Pace Mapping Research Articles

Intracardiac electrogram–based atrial pace mapping for detecting the earliest activation site in atrial arrhythmias

Intracardiac electrogram–based atrial pace mapping for detecting the earliest activation site in atrial arrhythmias

Ventricular Tachycardia Catheter Ablation: Retrospective Analysis and Prospective Outlooks-A Comprehensive Review.

Ventricular tachycardia is a potentially life-threatening arrhythmia associated with an overall high morbi-mortality, particularly in patients with structural heart disease. Despite their pivotal role in preventing sudden cardiac death, implantable cardioverter-defibrillators, although a guideline-based class I recommendation, are unable to prevent arrhythmic episodes and significantly alter the quality of life by delivering recurrent therapies. From open-heart surgical ablation to the currently widely used percutaneous approach, catheter ablation is a safe and effective procedure able to target the responsible re-entry myocardial circuit from both the endocardium and the epicardium. There are four main mapping strategies, activation, entrainment, pace, and substrate mapping, each of them with their own advantages and limitations. The contemporary guideline-based recommendations for VT ablation primarily apply to patients experiencing antiarrhythmic drug ineffectiveness or those intolerant to the pharmacological treatment. Although highly effective in most cases of scar-related VTs, the traditional approach may sometimes be insufficient, especially in patients with nonischemic cardiomyopathies, where circuits may be unmappable using the classic techniques. Alternative methods have been proposed, such as stereotactic arrhythmia radioablation or radiotherapy ablation, surgical ablation, needle ablation, transarterial coronary ethanol ablation, and retrograde coronary venous ethanol ablation, with promising results. Further studies are needed in order to prove the overall efficacy of these methods in comparison to standard radiofrequency delivery. Nevertheless, as the field of cardiac electrophysiology continues to evolve, it is important to acknowledge the role of artificial intelligence in both the pre-procedural planning and the intervention itself.

P-Wave Morphology From Common Nonpulmonary Vein Trigger Sites Following Pulmonary Vein and Posterior Wall Isolation

BackgroundNon-pulmonary vein (PV) triggers are increasingly targeted during atrial fibrillation (AF) ablation. P-wave morphology (PWM) can be useful because point mapping of AF triggers is challenging. The impact of prior ablation on PWM is yet to be determined. ObjectivesThis study sought to report PWM before and after left atrial (LA) ablation and construct a P-wave algorithm of common non-PV trigger locations. MethodsThis multicenter, prospective, observational study analyzed the paced PWM of 30 patients with persistent AF undergoing pulmonary vein isolation (PVI) and posterior wall isolation (PWI). Pace mapping was performed at the SVC, crista terminalis, inferior tricuspid annulus, coronary sinus ostium, left septum, left atrial appendage, Ligament of Marshall, and inferoposterior LA. The PWM was reported before PVI, then blinded comparisons were made post-PVI and post-PVI + PWI. A P-wave algorithm was constructed. ResultsA total of 8,352 paced P waves were prospectively recorded. No significant changes in the PWM were seen post-PVI alone in 2,775 of 2,784 (99.7%) and post-PWI in 2,715 of 2,784 (97.5%). Changes in PWM were predominantly at the IPLA (53 P waves) with a positive P-wave in leads V2 to V6 before biphasic post-PWI, LA appendage (9 P waves), coronary sinus ostium (6 P waves), and ligament of Marshall (3 P waves). A PWM algorithm was created before PVI and accurately predicted the location in 93% post-PVI + PWI. ConclusionsMinimal change was observed in PWM post-PV and PWI aside from the IPLA location. A P-wave algorithm created before and applied after PVI + PWI provided an accuracy of 93%. PWM provides a reliable tool to guide the localization of common non-PV trigger sites even after PV and PWI.

Electrophysiological characteristics and ablation of ventricular arrhythmias originating from the intramural basal inferior septum.

The electrocardiographic and electrophysiological characteristics of ventricular arrhythmia (VA) arising from the intramural basal inferior septum (BIS) have not been specifically addressed to date. The aim of the current study was to characterize intramural BIS-VA and distinguish it from those with endocardial origins besides clarifying the anatomical configurations of the pyramidal space. Fifty-five consecutive patients undergoing catheter ablation of VAs from BIS were identified and divided into three groups: the left ventricular (LV)-BIS group (n = 28), right ventricular (RV)-BIS group (n = 8), and intramural group (Intra, n = 19). Compared with the LV-BIS and RV-BIS groups, patients in the Intra group presented with no adequate earliest activation time at the two-sided BIS and epicardial coronary system [right: 7.79 ± 2.38 vs. left: 7.16 ± 2.59 vs. the middle cardiac vein (MCV): 6.26 ± 1.73 ms, P = 0.173] and poor-matched pacing-produced QRS at each site. Under the intracardiac echocardiography view, the pyramidal base was the broadest part of the septum and served as the division of the two-sided BIS. Focal ablation yielded promising acute-term and long-term procedural success in the LV-BIS and RV-BIS groups. But for the Intra group, VAs disappeared only after stepwise ablation successively targeted early preferential exit. After follow-up, three patients in the Intra group had recurrent VA, and all of them were treated well by a redo procedure or drug therapy. Intramural VAs were relatively common in the BIS region in our series. Intra-procedural mapping was important to distinguish the intramural VAs from other VAs by comparing the local activation time and pacing mapping. Procedural success could be achieved by stepwise ablation on the counterpart sides of the BIS and within the MCV.

