Cardiac ablation with pulsed electric fields: principles and biophysics

Pulsed Field Ablation for Atrial Fibrillation in Patients with Cardiac Implantable Electronic Devices

BACKGROUND

Multiple studies have demonstrated the safety of pulsed-field ablation (PFA) systems; however, patients with cardiac implantable electronic devices (CIEDs) have been excluded due to concerns about the impact of strong electrical fields on device function and integrity.

OBJECTIVES

This study assesses the effect of PFA on the function and integrity of CIEDs.

METHODS

Patients with AF undergoing ablation were studied at two sites. PFA was performed to achieve pulmonary vein (PV) and posterior wall isolation (PWI). CIEDs were interrogated before and after PFA to assess function (threshold, sensing), integrity (impedance), and arrhythmia episodes. Real-time interrogation of the CIEDs was also performed to examine the effect of PFA electrical noise on the CIEDs.

RESULTS

Over the last 24 months, we performed 329 PFA procedures, using four different PFA systems; 35 of them in patients with CIEDs. The mean age was 70.0 ± 8.8 years, 40.0% female. Post-procedural testing showed no significant changes in lead impedance, pacing threshold, or sensing of intrinsic activities. Real-time interrogation of the CIEDs showed that PFA electrical noise was commonly seen when the PFA catheter is in proximity (e.g right pulmonary veins and posterior wall). Moreover, PFA electrical noise resulted in ventricular pacing inhibition for 2.5 and 3.7 seconds in two patients, and atrial pacing inhibition for 2.1 seconds in one patient.

CONCLUSION

The function and integrity of CIEDs were not compromised by PFA in this study patient cohort; however, transient ventricular pacing inhibition was observed.

Bilirubin Elevation Associated With Pulsed Field Ablation Induced Hemolysis in Patients With Paroxysmal Atrial Fibrillation

BACKGROUND AND AIMS

Hemolysis-related renal failure after pulsed field ablation (PFA) has been described in recently published cases, we reported the incidence of bilirubin elevation after PFA utilizing a novel hexaspline PFA catheter.

METHODS

PFA was performed in patients with paroxysmal atrial fibrillation using novel hexaspline PFA catheter, and serum bilirubin, hemoglobin and renal function were measured at baseline and the next day post ablation.

RESULTS

A total of 94 patients were analyzed, and 30 of 94 (31.9%) patients had obvious total bilirubin elevation the next day post PFA. In the 30 patients, 26 (86.7%) patients had a predominantly indirect hyperbilirubinemia, suggesting a likely presence of PFA-induced hemolysis. The liver enzyme contents post ablation were normal in all patients and no signs of hemolytic anemia and renal function injury were detected. The impact factors associated with indrect hyperbilirubinemia were also analyzed and higher number of applications tented to produce PFA-induced hemolysis. More than 86.5 applications seem to have a better sensivity and specificity to predict hemolysis.

CONCLUSION

Intravascular hemolysis can occur after utilizing novel hexaspline catheter, but the severity of hemolysis was mild and temporary. The number of applications appears to be a determining factor leading to hemolysis.

Successful stimulation of myocardial ganglionic plexi by Tau-20 in the absence of cardiac damage

Atrial fibrillation (AF) is a major healthcare burden worldwide. The standard invasive treatment for AF that is resistant to pharmacological intervention is a pulmonary vein isolation (PVI) procedure. Ganglionated plexus (GP) ablation can be used as an adjunctive therapy to PVIs, which together reduce the likelihood of AF recurrence. High-frequency stimulation (HFS) is a technique used to identify ectopy-triggering GP sites. However, to locate GP sites, sequential HFS must be delivered over the whole atria. Therefore, ensuring the safety of HFS delivery is integral to avoid irreversible damage from excessive pacing. We tested the Tau-20 version 2 neural simulator, a prototype of a custom-built novel electrophysiological pacing and recording system (patent reference: ASW100372P.EPP) that has the potential to guide intracardiac AF treatments. Using an ex vivo porcine Langendorff model that closely resembles the anatomy and physiology of a human heart, we confirmed that HFS can successfully trigger AF, suggesting that HFS-positive locations contain GP sites. Additionally, we found that HFS delivered via Tau-20 version 2 did not cause any damage to the heart. These findings are evidence that once fully optimized, the Tau-20 system could be suitable for use in clinical settings.

