Mapping Catheter Research Articles

Left atrial appendage anatomical changes following radiofrequency-based ostial isolation

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial appendage (LAA) electrical isolation (ei) may be achieved via radiofrequency (RF) energy applications at the level of the appendage ostium targeting the sites of earliest activation recorded by a mapping catheter. Notably, RF has long been used in vascular, orthopedic, and aesthetic surgery to promote thermal-induced collagen matrix contraction, fibrosis, and tissue retraction. LAA anatomical changes associated to RF-induced tissue retraction have never been reported. Purpose To quantify the anatomical changes of the LAA ostium following RF-based LAAei. Methods Thirty-four consecutive patients requiring AF ablation with LAAei underwent transesophageal echocardiography (TEE) within 7 days before (baseline TEE) and apx 6 months after (follow-up TEE) ablation. The diameter of LAA orifice and landing zone were measured at 4 different views (0°, 45°, 90°, 135°). Measurements were performed by two independent reviewers blinded to the patient’s identity. Results Among 43 AF patients (67±6yrs, 72.1% males), the LAA morphology was classified as chicken wing in 19 (44.2%) patients, windsock in 12 (27.9%), cactus in 8 (18.6%), and cauliflower in 4 (9.3%). At baseline TEE, the mean maximum and mean minimum ostial diameters were 25±4mm and 22±4mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 26±4mm and 23±3mm, respectively. On average, LAAei was achieved after 17±6 minutes of RF at a power of 45W. Follow-up TEE was performed 294±136 days after LAAei. The median LAA contraction velocity was 0.1 m/s (IQR: 0.02-0.18) and was significantly impaired in all patients. At follow-up TEE, the mean maximum and mean minimum ostial diameters were 19±4mm and 17±3mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 20±4mm and 18±4mm, respectively. The mean relative reduction of the ostium and the landing zone was -24.4% and -22.5%, respectively. Box-Whisker plots of the maximum and minimum ostial diameters before and after LAAei are reported in Fig.1. Conclusion RF led to a >20% reduction of the diameters of the ostium and the landing zone. These changes may have important implications for a successful percutaneous occlusion procedure and justify a staged approach of isolation and occlusion.

Radiofrequency ablation for longstanding persistent atrial fibrillation: long-term outcome of a prospective randomized comparison of mapping with multipolar catheter vs. 4-pole ablation catheter

Abstract Funding Acknowledgements Type of funding sources: None. Background In patients with longstanding persistent atrial fibrillation (LSPAF), mapping with multipolar catheter can enhance identification of arrhythmogenic sources during ongoing AF/converted atrial tachycardia (AT), reduce procedure time, and improve outcome of catheter ablation. Purpose To compare procedural characteristics and long-term outcome of radiofrequency catheter ablation (RFA) for LSPAF between two mapping approaches in a prospective randomized bi-centric study. Methods Between 1/2019-9/2021, RFA was performed in in 172 patients with LSPAF. Mapping with multipolar catheter Pentaray (group 1, n=85) vs. mapping with ablation catheter Navistar STSF (group 2, n=87) were compared. Stepwise ablation to the desired AF termination included pulmonary vein isolation (PVI), electrogram guided left atrial (LA) ablation, CS isolation, and right atrial electrogram guided ablation. PVI, mitral isthmus, LA roof, and CTI block were Intermediate endpoints proved at the procedure end. Sinus rhythm (SR) restoration by ablation was the desired procedure endpoint. Follow-up included 7-day ECG monitoring every 3 months during the first year, and every 6 months afterwards. Results In groups 1 vs. 2, AF was terminated (into SR or AT) in 70 (82%) vs. 68 (78%) patients (p=0.81); and SR was restored by ablation in 54 (64%) vs. 46 (53%) patients(p=0.46), respectively. Procedure, fluoroscopy, and RF delivery times (min) were 251±46 vs. 257±45 (p=0.35); 10,4±2,8 vs. 11,0±3,1 (p=0.17), and 70±21 vs. 70±24 (p=0.98), respectively. At the end of 13-45 months follow-up, stable SR was present in 72 (85%) vs. 69 (79%), patients following repeat ablation in 42 (49%) vs. 42 (48%) patients. Only 29 (34%) vs. 26 (30%) patients remained free from any AF/AT recurrence (>30 s) after single ablation (all p=NS). Conclusion Mapping with multipolar catheter vs. standard ablation catheter was associated with nonsignificant differences in procedural characteristics and clinical results of RF catheter ablation for LSPAF.

