Posterior Left Atrium Research Articles

Real-world multicenter registry on a novel focal lattice tip catheter toggling between pulsed electric field and radiofrequency for atrial tachyarrhythmia ablation

Abstract Background Pulsed field ablation (PFA) has emerged as a novel non-thermal energy source for cardiac tissue ablation. A novel focal 9mm lattice tip catheter, namely Sphere-9 (Affera Inc), has recently received regulatory approval; the technology is part of a technology that allows the delivery of either pulsed electric field or radiofrequency energy and incorporates a proprietary 3D electroanatomical mapping system. Purpose To describe the first real-world, multicenter experience with the AfferaTM system. Methods Consecutive AF patients undergoing first-time or redo atrial tachyarrhythmia ablation with the AfferaTM system in two different centres between August and November 2023 were prospectively enrolled. PFA was always used to ablate the posterior left atrium, whereas anterior applications were performed using either radiofrequency energy (RF/PF strategy) or PFA (PF/PF strategy) based on operator's discretion. Data on first-pass pulmonary vein isolation (PVI) and posterior wall isolation (PWI), as well as success rate of extrapulmonary ablation were reported. Primary safety endpoint included any technology-related periprocedural complications. Results 46 patients (mean age: 67±10; 41.3% males, 60.8% non-paroxysmal AF) were included. 5 (10.8%) patients were in atrial flutter (AFlu) at the beginning of the procedure, whereas AF was the rhythm at presentation in 19 (41.3%) others. First-time PVI was performed in 37 (80.4%) patients, 68.4% of whom received concomitant PWI. PVI was performed with PFA-only in 27% of them. First-pass isolation was achieved in 97.3% and 100% of PVI and PWI cases, respectively. Additional lesions included an anterior or posterior mitral line (6 and 15 patients), CTI (4 patients) or substrate ablation in 3 patients. Evidence of first-pass line block was documented in 96.4% of patients. The remaining 9 (19.6%) patients had already undergone a previous ablation; remapping showed 27.7% of PVs requiring reisolation. PWI was performed in 88.9% of them, for the first time (75%) or due to reconnection (25%). Additional lesions included an anterior or posterior mitral line (3 and 3 patients) or CTI in 2 patients. Evidence of first-pass line block was documented in 100% of patients. In 3 AFlu patients, the arrhythmia was mapped and termination was achieved while performing an AML (2 patients) and CTI (1 patient). Procedural duration was 96.5±15.6 min for first time and 97.8±12.6 min for redo procedures. Mean left atrial dwelling and fluoroscopy times were 75.4±17.6 min and 7.36±2.1 min, respectively. No technology-related complications were documented. Conclusions AF ablation with the focal 9-mm lattice tip catheter Sphere-9 confirmed high efficacy and safety in a real-world population.

First multicenter experience of pulmonary vein and posterior wall isolation via a novel focal 9mm lattice tip catheter in a real-world scenario

Abstract Background Pulsed field ablation (PFA) is an innovative technology recently adopted for the treatment of atrial fibrillation (AF). Preclinical and clinical studies have reported a remarkable safety profile, as a result of its tissue specific effect targeting cardiomyocytes and sparing adjacent tissues. The AfferaTM system is a focal 9-mm lattice tip catheter that has recently received regulatory approval. No data currently exist on the feasibility of this technology for first-time pulmonary vein isolation (PVI) and posterior wall isolation (PWI) in a real-world scenario. Objective To evaluate the safety and efficacy of the focal 9-mm lattice tip catheter Sphere-9 (Affera Inc) in a real-world population undergoing PVI and PWI. Methods Consecutive AF patients undergoing first-time PVI plus PWI with the AfferaTM system in two different centres between August and November 2023 were prospectively included. PFA was always used to ablate the posterior left atrium, whereas anterior applications were performed using either radiofrequency energy (RF/PF strategy) or PFA (PF/PF strategy) based on operator's discretion. Primary efficacy endpoint was acute procedural success (successful PVI with evidence of bidirectional block at the end of the procedure). Primary safety endpoint included major technology-related complications occurring within 7 days post-ablation. Secondary endpoints were first pass isolation, acute reconnection, overall complications, procedural, dwelling, and fluoroscopy time. Results Thirty consecutive patients [mean age: 68±6.8 years; 61.7% males; CHA2DS2-VASc Score 2.0 (1.5 – 3.5)] were included. Among them, 66.7% (n=20) had non-paroxysmal AF. PVI was performed with an RF/PF strategy or PF/PF one in 10 (33.3%) and 20 (66.7%) patients, respectively. Posterior wall isolation (PWI) was performed in 30 (100%) cases. The primary endpoint was achieved in 100% of patients for both PVI and PWI with average procedural time of 95 min (77-120 min), dwelling time of 78 min (55-92 min) and fluoroscopy time of 6 min (5-10.5 min) (Figure 1). No technology-related complications were observed. First-pass isolation occurred in 100% of PVI and PWI, with no acute reconnection for PW and 1 case of right PV reconnection in the RF/PF strategy group. Conclusions AF ablation with the focal 9-mm lattice tip catheter Sphere-9 confirmed high efficacy and safety in PVI + PW in a real-world population.Figure 1

Case report: the effect of endovascular closure of an open oval window on the course of atrial fibrillation and the processes of reverse remodeling of the heart chambers

