Ablation Of Cardiac Tissue Research Articles

Pulsed Field Ablation in the Elderly via a Pentaspline Multielectrode Catheter: Safety, Efficacy, and Comparison with Cryoballoon and Radiofrequency Devices.

Catheter ablation is an effective treatment for atrial fibrillation (AF). Pulsed field ablation (PFA) has emerged as a novel energy modality, which relies on high-voltage electric fields to achieve cardiac tissue ablation. Data on its efficacy in the elderly are scarce. To evaluate the procedural details and clinical outcomes of PFA in patients > 75 years old. Consecutive AF patients > 75 years old undergoing PFA via the FarapulseTM system were enrolled at 6 high-volume centers. Procedural details and clinical outcomes were compared with those of patients undergoing second-generation cryoballoon (CBA) and radiofrequency (RFA) ablation. Among 983 patients, 221 underwent PFA, 216 CBA, and 546 RFA. Procedure times were shorter with PFA (72 ± 30 minutes) compared to CBA (77 ± 27 minutes) and RFA (99 ± 23 minutes) (p<0.001). Extra-PV ablation was performed in 74.2% PFA, 9.7% CBA, and 42.1% RFA (p<0.001). The major complication rate was 1.01% (n=10) and was not significantly different among groups (1 PFA, 2 CBA, and 7 RFA; p=0.578). Minor complications were observed in 1.4 % PFA, 5.1 % CBA, and 3.5 % RFA (p=0.093). The 1-year atrial tachyarrhythmia freedom in the propensity matched population was 77.2 % with PFA, 80.8 % with CBA, and 74.9 % with RFA) (p=0.52). PFA was a safe and effective option for elderly patients, offering the advantage of enabling extra-PV ablation without the concern of thermal injury risk.

The performance of a new nanosecond pulsed-field ablation surgical clamp in the ablation of cardiac tissue: Achronic porcine model.

The purpose of this chronic porcine model is to demonstrate the safety and efficacy of a new nanosecond pulsed-field ablation (nsPFA) parallel clamp in ablating different cardiac tissue. The Pulse Biosciences nsPFA CellFX Clamp System was tested on 6 pigs. Ablations were performed in all 4 heart chambers by delivering a sequence of very short-duration, high-amplitude electrical pulses taking 1.25seconds per application independent of tissue thickness or type. Testing for electrical exit block was performed at the time of surgery and at study termination. At 35days, animals were killed humanely and anonymized histopathology was performed to assess lesion width, depth, and transmurality. Lesion pattern and general safety were compared with 6 animals in which a bipolar radiofrequency clamp was used (AtriCure Synergy Isolator System). There were no device-related serious adverse events in the nsPFA group. There was 1 early device-related mortality at day 24 in the RFA group from perforation of 1 of the ventricular ablation sites. There were also 2 intracardiac thrombotic events with 1 systemic thromboembolic event in the radiofrequency group. Exit block was confirmed in all animals from both groups for the pulmonary veins and the posterior wall. Histologic findings were consistent and demonstrated mature scar formation in all nsPFA ablation specimens, whereas a 7.1% rate of incomplete histopathological scar maturation was present in the RFA group. In this chronic porcine model, a single 1.25-second application independent of tissue thickness with the CellFX Parallel Clamp System demonstrated promising safety and efficacy profile. All lesions produced by this technology resulted in persistent exit block around pulmonary veins and the posterior atrial wall consistent with a reliable, contiguous and transmural ablation without injury to adjacent organs.

First experience of focal pulsed field ablation for premature ventricular contractions