Pulsed Field Ablation: A Review of Preclinical and Clinical Studies

Pulsed field ablation (PFA) is an emerging technology that utilizes ultra-short high-voltage electric pulses to create nanopores in cell membranes, leading to cell death through irreversible electroporation (IRE). PFA is touted to be highly tissue-selective, which may mitigate the risk of collateral injury to vital adjacent structures. In the field of cardiac electrophysiology, initial studies have shown promising results for acute pulmonary vein isolation (PVI) and lesion durability, with overall freedom from recurrent atrial arrhythmia comparable to traditional thermal ablation modalities. While further large studies are required for long-term efficacy and safety data, PFA has the potential to become a preferred energy source for cardiac ablation for some indications. This review outlines the basic principles and biophysics of IRE and its application to cardiac electrophysiology through a review of the existing preclinical and clinical data.

Thermal and Non-Thermal Energies for Atrial Fibrillation Ablation

The cornerstone of ablative therapy for atrial fibrillation (AF) is pulmonary vein isolation (PVI). Whether PVI should be added with additional lesions in persistent atrial fibrillation (PerAF) or for any post-ablative recurrent AF is a matter of debate. Whatever the ablative strategy, it must determine the choice of energy source to achieve the most durable lesion sets with the least likelihood of complications. Radiofrequency (RF) is the most studied thermal ablation technique. It can be combined with high-density electroanatomic mapping and can be used for both pulmonary and extrapulmonary atrial ablation. Cryoenergy is at least as effective as radiofrequency for PVI; it is rapid, relatively safe, and has a steep learning curve. Therefore, it has been proposed as a first-line approach for PVI-only procedures. More recently, a non-thermal technique based on the application of pulsed direct current (Pulsed Field Ablation-PFA) has been introduced. PFA causes cell death by opening cell membrane pores (electroporation) without a significant increase in tissue temperature. It is fast and does not alter the extracellular matrix as thermal techniques do, although it ends up causing long-lasting, transmural lesions. Most importantly, it is relatively selective on cardiac myocytes and therefore potentially safer than thermal techniques. Some PFA systems can be combined with electroanatomic mapping systems. However, as of now, it appears that these ablation technologies should be considered complementary rather than alternative for a number of practical and theoretical reasons.

Catheter Ablation of Atrial Fibrillation: Technique and Future Perspectives

Atrial fibrillation is the most common sustained cardiac arrhythmia with a significant impact on quality of life in terms of symptoms and reduction of functional status. Also, it is associated with an increased risk of mortality, stroke, and peripheral embolism. Catheter ablation for atrial fibrillation has become a well-established treatment, improving arrhythmia outcomes without increasing the risk of serious adverse events compared to antiarrhythmic drug therapy. The field has undergone significant advancements in recent years, yet pulmonary vein isolation continues to be the cornerstone of any atrial fibrillation ablation procedure. The purpose of this review is to provide an overview of the current techniques, emerging technologies, and future directions.

Fundamentals of System Design for Cardiac Pulsed Field Ablation: Optimization of Safety, Efficacy, and Usability

The goal of a cardiac pulsed field ablation (PFA) system is to provide safe, effective, and usable therapy for the treatment of cardiac arrhythmias. Achieving this goal is a complex exercise in system design, requiring optimization of catheter, waveform, and dosing. This optimization is often iterative, as myriad design factors are balanced to achieve the goal while making use of computational modeling, bench testing, preclinical animal studies, and human clinical studies to evaluate system performance. It is important for both engineers and clinicians to understand the fundamentals of cardiac PFA system design in order to partner to continuously improve performance of this expanding ablation modality.

Effects of key parameters on pulsed field ablation of atrial fibrillation: potato experiments

Aims

The study aims to investigate the impact of key parameters of pulsed field ablation (PFA) on lesion depth, including voltage (V), pulse width (PW), number of pulses (P), and ablation number (N), using potato models.

Methods

Potatoes are utilized as a display of the irreversible electroporation lesion. The key ablation parameters were varied systematically to explore its influences on lesion depths.

Results and conclusion

The key ablation parameters have varying degrees of influence on lesion depths, following the order of PW>V; V>P; PW>P; N>P. Lesion depths increased with higher values of V and P. However, when the total number of pulses reached 9,600, there was no significant increase in injury depth.

Caudal vena cava isolation using ablation index-guided radiofrequency catheter ablation (CARTO™ 3) to treat sustained atrial tachycardia in horses

BACKGROUND

Myocardial sleeves of the caudal vena cava are the predilection site for atrial tachycardia (AT) in horses. Caudal vena cava isolation guided by the ablation index, a lesion quality marker incorporating power, duration and contact force, might improve outcome.