The volume of the left atrium is one of the key factors associated with both the development of primary atrial fibrillation and its progression. Open atrial communication is considered as a factor predisposing to dilation and remodeling of the heart cavities. We present a clinical case of endovascular closure of an open oval window in a patient with a persistent form of AF, a moderately reduced left ventricular ejection fraction, who had previously undergone radiofrequency ablation, and persistent manifestations of heart failure. A 58-year-old patient was hospitalized in November 2019 with clinical manifestations of increasing heart failure. History: persistent form of atrial fibrillation with pronounced ventricular tachysystole. In April 2019, the patient underwent radiofrequency ablation, during which signs of open oval window were revealed. The initial left ventricular ejection fraction is 41%, the anterior–posterior left atrium size is 47 mm, the NT-proBNP level is 912 pg/m. In the subsequent period, steady sine waves were recorded.

Chamber-specific wall thickness features in human atrial fibrillation.

Persistent atrial fibrillation (AF) is not effectively treated due to a lack of adequate tools for identifying patient-specific AF substrates. Recent studies revealed that in 30-50% of patients, persistent AF is maintained by localized drivers not only in the left atrium (LA) but also in the right atrium (RA). The chamber-specific atrial wall thickness (AWT) features underlying AF remain elusive, though the important role of AWT in AF is widely acknowledged. We aimed to provide direct evidence of the existence of distinguished RA and LA AWT features underlying AF drivers by analysing functionally and structurally mapped human hearts ex vivo. Coronary-perfused intact human atria (n = 7, 47 ± 14 y.o.; two female) were mapped using panoramic near-infrared optical mapping during pacing-induced AF. Then the hearts were imaged at approximately 170 µm3 resolution by 9.4 T gadolinium-enhanced MRI. The heart was segmented, and 3D AWT throughout atrial chambers was estimated and analysed. Optical mapping identified six localized RA re-entrant drivers in four hearts and four LA drivers in three hearts. All RA AF drivers were anchored to the pectinate muscle junctions with the crista terminalis or atrial walls. The four LA AF drivers were in the posterior LA. RA (n = 4) with AF drivers were thicker with greater AWT variation than RA (n = 3) without drivers (5.4 ± 2.6 mm versus 5.0 ± 2.4 mm, T-test p < 0.05; F-test p < 0.05). Furthermore, AWT in RA driver regions was thicker and varied more than in RA non-driver regions (5.1 ± 2.5 mm versus 4.4 ± 2.2 mm, T-test p < 0.05; F-test p < 0.05). On the other hand, LA (n = 3) with drivers was thinner than the LA (n = 4) without drivers. In particular, LA driver regions were thinner than the rest of LA regions (3.4 ± 1.0 mm versus 4.2 ± 1.0 mm, T-test p < 0.05). This study demonstrates chamber-specific AWT features of AF drivers. In RA, driver regions are thicker and have more variable AWT than non-driver regions. By contrast, LA drivers are thinner than non-drivers. Robust evaluation of patient-specific AWT features should be considered for chamber-specific targeted ablation.

Evaluation and comparison of impedance and amplitude changes in lesion index-guided pulmonary vein isolation.

The lesion index (LSI) has been used to estimate lesion formation after radiofrequency catheter ablation. However, the impedance drop and decrease in bipolar amplitude of intracardiac electrograms, which are parameters that are traditionally used to predict effective ablation lesions, are not used to calculate LSI. Therefore, we aimed to investigate the association between LSI and traditional parameters. We retrospectively investigated 1355 ablation points from 31 patients who underwent LSI-guided pulmonary vein isolation (PVI) using TactiCath. All points were classified into 3 groups based on the impedance drop: (i) <10 Ω (n = 67), (ii) 10-20 Ω (n = 909), and (iii) >20 Ω (n = 379). The LSI targets were 4.5 for the posterior left atrium and 5.2 for the anterior left atrium. After excluding 583 points at which it was difficult to measure the amplitude, 772 ablation points during sinus rhythm were included in the analysis of bipolar amplitude. The target LSI was achieved at 1177 points (86.9%). The median total impedance drop and amplitude just after ablation were 16.0 [13.0-20.0] Ω and 0.21 [0.14-0.30] mV, respectively. There were significant differences among the 3 groups in the impedance and amplitude before ablation, power, target LSI, final LSI, contact force, and interlesion distance. An impedance drop of >10 Ω or an amplitude reduction of >50% was achieved at 95% and 82% of the study points, respectively. There were no major complications at any of the ablation points. LSI-guided PVI seemed to be useful for making sufficient ablation lesions, as assessed by the conventional parameters of impedance and amplitude change.