Zero and near zero fluoroscopy catheter ablation of premature ventricular contractions: a multicentre experience

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation has become an established treatment option for premature ventricular complexes (PVCs). It is well known that the use of fluoroscopy exposes patients and medical staff to potentially harmful stochastic and deterministic effects of ionising radiations. Purpose We sought to analyse procedural outcomes in terms of safety and efficacy using a "zero" or "near zero" X rays approach for treatment of PVCs. Methods The present retrospective, multicentre, observational study included 131 patients having undergone catheter ablation of PVCs using zero or "near zero" (less than 2 minutes) fluoroscopy between 2016 and 2020. Baseline characteristics of the population, acute success and complications derived from the procedure were evaluated, as well as recurrence rate during follow-up. Results Median age was 51.0 years old [38-63], males were 77 (58.8%). Most often cause of ablation were palpitations (90.0%), followed by reduced left ventricular ejection fraction (4.6%) and pre-syncope (14.5%). Among the study population, 26 (19.8%) had a cardiopathy. The median PVC burden before ablation was 15.1% [6%-22.4%]. The most frequent PVC origin was right ventricular outflow tract (n=72; 55.0%) followed by the left ventricle (n=21; 16.0%), LVOT and cusps (n=18; 13.7%) ,aortomitral continuity (n=7; 5.3%). A 3D electro-anatomical mapping system was used in all cases as well as a contact force catheter for mapping and ablation. The mean maximum radiofrequency power applied was 32.9 ± 4.1 W (370 s median time). Median number of applications was 4.5 and mean total procedural time was 117.3 ± 47.5 minutes. Median best prematurity was 31.5 ms. We used isoprenaline in order to induce PVCs in 42% of cases and suppression of PVC was achieved in 127 patients (96.9%). There was only 2 complication (femoral hematoma and arteriovenous fistula conservatively treated). At 12 months, a complete success was documented in 109 patients (83.2%), a reduction in PVC burden was achieved in other 18 patients (13.7%) and a failure was recorded in 4 patients (3.1%). Conclusion The PVC ablation with "zero" or "near-zero" fluoroscopy is a safe procedure with no major complications and good rates of success and recurrence in our multicentre experience.

Pulsed-field ablation versus single catheter high-power short-duration radiofrequency ablation for atrial fibrillation: procedural characteristics, myocardial injury and midterm outcomes

Abstract Funding Acknowledgements Type of funding sources: None. Background Pulsed-field ablation (PFA) has emerged as a novel treatment strategy for patients with atrial fibrillation (AF). A direct comparison to high-power short-duration (HPSD) radiofrequency (RF) ablation using a single catheter is lacking. Aim To compare pulmonary vein isolation (PVI) using PFA versus single catheter HPSD-RF ablation regarding efficiency, safety, myocardial injury, and outcomes. Methods 119 patients underwent PVI and were included (age 65.6 ± 10 years, ejection fraction 0.55 ± 0.11, left atrial size 41 ± 6.6 mm, paroxysmal AF 55%). 56 patients (47%) underwent PFA using a multi-electrode pentaspline PFA catheter with a biphasic waveform and 63 patients (53%) underwent single catheter HPSD-RF ablation without a multipolar mapping catheter. Results Using PFA the median procedure time was significantly shorter compared to the single catheter HPSD-RF group with 58 (IQR 51-70) min versus 83 (IQR 71-99) min (p<0.001), while fluoroscopic time was significantly longer with 12 (IQR 10-16) min versus 2.2 (IQR 1.3-3.6) min (p<0.001). First-pass isolation was achieved in 91% of the PFA group and 88% in the HPSD-RF group. 3.3 catheters vs. 1.0 catheters were used in the PFA group versus the HPSD-RF group, p<0.01. One procedural complications was observed in the PFA group and one complication in the HPSD-RF group (Tamponades). High sensitivity cardiac troponin levels were on average significantly higher in patients using the PFA system, 1520 (IQR 1010-1980) ng/l compared to 897 (IQR 725-1240) ng/l in the HPSD-RF group. During a median follow-up of 177 days (IQR 92-300), AF recurrence was observed in five patients (9%) from the PFA group and in 15 patients (24%) from the HPSD-RF group. (Figure 1) Conclusion PFA showed shorter procedure times but longer fluoroscopy times, higher levels of hs cTnT, and a possible improved AF-free survival.