Abstract 13989: Automated VT Localization System Based on Patient-Specific Integration of Two-Dimensional (2D) Intracardiac Echocardiography (ICE) and 3DElectroanatomic (EA) Mapping

Introduction: We have previously developed an intraprocedural automated localization system to identify VT-exit sites projected onto a patient-specific CT geometry using 12-lead ECGs. However, the accuracy of the system depends on a registered reconstruction of the cardiac surface. Objective: To assess the feasibility of using a registered integration of 2D ICE and 3D EA mapping to perform intraprocedural localization, while avoiding errors being introduced by registration of the CT geometry and EA map. Methods: Four patients with 7 VTs (5 LV VTs, 2 RV VTs) were enrolled. A 3D patient-specific shell of both ventricles that combines ICE and EA map was reconstructed during the ablation procedure. It was imported into the automated localization system post-procedure for offline analysis. The system was used to estimate the location of VT-exit sites on the reconstructed 3D geometry. Localization accuracy was quantified for the VT-exit sites by comparing the distance of the calculated site to the site of successful ablation or that of best pacing site match. Results: Five reentrant VT-exit sites were identified using activation and entrainment mapping, supplemented by pace-mapping at the scar margin; two focal VTs were identified by pace mapping. The proposed system achieved mean localization accuracy of 6.4 mm for 7 VTs. Conclusions: ICE and EA mapping can be successfully integrated for intraprocedural automated localization of ventricular activation in both ventricular chambers and may avoid registration errors of CT geometry integration.

Utility of Very High-Output Pacing to Identify VT Circuits in Patients Manifesting Traditionally Inexcitable Scar

BackgroundEntrainment and pace mapping are used to identify critical components (CCs) of ventricular tachycardia (VT) circuits. In patients with dense myocardial scarring, VT circuits may elude capture at standard high pacing outputs (up to 10 mA at a 2-millisecond pulse width). ObjectivesThe purpose of this study was to assess the utility of very high–output pacing (V-HOP, 50 mA at 2 milliseconds) for identifying CCs of VT circuits after standard high pacing output failed to elicit capture in densely scarred myocardial tissue. MethodsOur standard VT ablation approach included electroanatomic mapping for substrate characterization and entrainment and/or pace mapping to identify CCs of VT circuits. Patients that required V-HOP to capture sites of interest comprised the study cohort. Ablation endpoints were VT termination and noninducibility. ResultsTwenty-five patients (71 ± 10 years of age, all males) undergoing 26 VT ablations met the inclusion criteria. The mean left ventricular ejection fraction was 30% ± 14%, and 85% had ischemic cardiomyopathy. V-HOP was used to successfully entrain VT in 17 patients, yielding central isthmus sites in 10 and entrance/exit sites in 4. VT terminated with radiofrequency ablation at these sites in 15 patients. In 9 patients, V-HOP identified scar locations with a delayed exit. Acute procedural success was achieved in 24 patients without any adverse events. Over a follow-up period of 16 ± 21 months, 2 patients experienced VT recurrence requiring repeat ablation during which the same location was targeted successfully in 1 patient. ConclusionsIn VT patients with a dense scar that is traditionally inexcitable, V-HOP can identify CCs of the re-entrant circuit and guide successful ablation.

Evaluation of Pacing Parameters to Induce Contractions in the Small Intestine.

Postoperative ileus and chronic intestinal pseudo-obstruction are intestinal motility disorders that can compromise bowel function resulting in a significant reduction in quality of life and prolonged hospital stays. While medication and nutritional support provides relief for some patients, a significant patient population remains untreated. Therefore, alternative treatment options are required. A novel framework that enables small intestine pacing and video mapping of the contractile response was developed. Pacing pulse parameters (pulse-period: 2.7, 10 s, pulse-width: 100, 400 ms, and pulse-amplitude: 4, 6, 8 mA) were systematically varied to investigate the effect of pacing on the small intestine contractility. The contractile response was quantified by computing the strain of the intestinal diameter at the pacing site. The framework was applied in vivo on porcine jejunal loops (n=4) where segmental contractions were induced in response to pacing pulses. Strain increased with increasing pulse-amplitude and pulse-width, while pacing at a period of 2.7 s elicited higher contractile strains compared to pacing at a period of 10 s at all settings (e.g., -0.18 ± 0.06 vs 0.12 ± 0.06 at 8 mA, 400 ms). For a pulse-width of 100 ms, the contractile strain continued to increase with increasing pulse-amplitude, while the induced strain was comparable for all pulse-amplitudes when paced with high pulse-width (400 ms). Therefore, pacing is an effective tool in modulating the intensity of segmental contractions.Clinical Relevance- Different pacing parameters can define contraction intensity and frequency in the small intestine. This is of therapeutic potential for treating motility disorders such as post-operative ileus and chronic intestinal pseudo-obstruction.