Abstract Introduction Pulsed field ablation (PFA) has emerged as a novel strategy to achieve ablation of cardiac tissue. Clinical evidence suggests a remarkable lesion durability and safety profile for AF ablation. Nonetheless, a growing interest exists in broadening its field of application for catheter ablation of ventricular arrhythmias (VA). The CENTAURI system arises as a promising PFA system for targeting VA as it allows pulsed electric field (PEF) delivery via standard, commercially available focal ablation catheters and concomitant coupling with their mapping systems. Purpose To assess, for the first time, the feasibility of focal PFA via the CENTAURI system for premature ventricular complex (PVC) ablation. Methods We conducted a prospective analysis of patients with either high burden (&amp;gt;10%) or symptomatic idiopathic PVC undergoing focal PFA using CENTAURI system at our institution. Procedures were performed between December 2022 and August 2023. Acute and long-term success were defined as no PVC recurrence during a 24h in-hospital monitoring period, and ≥80% burden reduction with absence of symptoms after at least 30 days post-ablation, respectively. PVC monitoring was performed by implantable loop recorder (ILR) or surface ECG Holter monitoring. Results Fourteen patients (age range: 16-87 years; 10 females) were included. Procedures were performed via the CENTAURI system in combination with CARTO 3 system and EnSite X EP system in 4 (28.6%) and 10 cases (71.4%) respectively. Targeted ablation sites were the right ventricular outflow tract (6 cases), right moderator band (2 cases), left postero-medial papillary muscle -PM- (2 cases), and right posterior PM, tricuspid annulus, left posterior fascicle and aortomitral continuity (AMC) in one case. On average, 6.5 applications were delivered to the site of origin with a mean contact force of 11g. Procedural duration and fluoroscopy time were 102 and 8.9 minutes. Two minor complications were observed: one transitory ST depression (solved after i.v. nitrate administration) after repeated applications to AMC, and a femoral pseudoaneurysm. The remaining 12 procedures were uneventful. Although most of the procedures were performed under general anesthesia due to concerns about potential significant muscular contraction, 3 cases (21.4%) were successfully managed with light sedation, without significant muscular contraction nor map shift. Incomplete abolishment of PVC during first 24 h was observed in 2 patients (14.3%). After a median follow-up of 113 days (IQR: 83-188), recurrences were detected in one patient (7.14%). Conclusion Herein we report the feasibility and efficacy of PVC ablation using a focal PEF delivery system (CENTAURI). Furthermore, we describe the possibility of performing PVC ablation with this technology under light sedation, which might be important for minimizing anesthesia impact on PVC burden.Table of characteristicsPVC morphologies

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.

Therapeutic perspectives of high pulse repetition rate electroporation

Electroporation, a technique that uses electrical pulses to temporarily or permanently destabilize cell membranes, is increasingly used in cancer treatment, gene therapy, and cardiac tissue ablation. Although the technique is efficient, patients report discomfort and pain. Current strategies that aim to minimize pain and muscle contraction rely on the use of pharmacological agents. Nevertheless, technical improvements might be a valuable tool to minimize adverse events, which occur during the application of standard electroporation protocols. One recent technological strategy involves the use of high pulse repetition rate. The emerging technique, also referred as “high frequency” electroporation, employs short (micro to nanosecond) mono or bipolar pulses at repetition rate ranging from a few kHz to a few MHz. This review provides an overview of the historical background of electric field use and its development in therapies over time. With the aim to understand the rationale for novel electroporation protocols development, we briefly describe the physiological background of neuromuscular stimulation and pain caused by exposure to pulsed electric fields. Then, we summarize the current knowledge on electroporation protocols based on high pulse repetition rates. The advantages and limitations of these protocols are described from the perspective of their therapeutic application.

Characterization of Experimentally Observed Complex Interplay between Pulse Duration, Electrical Field Strength, and Cell Orientation on Electroporation Outcome Using a Time-Dependent Nonlinear Numerical Model.

Electroporation is a biophysical phenomenon involving an increase in cell membrane permeability to molecules after a high-pulsed electric field is applied to the tissue. Currently, electroporation is being developed for non-thermal ablation of cardiac tissue to treat arrhythmias. Cardiomyocytes have been shown to be more affected by electroporation when oriented with their long axis parallel to the applied electric field. However, recent studies demonstrate that the preferentially affected orientation depends on the pulse parameters. To gain better insight into the influence of cell orientation on electroporation with different pulse parameters, we developed a time-dependent nonlinear numerical model where we calculated the induced transmembrane voltage and pores creation in the membrane due to electroporation. The numerical results show that the onset of electroporation is observed at lower electric field strengths for cells oriented parallel to the electric field for pulse durations ≥10 µs, and cells oriented perpendicular for pulse durations ~100 ns. For pulses of ~1 µs duration, electroporation is not very sensitive to cell orientation. Interestingly, as the electric field strength increases beyond the onset of electroporation, perpendicular cells become more affected irrespective of pulse duration. The results obtained using the developed time-dependent nonlinear model are corroborated by in vitro experimental measurements. Our study will contribute to the process of further development and optimization of pulsed-field ablation and gene therapy in cardiac treatments.

