MRI detected 2 new but transient silent cerebral lesions. Two patients (6.7%) had vascular access complications. Although there were changes in the biomarkers for hemolysis, none of the patient experienced clinical hemolysis or related acute kidney injury. This first-in-human study demonstrated that PFA using a novel variable loop catheter with a contact sensing system safely achieved 100% acute PVI/PWI with safety profile comparable to existing PFA systems.

The value of ripple mapping in the age of coherent mapping in scar-related atrial tachycardia.

An accurate display of scar-related atrial tachycardia (ATs) is a key determinant of ablation success. The efficacy of ripple mapping (RM) in identifying the mechanism and critical isthmus of scar-related ATs during coherent mapping is unknown. A total of 97 patients with complex ATs who underwent radiofrequency catheter ablation at our center between October 2018 and September 2022 were included. ATs was mapped using a multielectrode mapping catheter on the CARTO3v7 CONFIDENCE module. Coherent and RM were used to identify the reentrant circuit. The mechanisms of 128 ATs were analyzed retrospectively (84 anatomic-reentrant ATs and 44 non-anatomic reentrant ATs). The median AT cycle length was 264±25ms. The correct diagnosis was achieved in 83 ATs (68%) using only coherent mapping. Through coherent mapping plus RM, 114 ATs (84.2%) were correctly diagnosed (68% vs. 89%, p=.019). In non-anatomical reentrant ATs, 81% of the diagnostic rate was achieved by reviewing both coherent and ripple mapping compared to reviewing coherent mapping alone (81% vs. 52%, p=.03). Reviewing coherent mapping and ripple mapping showed a higher diagnostic rate in patients who underwent cardiac surgery than those with Coherent mapping alone (64% vs. 88%, p=.04). Coherent mapping combined with RM was superior to coherent mapping alone in identifying the mechanism of scar-related ATs post-cardiac surgery and non-anatomic reentrant ATs.

First clinical experience using a novel 8-spline ultra high-resolution mapping catheter to guide atrial fibrillation ablation

Abstract Background Multielectrode mapping catheters improve the detection of scarred and fibrotic tissue in patients with atrial fibrillation (AF) Recently, a novel multispline mapping catheter with 48 closely spaced microelectrodes has been introduced enabling fast high-resolution electroanatomical mapping. Objective This study sought to report our initial clinical experience with the novel Octaray catheter in patients with AF undergoing index ablation and to compare its impact on mapping and ablation with the 5-spline Pentaray catheter. Methods The study included consecutive patients who underwent index AF ablation using a multipolar mapping catheter and very high-power-short-duration guided ablation (Q4U-AF workflow; QDot; Qmode+; Biosense Webster) in conjunction with a visualized sheath (Vizigo; Biosense Webster). Arrhythmia recurrence was defined as any atrial fibrillation (AF)/ atrial tachycardia (AT) episode lasting > 30 s after a blanking period of 3 months. Results A total number of 183 patients undergoing AF ablation using the Octaray and QDot catheter were compared to a group of 166 matched patients who underwent ablation using Pentary and QDot. Utilization of the Octaray catheter resulted in an increased identification of areas with bipolar low-voltage representing fibrosis/scar or atrial cardiomyopathy (mean amount of left atrial bipolar low-voltage: Octaray 31% vs. Pentaray 18%; p= 0.03) and a higher rate of first-pass isolation (FPI) for the left-sided pulmonary veins (Octaray: FPI rate 73% vs. FPI rate 64% for Pentaray). A significantly higher number of mapping points was acquired using the novel 8-spline mapping catheter (right atrium: Octaray 1936 points vs. Pentaray 903 points; p < 0.001 left atrium: Octaray 5337 points vs. Pentaray 2385 points; p < 0.001). Procedural parameter, radiation time/dosage and acute procedural success were comparable between the two groups. During a mean follow-up of 12 months, the overall procedural success was 86 in the Octaray group vs. 84% in the control group (p=0.9). Conclusion The utilization of the novel Octaray mapping catheter resulted in an improved detection of atrial fibrosis and scar as well as a higher rate of first-pass pulmonary vein isolation. Figure: Institutional Q4U-AF-workflow using a multipolar mapping catheter, the QDot ablation catheter and a visualized sheath. High resolution mapping using the Octaray (A+B) and PentaRay catheter (C+D).

Focal pulsed field ablation for organised atrial tachyarrhythmias: one to rule them all