Septal Substrate Ablation Guided by Delayed Transmural Conduction Times: A Novel Ablation Approach to Target Intramural Substrates

BackgroundIntraprocedural identification of intramural septal substrate for ventricular tachycardia (ISS-VT) in nonischemic cardiomyopathy (NICM) is challenging. Delayed (>40 ms) transmural conduction time (DCT) with right ventricular basal septal pacing has been previously shown to identify ISS-VT. ObjectivesThis study sought to determine whether substrate catheter ablation incorporating areas of DCT may improve acute and long-term outcomes. MethodsWe included patients with NICM and ISS-VT referred for catheter ablation between 2016 and 2020. ISS-VT was defined by the following: 1) confluent septal areas of low unipolar voltage (<8.3 mV) in the presence of normal or minimal bipolar abnormalities; and 2) presence of abnormal electrograms in the septum. Substrate ablation was guided by the following: 1) activation and/or entrainment mapping for tolerated VT and pace mapping with ablation of abnormal septal electrograms for unmappable VTs (n = 57, Group 1); and 2) empirically extended to target areas of DCT during right ventricular basal septal pacing regardless of their participation in inducible VT(s) but sparing the conduction system when possible (n = 24, Group 2). ResultsThere were no significant baseline differences between Groups 1 and 2. Noninducibility of any VT programmed stimulation at the end of ablation was higher in Group 2 compared with Group 1 (80% vs 53%; P = 0.03). At 12-month follow-up, single-procedure VT-free survival was significantly higher (79% vs 46%; P = 0.006) and the time to VT recurrence was longer (mean 10 ± 3 months vs 7 ± 4 months; P = 0.02) in Group 2 compared with Group 1. ConclusionsIn patients with NICM and ISS-VT, a substrate ablation strategy that incorporates areas of DCT appears to improve freedom from recurrent VT.

Association of Sinus Wavefront Activation and Ventricular Extrastimuli Mapping With Ventricular Tachycardia Re-Entrant Circuits

BackgroundSubstrate-based ablation targets areas of delayed and fractionated electrograms during sinus rhythm, which are sensitive for identifying the ventricular tachycardia (VT) isthmus but is influenced by the activation wavefront direction and decremental pacing. ObjectivesThe aim of this study was to correlate the areas of latest activation during varying wavefront activation mapping and decremental pacing mapping with sites critical to the VT isthmus. MethodsThree high-density electroanatomical substrate maps were created in patients presenting for ablation of monomorphic VT: 1) native sinus rhythm; 2) right ventricular (RV) apical pacing; and 3) an RV apical S2 map following the S1 drive train at 20 ms above the ventricular effective refractory period. Areas corresponding to the latest activation were compared with the VT isthmus identified by conventional mapping. ResultsTwenty patients with structural heart disease with a mean age of 55.6 ± 16.9 years were included. The majority of the cohort consisted of patients with ischemic heart disease (50%) and arrhythmogenic RV cardiomyopathy (35%). Epicardial ablation was performed in 45% of patients. The concordance of the site of latest activation in sinus rhythm with the VT isthmus was 75%. The location of the latest activation during RV apical pacing corresponded with the VT isthmus in 85% of cases. However, in 95% of cases, the site of the latest activation following the S2 stimulus colocalized to the VT isthmus. ConclusionsIn a mix of underlying myocardial substrates, regions of conduction slowing during decremental pacing colocalize with the VT isthmus more frequently than sinus rhythm activation mapping and may have a role in substrate-based ablation where VT induction is undesirable.

Impact of pacing output and cycle length on QRS morphology in ablation of premature ventricular contractions (PACE-MAP-trial)

Abstract Funding Acknowledgements Type of funding sources: None. Background Pace mapping is an established technique to localize the origin of premature ventricular contractions (PVC). The QRS morphology induced by endocardial pacing is compared with a previously recorded template of the target arrhythmia. Based upon historic in-vitro models pacing at the arrhythmia’s coupling interval (CI) and stimulation threshold has become the gold standard in pace mapping. Purpose There is a paucity of data supporting pacing at the CI and stimulation threshold as the gold standard for pace mapping. In this prospective study, we sought to assess systematically the impact of variations of pacing output and cycle length on the resulting QRS morphology during pace mapping in the context of PVC ablation. Methods All patients undergoing ablation of idiopathic PVC were prospectively enrolled in this study. Pace mapping was performed using four different parameter settings: (1) A predefined fixed burst at maximum output (10V/2ms), (2) fixed burst at stimulation threshold, (3) coupling interval at maximum output and (4) coupling interval at stimulation threshold. Pacing cycle length (PCL) of the fixed burst was defined as follows: For a CI≤450ms = PCL of CI+100ms and for a CI≥450 = PCL of CI-100ms. Using an automated waveform comparison algorithm (Bard® LabSystem™ PRO software; Boston Scientific, MA, USA), the resulting QRS complexes were matched with the clinical PVC, and with the gold standard. For every parameter setting the mean of the matching percentage of three QRS complexes entered the analysis. Results We report data of the first 47 consecutive patients (57±18 years, 64% male) enrolled in this ongoing study between May 2021 and September 2022. The pacing protocols were performed at 75 different sites: 6/75 epicardially via great cardiac vein, 38/75 in the RVOT, 23/75 in LVOT and 8/75 in the left ventricular cavity. When comparing the QRS morphologies resulting from the four different pace mapping settings with the clinical PVC, the univariate analysis revealed no difference between groups (p=0.9). Furthermore, there was no difference comparing the paced QRS morphologies at different output and cycle length to the gold standard of threshold pacing at coupling interval (p=0.9). Conclusion Variations of pacing output and stimulation cycle length during pace mapping does not affect QRS morphology during PVC ablation. Applying a modern automated waveform comparison tool, no advantage was observed when comparing with the gold standard. It is therefore reasonable to assume, that pace mapping can be performed using an easily applicable setting of a fixed burst at maximum pacing output.