MRI-based numerical modeling of cardiac pulsed field ablation (PFA) with sub-microsecond pulses

Abstract Background The use of irreversible electroporation (IRE) for cardiac ablation in the management of cardiac arrhythmias, known as Pulsed Field Ablation (PFA), has gained the attention of many researchers, physicians and companies. Despite the demonstrated efficacy and safety profiles of the technique, there are still many open questions. One of them deals with the effective electric field thresholds necessary for cardiac tissue ablation. Contrary to radiofrequency (RF) ablation, where the thermotemporal thresholds for tissue damage are well established, the electric field thresholds for effective IRE are uncertain and depend on the tissue type and the waveform characteristics of the delivered electric field. Purpose The use of numerical models to understand the electric field distribution and the corresponding lesion for a specific electrode geometry are widely used in IRE for cancer treatment. Models can predict ablation volumes when the field thresholds are known or can be used to estimate the field thresholds when the lesion geometry is established post-treatment. The goal of the present study was to build a subject-specific realistic 3D numerical model to assess the ability of modeling to predict PFA lesions. Methods PFA experiments were performed in male mongrel dogs following a protocol approved by the Mayo Clinic Institutional Animal Care and Use Committee. Briefly, animals were sedated and intubated, and two non-irrigated deflectable catheters with an 8-mm tip were positioned on both sides of the interventricular septum under fluoroscopy guidance. Submicrosecond pulses were delivered in a bipolar fashion across both catheters. Sequences of pulses of 300 ns duration (or other durations in that range) were repetitively applied with voltage levels in the kV range. 30 days after the procedure, MRI with late gadolinium enhancement (LGE) were acquired to assess the presence of ablation lesions in the treated tissue. Ventricular areas were segmented from MRI images and 3D volumes were created. The generated 3D geometries were imported into software COMSOL Multiphysics. Realistic 3D geometries of the catheters were placed in the same positions than during the experiments, fluoroscopy videos recorded during the procedures were used as a guidance. The computed electric field intensity distributions were compared to the LGE areas to extract the range of electric field thresholds where the predicted lesion size was compatible with the real size of the LGE areas for each application site and pulsing protocol. Results and conclusions Our results show how the numerical model is able to reproduce the shape of the LGE fibrotic lesion areas observed 30 days after the procedure. Additionally, the model clearly confirms the dose-dependent lesion sizes observed experimentally. This study supports that numerical modeling is a valuable tool for understanding PFA treatments and that it could be used as patient-specific treatment planning tool. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie

Surgical Ablation of Cardiac Tissue with Nanosecond Pulsed Electric Fields in Swine.

Myocardial tissue can be ablated by the application nanosecond pulsed fields (nsPEFs). The applied electric fields irreversibly permeabilize cell membranes and thereby kill myocytes while leaving the extracellular matrix intact. In domestic pigs (n = 10), hearts were exposed via sternotomy and either ablated in vivo ([Formula: see text] = 5) or in excised, Langendorff-perfused hearts ([Formula: see text] = 5). The nsPEFs consisted of 6-36 pulses of 300 ns each, delivered at 3-6 Hz; the voltage applied varied from 10 to 12 kV. Atrial lesions were either created after inserting the bottom jaw of the bipolar clamp into the atrium via a purse string incision (2-3 lesions per atrium) or by clamping a double layer of tissue at the appendages (one lesion per atrium). Ventricular lesions were created after an incision at the apex. The transmurality of each lesion was determined at three points along the lesion using a triphenyl tetrazolium chloride (TTC) stain. All 27 atrial lesions were transmural. This includes 13/13 purse string lesions (39/39 sections, tissue thickness 2.5-4.5 mm) and 14/14 appendage lesions (42/42 sections, tissue thickness 8-12 mm). All 3 right ventricular lesions were transmural (9/9 sections, 18 pulses per lesion). Left ventricular lesions were always transmural for 36 pulses (3/3 lesions, 9/9 sections). All lesions have highly consistent width across the wall. There were no pulse-induced arrhythmias or other complications during the procedure. nsPEF ablation reliably created acute lesions in porcine atrial and ventricular myocardium. It has far better penetration and is faster than both radiofrequency ablation and cryoablation and it is free from thermal side effects.