Abstract Background Focal pulsed field ablation (fPFA) has emerged as a versatile and innovative strategy for ablating atrial tachyarrhythmias (1). The primary objective of this study is to present the short-term safety characteristics, feasibility and procedural outcomes of fPFA in the management of organised atrial tachyarrhythmias. This report focuses on the commercial use of an innovative pulsed field ablation (PFA) generator, utilized in conjunction with commercially available focal, solid-tip ablation catheters, and complemented by 3D electro-anatomical mapping (3D-EAM). Methods Patients with organised atrial tachycardia treated using fPFA between August 2022 and September 2023 at our center were included in this retrospective analysis. Tachycardia mechanisms were identified with high-definition, multi-electrode mapping catheter paired with 3D-EAM system. Ablation lines, when targeting macro-reentrant arrhythmias were strategicaly positioned to adress critical isthmi when recognised or they were empirically placed between the anatomical obstacles ( including LA roof, anterior, mitral isthmus, upper septal and cavotricuspid line as deemed appropriate). Positioning of the fPFA catheter was guided by 3D-EAM, intracardiac ultrasound, and fluoroscopy (Figure 1). Bidirectional block verification was performed using standard criteria to assess acute procedural success. Glyceryl trinitrate boluses were administered prior to ablation in proximity to coronary arteries. Results In a cohort of 36 patients (median age 62 years; 12 females), we effectively mapped and treated a total of 51 distinct organised atrial tachyarrhythmias. These included 18 typical flutters, 3 roof-dependent macro-reentries, 4 posterior-wall micro-reentries, 15 peri-mitral macro-reentries, 8 anterior-wall micro-reentries and 3 biatrial macro-reentries via Bachman bundle. Our ablation strategy involved creating 21 cavotricuspid isthmus lines, 3 roof lines, 18 posterior wall lines, 11 anterior lines, 8 septal lines, and 15 mitral isthmus lines (Figure 2). Impressively, first-pass acute isolation with bidirectional block was achieved in 93% (54 of 58) of isthmus ablations and 94% (17 of 18) of left posterior wall lines. No ST segment alterations or other complications were observed during the periprocedural period. Conclusion In our cohort fPFA proved as a feasible, effective, and safe approach for treating organised atrial tacharrhythmias. The primary reason for designating this setup as our preferred choice for redo procedures lies in its versatility in addressing a wide range of arrhythmias. As ultra-fast pulmonary vein isolation (PVI) procedures become more prevalent with the expansion of PFA, the demand for an ideal setup capable of effectively targeting various substrates will become even more pronounced (2). Notably, our findings suggest superior suitability and efficacy when compared to bulkier, single-shot design PFA devices (3).Figure 1Figure 2

Quantifying local cardiac substrate heterogeneity from high density recordings: an experimental study

Abstract Background and Purpose High-density (HD) grid catheters offer enhanced local electrical conduction characterization, owing to their unique grid arrangement. This arrangement enables the generation of orientation-independent EGMs, termed omnipolar EGMs (oEGMs), overcoming limitations associated with traditional unipolar and bipolar EGMs. This innovation holds potential for differentiating healthy tissue from scarred or arrhythmogenic areas. In this study, we introduce a novel metric, the Vector Field Heterogeneity (VFH), designed to quantify the heterogeneity of propagation wavefronts in local vector maps derived from oEGMs. Methods We developed and validated the VFH metric through a combination of simulations and experiment conducted on Langendorff-perfused rabbit hearts. Simulations involved creating a model that generated 100,000 simulated maps exhibiting various levels of disorganization. For experimental data, 68 propagation maps were utilized, including 29 from basal recordings, 39 from recordings with stimulation (4 or 6Hz), from five Langendorff-perfused rabbit hearts at 37ºC, using a multielectrode mapping catheter with 128 electrodes spaced 1mm apart. The VFH metric, based on vector field theory (see figure 2), was computed and compared to the widely adopted the Spatial Inhomogeneity Index (SI) from Statistical analysis was then performed to assess the distribution of heterogeneity values. Results The analysis of the VFH metric through simulations revealed a linear increase in VFH values with disorganization up to a 45º angle, followed by a plateau. Different catheter grid sizes demonstrated that larger grids reduced the standard deviation, with the VFH metric converging to a lower value of approximately 0.62 for larger grids. Experimental data indicated that for a 4x4 grid, VFH values averaged 0.35 without stimulation and decreased to 0.11 with stimulation. The VFH metric consistently outperformed the SI index in binary classification of basal vs stimulated conditions, as evidenced by higher Area Under Curve (AUC) values in both Receiver Operating Characteristic (ROC) and Precision-Recall (PR) analyses across various catheter sizes. For example, in the 4x4 grid, the AUROC for the VFH metric was 0.9752 compared to 0.8311 for the SI index, showcasing the VFH metric’s superior accuracy in assessing cardiac wavefront heterogeneity (see figure 2). Conclusion Vector Field Heterogeneity (VFH) emerges as an effective tool for characterizing cardiac tissue. It successfully differentiates between stimulated and non-stimulated tissue, accurately representing progressive disorganization in simulated maps. The VFH metric demonstrates superiority over the established Spatial Inhomogeneity (SI) index, making it a reliable parameter for assessing cardiac heterogeneity, especially on small high-density grids. It holds promise for clinical use in studying and understanding the cardiac substrate during arrhythmic conditions.Figure 1.Abstract Figure.Figure 2.Methods and Results.