The effect of scar imaging quality on in-silico pace-mapping of post-infarction ventricular tachycardia

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Wellcome Trust and British Heart Foundation. Background In-silico pacing mapping is a technique which involves using an anatomically-personalised image-based computational model to generate a ‘virtual’ clinical pace map for enhanced pre-procedural ablation planning of post-infarction ventricular tachycardia (VT). Utilising, as it does, a direct clinical ECG (or implanted device) recording of the clinical VT in order to construct the map, it has a number of advantages over other computational methods which attempt to simulate patient-specific VTs to identify ablation targets. However, accurate model construction relies on adequate scar imaging data, which may not be available with current clinical cardiac MR (CMR) sequences. Purpose To investigate the impact of scar imaging quality on the ability of in-silico pace-mapping to determine the VT origin. Methods VTs were simulated in three post-infarction porcine heart models reconstructed from high resolution (1mm isotropic) contrast-enhanced CMR data. Visual analysis of the VT circuits was performed to identify the VT site of origin (exit site) in each case (as the gold standard). The ECG of each simulated VT was computed and used as input for the construction of the in-silico virtual pace-mapping approach. Prior to pace map construction, the scar anatomy was modified to represent three different levels of imaging resolution: high resolution scar mapping (default); low resolution scar (representing standing clinical CMR sequences), obtained by performing dilation and erosion in the scar to close all inner pathways; and, finally, no scar (cardiac anatomy only, representing CT-based reconstructions). In-silico pace-mapping was performed by pacing the heart in N = 1000 sites from randomly chosen locations, on both surfaces and intramurally, within close proximity (&amp;lt;5mm) from the infarct. ECG signals computed following each paced activation wavefront were compared to the VT ECG through correlation analysis to construct the virtual pace map. The distance d between the VT exit site and the pacing location with the strongest correlation was also computed. Results As can be seen in Figure 1, correlation between VT and paced ECGs was found to be strongest at pacing locations near the VT exit site in all models. Correlation coefficients were similar in value and distribution in models with high- (min: -0.49±0.27 and max: 0.92±0.05) and low-resolution scars (min: -0.46±0.29 and max: 0.93±0.05). While the correlation map in the absence of scar had smaller values when compared to the other two models (min: -0.50±0.24 and max: 0.71±0.09), the VT exit was still located near the pacing location with the strongest correlation: d = 9.47±2.83 (high-res), d = 6.63±6.35mm (low-res) and d = 18.60±7.10mm (no scar). Conclusion In-silico pace-mapping successfully detected the VT exit sites regardless the resolution of the scar. This finding suggest that the level of infarct anatomical detail has a minor effect on simulated paced activation to localize VT ablation.

Double rhythm mapping for coherent electrophysiological substrate characterization in atrial fibrillation patients

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial fibrillation (AF) progresses with a cascade of combined structural, functional, and systemic dysfunctions. Electro-anatomical maps are employed to investigate pro-arrhythmic areas, characterized by abnormal electrical properties. However, single rhythm maps provide only a partial reconstruction: rhythm and wavefront directionality might mask some of these areas. Purpose To demonstrate that the combined quantitative analysis of different rhythm maps (i.e., parallel sinus rhythm and paced maps) could allow consistent identification of structural and functional defects sustaining AF. Methods Thirty AF clinical procedures have been performed with mapping system support. In particular, a sinus rhythm activation map and a paced map have been created with a multipolar catheter exploiting the parallel mapping feature by setting an extra beat (pacing interval = ERP + 40 ms) every three sinus beats. Areas of abnormal conduction have been identified and a comparison of electrophysiological biomarkers (EGMs voltage and fractionation) among the two rhythms has been performed. Results This comparative analysis allowed us to identify both structural and functional electrophysiological phenomena. Specifically, we distinguished: (i) abnormal conduction zones confirmed in both maps, both characterized by signal fractionation and a lower voltage (0,56 ± 0,18 mV) with respect to healthy atrial tissue (2,40 ± 0,41 mV), and (ii) abnormal conduction zones visible in only one of the two maps. In the latter, we distinguished whether the absence of the phenomena was due to wavefront orthogonality to the diseased area (revealed in paced rhythm thanks to a change in wavefront direction) or due to the presence of a functional phenomenon induced by the pacing. In the first group signal fractionation has been detected in both rhythms and a lower voltage has been found (1,79 ± 1,1 mV) with respect to normal conduction zones (3,26 ± 0,98 mV), while in functional cases EGMs fractionation has been identified only in paced maps and no significant difference has been observed in terms of voltage. Conclusion Double rhythm mapping provides a more robust characterization of atrial abnormal conduction phenomena. In fact, it allowed the distinction of true structural dysfunctions from dynamic (functional) ones thanks to the different wavefront directionality and rhythm. Moreover, the structural defects have been confirmed by EGMs analysis, which revealed both low voltage amplitude and high fractionation, characteristics that have not been reported in functional cases.