Abstract 12917: Incremental Utility of 3D Printing to Guide the Surgical Management of Cardiac Sarcoma

Background: Intimal sarcoma is an extremely rare and aggressive malignancy that originates in the heart and major vessels. Due to its rarity, ambiguous clinical presentation, and rapid progression, diagnosing and treating this neoplasm presents significant challenges. Case presentation: A 61-year-old female with a history of left atrial sarcoma underwent mass excision in 2019 and 2020, along with several rounds of chemotherapy and immunotherapy. A follow-up cardiac MRI revealed a concerning lesion in the posterior left atrium with evidence of interval size progression on a subsequent CT, suggestive of a recurrence (Panel A). To aid in surgical planning, 3D segmentation of the patient's CT scan was performed, and a 3D model of her heart and lesion were printed (Panel B). This was particularly valuable as it was her third redo surgery, and there were concerns about the surrounding anatomy. Upon reviewing the multimodality imaging and 3D model, the patient was deemed a suitable candidate for a redo surgery. She underwent left atrial sarcoma resection with left atrial floor reconstruction using a bovine pericardial patch and left inferior pulmonary vein reimplantation (Panel C). Histological studies were consistent with recurrent intimal sarcoma (Panel D). The patient is currently in remission. Conclusion: Multimodality imaging was crucial in diagnosing the recurrence of the sarcoma. However, 3D printing of the heart and lesion with detailed segmentation of the left atrium and surrounding structures played a significant role in surgical planning. This highlights the growing use of 3D printing in cardiac surgery planning.

Abstract 17728: Distribution and Predictors of Left Atrial Low Voltage Areas in Patients With Atrial Fibrillation Undergoing Catheter Ablation

Background: Low voltage areas (LVAs) in the left atrium (LA) are associated with a higher likelihood of non-pulmonary vein triggers for atrial fibrillation (AF), and ablation of LVAs has been shown to reduce AF recurrence. This study aimed to assess the distribution and predictors of LVAs in a large cohort of patients undergoing AF ablation. Methods: This study included patients who underwent first AF ablation at the Hospital of the University of Pennsylvania between November 2020 and December 2022. Patients with prior LA ablation, cardiac surgery, sarcoidosis, or amyloidosis were excluded. All patients underwent voltage mapping with multipolar mapping catheters and pulmonary vein isolation. LVAs were defined as contiguous areas with a bipolar voltage &lt;0.5mV. The associations between preprocedure risk factors, echocardiographic findings, and LVAs were assessed using univariable logistic regression. All variables with a p value &lt;0.1 were entered in a stepwise, backward, multivariable model. Results: A total of 857 consecutive patients (mean age: 64.7 years, 34% women, 33% non-paroxysmal AF) were included. LVAs were identified in 132 (15.4%) patients, of whom 72% had LVAs in posterior wall, 47.7% in roof/anterior, 43.9% in septum, 24.2% in floor/inferior, and 16.7% in lateral wall. The multivariable model showed that age (OR per 1 year increase 1.05, 95% CI 1.03-1.08), heart failure/left ventricular cardiomyopathy (OR 2.1, 95% CI 1.4-3.3), sinus node dysfunction (OR 3.7, 95% CI 1.8-7.3), persistent/permanent AF (OR 3.2, 95% CI 2.1-4.9), and severe LA enlargement on echocardiography (OR 1.9, 95% CI 1.1-3.5) were independent predictors of LVAs. Conclusion: LVAs are identified in 15% of patients undergoing first AF ablation and are typically located along the posterior and anteroseptal LA. Presence of LVAs can be anticipated using a readily available preprocedure risk assessment. This information may influence preprocedure planning and choice of ablation strategy.

Abstract 13928: Targeted Atrial Inhibition of Galphaq Signaling With Inhibitory Peptides Attenuates Fibrosis and Inducibility of Atrial Fibrillation in a Canine Heart Failure Model

Introduction: Endothelial dysfunction, a hallmark of heart failure (HF), is closely associated with atrial fibrillation (AF). However, the precise role of endothelial dysfunction in creating an atrial arrhythmogenic substrate is unknown. Endothelin-1 (ET-1) and its downstream Gα q signaling are significantly upregulated in the atria of patients with HF. We therefore hypothesized that ET-1-Gα q signaling contributes to adverse structural remodeling in the atria in the setting of HF. Hypothesis: Inhibition of atrial ET-1-Gα q signaling with Gα q inhibitory peptides (Gα q -ct) will attenuate the development of atrial fibrosis and AF inducibility in a HF model. Methods: Plasmids expressing Gα q -ct were injected and electroporated in the left atria of 4 dogs. LacZ or scrambled plasmids were used in 8 control dogs. HF was induced by ventricular tachypacing (VTP) at 240 bpm for 3 weeks. At terminal EP study, left atrial conduction vectors were recorded with high-density mapping and AF inducibility assessed. Left atrial fibrosis was quantified by Masson Trichrome. Results: All animals developed clinical HF (prolonged capillary refill time, ascites, reduced activity level) and LV systolic dysfunction by echocardiogram (LVEF 17.5±8.3% in Gα q -ct, 13.7±3.1% in controls, p=0.55). Conduction inhomogeneity was reduced in Gα q -ct animals (example of posterior left atrium recordings in Fig. A). AF was less inducible in Gα q -ct than control animals (4.8% of pacing attempts Vs 17.8%, p&lt;0.001, Fig. B) and AF episodes were shorter (5.6±0.9 sec Vs 63.8±11.9 sec). Left atrial fibrosis was significantly attenuated in Gα q -ct animals Vs controls (Fig. C). Conclusions: Gα q signaling contributes to atrial fibrosis and subsequent AF susceptibility in VTP-induced HF, thereby highlighting an important role for ET-1 signaling in HF-related atrial remodeling. Future optimization of gene therapy targeting ET-1 signaling may lead to novel, mechanism-guided treatments for AF in the context of HF.