OBJECTIVES

Describe the feasibility and outcome of caudal vena cava isolation using ablation index-guided radiofrequency catheter ablation (RFCA) to treat AT in horses.

ANIMALS

Ten horses with sustained AT.

METHODS

Records from 10 horses with sustained AT treated by three-dimensional electro-anatomical mapping and ablation index-guided RFCA (CARTO™ 3) were reviewed.

RESULTS

Three-dimensional electro-anatomical mapping of the right atrium identified a macro-reentry circuit in the caudomedial right atrium (n = 10). Point-by-point RFCA was performed to isolate the myocardial sleeves of the caudal vena cava in power-controlled mode with a mean of 17 ± 7 applications. The ablation index target was 400-450. A median ablation index of 436 (range, 311-763) was reached using a median maximum power of 35 (range, 24-45) W for a median duration of 20 (range, 8-45) seconds, with a median contact force of 10 (range, 3-48) g. Sinus rhythm was restored in all 10 horses. To date, 9-37 months post-ablation, none of the horses have had recurrence.

CONCLUSIONS AND CLINICAL IMPORTANCE

Caudal vena cava isolation using ablation index-guided RFCA was feasible and effective to permanently treat sustained AT in horses. Ablation index guidance ensured efficient lesion creation, and isolation of the caudal vena cava eliminated the arrhythmogenic substrate, thereby minimizing the risk of recurrence.

Cardiac selectivity in pulsed field ablation

PURPOSE OF REVIEW

This review examines the selective cardiac injury induced by pulsed electric fields during atrial fibrillation ablation. It consolidates findings from both preclinical and clinical studies on cardiac selectivity and explores the potential mechanisms behind this selectivity.

RECENT FINDINGS

Preclinical studies indicate that pulsed electric fields cause significantly more myocardial injury compared with other tissues. Clinical studies have similarly shown that complication rates for pulsed field ablation are notably lower than those for radiofrequency and cryoballoon ablation.

SUMMARY

Pulsed field ablation demonstrates a notable selectivity for myocardial injury, likely because of the unique functional and metabolic characteristics of cardiomyocytes. This review delves into the underlying principles of cardiac selectivity and proposes future directions for improving this selectivity. It is important to note that while pulsed field ablation shows promise, its cardiac selectivity is not absolute, as some complications still occur, necessitating further research.

Pulsed Field Ablation Using Focal Contact Force-Sensing Catheters for Treatment of Atrial Fibrillation: 1-Year Outcomes of the ECLIPSE AF Study

BACKGROUND

Pulsed field ablation (PFA) is a promising treatment for atrial fibrillation. We report 1-year freedom from atrial arrhythmia outcomes using monopolar PFA delivered through 3 commercial, contact force-sensing focal catheters.

METHODS

ECLIPSE AF (Safety & Clinical Performance Study of Catheter Ablation With the Centauri System for Patients With Atrial Fibrillation; NCT04523545) was a prospective, single-arm, multicenter study evaluating acute and chronic safety and performance using the CENTAURI system to deliver focal PFA with TactiCath SE, StablePoint, and ThermoCool ST. Patients with paroxysmal or persistent atrial fibrillation underwent pulmonary vein (PV) isolation under deep sedation or general anesthesia and returned for remapping at 90 days to evaluate chronic durability. Freedom from atrial arrhythmia was evaluated continuously through 12 months using standard rhythm monitoring for symptomatic episodes and 24-hour Holter at 6 and 12 months.

RESULTS

Eighty-two patients (74% male, 51.2% paroxysmal, and 58.5% deep sedation) were treated. PV isolation was achieved in 100% of targeted veins (322/322) with first-pass isolation in 92.2% (297/322). There were 4 primary safety events in 4 patients (4.9%, 4/82); 1 nonembolic stroke due to exacerbated cardiac tamponade secondary to catheter perforation and 3 hemorrhagic vascular access complications. There were no incidences of adverse event fistula, diaphragmatic paralysis, myocardial infarction, pericarditis, thromboembolism, PV stenosis, transient ischemic attack, or death. Eighty patients (98%) underwent remapping. Optimized PFA cohorts 3, 4, and 5 showed per-patient isolation rates of 60%, 73%, and 81% and per-PV isolation rates of 84%, 90%, and 92%, respectively. One-year freedom from atrial arrhythmia was 80.2% (95% CI, 69.7%-87.4%) for the entire patient sample, including 41 patients who underwent repeat focal PFA with the CENTAURI system at remapping.