Consideration of technique for prevention of phrenic nerve injury due to right pulmonary vein ablation of atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Back ground: Right phrenic nerve injury has been known well as a rare complication associated with ablation of right pulmonary vein (RPV) in patients with atrial fibrillation (AF) and pace mapping of the sites where the nerve can be stimulated from the endocardium has been the most commonly accepted real-time technique. Purpose To assess techniques of right phrenic nerve stimulation (PNS) and to consider effective ablation while avoiding phrenic nerve injury (PNI). Methods The consecutive 240 patients who underwent the initial radiofrequency catheter ablation (RFCA) of AF during May 2018 to July 2022 were studied retrospectively. All patients were performed point- by-point ablation and they had PNS from the ablation catheter for each point before ablation the anterior line of RPV. RFCA was performed with a 3.5 mm irrigated catheter using Carto3. Results Mean age 72.7-years, female 95 (39.6%), 123 patients (51.3%) with paroxysmal AF (PAF), mean body mass index (BMI) 23.4 kg/m2, mean left atrial diameter (LAD) 43.3mm. 5 patients (2.1%) confirmed capture on PNS given at 10v stimulation. Although the five patients had nothing in common in terms of age, gender, BMI, or LAD, the site of PNS capture was almost identical, from RPV carina to right superior pulmonary veins (RSPV) anterior area (Fig.1-5). The area captured by 10v stimulation is often large, diverting the ablation largely to the anterior wall to avoid PNI, which can contribute to recurrence if there is epicardial conduction from the right atrium. Therefore, in order to reduce the application area, pace map with 5v stimulation was performed and it detailed PN positioning. The yellow tags in Fig. 1-4 and light blue tags in Fig 5 showed pointes of PNS capture stimulated by 5v. There was no PNS capture exactly next to these tags and no PNI was occurred by RFCA there. RFCA including just next to the area of PNS capture was performed at the surgeon's discretion with an output of 30-45w, 10-25 seconds, and ablation index (AI) target of 400-450, and RPV isolation was achieved without PNI in all patients. Four months later, one patient showed in Fig.1 had recurrent AF, but no reconnection between 4PV and LA was recognized at the 2nd session. Conclusion 2.1% of all patients showed PNS capture in this study. The area of PNS capture was almost same, and a pace map by 5v was effective for detailed identification of the area. Furthermore, PNI did not appear when the application was added just next to the area identified in 5v.

Functional mapping: a new approach for substrate characterization in patients affected by atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background The ongoing challenge is to generate meaningful data during electrophysiological (EP) studies, integrating the knowledge on atrial fibrillation (AF) progression gained by the EP community in the latest years. At the present time there is a lack of EP protocols: most of the centers perform electroanatomical (EA) ablation to isolate pulmonary veins or, in persistent AF forms, some centers propose the performance of additional lines for atrial compartmentalization. However, none of these approaches take in consideration neither the wavefront propagation nor the analysis of functional phenomena. Purpose To investigate whether zones of delayed conduction (slow conduction, SC) or functional propagation (pivot sites, PS) may play a role in terms of maintenance of paroxysmal (PAF) and persistent (PsAF) AF. Methods Twenty-seven consecutive patients with PAF (14 patients) and PsAF (13 patients) have been enrolled in this study. For each patient, a sinus rhythm activation map and a paced map have been created with a multipolar catheter exploiting the parallel mapping feature. According to these activation maps, we analyzed the wavefront propagation. Abnormal conduction was defined as a delimited zone in which the propagation became suddenly slower (&amp;lt;0.5 m/s, slow conduction corridors) or changed in direction (&amp;gt;90°, pivot sites). At each of these sites, EGMs were collected and analysed in terms of amplitude (mV), location and fractionation. Results In sinus rhythm maps, a total number of 65 pivot sites and slow conduction corridors was identified. In the PAF group 22 PS and SC were found (1,6/pt), whereas those included in the PsAF one showed a significantly higher number: 43 (3,3/pt). The bipolar voltage value reported at abnormal conduction areas amounted to 1,95 ± 0,93 mV and 1,78 ± 0,54 mV for PAF and PsAF patients, respectively, showing a lower value with respect to healthy tissue areas (2,94 ± 4,81 mV). More than four deflections per signal were identified in 57/65 PS and SC zones. In PsAF cases, these areas were mainly found on the posterior wall. A concordance with esophagus location occurred in the 89%. In paced maps, instead, we documented an average value of 38 PS and SC zones (1,5/pt), of which 27 in persistent patients. As for bipolar values, a lower voltage value was reported in PS and SC zones (1,91 ± 0,69 mV for PAF and 1,52 ± 0,36 mV for PsAF) with respect to normal conductive tissue. Fractionation of EGMs was confirmed in almost all cases. Conclusion The main findings of this analysis are: (i) in PsAF patients the number of pivot sites is higher with respect to PAF cases; (ii) In PsAF patients, abnormal conduction phenomena are predominantly localized on the posterior wall, with a strong correlation with esophagus location; (iii) slow conduction zones and pivot sites are characterized by lower voltage amplitude and higher fractionation with respect to normal conduction areas.