Pulsed Field Ablation: a Novel Therapeutic Tool for Catheter-Based Treatment of Atrial Fibrillation

With catheter ablation of atrial fibrillation becoming increasingly common, the field of electrophysiology is searching for tools to improve procedural efficacy and safety. This review focuses on a novel ablation tool, pulsed field ablation, which promises to push the needle forward. Pulsed field ablation uses high-frequency electrical pulses to ablate cardiac tissue. A number of pre-clinical and clinical studies have shown pulsed field ablationoffers an efficient means of ablating cardiac tissue with minimal risk of collateral injury. Pulsed field ablation provides a non-thermal means of cardiac tissue ablation with minimal risk of injury to adjacent structures. Future studies will define the optimal current delivery, number of lesions needed to achieve the desired tissue effect, and how best to integrate pulsed field ablation catheters into 3-dimensional mapping systems.

Muscle contractions and pain sensation accompanying high-frequency electroporation pulses

To minimize neuromuscular electrical stimulation during electroporation-based treatments, the replacement of long monophasic pulses with bursts of biphasic high-frequency pulses in the range of microseconds was suggested in order to reduce muscle contraction and pain sensation due to pulse application. This treatment modality appeared under the term high-frequency electroporation (HF-EP), which can be potentially used for some clinical applications of electroporation such as electrochemotherapy, gene electrotransfer, and tissue ablation. In cardiac tissue ablation, which utilizes irreversible electroporation, the treatment is being established as Pulsed Field Ablation. While the reduction of muscle contractions was confirmed in multiple in vivo studies, the reduction of pain sensation in humans was not confirmed yet, nor was the relationship between muscle contraction and pain sensation investigated. This is the first study in humans examining pain sensation using biphasic high-frequency electroporation pulses. Twenty-five healthy individuals were subjected to electrical stimulation of the tibialis anterior muscle with biphasic high-frequency pulses in the range of few microseconds and both, symmetric and asymmetric interphase and interpulse delays. Our results confirm that biphasic high-frequency pulses with a pulse width of 1 or 2 µs reduce muscle contraction and pain sensation as opposed to currently used longer monophasic pulses. In addition, interphase and interpulse delays play a significant role in reducing the muscle contraction and/or pain sensation. The study shows that the range of the optimal pulse parameters may be increased depending on the prerequisites of the therapy. However, further evaluation of the biphasic pulse protocols presented herein is necessary to confirm the efficiency of the newly proposed HF-EP.

In vivo porcine characterization of atrial lesion safety and efficacy utilizing a circular pulsed-field ablation catheter including assessment of collateral damage to adjacent tissue in supratherapeutic ablation applications.

IntroductionPulsed‐field ablation (PFA), an ablative method that causes cell death by irreversible electroporation, has potential safety advantages over radiofrequency ablation and cryoablation. Pulmonary vein (PV) isolation was performed in a porcine model to characterize safety and performance of a novel, fully‐integrated biphasic PFA system comprising a multi‐channel generator, variable loop circular catheter, and integrated PFA mapping software module.MethodsEight healthy porcine subjects were included. To evaluate safety, multiple ablations were performed, including sites not generally targeted for therapeutic ablation, such as the right inferior PV lumen, right superior PV ostium, and adjacent to the esophagus and phrenic nerve. To evaluate the efficacy, animals were recovered, followed for 30(±3) days, then re‐mapped. Gross pathological and histopathological examinations assessed procedural injuries, chronic thrombosis, tissue ablation, penetration depth, healing, and inflammatory response.ResultsAll eight animals survived follow‐up. PV narrowing was not observed acutely nor at follow‐up, even when ablation was performed deep to the PV ostium. No injury was seen grossly or histologically in adjacent structures. All PVs were durably isolated, confirmed by bidirectional block at re‐map procedure. Histological examination showed complete, transmural necrosis around the circumference of the ablated section of right PVs.ConclusionThis preclinical evaluation of a fully‐integrated PFA system demonstrated effective and durable ablation of cardiac tissue and PV isolation without collateral damage to adjacent structures, even when ablation was performed in more extreme settings than those used therapeutically. Histological staining confirmed complete transmural cell necrosis around the circumference of the PV ostium at 30 days.

Acute Lesion Imaging in Predicting Chronic Tissue Injury in the Ventricles.