CONCLUSIONS

This study demonstrated that optimization of focal PFA with 3 contact force-sensing, solid-tip ablation catheters resulted in the progressive improvement of PV isolation durability at 3-month remapping and high freedom from atrial arrhythmia survival rates, providing a promising focal PFA treatment option integrated with current ablation workflows.

Pulsed Field Ablation of Paroxysmal Supraventricular Tachycardia: A Prospective Multicenter Single-Arm Study in China

BACKGROUND

Pulsed field ablation (PFA) has gained attention in cardiac electrophysiology, but data on its application to paroxysmal supraventricular tachycardia are limited. This study aimed to assess the feasibility and safety of PFA and its combination with radiofrequency ablation for treating paroxysmal supraventricular tachycardia.

METHODS

A prospective, multicenter, single-arm study was conducted across 8 centers in China. Patients with atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia, or Wolff-Parkinson-White syndrome underwent ablation using a focal point dual-mode PFA/radiofrequency ablation catheter. PFA was used to achieve acute ablation success, with consolidation using PFA for atrioventricular nodal reentrant tachycardia or near-His accessory pathways and radiofrequency ablation for far-His accessory pathways. Primary and secondary end points were acute ablation success and 180-day follow-up success, respectively.

RESULTS

A total of 158 patients (77 with atrioventricular nodal reentrant tachycardia, 63 with atrioventricular reentrant tachycardia, 16 with Wolff-Parkinson-White, and 2 with both atrioventricular nodal reentrant tachycardia and atrioventricular reentrant tachycardia) completed the trial. Acute ablation was successful in 157 patients (99.37%). The skin-to-skin procedure time was 89.9±35.5 min. The median number of PFA discharges was 12 (8-19) with a median effective PFA discharge time of 4.6 (3.2-6.4) ms. Five patients (4 with atrioventricular reentrant tachycardia and 1 with Wolff-Parkinson-White syndrome) experienced paroxysmal supraventricular tachycardia recurrence during the 180-day follow-up period. One patient had a transient first-degree atrioventricular block resolving in 12 hours, and one patient had a transient third-degree atrioventricular block resolving in 24 hours. No permanent atrioventricular block or other adverse events occurred during the ablation procedure or 180-day follow-up period.

CONCLUSIONS

PFA demonstrated the feasibility of the treatment of SVT. Reversible first- and third-degree atrioventricular blocks were observed following ablation in one patient each. The preliminary results indicated the safety and feasibility of a combination of PFA and radiofrequency ablation treatment for atrioventricular accessory pathways although it is impossible to determine the relative contribution of PFA.

Pulsed-field ablation: an alternative ablative method for gastric electrophysiological intervention

Pulsed-field ablation (PFA) is an emerging ablative technology that has been used successfully to eliminate cardiac arrhythmias. As a nonthermal technique, it has significant benefits over traditional radiofrequency ablation with improved target tissue specificity and reduced risk of adverse events during cardiac applications. We investigated whether PFA is safe for use in the stomach and whether it could modulate gastric slow waves. Female weaner pigs were fasted overnight before anesthesia was induced using tiletamine hydrochloride (50 mg·mL-1) and zolazepam hydrochloride (50 mg·mL-1) and maintained with propofol (Diprivan 2%, 0.2-0.4 mg·kg-1·min-1). Pulsed-field ablation was performed on their gastric serosa in vivo. Adjacent point lesions (n = 2-4) were used to create a linear injury using bipolar pulsed-field ablation consisting of 40 pulses (10 Hz frequency, 0.1 ms pulse width, 1,000 V amplitude). High-resolution electrical mapping defined baseline and postablation gastric slow-wave patterns. A validated five-point scale was used to evaluate tissue damage in hematoxylin and eosin-stained images. Results indicated that PFA successfully induced complete conduction blocks in all cases, with lesions through the entire thickness of the gastric muscle layers. Consistent postablation slow-wave patterns emerged immediately following ablation and persisted over the study period. Pulsed-field ablation induces rapid conduction blocks as a tool to modulate slow-wave patterns, indicating it may be suitable as an alternative to radiofrequency ablation.NEW & NOTEWORTHY Results show that pulsed-field ablation can serve as a gastric slow-wave intervention by preventing slow-wave propagation across the lesion site. Stable conduction blocks were established immediately following energy delivery, faster than previous examples of radiofrequency gastric ablation. Pulsed-field ablation may be an alternative for gastric slow-wave intervention, and further functional and posthealing studies are now warranted.