Pinpointing atrial fibrillation drivers by informed sequential endocardial mapping in the presence and absence of fibrosis: an in-silico study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work is part of Personalize AF. This project received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860974. This work was also supported by the Swiss National Supercomputing Centre (CSCS), project s1074. Background We recently developed a novel technique to localize spatially stable atrial fibrillation (AF) drivers using the combined information from sequential endocardial mapping recordings. The robustness of this technique to localize drivers in the presence of complex substrate with a high degree of fibrosis and with unstable and meandering drivers is not known. Purpose To evaluate the effect of spatial instability of drivers and high AF substrate complexity caused by atrial fibrosis on the performance of the recently developed technique for AF driver localisation using sequential endocardial mapping. Methods We used a previously validated volumetric 3D atrial model to simulate AF initiated by incremental pacing. Two sets of simulation were generated, with no structural changes (n=7), and with severe remodelling (n=11), implemented as patches of endomysial fibrosis covering 70% of the atria. Simulated endocardial unipolar electrograms were generated sequentially in a 4x4 electrode grid (3 mm spacing, 2.5 s) starting from 20 uniformly spaced positions in the atria. The subsequent catheter positions were determined by analysing the propagation direction in the grid. If the measured activity was repetitive, the dominant direction of propagation was determined, and the catheter was repositioned 10 mm upstream within the same atrium. Otherwise, the catheter was moved 5 mm in a random direction. This procedure continued until either 1) a driver (re-entry or radial spread of activations) was detected directly at the recorded region by evaluating the corresponding propagation patterns, or 2) the previous catheter positions defined an enclosed region in the atrium, encircling the AF driver. The performance of the algorithm was compared between the two remodelling stages with respect to number of steps required to locate a driver, and to the distance to the closest driver. Results In the simulations with fibrosis more drivers were present than in the simulations without fibrosis (4 [2, 6] vs. 3 [2; 4] simultaneous reentries, p < 0.001). Drivers were spatially unstable and meandered substantially through the atrium. The performance of the algorithm to localize the drivers was similar in both groups. The tracking procedures located a driver after 6 [IQR: 4; 9] vs. 5 [3; 8] steps (p<0.01). The algorithm localized the driver correctly in 72.8% vs. 78.2% (p = 0.30) of the cases and the final distances to a driver were 7.87 [5.88; 11.04] mm and 7.78 [5.55, 11.35] mm (p=0.95), respectively. More drivers were detected by encircling them with sequential catheter positions in the cases without remodelling (62.6% vs. 40.9%, p<0.001). Conclusion Guiding mapping catheters by functional aspects of AF and combining sequential recordings may increase the efficiency and accuracy of mapping procedures. The developed algorithm successfully localizes AF drivers even in complex substrates for AF.

The Omnipolar Mapping Technology - a new mapping tool to overcome bipolar blindness resulting in true high-density maps

Abstract Funding Acknowledgements Type of funding sources: None. Background Mapping, using the novel omnipolar technology (OT) obtains omnipolar signals displaying true voltage, real-time wavefront direction and speed, independent of catheter orientation and external reference. Employment of OT potentially overcomes so called "bipolar blindness" (conventional bipolar electroanatomic mapping). Hence, OT potentially improves substrate assessment, comprehension of tachycardia mechanisms and gap detection after previous catheter ablation (CA). Purpose Purposes of our study was to analyze previously performed left atrial (LA) and left ventricular (LV) maps for differences using automated OT vs. SD vs. the previously published HD Wave (HDW) algorithm. Methods Maps of patients undergoing CA for atrial or ventricular arrhythmia were initially acquired using HDW settings in conjunction with the Advisor HD Grid mapping catheter. These maps were then analyzed retrospectively applying the automated OT algorithm vs. SD vs. HDW. to reveal differences in voltage and point density. Additionally, detection of pulmonary vein (PV) gaps and LV scar area was evaluated. Results In 45 consecutive patients 135 maps were analyzed. The study population undergoing CA consisted of: 30 (22.2%) patients undergoing repeated CA for recurrence of persistent atrial fibrillation (persAF)/left atrial tachycardia (AT) and 15 (11.1%) patients with ventricular tachycardia (VT) or premature ventricular contractions (PVC). Atrial maps revealed a significantly higher point density using OT (21471) vs. SD (6682) or HDW (12189, p<0.001). Mean voltage was significantly higher using OT (0.75mV) vs. SD (0.61mV) or HDW (0.64mV, p<0.001). OT maps detected significantly more PV gaps vs. SD (4 vs. 2, p=0.001). In LV maps, OT revealed a significantly higher point density (25951) vs. SD (8582) and HDW (17071), p<0.001. Mean voltage was significantly higher for OT (1.49mV) vs. SD (1.19mV) and HDW (1.2mV), p<0.001. Detected scar area was significantly smaller using OT (25.3%) vs. SD (33.9%, p<0.001). Conclusion Using OT results in a higher voltage and point density compared to SD and HDW. Therefore displayed scar extend is significantly smaller in atrial and ventricular maps. Also, more PV gaps were detected using OT. The OT algorithm potentially improves scar delineation, facilitates substrate characterization, and may improve procedural outcome.

Voltage characterization of abnormal conduction zones in patients affected by atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background In case of persistent atrial fibrillation (AF), atrial substrate assumes a dominant role in sustaining the arrhythmia. Recent studies prove that low voltage areas (LVA, Voltage Amplitude < 0,5 mV) represent an additional target for ablation of AF patients. Purpose The purpose of this study is to analyse whether structural atrial conduction abnormalities (i.e., pivot sites and slow conduction corridors) may occur outside low voltage areas. Methods The study is based on the retrospective analysis of 31 consecutive maps of patients undergoing AF ablation (16 paroxysmal and 15 persistent cases). The clinical procedures have been performed with the support of a mapping system. Sinus rhythm activation maps and bipolar maps used for this analysis have been created with a multipolar mapping catheter. Map points were only acquired when the electrode was in contact with the endocardial tissue to avoid misleading voltage amplitude information. Slow conduction corridors and pivot sites have been analysed. At these sites, EGMs characterization included voltage amplitude (mV), signal duration (ms) and fractionation. Results The average value of EGMs amplitude reported at pivot sites and slow conduction zones, respectively, amounted to 2,08 ± 0,63 mV and 2,1 ± 0,66 mV in paroxysmal cases. In persistent cases, there were slight decreased values to 1,95 ± 0,93 mV and 1,89 ± 0,89 mV. Characterization at pivot sites documented a mean duration value of 45,4 ± 4,64 ms and 49,93 ± 5,51 ms in paroxysmal and persistent patients, respectively, while in slow conduction zones 41,53 ± 7,94 ms and 49,04 ± 6,41 ms have been reported. As for fractionation, more than five deflections per signal have been identified in all abnormal conduction areas. Conclusion Our study proves that functional electrophysiological phenomena can occur outside low voltage areas, even in persistent cases. According to this analysis, not all LVA represent the correct target for catheter ablation, encouraging the development of further methods for investigation of atrial substrate.