Role of high-density voltage map guiding parosysmal atrial fibrillation ablation

Abstract Background High-density mapping of the pulmonary vein antra has been demonstrated to improve the detection of conduction gaps in wide antral catheter ablation (WACA) approach for the treatment of paroxysmal atrial fibrillation (AF). Purpose We aimed to compare the AF recurrencies in patients treated with WACA for pulmonary veins isolation (PVI) guided by high-density bipolar voltage map (BVM) vs WACA guided by a standard 20-pole circumferential mapping catheter (CMC-20). Methods This prospective study included patients scheduled for AF ablation in a single center. In group A (85 patients) PVI was achieved with a conventional approach using CMC-20; in group B (96 patients) high density BVM was acquired by sequential multielectrode mapping through Pentaray Catheter (Biosense Webster). More than 1000 voltage points per map were acquired. Acute PVI was defined as an entrance and exit block after ≥ 20 min waiting period. In both groups WACA was perfomed using a contact force sensing catheter targeting an interlesion distance ≤6 mm and ablation index ≥400 at posterior wall and ≥550 at anterior wall. The primary endpoint was the AF recurrencies in the two groups. Results A total of 181 patients were included (mean age 64.9±10.6 years, 33.1% female): in 85 patients AF ablation was guided by CMC-20, in 96 patients AF ablation was guided by BVM; WACA PVI was achieved in all patients. There were no significant differences in the clinical characteristics of the two groups (table 1). At 12-month follow-up, AF recurrencies were significantly lower in the BVM group compared with CMC-20 group [11/96 (11.4%) vs 19/85 (22.3%) respectively, p=0.01]. Conclusions High-density BVM might increase success rate of AF ablation compared with a conventional 20-pole circumferential mapping approach.

Multipolar Electrograms: A New Configuration That Increases the Measurement Accuracy of Intracardiac Signals

BackgroundAccurate measurements of intracardiac electrograms (EGMs) remain a clinical challenge because of the suboptimal attenuation of far-field potentials. Multielectrode mapping catheters provide an opportunity to construct multipolar instead of bipolar EGMs for rejecting common far-field potentials recorded from a multivectorial space. ObjectivesThe purpose of this study was to develop a multipolar EGM and compare its characteristics to those of bipolar EGMs MethodsUsing a 36-electrode array catheter (Optrell-36, Biosense Webster), a far-field component was mathematically constructed from clusters of electrodes surrounding each inspected electrode. This component was subtracted from the unipolar waveform to produce a local unipolar, referred to as a “multipolar EGM.” The performance of multipolar EGMs was evaluated in 7 swine with healed anteroseptal infarction. ResultsMultipolar EGMs proved superior in attenuating far-field potentials in infarct border zones, increasing the near-field to far-field ratio from 0.92 ± 0.2 to 2.25 ± 0.3 (P < 0.001). Removal of far-field components reduced the voltage amplitude (P < 0.001) and enlarged the infarct surface area (P = 0.02), aligning more closely with histological findings. Of 379 EGMs with ≥20 ms activation time difference between bipolar and multipolar EGMs, 95.3% (361 of 379) were accurately annotated using multipolar EGMs, while annotation based on bipolar EGM was predominantly made on far-field components. ConclusionsMultielectrode array catheters provide a unique platform for constructing multipolar EGMs. This new EGM may be beneficial for "purifying" local potentials within a complex electrical field, resulting in more accurate voltage and activation maps.

Quantification of local heterogeneity from activation maps of omnipolar multielectrode recordings

Abstract Background and Purpose The study of cardiac arrhythmias requires understanding the heart's electrical conduction patterns. Using multielectrode catheters and other mapping systems have allowed a futher understanding of the wavefront. In particular, novel high-density (HD) grid catheters, enable the recording of omnipolar electrograms, which are purportedly not influenced by catheter orientation, allowing real-time determination of signal propagation direction. We propose a novel heterogeneity metric to quantify the degree of disorganisation in the vector maps from reconstructed omnipolar electrograms, which could potentially be utilised to detect and assess the degree of fibrosis in cardiac tissue. Methods We utilised basal and stimulated recordings from 5 Langendorff-perfused rabbit hearts, where signals were obtained using a multielectrode mapping catheter with 128 electrodes spaced at 1mm. Three recordings were taken for each series, basal at 37°C, plus stimulation performed using a bipolar electrode at 4 Hz and 6 Hz . An angle propagation matrix is computed for the local area of recording, by means of the orthogonal bipolar loops of each clique. A local heterogeneity metric is derived from the summation of angular variations of neighbouring elements. An illustration of the heterogeneity map, and heterogeneity metric for the recording area (H) is illustrated in figure 1. A statistical analysis is performed then to assess the distribution of heterogeneity values. Results Heterogeneity values for each experimental heart, and the distributions of H values obtained according to the stimulation type are shown in figure 2A. The ROC curve obtained from the values of H has an AUC of 0.996, with an optimal threshold value of 0.113, resulting in a confusion matrix presented in 12 TP, 30 TN, 3 FP and 0 FN. The study shows that the proposed heterogeneity metric can quantify the degree of disorganization in the vector maps and can be used to differentiate between basal and stimulated groups with p&amp;lt;0.001. Conclusion This study proposes a novel heterogeneity metric to quantify the degree of disorganization in the vector maps from reconstructed omnipolar electrograms. The methodology was assessed on basal and stimulated epicardial rabbit recordings and found to be effective in differentiating between the two groups with high accuracy. Future studies should focus on the efficiency of assessing fibrotic tissue using the proposed metric.Figure 1Figure 2