Considerations regarding safety with pulsed field ablation for atrial fibrillation

The introduction of pulsed field ablation (PFA) in electrophysiology marks a significant advancement, promising efficacy comparable to thermal ablation methods while potentially providing safety advantages. Despite a generally favorable safety profile in human trials and postmarket registries, cautious evaluation of PFA's safety is essential. This review provides a comprehensive overview of key safety considerations as we discuss a myriad of considerations ranging from thermal effects, gaseous microbubble formation, muscle contractions, and proarrhythmia to procedural techniques. We explore specific safety concerns with phrenic nerve injury, cerebral lesions, coronary artery spasm, hemolysis and pulmonary bleeding. Vigilance in safety monitoring, coupled with advancements in procedural techniques and understanding of PFA's unique effects, is crucial for optimizing the safe and effective use of PFA.

Investigate the relationship between pulsed field ablation parameters and ablation outcomes

BACKGROUND

Pulsed field ablation (PFA) is an emerging non-thermal ablation method. The primary challenge is the control of multiple parameters in PFA, as the interplay of these parameters remains unclear in terms of ensuring effective and safe tissue ablation.

PURPOSE

This study employs the response surface method (RSM) to explore the interactions between various PFA parameters and ablation outcomes, and seeks to enhance the efficacy and safety of PFA.

METHODS

In vivo experiments were conducted using rabbit liver for varying PFA parameters: pulse amplitude (PA), pulse interval (PI), number of pulse trains (NT), and number of pulses in a pulse train (NP). Ablation outcomes assessed included three ablation sizes, surface temperature, and muscle contraction strength. Additionally, histological analysis was performed on the ablated tissue. We analyzed the relationship between PFA parameters and ablation outcomes, and results were then compared with those from a simulation using an electric-thermal coupling PFA finite element model.

RESULTS

A linear relationship between ablation outcomes and PFA parameters was established. PA and NT exhibited extremely significant (P < 0.0001) and significant effects (P < 0.05) on all ablation outcomes, respectively. NP showed an extremely significant impact (P < 0.0001) on surface temperature and muscle contraction strength, while PI significantly influenced (P < 0.05) muscle contraction strength alone. Histological analysis revealed that PFA produces controlled, well-defined areas of liver tissue necrosis. Surface temperature results from simulations and experiments were highly consistent (R2 > 0.97).

CONCLUSIONS

This study clarifies the relationship between various PFA parameters and ablation outcomes, and aims to improve the efficacy and safety of PFA.

Voltage Independent Depth Control and Acute Lesion Formation Findings in Epicardial Pulsed Field Ablation System for Surgical Ablations

Pulsed Field Ablation (PFA) is a novel ablation technology that utilizes electric field strength to ablate tissue. PFA is unique in its cell selectivity, which is found in the biophysics of the bilipid membrane's sensitivity to electric fields. PFA permits an unseen level of flexibility in its delivery due to its non-abrasive ablation methods and ability to selectively ablate regardless of direct contact. With the ability to electrically isolate each electrode, it is possible to dynamically map and ablate according to patient-specific "mechanistic" targets. Testing was done to determine the efficacy of the PFA system, the influence that electrode configuration has on PFA lesion size, and the acute lesion formation timeline. PFA lesion depth can be doubled (1mm to 2mm) through modulating electrode configuration and polarity. Significant electrophysiological changes were only recorded immediately post ablation. Electrode configurations appeared to generate the same level of tissue damage at PFA sites while significantly increasing depth without increasing voltage, which could introduce more risks and complications.

Pulsed field ablation in patients with cardiac implantable electronic devices: an ex vivo assessment of safety

BACKGROUND

Pulse field ablation (PFA) is a novel catheter ablation technology with potential safety benefits due to its tissue selectivity. It has the potential to directly damage or interact with the functionality of cardiac implantable electronic devices (CIEDs) in the form of electromagnetic interference (EMI). The aim of our study was to assess the impact of PFA on CIEDs.

METHODS

PFA lesions (45 per CIED) were applied from the Farapulse system to CIEDs (< 5 cm from the lead tip and < 15 cm from the generator). All devices were checked before and after PFA application for proper sensing and pacing functionality as well as for integrity of shock circuits in ICDs using a heart simulator. Moreover, devices were then interrogated for any spontaneous reprogramming, mode switching or other EMI effects.