An Early Prosthetic Valve Endocarditis in Presence of COVID-19-Associated Pneumonia

Introduction. Coronavirus disease (COVID-19)-associated pneumonia was a dangerous disease at the beginning of 2021. However, there are almost no records of early infectious endocarditis of prosthetic heart valve in the presence of such a disease. We present an interesting clinical case of successful treatment of complicated pathology.&#x0D; The COVID-19 outbreak involved unique clinical complications that were superimposed on the progressive heart failure due to prosthetic mitral valve dysfunction (its detachment) which did not allow time for active antiinflammatory therapy. Urgent replacement of the prosthesis made it possible to eliminate the infection and paved the way for successful long-term antibacterial, antifungal and antiviral therapy.&#x0D; The aim. To determine the features of management of patients with complex clinical pathology: prosthetic valve endocarditis associated with COVID-19 and severe lung inflammation in the early postoperative period.&#x0D; Case report. This work presents rare clinical case. A 46-year old male patient underwent successful surgery (mitral valve replacement with posterior leaflet preservation and left atrium resection) at the Department of Surgical Treatment of Acquired Heart Diseases of the National Amosov Institute of Cardiovascular Surgery and was discharged in satisfactory condition. One month later, he was hospitalized again and diagnosed with an early infectious endocarditis of prosthetic mitral valve and bilateral polysegmental COVID-19-associated pneumonia. After a week of medicinal preparation (antibacterial therapy), the patient underwent repeat mitral valve replacement in the presence of progressive heart insufficiency due to increasing paravalvular insufficiency. Postoperative period elapsed without significant complications. The patient was discharged in satisfactory condition on day 15 after surgery and primary rehabilitation.&#x0D; Conclusion. Having a specific etiology, pneumonia significantly damaged mitral prosthesis structures by increasing paravalvular insufficiency. Consequently, the patient underwent life-saving repeat mitral valve replacement in the presence of COVID-19-associated pneumonia and under massive antibacterial treatment which continued for 60 days after the patient’s discharge. An important element of successful treatment of COVID-19-associated pneumonia is the selection of adequate antibacterial, antifungal and antiviral drugs.

Differences in atrial substrate localization using late gadolinium enhancement-magnetic resonance imaging, electrogram voltage, and conduction velocity: a cohort study using a consistent anatomical reference frame in patients with persistent atrial fibrillation.

Electro-anatomical voltage, conduction velocity (CV) mapping, and late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) have been correlated with atrial cardiomyopathy (ACM). However, the comparability between these modalities remains unclear. This study aims to (i) compare pathological substrate extent and location between current modalities, (ii) establish spatial histograms in a cohort, (iii) develop a new estimated optimized image intensity threshold (EOIIT) for LGE-MRI identifying patients with ACM, (iv) predict rhythm outcome after pulmonary vein isolation (PVI) for persistent atrial fibrillation (AF). Thirty-six ablation-naive persistent AF patients underwent LGE-MRI and high-definition electro-anatomical mapping in sinus rhythm. Late gadolinium enhancement areas were classified using the UTAH, image intensity ratio (IIR >1.20), and new EOIIT method for comparison to low-voltage substrate (LVS) and slow conduction areas <0.2 m/s. Receiver operating characteristic analysis was used to determine LGE thresholds optimally matching LVS. Atrial cardiomyopathy was defined as LVS extent ≥5% of the left atrium (LA) surface at <0.5 mV. The degree and distribution of detected pathological substrate (percentage of individual LA surface are) varied significantly (P < 0.001) across the mapping modalities: 10% (interquartile range 0-14%) of the LA displayed LVS <0.5 mV vs. 7% (0-12%) slow conduction areas <0.2 m/s vs. 15% (8-23%) LGE with the UTAH method vs. 13% (2-23%) using IIR >1.20, with most discrepancies on the posterior LA. Optimized image intensity thresholds and each patient's mean blood pool intensity correlated linearly (R2 = 0.89, P < 0.001). Concordance between LGE-MRI-based and LVS-based ACM diagnosis improved with the novel EOIIT applied at the anterior LA [83% sensitivity, 79% specificity, area under the curve (AUC): 0.89] in comparison to the UTAH method (67% sensitivity, 75% specificity, AUC: 0.81) and IIR >1.20 (75% sensitivity, 62% specificity, AUC: 0.67). Discordances in detected pathological substrate exist between LVS, CV, and LGE-MRI in the LA, irrespective of the LGE detection method. The new EOIIT method improves concordance of LGE-MRI-based ACM diagnosis with LVS in ablation-naive AF patients but discrepancy remains particularly on the posterior wall. All methods may enable the prediction of rhythm outcomes after PVI in patients with persistent AF.

Validation of a new species for studying postoperative atrial fibrillation: Swine sterile pericarditis model.