Effects of contemporary hard- and software mapping and ablation features on acute and long-term success in premature ventricular complex ablation

BackgroundCurrent standards of ablation of premature ventricular complexes (PVC) combine modern hard- and software mapping and ablation features like multielectrode mapping catheters (MEC), contact force (CF) guided ablation catheters and pattern matching filters (PMF). Benefits of these individual tools were described for selected patients with PVC, but data on combination of these features in the real world setting is sparse. MethodsBetween 2015 and 2021 we retrospectively enrolled 172 consecutive patients undergoing PVC ablation in our center. The utilization of MEC, CF guided ablation catheters and PMF software was analyzed in terms of procedural data, acute and long-term success after 12 months. ResultsAcute ablation success was reached in 71% of patients (n = 118) with an overall recurrence rate of 34% after 12 months. PMF software was used in 130 patients (78%), MEC in 131 patients (79%) and ablation was guided using CF in 99 patients (60%). PMF significantly reduced procedural duration and time of radiofrequency application (RF, 150 vs. 185 min, p 0.04 and 325 vs. 556 min, p 0.01). CF enabled significantly shorter radiation time (7.9 vs. 12.3 min, p 0.01), whereas MEC did not influence procedural data. Acute and long-term outcomes were not affected by these modern mapping and ablation features, yet, multivariable regression analysis revealed an underlying cardiomyopathy and the respective focus as independent predictors for recurrence. ConclusionContemporary hard- and software mapping and ablation features could reduce procedural, radiation and RF time in PVC ablation. Furthermore, patient characteristics rather than technical factors alter outcome of this all-comer collective.

Role of diagnosis-to-ablation time in paroxysmal atrial fibrillation: preliminary results of the MULTI AF trial

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Diagnosis-to-ablation time (DAT) has been already defined as a predictor of atrial fibrillation (AF) ablation outcome. AF promotes pathological atrial remodelling at electrical, cellular, and structural levels. The aims of this study were to determine the role of DAT in atrial electrical remodelling and its impact on AF recurrencies. Methods Between January 2020 and February 2022, 122 patients (62% male, age 63.5±10.8 y) underwent pulmonary veins isolation (PVI) for paroxysmal atrial fibrillation in 7 Italian centres. For each patient, a high-density bipolar voltage map (BVM) of the left atrium (LA) was acquired by sequential multielectrode mapping in sinus rhythm through the Pentaray™ Catheter and the CARTO3® mapping system. More than 200 voltage points per map were acquired in different segments of the LA (posterior, anterior, lateral, superior, septal and inferior ). The procedural endpoint was PVI by circumferential ablation around the pulmonary vein antra. On top of PVI no "adjunctive" ablations, were performed. All patients were monitored as outpatients for AF recurrence. Results For the 122 patients enrolled the mean DAT was 37.6±35.2 months. Two groups were identified according to DAT: 51 patients in Group A with DAT ≤ 12 months and 71 patients in Group B with DAT &amp;gt; 12 months. The two groups have similar clinical, electrocardiographic and echocardiographic characteristics. Intraprocedural pulmonary vein isolation was achieved in all patients. At the high-density left atrial BVM a concealed electrical remodelling was detected in group B in each LA segment (Fig.1), with the mean global LA voltage amplitude significantly lower in patients with DAT&amp;gt;12 months (group A 2.32±0.81 mV vs group B 1.47±0.74 mV, p&amp;lt;0.01). After a median follow-up of 11.9±9.4 months, 14 patients (11.4%) had AF recurrencies following the first ablation procedure. A significant lower rate of AF recurrence was found among patients with DAT &amp;lt; 12 months (Fig. 2): 2 patients in group A vs 12 patients in group B (4% vs 18.2%, p&amp;lt;0.01). Conclusion Patients with paroxysmal atrial fibrillation with DAT&amp;gt;12 months have significantly lower bipolar LA voltages, revealing a concealed atrial remodelling. Furthermore, DAT&amp;gt;12 months is associated with poor AF ablation outcome.