Combining atrial activation maps for the big picture of simulated atrial fibrillation mechanisms

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work was supported by PersonalizeAF project. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860974. Background Pulmonary vein isolation (PVI) alone is not sufficient for all persistent atrial fibrillation (AF) patients. Ablation of localized AF drivers might be a promising adjunctive ablation strategy but detecting such drivers is limited by the small field of view of current mapping catheters. Purpose We propose a technique to detect localized AF drivers that combines sequential mapping of repetitive activation patterns into a larger composite map. The performance of this technique was evaluated in several simulated scenarios of known mechanisms during AF. Methods Representative repetitive conduction patterns that may occur in AF were simulated in a detailed volumetric 3D model of the atria: a large peripheral wave, stable and meandering re-entries, and single and multiple ectopic foci. Endocardial electrograms were sequentially generated from overlapping regions in the left posterior wall (4x4 grid, 3mm spacing, 0.5-1.5 seconds), and repetitive activation patterns were detected. Overlapping areas between sequential maps were used to align the repetitive patterns. Local patterns were then combined into larger composite maps (Fig. 1A). Reconstruction performance was quantified by the average local activation time (LAT) difference between original and reconstructed activation patterns. The relation between electrode overlaps and the quality of reconstructions were assessed at different degrees of spatial overlap (approximately 10% to 25% of the grid area, corresponding to 1.6 ± 0.6 and 4.1 ± 1.2 overlapping electrodes, respectively). Results All simulated patterns could be reconstructed from sequential recordings (Fig. 1B). LAT errors in recordings with 25% overlap were low in all cases: 5±2 msec for the peripheral wave, 5±2 and 3±1 msec for focal and multifocal activities and 6±2 and 11±2 & 17±3 msec for stable, meandering and highly meandering re-entries respectively (Fig. 2). Composite maps of meandering and highly meandering re-entries presented significantly higher reconstruction errors than other more stable patterns (p<0.01). Reducing spatial overlap to 10% did not significantly increase the errors, except for the highly meandering re-entrant activity (p<0.05). Conclusion We developed a novel methodology to combine high-density sequential recordings with limited coverage into larger composite activation maps. Using this method, we reconstructed highly accurate activation maps for multiple simulated AF mechanism scenarios. Results were promising even with a small overlap between sequential recording sites and relatively unstable patterns, providing a proof of principle to apply this approach in clinical recordings of human AF.

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 < 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.

Evaluation of laser balloon pulmonary vein isolation lesions during the acute and chronic phases using a high-resolution mapping system

Abstract Funding Acknowledgements Type of funding sources: None. Background Visually guided laser balloon (VGLB) has proven ample efficacy in achieving durable pulmonary vein (PV) isolation (PVI). Though the isolation area post-cryoballoon ablation has been reported to regress at the chronic phase, the shrinkage of the isolation area using VGLB during the chronic phase has not been described. Purpose This study aims to evaluate the differences in isolation areas created by VGLB between the acute and chronic phases using a high-resolution mapping system. Methods We assessed 26 patients who underwent a second procedure due to atrial fibrillation recurrence. Of them, 8 patients were treated with the third-generation VGLB and 18 patients were treated with the first-generation VGLB at the first session. In all patients, the voltage maps were created with high-resolution mapping catheters just after PVI (acute phase) and during the second session (chronic phase). With each map, the isolation area (<0.1mV) around the PV antrum was calculated. We validated the persistent durability of PVI, and then the regression of isolation lesions was analyzed in patients without any PV reconnections. Results The isolation areas were re-evaluated at 8.3±6.6 months after the initial procedure. Twenty patients (76.9%) preserved persistent isolation lesions of all four PVs. Of them, the reduction of the isolation areas on the left- and right-sided PV antrum were 1.6±3.2 cm² (10.7±23.1% of the acute phase) and 4.8±3.6 cm² (27.8±18.9%), respectively. The analysis of the results revealed that the isolation area of the right-sided PV antrum yielded statistical shrinkage during the chronic phase (P=0.001), even though the electrical isolation was preserved. Conclusion After VGLB ablation, the isolation area of the right-sided PV antrum significantly regressed at the chronic phase, while the rate of durable PVI was high in line with the previous report.