The canine sterile pericarditis model associated with atrial inflammation is an experimental counterpart of postoperative atrial fibrillation (POAF). However, the use of canines for research is restricted by ethics committees in many countries, and social acceptance is declining. To validate the feasibility of the swine sterile pericarditis model as an experimental counterpart to study POAF. Seven domestic pigs (35-60kg) underwent initial pericarditis surgery. On two or more postoperative days in the closed-chest state, we performed electrophysiological measurements of pacing threshold and atrial effective refractory period (AERP) while pacing from the right atrial appendage (RAA) and the posterior left atrium (PLA). The inducibility of POAF(>5min) by burst pacing was determined in both the conscious and anesthetized closed-chest state. These data were compared to previously published canine sterile pericarditis data for validation. The pacing threshold increased from day 1 to day 3 (2±0.1 to 3.3±0.6mA in the RAA, 2.5±0.1 to 4.8±0.2mA in the PLA). Also, the AERP increased from day 1 to day 3 (118±8 to 157±16ms in the RAA; 98±4 to 124±2ms in the PLA, both p<.05). Induction of sustained POAF occurred in 43% (POAF CL range 74-124ms). All electrophysiologic data from the swine model were consistent with the canine model with respect to (1) the range of both pacing threshold and AERP; (2) the progressive increase in threshold and AERP over time; (3) a 40%-50% incidence of POAF. A newly developed swine sterile pericarditis model demonstrated electrophysiologic properties consistent with the canine model and patients after open heart surgery.

Volumetric quantification of peri-atrial fat inflammation in atrial fibrillation patients

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Centre for Research Excellence Award III (RE/18/5/34216). SEW is supported by the British Heart Foundation (FS/20/26/34952). MCW is supported by the British Heart Foundation (FS/ICRF/20/26002) Introduction Peri-atrial fat may have pro-inflammatory and pro-fibrotic effects on atrial myocardium and increase the risk of developing atrial fibrillation. Both peri-atrial fat volume and density have been proposed as markers for atrial fibrillation risk, but prior studies considered only single-plane analysis or peri-atrial fat attenuation limited to the posterior left atrium. Purpose We aimed to assess total peri-atrial fat volume and attenuation and to explore the relationship between both parameters and the occurrence of atrial fibrillation. Methods Contrast-enhanced cardiac computed tomography (CT) imaging was performed pre-ablation in atrial fibrillation patients (n=32) and in control patients (n=37) without atrial fibrillation undergoing investigation for chest pain. We developed a volumetric method for peri-atrial fat segmentation and quantification using seg3D2 and CEMRGapp. Peri-atrial fat volume and attenuation (Hounsfield units, HU) were compared between patients with and without atrial fibrillation in univariable and multivariable analyses. A sensitivity analysis was performed to assess the impact of fat proximity to the left atrial wall. Results Atrial fibrillation participants were older (64±11 years vs 58±7 years, P=0.004) and more likely to have a history of coronary artery disease (50% vs 25%, P=0.03). Participants with atrial fibrillation had greater left atrial volume (88±28 ml vs 69±19 ml, P=0.002) and mass (29±6 g vs 14±0.9 g, P=0.018) compared to controls. Peri-atrial fat volume was greater in those with than without atrial fibrillation (18.5±6.6 ml vs 14.2±7.0 ml, adjusted odds ratio (AOR) per ml 1.21; 95% confidence interval [CI] 1.03-1.48), after adjusting for age, body mass index, comorbidities, left atrial dimensions and mass. However, total peri-atrial fat attenuation was not significantly different between groups (-74.8 vs -73.0 HU; AOR per HU 1.01; 95% CI 0.82-1.22). Sensitivity analysis did not identify an interaction between interrogation distance from the left atrial wall and peri-atrial fat attenuation on prevalent atrial fibrillation (p=0.872). Conclusion Peri-atrial fat volume, but not attenuation, is associated with prevalent atrial fibrillation. Further mechanistic studies are needed to study the role of peri-atrial fat in atrial fibrillation pathogenesis.

Pulsed-field ablation: analysis of a new ablation technique for atrial fibrillation. A single centre experience

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Pulsed-field ablation (PFA) is a new non-thermal, tissue-specific ablation technique. Through the application of a local electric field, it is possible to induce a selective electroporation of cardiomyocytes membranes, resulting in myocytic apoptosis and sparing of non-myocardial structures (nerves, connective tissue, esophagus, vessels). Purpose A new PFA system for atrial fibrillation (AF) ablation has recently been introduced in our hospital. The aim of this retrospective review is to share the initial results of our experience in terms of acute efficacy and safety. Methods A total of 41 adult patients suitable for AF percutaneous ablation underwent PFA between April and November 2022 in our Institute. PFA system consisted of a current generator, a deflectable sheath and a multielectrode PFA catheter. Once inside the left atrium (LA), the PFA catheter was directed to the pulmonary veins (PVs) ostia through an over-the-wire system. Then, 8 electric impulses were applied for each PV to achieve electrical isolation; in some cases, applications to the posterior left atrium wall (LAPW) were delivered to obtain LAPW isolation (LAPWI). A moderate-to-deep sedation was provided by an anesthesiologist during all the procedures. Acute ablation efficacy was defined as absence of intracavitary signals at the electroanatomic mapping and local capture failure at the pacing maneuvers. Intra and peri-procedural safety was defined as the absence of major complications (pericardial effusion/ tamponade, stroke, vascular complications, death) during the procedure and the hospitalization period. Results Of the 41 patients included, 24 (58.5%) were treated for paroxysmal AF and 17 (41.5%) for persistent AF. In almost all cases (n=40, 97.6%) pulmonary veins isolation (PVI) was performed; in 14 cases (34.1%, almost all persistent AF patients) a LAPWI was performed with the application of a variable number of pulses (mean value = 13). In most of the cases (n=28, 68.3%) an electroanatomic mapping was acquired before and after the ablation. Acute efficacy was observed in all PVI cases (n=40, 100%) and in all LAPWI cases (n=14, 100%). No periprocedural major complications were observed (n=0, 0%). Conclusions PFA is a promising ablation technique capable of inducing selective myocytic apoptosis through electroporation, causing a thick damage across the muscle with no injury of other tissues, and could become a game changer in electrophysiology in the next future. Our initial data report a combination of ease of use and high efficacy and safety profiles.