The critical isthmus of left atrial anterior wall flutter is mostly circumscribed into a small area immediately behind the aortic root. Implications for catheter ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial flutters (LAFL) are typically observed in patients with previous ablation lines or surgery in the left atrium (LA). Less frequently, scar-related left atrial anterior wall (LAAW) flutters may occur. Although the presence of low-voltage areas (LVAs, a surrogate of scar) in the LA is considered an arrhythmogenic substrate and a marker of atrial cardiomyopathy, the pathophysiologic factors responsible for its formation remain unclear. We hypothesized that compression of the LAAW by the aortic root could be responsible of LVAs found in the LAAW, and therefore, be the substrate for the development of LAAW flutter. Purpose We aimed to describe: 1) the relationship between the aortic root and the presence of LVAs in the LAAW, which is the substrate for reentry; and 2) the clinical and electrophysiological characteristics of LAAW atrial flutter. Methods Consecutive patients referred for LAFL ablation between April 2019 and September 2022 in a single center were retrospectively collected. Among 55 patients with LAFL, 10 (18%) demonstrated a macroreentrant circuit with a critical isthmus identified in the LAAW, in the absence of previous ablation lines or surgery, and were included in the analysis. Previous pulmonary vein isolation (PVI) was not an exclusion criterion. All patients underwent a multidetector computerized tomography (MDCT) prior to the procedure and the images were analyzed using ADAS 3DTM imaging platform. Activation mapping was performed in all patients using a multielectrode mapping catheter and CARTO 3 navigation system. Results 9 of 10 patients were male (mean age 74,3 ± 6,3 years). LA enlargement was present in all patients (48,3 ± 4,7 mm) and the mean aortic root diameter was 34,8 ± 3,4 mm. The mean LAAW flutter cycle length was 293,4 ± 68,3 ms. In 9 of the patients (90%), the LAAW flutter critical isthmus was just behind the aortic root, separated by &amp;lt; 1 mm according to the LA-aortic root fingerprinted isodistance map (mean fingerprinted isodistance area was 5,8 ± 2,5 cm2). The remaining patient had the critical isthmus just below the aortic root, between the area in contact with the latter and the mitral annulus. Furthermore, in all cases, the critical isthmus was immersed in LVAs. All but 1 LAAW flutter terminated during radiofrequency (RF) energy applications and rendered it non-inducible. After a median follow-up of 13,6 months (IQ range 5,3-21,6), 7 patients (70%) remained without recurrences. Conclusion In patients with LAAW atrial flutter, the presence of LVAs and the critical isthmus of the tachycardia are mostly circumscribed into small areas immediately behind the aortic root. Knowledge of this close relationship and the use of the isodistance map could be useful when mapping and ablating LAAW flutter, helping to straightforward the ablation procedure.

C46 ELECTROPHYSIOLOGICAL ASSESSMENT OF ATRIAL TACHYCARDIA SUBSTRATES IN PATIENTS WITH REPAIRED TETRALOGY OF FALLOT

Abstract Introduction Adults with repaired tetralogy of Fallot (rToF) experience episodes of atrial tachycardia (AT) and radiofrequency catheter ablation (RFCA) is often required but systematic evaluation of the mechanisms and recurrences is lacking. Methods Between January 2013 and October 2021, 20 rToF patients with AT referred for catheter ablation were enrolled. Electrophysiologic study with 3D electroanatomic mapping with multi–electrode mapping catheters was done, with right atrial bipolar voltage and activation mapping of the AT. Three mechanisms were searched: intra–atrial re–entrant tachycardias (IART), focal (FAT), other. Critical isthmus (CI) for IART was identified with activation mapping. FATs were localized according to the earliest uni/bipolar signal. All induced AT were treated. RFCA was aimed at the earliest activation point for FAT and at the critical isthmus for IART, anchoring lesion to fixed obstacles (valve annuli or scar). Written informed consent was provided. Results Among 20 adult (age 46±14 years) and mainly females (n=11, 55%) enrolled pts, 36 AT were documented: 25 (70%) IART, 10 (27%) FAT and only 1 (3%) had a typical atrioventricular nodal reentrant tachycardia. Mean tachycardia cycle length was 307±95 ms. Two ATs were induced in 11 pts, 3 in 4 pts and 4 in 2 during index EPS. Among IART, cavo–tricuspid isthmus (CTI) was the prevalent CI (n=14, 60%), while incisional IART (IARTinc, atriotomy and superior and inferior vena cava orifices, SVC and IVC, respectively) was the second mechanism (n=9, 39%). In two pts, due to non–inducibility, a pre–emptive lesion set comprising in one case CTI and in the second case CTI+SVC–atriotomy–IVC line was performed. Among FAT, in 3 cases the AT was mapped in the coronary sinus, in two at the tricuspid annulus, other at the crista terminalis, right appendage base, posterolateral scar or between atriotomy and SVC. During a median follow–up of 23 months (interquartile range, 6–37) recurrence occurred in 8 pts (25% of pts, 22% of tachycardias). Pts with recurrences were younger (43±7 vs. 48±17 y, p=0.04); no differences were found according to critical isthmus location (4 CTI and 4 IARTinc, 50%, p=ns). Conclusions Among rToF pts with AT, IART is the prevalent mechanism and CTI is the prevalent CI; atriotomy scar, however, is involved in a substantial portion of the critical isthmuses of the IART; FAT location is much more variable. Long–term freedom from AT in this clinical setting is encouraging.