BackgroundChronic lesion formation after cardiac tissue ablation is an important indicator for procedural outcome. Moreover, there is a lack of knowledge regarding the features that predict chronic lesion formation.ObjectiveThe aim of this study is to determine whether acute lesion visualization using late gadolinium enhanced magnetic resonance imaging (LGE-MRI) can reliably predict chronic lesion size.MethodsFocal lesions were created in left and right ventricles of canine models using either radiofrequency (RF) ablation or cryofocal ablation. Multiple ablation parameters were used. The first LGE-MRI was acquired within 1–5 h post-ablation and the second LGE-MRI was obtained 47–82 days later. Corview software was used to perform lesion segmentations and size calculations.Results:Fifty-Five lesions were created in different locations in the ventricles. Chronic volume size decreased by a mean of 62.5 % (95% CI 58.83–67.97, p < 0.0005). Similar regression of lesion volume was observed regardless of ablation location (p = 0.32), ablation technique (p = 0.94), duration (p = 0.37), power (p = 0.55) and whether lesions were connected or not (p = 0.35). There was no significant difference in lesion volume reduction assessed at 47–54 days and 72–82 days after ablation (p = 0.31). Chronic lesion volume was equal to 0.32 of the acute lesion volumes (R2 = 0.75).ConclusionChronic tissue injury related to catheter ablation can be reliably modeled as a linear function of the acute lesion volume as assessed by LGE-MRI, regardless of the ablation parameters.

Characterization of atrial lesion safety and efficacy utilizing a circular catheter and the IRE generator with an in vivo porcine model

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Biosense Webster, Inc. Introduction/Objectives: Pulsed field ablation (PFA) is a non-thermal ablative method that delivers high voltage, very-short duration pulses that cause pore formation in the cytoplasmic membrane and cell death. The tissue selectivity of PFA is expected to reduce the risk of collateral tissue injury compared to radiofrequency catheter ablation (RFCA), while maintaining effectiveness. The objective of this study was to perform pulmonary vein (PV) isolation in a porcine model to characterize the safety and performance of a novel, fully-integrated biphasic PFA system. The system is comprised of a multi-channel generator, a variable loop circular catheter, and an integrated irreversible electroporation (IRE) mapping software module. Methods The study evaluated safety and efficacy of IRE in 8 healthy swine. First, to evaluate safety, multiple ablations were performed at various cardiac structures, including within the lumen of the right pulmonary vein (RIPV), at the right superior pulmonary vein (RSPV) ostium, and adjacent to the esophagus. Second, to evaluate efficacy, animals were recovered and followed for 30 (±3) days, then re-mapped. Gross pathological and histopathological examinations were performed to assess for procedural injury, chronic thrombosis, tissue ablation, depth of penetration, healing, and level of inflammatory response. Results All 8 swine survived for the 30 (±3) day follow up (FU) period. There were no acute (day of procedure) incidents of pulmonary vein narrowing of &amp;gt;70%, nor at 30 d follow-up (FU), even when ablation was purposefully performed directly deep to the ostium of the vein. No injury was seen grossly or histologically in the adjacent esophagus. All PVs were durably isolated as confirmed by bidirectional block at the 30 (±3) day re-map procedure, and histological examination showed complete, transmural necrosis around the entire circumference of the ablated section of the right PVs [Figure]. Conclusion(s): This pre-clinical evaluation of a fully integrated PFA system demonstrated effective and durable ablation of cardiac tissue and PV isolation with no collateral damage to adjacent structures. Notably, histological staining confirmed complete transmural cell necrosis around the circumference of the ostial PV at 30 days. Abstract Figure. PVI maps (A) histology (B) and safety(C)

Key factors behind autofluorescence changes caused by ablation of cardiac tissue

Radiofrequency ablation is a commonly used clinical procedure that destroys arrhythmogenic sources in patients suffering from atrial fibrillation and other types of cardiac arrhythmias. To improve the success of this procedure, new approaches for real-time visualization of ablation sites are being developed. One of these promising methods is hyperspectral imaging, an approach that detects lesions based on changes in the endogenous tissue autofluorescence profile. To facilitate the clinical implementation of this approach, we examined the key variables that can influence ablation-induced spectral changes, including the drop in myocardial NADH levels, the release of lipofuscin-like pigments, and the increase in diffuse reflectance of the cardiac muscle beneath the endocardial layer. Insights from these experiments suggested simpler algorithms that can be used to acquire and post-process the spectral information required to reveal the lesion sites. Our study is relevant to a growing number of multilayered clinical targets to which spectral approaches are being applied.