High efficacy single catheter standardized workflow for radiofrequency ablation of atrial fibrillation in the high-power short-duration era

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Dr. Valeriano and Dr. Fabbricatore have been supported by a research grant provided by the Cardiopath PhD program (University of Naples Federico II) Background Recent developments in radiofrequency (RF) ablation technologies have improved the efficacy of pulmonary vein isolation (PVI). The combination of the ablation index, lesion tags, and optimized inter-lesion distance (CLOSE protocol) has further reduced the incidence of gaps along the ablation lines. This high acute success rate challenged the use of conventional circular mapping catheters and prompted a single catheter-approach ablation strategy. Modulating the relationship between resistive and conductive heating, high-power short-duration (HPSD) ablation technology can potentially increase lesion-to-lesion consistency. A novel catheter with optimized temperature control and microelectrodes has been recently designed to further improve workflow efficiency. Purpose: This study aimed to assess the efficacy and efficiency of HPSD ablation in a standardized single-catheter workflow for PVI. Methods: Data on consecutive AF ablations performed with HPSD catheter from December 2020 to December 2021 at a single tertiary-care center were prospectively collected. The workflow consisted of a procedure sequence including single transeptal access with a bidirectional steerable sheath, 3D modeling with 3D rotational angiography, assessment of PV potentials with microelectrodes in each vein (figure 1), followed by radiofrequency encircling of the PVs using a high-power setting of 50W in a temperature- and flow-controlled mode with CLOSE-guided protocol. Isolation was validated by reassessing the previously observed PV potentials and by pacing within the lesion set. Results: A total of 73 consecutive AF patients (67% paroxysmal, 33% persistent) were included. All patients received PVI, 15 underwent additional cavotricuspid isthmus ablation and 6 received additional treatments (table 1). Mean procedure time was 68±27 min with minimal fluoroscopy time and dose (3.2±2.1 min; 4.7±3.9 Gycm2). Complications were infrequent with 1 cardiac tamponade and 1 pericarditis. First-pass isolation was achieved in 91% of the circles and validation by microelectrodes successfully identified the residual gaps with 100% of acute procedural success. In a selected cohort of 20 patients with paroxysmal AF undergoing PVI-only procedure performed by an expert operator, the ablation time was 22.8±5.1 min with a skin-to-skin time of 47.3±7.1 min (table 2). The median follow-up duration was 397 days (IQR: 367-462). AT/AF free survival rate was 90% at 12 months. Conclusions: HPSD ablation using a standardized single-catheter workflow improved the procedural efficiency of PVI and resulted in a high rate of first-pass isolation with a low recurrence rate at 12-month follow-up.

Electroanatomical features of biopsy-proven cardiac amyloidosis

Abstract Funding Acknowledgements Type of funding sources: None. Background Cardiac amyloidoses (CA) are an increasingly recognized group of infiltrative cardiomyopathies associated with high risk of heart failure, thromboembolic events, arrhythmias, and sudden death. Endomyocardial biopsy may be required to differentiate the amyloid type (mainly, Immunoglobulin light chain [AL] versus transthyretin-related [ATTR]) in some cases. Purpose to provide a first description of electroanatomical characteristics of amyloid cardiomyopathy, and relate them to endomyocardial biopsy findings. Methods we enrolled ten consecutive patients (median age, 68 [63-77]; male, 50%) in an observational, retrospective study. All of them had a clinical diagnosis of CA, but a diagnosis of CA type was hampered by the presence of inconclusive or discordant laboratory-imaging findings (abnormal serum free light chain assay and positive bone scintigraphy, n=5; ambiguous imaging results, n=4; abnormal serum free light chain assay and TTR gene mutation, n=1). Therefore, all patients underwent right ventricular high-density electroanatomical mapping (EAM) using a multipolar catheter (Advisor HD Grid, Abbott), and EAM-guided endomyocardial biopsy (EMB). We recorded electrogram features at EMB sampling site, and explored their correlation with histological findings with mixed effect models. Results The clinical, electroanatomical, and histological features of enrolled patients according to the EMB-proven type of CA (AL, n=6; ATTR, n=4) are resumed in Table. Electrogram amplitudes in both the bipolar and the unipolar configuration were generally normal both in the overall right ventricle, and at EMB sites. We found a significant correlation between both unipolar and bipolar electrogram amplitude and the percentage of both amyloid tissue (p<0.01 and p=0.016, respectively) and fibrous tissue (both p<0.01) at EMB (Figure). We observed the strongest linear association (i.e., highest R2) between unipolar electrogram amplitude and amyloid tissue, as well as between bipolar electrogram amplitude and fibrous tissue. On the other hand, electrogram duration and the number of electrogram peaks were unrelated to histological findings. The unipolar voltage cutoff that best identified regions with >15% amyloid tissue infiltration according to Youden index was 9.1 mV (sensitivity, 43%; specificity, 100%; accuracy, 77%). Conclusion CA is associated with normal electrogram amplitudes using ahigh density mapping catheter and conventional voltage cutoffs. Nevertheless, unipolar electrogram amplitude is strongly related to the extent of amyloid infiltration, and unipolar voltage<9.1 mV is 100% specific for >15% amyloid tissue deposition.