Left bundle branch area pacing guided by electroanatomical mapping in patients with structural heart disease and advanced conduction abnormalities

Abstract Funding Acknowledgements Type of funding sources: None. Background Left bundle branch area pacing (LBBAP) can be technically challenging and fluoroscopy-intense, particularly in patients with structural heart disease (SHD) and advanced conduction abnormalities. Three-dimensional electroanatomical mapping (EAM) facilitates high-resolution, real-time, and non-fluoroscopic lead navigation, electrogram and pace mapping. Purpose The purpose of the study was to prospectively evaluate the feasibility, safety, and outcomes of routine EAM-guided LBBAP in patients with SHD and advanced conduction abnormalities. Methods Consecutive patients with SHD and advanced conduction abnormalities (defined as second or third-degree atrioventricular (AV) block and/or complete bundle branch block) who underwent an attempt at EAM-guided LBBAP were included. EAM-guided lead implantation was performed in all patients following a standardized protocol irrespective of the pacing indication and type of conduction disturbance. The feasibility, safety, procedural and mid-term outcomes were evaluated. Electrical, echocardiographic, and clinical parameters were assessed at implantation and last follow-up. Results Thirty-two patients (68±18 years; 19% female) were included. The indication for pacing was cardiac resynchronization therapy in 50%, AV block in 44%, and pace-and-ablate in 6% of patients; 24 patients (75%) had an intrinsic QRS &amp;gt;150 ms, 17 (53%) had LBBB. Primary EAM-guided LBBAP was successful in 29 patients (91%). Procedural duration was 95 (70-110) min, total fluoroscopy time 0.93 (0.40-1.73) min, and total fluoroscopy dose 35.4 (20.5-77.2) cGycm2 (Figure 1A). The paced QRS duration during LBBAP was significantly shorter than the baseline intrinsic QRS duration (121.9±10.7 vs. 159.2±34.4 ms; p&amp;lt;0.001) (Figure 1B) and remained stable (120.3±11.1 ms; p=0.370) during a mean follow-up of 7.0±5.9 (median 5.4 [IQR 2.1-12.6]) months. LBBAP capture threshold was 0.57±0.23V/0.4ms at implantation and remained low during follow-up (0.58±0.18V/0.5±0.2ms; p=0.877). There was no increase in LBBAP capture threshold &amp;gt;1.0V/0.4 ms during follow-up. Overall LVEF improved significantly from 44.2±14.3% at baseline to 49.4±13.1% at last follow-up (p=0.009), NYHA functional class from 2.4±0.6 to 1.8±0.6 (p=0.002), respectively (Figure 1C+D). No complications occurred that required intervention. Conclusion Routine near-zero fluoroscopy EAM-guided LBBAP can safely be performed in patients with SHD and advanced conduction abnormalities with high success rates and favourable mid-term outcomes. Further studies are needed to investigate whether the use of EAM improves overall outcome of conduction system pacing, and to identify specific patient populations who benefit the most from EAM-guided lead implantation.

Outcomes of functional substrate mapping of ventricular tachycardia (Func-VT) - an international propensity-matched prospective registry

Abstract Funding Acknowledgements Type of funding sources: None. Background Dynamic substrate changes play a key role in facilitating conduction delay and re-entry in ventricular tachycardia (VT) circuits. Extrastimuli pacing can unmask functional channels demonstrated by dynamic delay, which may play a role in the VT circuit. We have previously developed sense protocol mapping, using short coupled single extrastimuli to delineate areas of maladaptive conduction delay, which play an essential part in VT development. Purpose We conducted a multicentre prospective propensity-matched registry of functional VT substrate mapping (Func-VT registry) compared with conventional mapping. Procedure times, mortality, and probability of ATP/ICD shocks were compared to the matched institutional cohort. Methods Data prospectively analysed from an international registry of patients undergoing ablation for Ventricular tachycardia. Data was gathered from multiple sites evaluating outcomes of VT ablation using sense protocol mapping and comparing the results with institutional cohort using conventional methods of entrainment, activation mapping, late potential and pace mapping. The date was propensity-matched to age and left ventricular ejection fraction. Results There were 41 patients (mean age of 60 years, 80% males, mean ejection fraction: 35%) in the func-VT registry. The median procedure time was 161 minutes compared with 305 in the institutional cohort (p=&amp;lt;0.001). 85% of patients were free from symptomatic VT/ anti-tachycardia pacing or ICD shocks at a median follow-up of 340 days. Mean shocks per-patient burden decreased from 3.5 to 0.08 in the same period (p=0.03). Figure 1 shows survival curves demonstrating the probability of death in the Funct-VT registry patients vs institutional cohort (p=0.011). Conclusions VT functional mapping registry provides real-world data regarding acute and long-term outcomes and complications. It shows better outcomes and improved survival in patients who underwent ablation using sense protocol mapping.