P166 LEFT VENTRICULAR SUMMIT PVC–INDUCED CARDIOMYOPATHY: A CASE REPORT

Abstract A 76 y.o. patient referred to our attention for syncopal and presyncopal episodes. His ECG showed several premature ventricular contractions (PVC) with the morphology of a right bundle branch block (RBBB)– positive concordance in precordial leads and transtion in V3 lead– and an inferior axis. Echocardiographic finding was a moderate reduced ejection fraction. Furthermore coronarography did not identify critical stenosis, excluding an ischemic etiology. Cardiac MRI was performed, confirming the reduce ejection fraction and excluding LGE. Because of high burden of 25000 PVCs on 24 h ECG registration and progressive deterioration of ejection fraction, despite antiarrhythmic drugs, catheter ablation was considered. An high density multielectrode mapping catheter was used and an initial right ventricular mapping was perfomed, recording local electrograms but without identification of a clear earliest site of activation. Therefore a retrograde transaortic left ventricular mapping was performed. Earliest site of activation was not significant (about 15 milliseconds), as well as percentage of correlation during pace–mapping. Epicardial mapping through coronary sinus into the anterior interventricular vein (AIV) showed a significant earliest activation site (greater than 30 ms) and a negative unipolar signal (QS) was detected. Pacing in this region highlighted a significant percentage of correlation with native PVC (92%), then catheter ablation was attempted. A first short duration application of radiofrequency was erogated on the endocardial side in front of the projection of the catheter in the AIV, because of possible risks of procedure, obtaining a temporary PVC suppression. Subsequently, after execution of a coronary angiogram proving a distance of the ablator in AIV and IVA/Cx vessels greater than &amp;gt; 1 cm, an endovenous approach was attempted with application of radiofrequency into the AIV, obtaing complete PVC suppression. At a 6 months follow–up ejection fraction improved (FE 50%) and PVC were not detected. Discussion Epicardial approach throught coronary sinus is an effective strategy to map and ablate arrhythmias of left ventricular summit. In addiction this stretegy allows a less invasive epicardial approach than other procedures, requiring a cardiosurgery standby.

PO-05-096 PROGNOSTIC VALUE OF NEAR-FIELD ELECTROGRAMS AT CRITICAL ABLATION SITES DURING VENTRICULAR TACHYCARDIA ABLATION

Electrogram (EGM) annotation during VT is challenging due to complexity of EGMs and difficulty in distinguishing far-field and near-field (NF) EGMs. EGM frequency increases with greater EGM proximity to the recording electrode. The prognostic value of high-frequency EGMs at critical ablation sites during VT ablation is unknown. The utility of recently developed algorithms to annotate local EGM frequency during 3D mapping (Ensite X, Abbott, Inc.) is unknown. The absence of high frequency EGMs at critical sites for VT ablation may suggest that the EGM of interest is deep to or remote from the recording electrode. To investigate the utility of the EGM frequency annotation at critical ablation sites during VT ablation. Consecutive patients with scar-related VT undergoing catheter ablation (RFA) were analyzed. High density substrate maps were created in presenting ventricular rhythm using a High-definition multi-electrode mapping catheter (HD Grid, Abbott, Inc.). Critical sites for induced VT were identified based on pace-mapping, activation mapping, entrainment mapping, or termination of VT with RFA. Substrate maps were retrospectively analyzed with EGM annotation based on NF EGM. The highest frequency EGM within 5mm of the critical ablation site was identified and analyzed. Thirty-four critical sites were identified and ablated in twenty-two patients, 14 (64%) with ischemic cardiomyopathy, age 65±10 years with LVEF was 33±13 %. VT recurred in 9 patients (41%). The peak frequency in the critical site using the NF annotation in patients with recurrence was significantly lower than in patients without recurrence (192 vs 397 Hz; p=0.01). Cox regression analysis shows statistically significant higher risk to have VT recurrence when the frequency is below the median frequency (HR 5.09, 95% C.I 1.05-24.68, p=0.04). Area under the receiver operator characteristic curve for peak EGM frequency at VT critical site as a predictor of VT recurrence was 0.81, with critical site EGM frequency < 286 Hz providing 89% sensitivity and 69% specificity for VT recurrence. Low frequency EGMs at VT critical sites measured by EGM frequency annotation software identify patients at greater risk of VT recurrence. A finding of low frequency EGMs at apparent critical site implies that the successful ablation may require additional mapping, including consideration of epicardial or venous mapping, to localize better the true critical site or ablation techniques to provide deeper ablation.

Multielectrode mapping for premature ventricular contraction ablation – A prospective, multicenter study

PurposeWe aim to evaluate whether the use of a multielectrode mapping catheter could lead to higher efficacy of premature ventricular contraction (PVC) ablation. MethodsProspective, multicenter nonrandomized study of consecutive patients referred for PVC ablation from January 2018 to June 2021. Patients were separated into two groups: activation map performed with the PentaRay catheter (Study group) or with the ablation catheter (Control group). PMF software was used in both groups. Procedural endpoints and 1-year freedom from ventricular arrhythmia were assessed. ResultsDuring the enrollment period 136 patients (60% males, mean age of 55 ± 17 years, 60% left-sided origin) fulfilled the inclusion criteria - 68 patients in each group. Patients in the Study Group had a sevenfold higher number of acquired activation points (768 ± 728 vs. 110 ± 79, p < 0.01), a shorter mapping time (28 ± 19 min vs. 49 ± 32 min, p < 0.01) and a quicker procedure time (110 ± 33 min vs. 134 ± 50 min, p < 0.01), compared to patients in the Control Group. While there were no significant differences in the acute success (95.6% in the Study Group vs. 90.1% in Control group, p = 0.49), or adverse events (4% in the Study group vs. 7% in the Control group, p = 0.72), patients in the Study group had a higher freedom from ventricular arrhythmia at 1-year (89.7% vs. 70.6%, p = 0.01). The use of the PentaRay catheter was an independent predictor of success (HR = 6.20 [95% CI, 1.08–35.47], p = 0.003). ConclusionsThe use of the PentaRay catheter may improve the outcome of PVC ablation while reducing procedure time.