PO-455617-1 EXPLORING THE INTERPLAY OF FUNCTIONAL AND STRUCTURAL REMODELING PROGRESSION IN ATRIAL FIBRILLATION IN A RAPID ATRIAL PACING CANINE MODEL

In sustained atrial fibrillation (AF) it is still unclear to what extent, at which time points functional and structural remodeling processes develop over time, and which parameters can measure the progression state. We hypothesized that persistent AF progression state induced by rapid atrial pacing (RAP) can be uncovered by measuring electrogram characteristics, OS levels, nerve activity, and the degree of fibrosis with MRI imaging. AF was induced in 15 dogs (25-35 kg, ≥1 year) by RAP (3-17 weeks RAP, 600 beats/min), and 8 controls were used. We performed high-resolution epicardial mapping (6 regions, 130 electrodes, distance 2.5mm) (Figure 1) and analyzed bipolar peak-to-peak voltage, cycle length (CL), and organization index (OI). We quantified OS levels as damaged nuclei against total number in 8-OHdG staining (N=36 samples, 6 animals) and degree of fibrosis (Masson’s trichrome) (N=24, 4 dogs). We also quantified in implantable telemetry recordings (DSI) parasympathetic nerve activity (PNA) (2 hours) assessed as the time between PNA spikes (3 AF dogs, 3 controls). MRI native T1, post-contrast T1, and T2 mapping, and late gadolinium enhancement (LGE) were assessed (1.5T clinical scanner, Siemens Aera) in the posterior left atrium (PLA) (7 AF, 8 at baselines). Voltage, CL, and OI decreased (R=0.9, P<0.05), (R=0.6, P<0.05), (R=0.5, P<0.05) over time of RAP (Figure 1). After 80 RAP days voltage changed, but no more changes in other EGM measures were observed. OS levels in AF were highest in the left atrial free wall and lowest in the appendages (Figure 2). The electrogram measures OI and CL decreased with increased oxidative stress levels (Figure 2). Fibrosis (R=0.6, P<0.05) increased with OS (R=0.6, P<0.05) in all atrial regions (Figure 2). Parasympathetic nerve activity increased by factor 5 after 120 RAP days, (Figure 3). Native T1, T2 times increased with RAP days (R=0.6, P<0.05), (R=0.4, P<0.05) in PLA (<120 pacing days) (Fig. 4). Functional and structural remodeling in persistent AF is the result of an interplay among the development of increased OS, fibrosis, and nerve activity in a RAP canine model and can moderately be uncovered using the electrogram measures CL and OI until the saturation point after 80 RAP days. Voltage also uncovers the AF progression state post 80- RAP days with a strong correlation coefficient. Additional parasympathetic nerve recordings and MRI imaging including T1 mapping may be complementary to detect AF remodeling states.

PO-01-107 INTRA-CARDIAC SPINDLE CELL CARCINOMA FOLLOWING CATHETER ABLATION OF ATRIAL FIBRILLATION AND LEFT ATRIAL APPENDAGE CLOSURE

Spindle cell carcinoma (SpCC), a type of squamous cell carcinoma (SCC), is a rare tumor with features similar to sarcoma that often arises from the respiratory system. Myocardial involvement of these tumors has not been described. We present a case of metastatic SpCC diagnosed through routine transesophageal echocardiography (TEE) following left atrial appendage occlusion (LAAO). To describe a rare occurrence of metastatic SpCC diagnosed through routine TEE following LAA occlusion. NA A 61 year old male with a history of coronary artery disease and heart failure presented with persistent symptomatic atrial fibrillation (AF) despite anti-arrhythmic therapy. We performed pulmonary vein isolation (PVI) and during intubation a laryngeal mass was noted. He was diagnosed with T2N0M0 sarcomatoid SCC and had surgery, radiation and chemotherapy (cisplatin). At that time, he was felt to have a favorable 5 year survival prognosis. Six months later he represented with symptomatic AF and underwent repeat PVI. Due to concerns regarding bleeding risk, LAAO was later performed. During follow up TEE at day 45, a new cystic lesion arising from the posterior left atrium and a 2x3cm heterogenous mass associated with the interatrial septum was noted (Figure 1 A-D). CT scan showed new mediastinal masses with extension into the left atrium in the region treated with radiofrequency ablation (Figure 1 E-H). Biopsy revealed SpCC consistent with the initial laryngeal mass. Tumor extending from the perihilar mass and in the fossa ovalis, given the proximity of prior work and prior transseptal puncture, raises the concern for inadvertent iatrogenic spread of tumor and that catheter manipulation facilitated invasion into the LA with the pedunculated mass and seeded the septum. The patient unfortunately continued to decline clinically and shortly thereafter transitioned to comfort care and passed away. We present a case of persistent symptomatic AF in which laryngeal SpCC was diagnosed during initial PVI and rapidly progressive metastatic SpCC diagnosed via TEE in follow up after LAAO. This presentation is concerning for inadvertent iatrogenic spread of tumor from an extracardiac source through PVI. SpCC is more aggressive than typical SCC, however rapid invasion through the chest wall, lung and myocardium within 1.5 months is extremely rare. While primary spindle cell sarcoma of the myocardium has been reported, to our knowledge we report the first case of metastatic SpCC to the heart.