Detection of the most dominant drivers of atrial fibrillation based on repetitive activity in sequential electro-anatomical mapping

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work is part of Personalize AF. This project received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860974, This work was also supported by the Swiss National Supercomputing Centre (CSCS), project s1074. Introduction Detecting and targeting the most dominant drivers of atrial fibrillation (AF) might improve the outcome of AF ablation procedures. We hypothesize that dominant drivers entrain their vicinity in a temporally and spatially stable manner resulting in local as well as adjacent repetitive activation patterns. Purpose We present a novel approach to detect the most dominant drivers of AF based on driver repetitiveness and the degree to which they entrain their vicinity. Methods We retrospectively analyzed a dataset of high-density bi-atrial sequential mapping in ablation-naive persistent AF patients (n=13, 30s recording per site). Candidate drivers (focal activity or re-entry) were detected based on local activation time analysis of unipolar electrograms. Focal activity was defined as radial spread of activation, re-entry as a circular activation sequence on at least 4 splines of the mapping catheter that covered >50% of the AF cycle length. As a measure of driver stability, we determined the driver's local repetitiveness (in % of recording). As a measure of driver-associated entrainment, we determined the directionally coherent repetitiveness of adjacent recordings within 30 mm (Figure 1). Following our hypothesis, most dominant drivers can be recognized by their high local and directional coherent adjacent repetitiveness. Results A total of 459 recordings were analyzed (35±5 per patient). We detected 130 focal activities (10±3 per patient) and 42 re-entries (4±2 per patient) in total. The spatial distribution of all drivers is shown in Figure 2 (blue bars). Focal activities were more repetitive than re-entries (Figure 2, median [IQR] 3.2% [1.9%, 5.6%] vs. 1.8% [1.8%, 2.2%], p<0.001 Mann-Whitney U-test). When applying a 90th percentile threshold (8.2%) to both the local and directional coherent adjacent repetitiveness to detect the most dominant drivers, we were able to detect 9 dominant drivers (all focal activities, 7 patients). Most dominant drivers were located in the upper right atrium or left pulmonary vein region (Figure 2). Interestingly, only 9 of the 130 initially detected drivers (7%) showed an activation pattern in line with a repetitive entrainment of their vicinity. Furthermore, in 6 patients (46%), no dominant drivers were detected. This might indicate that not all patients have temporally and spatially stable drivers. Conclusion In this abstract we present a novel methodology to detect the most dominant drivers of AF. Using this method, we found that some (but not all) patients have temporally and spatially stable drivers that are able to entrain their vicinity.

Study of the omnipolar EGM reconstruction for robustness against wavefront propagation in epicardial signals

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): National Research Program, Ministerio de Ciencia e Innovación, Spanish Government, Instituto de Salud Carlos III. Background Characterisation of electrophysiological substrate is commonly performed by examining cardiac tissue locally by using high-density (HD) arrays of equispaced electrodes – e.g. Advisor™ HD Grid Mapping Catheter, Sensor Enabled™ (SE). These allow creating activation maps of local tissue and substrate exploration. Recently, a novel operation mode arouse: the omnipole, which overcomes many limitations of bipolar and unipolar electrograms, as they are claimed to be orientation independent. Nevertheless, the current technique to reconstruct omnipolar EGMs has pitfalls as the estimation of some incidence angles of the propagation wavefront. We propose a novel reconstruction method to estimate omnipolar EGMs which overcomes the angle dependence weakness of the current one, providing a more robust EGM representation. We hypothesise that this technique will improve reconstruction of electrophysiological signals. Methods Prior electrophysiological experiments on isolated rabbit hearts were used [1], including recordings with a 128-electrode array 1mm apart over ventricular epicardium at 37ºC, with bipolar electrode stimulation. Four-electrodes cliques were designed from these experiments, with different inter-electrode distances as depicted in fig. 1A, reconstructing the current, and novel omnipolar configuration. Metrics to assess the quality of the EGM signals were designed, including the bipolar loop area, and the ratio of the bipolar components of the omnipole (ox and oy) – see fig. 1B. The bipoles were calculated from unipolar EGMs, the signal was corrected with the 45º offset in the cross, the propagation angle was then detected, and the local activation time (LAT) was estimated. Results In the bipole plots, it was observed that the morphology of the bipolar loop gets distorted with an increase in the interelectrode distance – thinner for distances <2mm. There is a direct relation between the areas in the bipolar loop and the inter-electrode distance (see fig. 2A). Furthermore, the values of the area in the cross are always comparable to the best performing triangular clique. For the ratio of bipoles, the relation is inversely to distance (see fig. 2B), similarly, the performance of the cross is comparable to the best performing triangular omnipole. Conclusion For reconstructing omnipolar EGMs, inter-electrode distances smaller than 2mm should be employed. Furthermore, if that condition is satisfied, the novel omnipolar reconstruction method proposed based on the cross configuration is more accurate and robust to wavefront propagation, given that the omnipolar EGM performs similarly or better than the best triangular configuration – and which triangle is fixed for the whole procedure, being the current reconstruction method less robust. Thus, a new standpoint to omnipolar reconstruction in high density electrode catheters is open, towards the design of new devices, and the practice in the clinic.