Novel pulsed-field ablation technology for pulmonary vein isolation in patients with atrial fibrillation: preliminary experience from a large multicenter clinical practice

Abstract Funding Acknowledgements Type of funding sources: None. Background Complete electrical pulmonary vein isolation (PVI) by thermal energy sources is a well-established ablation strategy of atrial fibrillation (AF). Recently, a non-thermal ablation approach by means of irreversible cellular electroporation has been made available for clinical use. Purpose We report the preliminary experience of a new pulsed-field ablation (PFA) system in the context of AF ablation in a multicenter Italian setting. Methods All consecutive patients (pts) undergoing AF ablation with PFA at 7 Italian centres were included. Protocol-directed PVI was delivered using 2000 V with eight applications per vein, that is, four applications each in the basket and flower poses. Applications were delivered in pairs at any given catheter position, rotating by ≈30–40° after the first two applications in each configuration. Additional lesions were performed at the operator’s discretion. The ablation endpoint was PVI as assessed by entrance and exit block. Data are reported as median [IQ range]. Results With a median of 32[25-38] pts treated per center, a total of 205 cases were included (n=150 73.2%, paroxysmal AF, n=55, 26.9% persistent AF). Of them 187 (91.2%) were de novo cases, whereas 18 (8.8%) were redo cases. A mapping system was used in 55 (21.5%) procedures and an intracardiac echocardiography in 65 (31.7%) cases. The number of PFA applications to reach PVI was 32[32-36]. Procedural parameters were: fluoroscopy time = 16[12-22] min, skin-to-skin time = 60[55-85] min, support time (preparation plus skin-to-skin) =75[64-95] min, lab occupancy time was 97[75-120] min and PFA LA dwell time was 23[20-28] min. The first pass isolation (FPI) rate per vein was 99.6% resulting from 202 patients (98.5%) with FPI. At the end of the procedure, PVI was achieved in all pts (100%) using only PFA. Additional PFA delivery outside PVs was performed in 19% (n=39) of the cases, mostly at the posterior wall area only (n=34, 87%), requiring 16[12-24] PFA deliveries. All the additional lesion sets were validated through differential pacing and/or 3D mapping. The learning curve was extremely fast. After only 5 cases time to PVI and total support time have significantly improved, whereas we did not notice any additional improvement after 10 or 20 cases (LA dwell time: 27[22-32] min during the first 5 cases vs 23[19-27] min after the first 5 cases, p=0.0172; support time: 100[65-120] min vs 75[65-90] min, p=0.0181, respectively). In 13 (6.3%) cases a transient bradycardia or asystole occurred after the first PFA application requiring temporary high-output pacing. No major procedure-related adverse events were reported. Conclusion In this first multicentric experience, the novel PFA system proved to be safe and effective in both paroxysmal and persistent AF patients. The learning curve seems to be very fast according with procedural parameters.

Zero or near-zero x-ray pacemaker implantation in paediatric patients. dream or reality?

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Transvenous implantation of pacemaker is performed with fluoroscopy for leads’ insertion and implantation in the heart. This implies radiation exposure for patients and operators. Fluoroscopy allows a two-dimensional view of lead movements, and sometimes it is difficult to implant lead in the complex heart anatomy, or in alternative right ventricular (RV) pacing sites, that often requires higher radiation doses. These alternative pacing sites may prevent pacing-induced ventricular dysfunction. They are his bundle pacing area (HBP), ventricular septum close to the conduction system area (VS), RV outflow tract (RVOT). The use of three-dimensional-electroanatomic mapping system (3D-EAM) may reduce fluoroscopy and guide lead implantation. Published median fluoroscopy data for similar procedure are: 6 mGy (1), 13 mGy and 231 microGy/m2 (2). Purpose of this study is to seek out if a 3D-EAM-guided transvenous implantation into RV alternative sites pacing in paediatric patients can be accomplished with zero or near-zero X-rays. Methods Retrospective analysis of children and adolescents with congenital or acquired (idiopathic) complete atrioventricular block (CAVB) without other congenital heart defects who underwent 3D-EAM-guided pacing in alternative RV sites. The implant procedure was divided in 4 steps: 1-contrast venography; 2- 3D mapping: with a steerable catheter (femoral vein), the 3D-EAM acquired geometric reconstruction of the right heart and a pacing map identified RV sites with narrower paced QRS; 3-axillary vein puncture; 4-lead and pacemaker implantation: 3D-EAM guided stylet-directed screw-in lead implantation toward desired RV sites. Data are reported as median (25th-75th centiles). Results 54 CAVB patients (42 females), underwent 3D EAM-guided pacing (27 VVIR, 27 DDD) at age 11.5 (7.7-14) years, weight 42 (26-54) kg. Pacing sites were: 10 HBP, 4 RVOT, 40 VS (Figure 1). Procedure time was 170 (143-193) min, total fluoroscopy exposure and that of the 4 steps are reported in Table 1. The lowest exposures were: 0.2 mGy, 8 microGy/m2 (VVIR) and 0.6 mGy, 15 microGy/m2 (DDD). Paced QRS was 115 (100-120) ms. Conclusions 3D-EAM-guided alternative RV pacing sites was accomplished with very low fluoroscopic exposure, close to zero in some cases. Therefore, with 3D-EAM we can significantly reduce radiological doses also in difficult pacing procedures in paediatric patients, thus reducing radiological risks and preserving ventricular function. The dream is becoming reality.