Development of adaptive resistance to electric pulsed field treatment in CHO cell line in vitro

Pulsed electric field treatment has increased over the last few decades with successful translation from in vitro studies into different medical treatments like electrochemotherapy, irreversible electroporation for tumor and cardiac tissue ablation and gene electrotransfer for gene therapy and DNA vaccination. Pulsed electric field treatments are efficient but localized often requiring repeated applications to obtain results due to partial response and recurrence of disease. While these treatment times are several orders of magnitude lower than conventional biochemical treatment, it has been recently suggested that cells may become resistant to electroporation in repetitive treatments. In our study, we evaluate this possibility of developing adaptive resistance in cells exposed to pulsed electric field treatment over successive lifetimes. Mammalian cells were exposed to electroporation pulses for 30 generations. Every 5th generation was analyzed by determining permeabilization and survival curve. No statistical difference between cells in control and cells exposed to pulsed electric field treatment was observed. We offer evidence that electroporation does not affect cells in a way that they would become less susceptible to pulsed electric field treatment. Our findings indicate pulsed electric field treatment can be used in repeated treatments with each treatment having equal efficiency to the initial treatment.

Alcohol Ablation of Cardiac Tissues Quantified and Evaluated Using CIELAB Euclidean Distances.

Ethanol solubilizes cell membranes, making it useful for various ablation applications. We examined the effect of time and alcohol type on the extent of ablation, quantified as Euclidean distances between color coordinates. We obtained biopsy punch samples (diameter, 6 mm) of left atrial appendage, atrial, ventricular, and septal tissue from porcine hearts and placed them in transwell plates filled with ethanol or methanol for 10, 20, 30, 40, 50, or 60 min. Control samples were taken for each time point. At each time point, samples were collected, cut transversely, and photographed. With use of a custom MATLAB program, all images were analyzed in the CIELAB color space, which is more perceptually uniform than the red-green-blue color space. Euclidean distances were calculated from CIELAB coordinates. The mean and standard error of these distances were analyzed. Two-way analysis of variance was used to test for differences among time points, and 2-tailed t tests, for differences between the alcohol datasets at each time point. Generally, Euclidean distances differed significantly between all time points, except for those immediately adjacent, and methanol produced larger Euclidean distances than ethanol did. Some tissue showed a plateauing effect, potentially indicating transmurality. Mean Euclidean distances effectively indexed alcohol ablation in cardiac tissue. Furthermore, we found that methanol ablated tissue more effectively than ethanol did. With ethanol, the extent of ablation for atrial tissue was largest at 60 min. We conclude that to achieve full transmurality in clinical applications, ethanol must remain in contact with atrial tissue for at least one hour.

Development of Adaptive Resistance to Electric Pulsed Field Treatment in CHO Cell Line &lt;i&gt;In Vitro&lt;/i&gt;

Background: Pulsed electric field (PEF) treatment has increased over the last few decades. It has been successfully translated from in vitro studies into different medical treatments like electrochemotherapy, Irreversible Electroporation for tumor and cardiac tissue ablation and gene electrotransfer for gene therapy and DNA vaccination. PEF treatment is efficient but local and sometimes there is a need to repeat the treatment, e.g. due to partial response and recurrence of disease. It has been recently suggested that cells may become resistant to electroporation in repetitive treatments. In our study, we thus evaluated the possibility of developing adaptive resistance in cells exposed to PEF treatment. Methods: CHO cells were exposed to electroporation pulses, 8 x 100 μs at electric field 1000 V/cm, initially causing 80 % permeabilization and 80 % survival of cells, for 30 generations. Every 5 th generation was analyzed by determining permeabilization using propidium iodide assay and survival curve using colorimetric MTS test. Findings: No statistical difference between cells in control and cells exposed to PEF treatment was observed. The results of our study provide evidence that electroporation does not affect cells in a way that they would become less susceptible to pulsed electric field treatment. Interpretation: Our findings indicate pulsed electric field treatment can be used in repeated treatments with equal efficiency as the initial treatment. Funding Statement: Slovenian Research Agency (research core funding No. P2-0249). The research was in part supported by Medtronic. The work was performed within the network of research and infrastructural centers of University of Ljubljana, which is financially supported by Slovenian Research Agency through infrastructural grant IP-0510. Declaration of Interests: The authors have declared that no competing interests exist.