Novel reconstruction technique of omnipolar signals in high density electrode arrays

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): National Research Program, Ministerio de Ciencia e Innovación, Spanish Government; Instituto de Salud Carlos III. Background Novel multi-electrode array catheters with equidistant spacing between the electrodes, have emerged in recent years - e.g. Advisor™ HD Grid Mapping Catheter, Sensor Enabled™ (SE). These systems typically use unipolar signals, sensitive to low-frequency noise, and bipolar signals - highly dependent on the direction of propagation. Thus, the full potential of these new devices is not yet fully exploited. We hypothesise that, a new clique (4-electrode in a squared 2x2 matrix) configuration for the computation of omnipolar signals allows to take full advantage of novel multi-electrode catheters, more robust to the direction of propagation of the wavefront against the one currently proposed in literature – thus helpful in the clinic given the challenging positioning of the catheter in the heart cavity during electrophysiologic studies. Methods In the current 3-electrode clique, the centre of the signal obtained does not correspond to the centre of the area of the clique, being less robust to wavefront propagation direction (see fig. 1A). A new configuration, the cross clique, is proposed for calculating the electrogram to improve the robustness and reduce the errors in the estimation local activation time (LAT) and others – see figure 1. One thousand simulated signals with stratified propagation angles and variable parameters were implemented to emulate flat waves and homogeneous propagation over cardiac tissue. The methods used to calculate the signal with the proposed shape are: obtaining the bipoles, 45 degree correction of the signal, detection of the propagation angle, rotation of the detected angle and estimation of the LAT. Results The average amplitude of the bipolar loop increased from the old triangular clique configuration: 600.36 ± 116.40 mV; to the novel one cross-clique: 840.47 ± 160.09 mV. Regarding the local activation time estimation, a decrease in the error is observed from the current omnipolar reconstruction: 207.50 ± 256.91 μs, to the one proposed 22.75 ± 29.426 μs. When the bEGM propagation angle estimation is activated, the angle estimation error is 2.77 ± 25.26o for the current reconstruction method, in contrast to 1.09 ± 11.35o in the proposed one – see figure 1B. Conclusion Our novel configuration considerably reduces the LAT estimation error and, on average, captures a larger signal amplitude than the classic triangular clique method. Thus, it allows using the full potential of new catheters, improving the omnipolar analysis. hen applying automatic angle detection to the methods, in the case of the traditional method, it is influenced by the desynchronisation of the components of the traditional model as it widens the bipolar EGM loop – see figure 1.B. Thus, a novel omnipolar reconstruction method is proposed to better estimate intracardiac EGMs, more robustly against the direction of the wavefront propagation. Further studies are under consideration with clinical signals.

Omnipolar mapping improves substrate characterization and critical isthmus identification in atypical atrial flutters

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Characterizing atrial substrate and conduction properties is crucial to treat complex arrhythmias during catheter ablations. Unipolar and bipolar electrogram signals are routinely used with significant limits due to low detailed mapping, the impact of poor contact and far-field electrical signals. Moreover, signals morphology is dependent on the relative orientation of the catheter inter-electrode axis to the direction of activation. Omnipolar signals try to overcome this direction-dependence by using three adjacent electrodes to infer directional information about the local electric field. Purpose We compared omnipolar mapping (OM) signals with the traditional high-density bipolar mapping (BM) ones. Methods All the procedures were performed using a high-density grid-designed mapping catheter. The atypical left atrial flutters were mapped using both OM and BM configuration. All the analysis about voltage and potential duration are related to the entire left atrial surface excluding pulmonary veins. Results Ten atypical atrial flutters were mapped in the left atrium in seven patients (median age 70 y, 5 males). OM identified 7 double loops and 3 triple loops while BM identified 7 double loops, 2 triple loops and 1 single loop, missing 2 critical circuits (an example is shown in figure 1) Significant differences were present also in potentials amplitude (peak-to-peak voltage amplitude) in the critical isthmus with OM higher than BM (OM median 0.22 mV IQR [0.16 – 0.30] vs BM median 0.19 mV IQR [0.13 – 0.24], P= 0.002). Dense scar area (defined as voltage amplitude <0.05 mV) identified with OM was smaller compared to BM (1.3 cm2 IQR [0.13-1.73] vs 1.7 cm2 IQR [0.23-3.10]; P= 0.06). OM showed longer signal duration (+10.1%) compared to BM in the entire left atrium and in particular the mean signal duration in the critical isthmus (OM median 79.1 ms IQR [70.7 – 88.9] vs BM median 62.5 ms IQR [55.2 – 85.2], P= 0.006). Percentage of tachycardia cycle lenght (TCL) mapped at the critical isthmus (maximum signal duration at the isthmus/ TCL) was greater with OM than BM (OM mean 60% ± 11%, BM mean 54% ± 12% (P= 0.02)(a summary of the results are shown in table 1). Conclusions OM identifies higher amplitude and longer signal duration especially in the critical isthmus region also reducing the extension of dense scar area. This finding may be crucial in the definition of complex and localized reentrant activities, leading to a faster and more precise catheter ablation.