Catheter ablation of ventricular premature depolarizations originating from the mid interventricular septum: Significance of electrocardiographic morphology for predicting origin

Ventricular premature depolarizations (VPDs) originating from the mid interventricular septum (IVS) adjacent to the atrioventricular annulus between the His bundle and the coronary sinus ostium (mid IVS VPDs) have not been characterized. The aim of this study was to investigate the electrophysiological characteristics of mid IVS VPDs. Thirty-eight patients with mid IVS VPDs were enrolled. VPDs were divided into different types according to precordial transition of the electrocardiogram (ECG) and QRS morphology in lead V1. Four types of VPDs were divided. The precordial transition zone appeared earlier and earlier from types 1 to 4. The notch in lead V1 moved gradually backward, and its amplitude gradually became higher, resulting in the transition from left to right bundle branch block morphology in lead V1 from types 1 to 4. Based on activation and pace mapping, ablation response, and 3830 electrode pacing morphology in the mid IVS, the 4 types of ECG morphology corresponded to an origin in the right endocardial side, right/mid intramural region, left intramural region, and left endocardial side of the mid IVS, respectively. An intramural origin was identified for 50% of VPDs. Eighty-nine percent of mid IVS VPDs could be eliminated. Bilateral ablation (waiting for delayed efficacy) or bipolar ablation was sometimes needed for intramural VPDs. Mid IVS VPDs were found to have unique electrophysiological characteristics. The ECG characteristics of mid IVS VPDs were important in terms of prediction of its exact origin, the choice of ablation method, and the likelihood of treatment being successful.

C4 DOUBLE RHYTHM MAPPING FOR COHERENT ELECTROPHYSIOLOGICAL SUBSTRATE CHARACTERIZATION IN ATRIAL FIBRILLATION PATIENTS

Abstract Background Atrial fibrillation (AF) progresses with a cascade of combined structural, functional, and systemic dysfunctions. Electro–anatomical maps are employed to investigate pro–arrhythmic areas. However, single rhythm maps provide only a partial reconstruction: rhythm and wavefront directionality might mask some of these areas. Purpose. To demonstrate that the combined quantitative analysis of different rhythm maps (i.e., parallel sinus rhythm and paced maps) could allow consistent identification of structural and functional defects sustaining AF. Methods Thirty AF clinical procedures have been performed with mapping system support. In particular, a sinus rhythm activation map and a paced map have been created with a multipolar catheter by setting an extra beat every three sinus beats. Areas of abnormal conduction have been identified and a comparison of electrophysiological biomarkers (EGMs voltage and fractionation) among the two rhythms has been performed. Results This comparative analysis allowed us to identify both structural and functional electrophysiological phenomena. Specifically, we distinguished: (i) abnormal conduction zones confirmed in both maps, both characterized by signal fractionation and a lower voltage (0,56 ± 0,18 mV) with respect to healthy atrial tissue (2,40 ± 0,41 mV), and (ii) abnormal conduction zones visible in only one of the two maps. In the latter, we distinguished whether the absence of the phenomena was due to wavefront orthogonality to the diseased area (revealed thanks to a change in wavefront direction) or due to the presence of a functional phenomenon induced by the pacing. In the first group signal fractionation has been detected in both rhythms and a lower voltage has been found (1,79 ± 1,1 mV) with respect to normal conduction zones (3,26 ± 0,98 mV), while in functional cases EGMs fractionation has been identified only in paced maps and no significant difference has been observed in terms of voltage. Conclusion Double rhythm mapping provides a more robust characterization of atrial abnormal conduction phenomena which better represent AF electrical substrate. It allows the distinction of true structural dysfunctions from dynamic ones thanks to the different wavefront directionality and paced rhythm. Moreover, the structural defects have been confirmed by EGMs analysis, which revealed both low voltage amplitude and high fractionation, characteristics that have not been reported in functional cases.