PO-01-075 TRANSTHORACIC ECHOCARDIOGRAPHY FOR EARLIER DIAGNOSIS OF ATRIOESOPHAGEAL FISTULA AFTER ABLATION FOR ATRIAL FIBRILLATION

Atrioesophageal fistula (AEF) is a rare complication of radiofrequency ablation for atrial fibrillation (AF). Early diagnosis and surgical management are keys to mitigate progression of this often moribund complication. Although chest CT is the preferred first line imaging tool for diagnosis, AEF symptoms are often variable and counterintuitive which prompts the need to understand echocardiographic findings that may lead to an earlier diagnosis. To report the initial echocardiogram findings of two patients that were ultimately diagnosed with AEF. N/A A 79-year-old male with symptoms AF and gastroesophageal reflux underwent an uneventful pulmonary vein isolation (PVI). Approximately 3 weeks after the ablation, the patient presented to his local hospital with profound fatigue and was found to have nonspecific ST/T changes with an elevated troponin. The transthoracic echocardiogram (TTE) showed moderate left ventricular dysfunction and echo dense microbubbles in the left atrium and ventricle, but not in the corresponding right-sided chambers (Figure A). An emergent CT scan based upon the TTE showed an AEF and he underwent and emergent surgery to repair the AEF. A 49-year-old male underwent a PVI with additional targeting of regions of complex fractionated electrograms on the posterior wall. Two weeks later he developed worsening dyspnea on exertion and chest pain. A CT scan found multiple septic pulmonary emboli and a TTE noted a mobile density crossing the intra-atrial septum. During transfer to our center, he developed progressive respiratory failure and required intubation. Upon arrival he was found to have multiple embolic injuries to his brain and focal neurologic findings. A transesophageal echocardiogram (Figure B) confirmed the mobile density in the right atrium that was an extension of a lesion originating from the posterior left atrium and extending to the iatrogenic atrial septal defect. AEF requires very early diagnosis for survival. In the setting of often non-specific symptoms, such as in these two cases that can lead to an initial incorrect diagnosis, the TTE provided key information to support the underlying diagnosis and guide expedited work-up and intervention.

Superior vena cava isolation with pulsed field ablation in the presence of defibrillator leads.

Two patients with a history of dilated cardiomyopathy, dual chamber defibrillator implantation, and worsening heart failure because of persistent atrial fibrillation (AF) underwent catheter ablation of AF. Pulsed field ablation (PFA) was selected for the index procedure in these decompensated heart failure patients with enlarged atria.1 The 12-Fr over-the-wire pentaspline PFA catheter (Farawave) was advanced through a 13-Fr steerable sheath (Faradrive) to the ostium of each PV, and a total of eight PFA lesions were applied per vein. Phrenic nerve function was evaluated by direct phrenic capture and by observing diaphragmatic motion during inspiration. For posterior wall ablation, the catheter was placed into a flower configuration and positioned along the posterior left atrium to deliver overlapping sets of pulses at each location. As per institution protocol, superior vena cava (SVC), as a potential nonpulmonary trigger for AF, is isolated when active despite a risk of sinus node injury.2 Basket configuration (Figure 1) and two sets of two lesions at the trunk of the vessel (with rotation between each pair) were used for SVC isolation in the presence of atrial and defibrillator leads, without any impact on device and leads measurements or sinus node function (Figure 2). We observed incidence of phrenic capture during PFA, and no evidence of phrenic injury was detected after the procedure. Both patients were in AF and cardioverted into sinus rhythm post-SVC isolation. They remained at sinus rhythm at regular 3-month follow-up while device interrogation revealed intact sinus node function. Only 4.2% of operators in the MANIFEST-PF multinational survey (including 1758 consecutive unselected AF patients) performed SVC isolation by mean of PFA occasionally.3 This is the first report of off-label pulsed field ablation-mediated SVC isolation without device or lead malfunction. Human studies evaluating cardiac implantable electrical devices during ablation procedure remain limited. A recent study by a high-volume center indicated that PFA is a safe and feasible method in patients with devices in the terms of alterations in pacing, sensing, or impedance parameters, inappropriate anti-tachycardia pacing, and ICD shock and leads dislodgment.4 Indeed, our pilot procedures with PFA applications in the SVC of AF patients with implanted devices confirmed the previous results without apparent additional risk because of energy application adjacent to the electrodes. None declared. None. The authors declare no conflict of interests for this article. Approval of the research protocol: N/A. Informed Consent: Ν/Α. Registry and the Registration No. of the study/trial: N/A. Animal Studies: N/A. Data are available in the article.

Conduction velocity is reduced in the posterior wall of hypertrophic cardiomyopathy patients with normal bipolar voltage undergoing ablation for paroxysmal atrial fibrillation.