The value of functional substrate mapping in ventricular tachycardia ablation.

In the setting of structural heart disease, ventricular tachycardia (VT) is typically associated with a re-entrant mechanism. In patients with hemodynamically tolerated VTs, activation and entrainment mapping remain the gold standard for the identification of the critical parts of the circuit. However, this is rarely accomplished, as most VTs are not hemodynamically tolerated to permit mapping during tachycardia. Other limitations include noninducibility of arrhythmia or nonsustained VT. This has led to the development of substrate mapping techniques during sinus rhythm, eliminating the need for prolonged periods of mapping during tachycardia. Recurrence rates following VT ablation are high; therefore, new mapping techniques for substrate characterization are required. Advances in catheter technology and especially multielectrode mapping of abnormal electrograms has increased the ability to identify the mechanism of scar-related VT. Several substrate-guided approaches have been developed to overcome this, including scar homogenization and late potential mapping. Dynamic substrate changes are mainly identified within regions of myocardial scar and can be identified as local abnormal ventricular activities. Furthermore, mapping strategies incorporating ventricular extrastimulation, including from different directions and coupling intervals, have been shown to increase the accuracy of substrate mapping. The implementation of extrastimulus substrate mapping and automated annotation require less extensive ablation and would make VT ablation procedures less cumbersome and accessible to more patients.

Abstract 15179: Histology-Validated Delayed Enhancement Magnetic Resonance Imaging of Atrial Fibrillation Driver Substrate

Introduction: Persistent (per) AF may be maintained by localized extra-PV drivers (DRs). Regional fibrosis can serve as a substrate for AF DRs, but its visualization by delayed enhancement (DE)-MRI lacks proper validation for driver substrates. The objective of this study is to evaluate if histology-validated normalized (HVN) DE-MRI thresholds can define arrhythmogenic fibrotic content in multielectrode mapping (MEM)-defined DRs from perAF patients’ (Pts) DE-MRI. Methods: PerAF Pts (n=14, 71% male; 63±10 y/o) had DE-MRI at 3T (0.63x0.63x0.63mm 3 , 0.2mmol/kg Gd) before their perAF ablation procedure. Chamber-specific DE-MRI intensity was normalized to the healthy atria (mean lowest 5% intensity, 0 AU) and mitral (LA) or tricuspid (RA) valve (100 AU). 3 control and 5 perAF canines had DE-MRI and regional histology to validate DE-MRI fibrotic thresholds for the LA and RA, which were defined as standard deviations (SD) above 40% of the mean healthy atrial tissue intensity (LA: 3.7 SD, RA: 2.7 SD). Fibrosis-enhancement of segmented MEM-defined DRs (LA: n=25, RA: n=11) were analyzed using conventional, non-normalized 3 SD and HVN thresholds and compared to 5 random regions (non-DRs) within the same anatomical region(s). Results: Only our HVN approach could reveal arrhythmogenic fibrotic substrates in LA DR regions, but not the conventional approach. Both approaches could not provide significant differences for RA DR vs non-DR fibrosis regions. The cut-off of 33.6% of LA DE-MRI fibrotic enhancement using the HVN approach allowed to distinguish LA DR vs. non-DR regions with 56% sensitivity and 70% specificity. At 12 months follow-up, 10 Pts remained free of AF. Conclusion: MEM-defined DRs within fibrotic regions, identified by HVN DE-MRI, may represent efficient targets for ablation of LA arrhythmogenic perAF substrates. Integration of MEM and MRI may lead to improved targeted ablation and long-term AF freedom.

Comparison between Standard and High-Definition Multi-Electrode Mapping Catheter in Ventricular Tachycardia Ablation.

A high-definition mapping catheter has been introduced, allowing for bipolar recording along and across the spline with a rapid assessment of voltage, activation, and directionality of conduction. We aimed to evaluate differences in mapping density, accuracy, time, and consequently RF time between different mapping catheters used for ventricular tachycardia (VT) ablation. We enrolled consecutive patients undergoing VT ablation at our center. Patients were divided into the LiveWire 2-2-2 mm catheter (group A) and the HD Grid SE (group B). Primary endpoints were total RF delivery time, the number of points acquired in sinus rhythm and VT, and the scar area. Fifty-one patients were enrolled, 22 in group A and 29 in group B. More points were acquired in the Grid group in sinus rhythm (SR) and during VT (2060.78 ± 1600.38 vs. 3278.63 ± 3214.45, p = 0.05; 4201.13 ± 5141.61 vs. 10,569.43 ± 13,644.94, p = 0.02, respectively). The scar area was smaller in group B (Bipolar area, cm2 4.52 ± 2.72 vs. 2.89 ± 2.81, p = 0.05. Unipolar area, cm2 7.47 ± 4.55 vs. 5.56 ± 2.79, p = 0.03). Radiofrequency (RF) time was shorter in the Grid group (30.52 ± 13.94 vs. 22.16 ± 11.03, p = 0.014). LPs and LAVAs were eliminated in overall >93% of patients. No differences were found in terms of arrhythmia-free survival at follow-up. In conclusion, the use of a high-definition mapping catheter was associated with significantly shorter mapping time during VT and RF time. Significantly more points were acquired in SR and during VT. During remap, we also observed more LAVAs and LPs requiring further ablation.