P2866Automated ultrasound ablation parameters predict lesion depth in a perfused thigh model

Abstract Background The accuracy and safety of lesions created during catheter ablation of cardiac tissue rely on the user's ability to predict the size of lesions that form under variable conditions during treatment. A user-directed robotic system was developed that uses Low-Intensity Collimated Ultrasound (LICU) for cardiac imaging and to produce linear lesions without tissue contact. Molecular absorption of mechanical energy induced in the tissue by LICU causes a temperature rise resulting in thermal tissue necrosis. Purpose By varying the speed of the LICU beam as it traces the desired lesion path, while considering the beam intensity, distance from catheter tip to tissue, and relative motion of the target tissue, we demonstrate the capability to deposit lesions of known depth according to a predictive model. Methods The LICU catheter was mounted in a servo-controlled, 3 axis stage suspended above a perfused porcine thigh that simulates the thermodynamic properties of the myocardium such as acoustic attenuation, thermal conduction, and specific heat capacity. Therapy was delivered along a linear path while varying the distance to tissue, speed of the beam, and motion of the catheter relative to the tissue in 3 dimensions. Programmed relative motion was representative of typical and extreme motion in humans. Pathological analysis after necropsy was used to quantify lesion depth which was then compared to lesion depth as predicted by a mathematical model from approx. 4–12 mm. Results Data from 66 samples were categorized according to typical and extreme motion at 4 different distances (3, 8, 9 and 13 mm). Measured vs predicted lesion depth was well correlated (R = 0.898) with 98.5% of the samples within ±2 mm. Assessment of LICU lesion depth Conclusion Lesion depth using LICU is well controlled in an animal model for the range of distances and relative motion typically encountered in a human subject. The range of acoustic beam speeds and acoustic power density with LICU predictably produces lesions up to 12 mm deep. The LICU thermal model may be useful to create lesions of known depth thus ensuring transmurality of lesions while potentially avoiding unintended extra-cardiac injury.

Irreversible electroporation for catheter-based cardiac ablation: a systematic review of the preclinical experience.

Irreversible electroporation (IRE) utilizing high voltage pulses is an emerging strategy for catheter-based cardiac ablation with considerable growth in the preclinical arena. A systematic search for articles was performed from three sources (PubMed, EMBASE, and Google Scholar). The primary outcome was the efficacy of tissue ablation with characteristics of lesion formation evaluated by histologic analysis. The secondary outcome was focused on safety and damage to collateral structures. Sixteen studies met inclusion criteria. IRE was most commonly applied to the ventricular myocardium (n = 7/16, 44%) by a LifePak 9 Defibrillator (n = 9/16, 56%), NanoKnife Generator (n = 2/16, 13%), or other custom generators (n = 5/16, 31%). There was significant heterogeneity regarding electroporation protocols. On histological analysis, IRE was successful in creating ablation lesions with variable transmurality depending on the electric pulse parameters and catheter used. Preclinical studies suggest that cardiac tissue ablation using IRE shows promise in delivering efficacious, safe lesions.

High-frequency irreversible electroporation for cardiac ablation using an asymmetrical waveform

BackgroundIrreversible electroporation (IRE) using direct current (DC) is an effective method for the ablation of cardiac tissue. A major drawback of the use of DC-IRE, however, are two problems: requirement of general anesthesia due to severe muscle contractions and the formation of bubbles containing gaseous products from electrolysis. The use of high-frequency alternating current (HF-IRE) is expected to solve both problems, because HF-IRE produces little to no muscle spasms and does not cause electrolysis.MethodsIn the present study, we introduce a novel asymmetric, high-frequency (aHF) waveform for HF-IRE and present the results of a first, small, animal study to test its efficacy.ResultsThe data of the experiments suggest that the aHF waveform creates significantly deeper lesions than a symmetric HF waveform of the same energy and frequency (p = 0.003).ConclusionWe therefore conclude that the use of the aHF enhances the feasibility of the HF-IRE method.