We investigated characteristics of left atrial conduction in patients with HCM, paroxysmal AF and normal bipolar voltage. Patients with hypertrophic cardiomyopathy (HCM) exhibit abnormal cardiac tissue arrangement. The incidence of atrial fibrillation (AF) is increased fourfold in patients with HCM and confers a fourfold increased risk of death. Catheter ablation is less effective in HCM, with twofold increased risk of AF recurrence. The mechanisms of AF perpetuation in HCM are poorly understood. We analyzed 20 patients with HCM and 20 controls presenting for radiofrequency ablation of paroxysmal AF normal left atrial voltage(> 0.5mV). Intracardiac electrograms were extracted from the CARTO mapping system and analyzed using Matlab/Python code interfacing with Core OpenEP software. Conduction velocity maps were calculated using local activation time gradients. There were no differences in baseline demographics, atrial size, or valvular disease between HCM and control patients. Patients with HCM had significantly reduced atrial conduction velocity compared to controls (0.44 ± 0.17 vs 0.56 ± 0.10m/s, p = 0.01), despite no significant differences in bipolar voltage amplitude (1.23 ± 0.38 vs 1.20 ± 0.41mV, p = 0.76). There was a statistically significant reduction in conduction velocity in the posterior left atrium in HCM patients relative to controls (0.43 ± 0.18 vs 0.58 ± 0.10m/s, p = 0.003), but not in the anterior left atrium (0.46 ± 0.17 vs 0.55 ± 0.10m/s, p = 0.05). There was a significant association between conduction velocity and interventricular septal thickness (slope = -0.013, R2 = 0.13, p = 0.03). Atrial conduction velocity is significantly reduced in patients with HCM and paroxysmal AF, possibly contributing to arrhythmia persistence after catheter ablation.

Evaluating temperature gradients across the posterior left atrium with radiofrequency ablation.

Esophageal injury is a well-known complication associated with catheter ablation. Though novel methods to mitigate esophageal injury have been developed, few studies have evaluated temperature gradients with catheter ablation across the posterior wall of the left atrium, interstitium, and esophagus. To investigate temperature gradients across the tissue, we developed a porcine heart-esophageal model to perform ex vivo catheter ablation on the posterior wall of the left atrium(LA), with juxtaposed interstitial tissue and esophagus. Circulating saline (5 L/min) was used to mimic blood flow along the LA and alteration of ionic content to modulate impedance. Thermistors along the region of interest were used to analyze temperature gradients. Varying time and power, radiofrequency (RF) ablation lesions were applied with an externally irrigated ablation catheter. Ablation strategies were divided into standard approaches (SAs, 10-15 g, 25-35 W, 30 s) or high-power short duration (HPSD, 10-15 g, 40-50 W, 10 s). Temperature gradients, time to the maximum measured temperature, and the relationship between measured temperature as a function of distance from the site of ablation was analyzed. In total, fiveexperiments were conducted each utilizing new porcine posterior LA wall-esophageal specimens for RF ablation (n = 60 lesions each for SA and HPSD). For both SA and HPSD, maximum temperature rise from baseline was markedly higher at the anterior wall (AW) of the esophagus compared to the esophageal lumen (SA: 4.29°C vs. 0.41°C, p < .0001 and HPSD: 3.13°C vs. 0.28°C, p < .0001). Across ablation strategies, the average temperature rise at the AW of the esophagus was significantly higher with SA relative to HPSD ablation (4.29°C vs. 3.13°C, p = .01). From the start of ablation, the average time to reach a maximum temperature as measured at the AWof the esophagus with SA was 36.49 ± 12.12 s, compared to 16.57 ± 4.54 s with HPSD ablation, p < .0001. Fit to a linear scale, a 0.37°C drop in temperature was seen for every 1 cm increase in distance from the site of ablation and thermistor location at the AW of the esophagus. Both SA and HPSD ablation strategies resulted in markedly higher temperatures measured at the AW of the esophagus compared to the esophageal lumen, raising concern about the value of clinical intraluminal temperature monitoring. The temperature rise at the AW was lower with HPSD. A significant time delay was seen to reach the maximum measured temperature and a modest increase in distance between the site of ablation and thermistor location impacted the accuracy of monitored temperatures.

Anterior vs. posterior position of dispersive patch during radiofrequency catheter ablation: insights from in silico modelling.

To test the hypothesis that the dispersive patch (DP) location does not significantly affect the current distribution around the catheter tip during radiofrequency catheter ablation (RFCA) but may affect lesions size through differences in impedance due to factors far from the catheter tip. An in silico model of RFCA in the posterior left atrium and anterior right ventricle was created using anatomic measurements from patient thoracic computed tomography scans and tested the effect of anterior vs. posterior DP locations on baseline impedance, myocardial power delivery, radiofrequency current path, and predicted lesion size. For posterior left atrium ablation, the baseline impedance, total current delivered, current distribution, and proportion of power delivered to the myocardium were all similar with both anterior and posterior DP locations, resulting in similar RFCA lesion sizes (< 0.2 mm difference). For anterior right ventricular (RV) ablation, an anterior DP location resulted in slightly higher proportion of power delivered to the myocardium and lower baseline impedance leading to slightly larger RFCA lesions (0.6 mm deeper and 0.8 mm wider). An anterior vs. posterior DP location will not meaningfully affect RFCA for posterior left atrial ablation, and the slightly larger lesions predicted with anterior DP location for anterior RV ablation are of unclear clinical significance.