Incidence of silent cerebral lesions after pulmonary vein isolation with a novel radiofrequency balloon

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Speaker fees by Biosense Webster (not specific to this research) Background A novel radiofrequency balloon (RFB) is currently used for pulmonary vein isolation (PVI) in selected centres. The incidence of silent cerebral lesions (SCL) detected by magnetic resonance imaging (MRI) has already been researched for common energy sources such as the cryoballoon and irrigated-tip radiofrequency catheters. Purpose We aimed to investigate the incidence of SCL after RFB ablation. Methods 105 patients were treated with RFB PVI between December 2020 and November 2022. Cerebral MRI was performed in 38 unselected patients after a median of 1 day after the procedure. Neurological symptoms as well as size and location of SCL were assessed. The RFB allows for assessment of real time isolation using a spiral catheter which can be inserted through a central lumen of the balloon. During the investigated period the procedure underwent a streamlining process. Initially a 3D high resolution map of the left atrium (LA) was obtained before and after the ablation. To create this post-ablation map, the RFB had to be exchanged for a circumferential mapping catheter. After the first 50 procedures post-ablation re-mapping was omitted. This reduced the number of necessary catheter exchanges through the transseptal sheath. Results None of the patients developed neurological symptoms after the procedure. SCLs were detected in 28,9% (11) of patients. Analysis of patient baseline characteristics (gender, age, BMI, comorbidities, LA size, LVEF) as well as procedural data (procedure length, LA dwell time, ablation time, number of radiofrequency applications, cardioversion, activated clotting time) showed no significant independent predictor for SCL. We compared procedural data and SCL incidence prior to streamlining of the procedure (non-streamlined, NSL) to those after streamlining (SL). We observed a numerical difference in incidence of SCL between the NSL group (42,1%, 8 of 20) and the SL group (16,7%, 3 of 18), but the difference did not meet criteria for statistical significance (p = 0,159). Procedure time (NSL: 69.4 ± 10.8, SL: 51.1 ± 8.6, p = 0.009) and LA dwell time (NSL: 63.8 ± 10.9, SL: 45.8 ± 8.3, p = 0.009) were significantly shorter in the SL group. Conclusion This is the first report of the incidence and possible predictors of silent cerebral lesions after PVI with a novel radiofrequency balloon. We initially observed a higher-than-expected number of SCL. After streamlining of the procedure and especially reducing the necessary catheter exchanges this incidence dropped. It is now comparable to data of SCL after PVI with other technologies in our centre. This supports our assumption that the number of left atrial catheter exchanges might be an important factor for the development of SCL. Furthermore, this data emphasize the necessity of caution during the initial learning phase with new ablation devices. Further MRI after the procedure could reveal statistically significant predictors of SCL.

Electrophysiological findings in patients undergoing left atrial appendage occlusion following previous electrical isolation

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial appendage electrical isolation (LAA) is an important adjunctive ablation strategy in patients with nonparoxysmal atrial fibrillation. If impaired mechanical function following isolation is observed, long-term oral anticoagulation (OAC) or, as an alternative, LAA occlusion are required. Although focal electrical potentials from the LAA do not result in normalization of appendage mechanical function, they may potentially be a source of arrhythmogenic triggers. Those focal areas might be challenging to ablate after LAA occlusion device implantation. Purpose We sought to report the incidence of focal electrical potentials in patients with a previously isolated LAA and transesophageal echocardiography (TEE) evidence of severely impaired LAA mechanical function undergoing endocardial LAA occlusion. Methods In 124 patients undergoing LAA occlusion following LAA isolation, a circular mapping catheter (CMC) was used before occlusion to document any residual LAA electrical activity. Results At preprocedural TEE, the median LAA contraction velocity was 0.13 m/s (IQR: 0.05-0.19) and was significantly impaired in all patients. Of the 124 patients (mean age: 69±8 years; 71.7% males), 61 (49.2%) did not display any evidence of residual LAA electrical activity. In the remaining 63 (50.8%) patients, residual electrical potentials resulting in LAA reconnection were recorded on the CMC positioned into the appendage. On average, 4.9±1.7 radiofrequency energy applications (45W, mean duration of each RFA: 14.2±3.4s) were required to re-achieve complete isolation. Subsequent appendage occlusion was successful in all patients. No leaks ≥5mm and 3 (2.4%) 3-4mm-leaks were documented at 45day-TEE. Conclusions Focal electrical activity from the LAA was documented in approximately half of our patients. Although focal electrical potentials do not result in normalization of LAA mechanical function, they may potentially act as arrhythmogenic triggers. Since it may be challenging after device implantation, assessment and ablation of those areas should be considered before occlusion device deployment.

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 > 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.

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.