Safety and feasibility of a novel multilectrode array catheter in mapping atrial and ventricular arrhythmias with high density: results from the multi-center OPTIMUM study

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): This study was funded by Biosense Webster, Inc. Background/Introduction The novel multielectrode array mapping catheter includes 48 electrodes symmetrically distributed across and along 6 splines (Picture), with an additional unipolar reference electrode to reduce far-field signals built in at the tip of the irrigation lumen. Preclinical studies demonstrated its ability to provide high density and high resolution mapping in complex substrates, but its usability and safety in patients with atrial or ventricular arrhythmias have not been investigated. Purpose To assess the safety and mapping performance of the catheter with the electroanatomical navigation system for mapping in the atria and ventricle in patients with a variety of complex arrhythmias. Methods The OPTIMUM study was a prospective, single arm study conducted at 3 European sites. Patients with scar-related atrial tachycardia (AT), PAF and persistent AF (PsAF), ventricular tachycardia (VT), or premature ventricular complexes (PVC) underwent pre-ablation mapping with the study catheter, and subsequent ablation according to institutional standard of care practice; the follow up period was 7 days. The primary safety endpoint was the incidence of device-related serious adverse events (SAE) within 7 days following the procedure. The primary effectiveness endpoint was the completion of protocol-required fast activation and electro anatomical pre-ablation mapping without resort to non-study mapping catheter(s), including fast anatomical mapping, mapping of substrate or any area of interest, and identification of conduction channel(s), gap(s) and critical isthmuses. General procedural characteristics as well as physician feedback (7-point Likert scale: 1 = poor and 7 = excellent) on various aspects of deployment, signal quality, and learning curve were also evaluated. Results Thirty-one patients (mean age: 59.8±14 years, 71.0% male) were enrolled and treated (9 scar-related AT, 12 PAF, and 1 PsAF, 6 VT, and 3 PVC). There was no (0/31) SAE reported, and the primary effectiveness endpoint was achieved in all subjects (31/31). Almost all operators rated highly (≥ 5) on noise reduction in bipolar maps (30/31) and short learning curve (27/31). Bipolar signals and catheter maneuverability were rated highly favorable (≥5) in the left and right atria and met-expectation-and-above (≥4) in the left and right ventricles. Conclusion(s) The first-in-human clinical data demonstrate the safety and effectiveness of the novel microelectrode array mapping catheter to efficiently map various atrial and ventricular complex arrhythmias with good signal quality. Physicians indicated high satisfaction with the learning curve, catheter maneuverability, tissue characterization in all cardiac chambers.

A novel dipole charge density mapping system integrated in robotics offers advantages for ablation of atrial tachycardias: first-in-human experience

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation (CA) for atrial tachycardia (AT) and atrial flutter (AFL) offers favorable acute and long-term outcomes. Until recently, mapping of AT/AFL was only possible with sequential mapping methods using manually controlled catheters. Even by implementing multielectrode mapping, some limitations exist during mapping of short-lived arrhythmias and ATs with unstable CL. Remote magnetic navigation (RMN) with its atraumatic catheter design has superior safety profile and excellent accuracy. Recently, a novel high-resolution mapping system (AcQMap) can be used in combination with RMN (AcQMap-RMN). Purpose To assess the feasibility, safety and efficacy of AcQMap-RMN guided ablation in the management of complex ATs. Methods All patients undergoing CA for AT/AFL using AcQMap-RMN were included. The AcQMap system utilizes two different types of mapping: Single Position Map (SMP) and SuperMap, allowing mapping of both non-sustained and sustained ATs. Procedural efficiency was characterized by procedure time, total ablation time and radiation doses. Acute success was defined by arrhythmia source elimination. Efficacy data are based on 12-month follow up and number of redo procedures. Procedural safety was evaluated by intra- and post-procedural complications. Results A total number of 76 patients were referred for CA with AT/AFL (mean age 59.0±13.2), including 3 patients with inappropriate sinus tachycardia and 73 patients with AT/AFL. Out of 73 patients, 8 had perinodal AT. From the remaining 65 patients, 38 had de novo, 22 had post-PVI, and 5 patients had post-MAZE AT/AFL. Twenty-nine patients had short-lived ATs and were mapped exclusively by SPM. The mean procedure time was 175.9±61.4 min, mean ablation time 964.0 (IQR 422.0-1693.0) s, and mean radiation dose was 152.0(IQR 86.7-294.0) mGy. Acute success was documented in 70 procedures (92.1%). From de novo AT/AF patients 4 (10.5%), from post-PVI and post-MAZE AT/AFL patients 3 had recurrence at the end of the follow-up period (11.1%). Four patients had redo procedure. Three patients had post-procedural complications including 2 patients with groin hematoma and 1 patient with transient ischemic attack. Conclusion AcQMap-RMN integration offers improved efficiency, high success and low complication rates in complex AT ablation.