RESULTS

In total, 44 CIEDs were tested (16 pacemaker, 21 ICDs, 7 CRT-P/D) with 1980 PFA applications. There was no change in device settings, functionality and electrical parameters, and there was no macroscopic damage to the devices. The risk of damage to the electric components or leads on a patient-based analysis is 0/44 (95% CI 0-8%) and on a PFA pulse-based analysis is 0/1980 (95% CI 0-0.2%). Clinically relevant EMI appeared with oversensing and pacing inhibition but not tachycardia detection.

CONCLUSIONS

Bipolar PFA appears safe and does not result in damage to CIEDs or leads. Clinically relevant EMI does occur, but appropriate peri-procedural programming may mitigate this. In vivo studies are needed to confirm our findings.

Pulsed Field Energy in Atrial Fibrillation Ablation: From Physical Principles to Clinical Applications

Atrial fibrillation, representing the most prevalent sustained cardiac arrhythmia, significantly impacts stroke risk and cardiovascular mortality. Historically managed with antiarrhythmic drugs with limited efficacy, and more recently, catheter ablation, the interventional approach field is still evolving with technological advances. This review highlights pulsed field ablation (PFA), a revolutionary technique gaining prominence in interventional electrophysiology because of its efficacy and safety. PFA employs non-thermal electric fields to create irreversible electroporation, disrupting cell membranes selectively within myocardial tissue, thus preventing the non-selective damage associated with traditional thermal ablation methods like radiofrequency or cryoablation. Clinical studies have consistently shown PFA's ability to achieve pulmonary vein isolation-a cornerstone of AF treatment-rapidly and with minimal complications. Notably, PFA reduces procedure times and has shown a lower incidence of esophageal and phrenic nerve damage, two common concerns with thermal techniques. Emerging from oncological applications, the principles of electroporation provide a unique tissue-selective ablation method that minimizes collateral damage. This review synthesizes findings from foundational animal studies through to recent clinical trials, such as the MANIFEST-PF and ADVENT trials, demonstrating PFA's effectiveness and safety. Future perspectives point towards expanding indications and refinement of techniques that promise to improve AF management outcomes further. PFA represents a paradigm shift in AF ablation, offering a safer, faster, and equally effective alternative to conventional methods. This synthesis of its development and clinical application outlines its potential to become the new standard in AF treatment protocols.

Difference between endocardial and epicardial application of pulsed fields for targeting Epicardial Ganglia: An in-silico modelling study

BACKGROUND

Pulsed Field Ablation (PFA) has recently been proposed as a non-thermal energy to treat atrial fibrillation by selective ablation of ganglionated plexi (GP) embedded in epicardial fat. While some of PFA-technologies use an endocardial approach, others use epicardial access with promising pre-clinical results. However, as each technology uses a different and sometimes proprietary pulse application protocol, the comparation between endocardial vs. epicardial approach is almost impossible in experimental terms. For this reason, our study, based on a computational model, allows a direct comparison of electric field distribution and thermal-side effects of both approaches under equal conditions in terms of electrode design, pulse protocol and anatomical characteristics of the tissues involved.

METHODS

2D computational models with axial symmetry were built for endocardial and epicardial approaches. Atrial (1.5-2.5 mm) and fat (1-5 mm) thicknesses were varied to simulate a representative sample of what happens during PFA ablation for different applied voltage values (1000, 1500 and 2000 V) and number of pulses (30 and 50).

RESULTS

The epicardial approach was superior for capturing greater volumes of fat when the applied voltage was increased: 231 mm3/kV with the epicardial approach vs. 182 mm3/kV with the endocardial approach. In relation to collateral damage to the myocardium, the epicardial approach considerably spares the myocardium, unlike what happens with the endocardial approach. Although the epicardial approach caused much more thermal damage in the fat, there is not a significant difference between the approaches in terms of size of thermal damage in the myocardium.

CONCLUSIONS

Our results suggest that epicardial PFA ablation of GPs is more effective than an endocardial approach. The proximity and directionality of the electric field deposited using an epicardial approach are key to ensuring that higher electric field strengths and increased temperatures are obtained within the epicardial fat, thus contributing to selective ablation of the GPs with minimal myocardial damage.

Procedural performance and outcome after pulsed field ablation for pulmonary vein isolation: comparison with a reference radiofrequency database

Aims

Pulsed field ablation (PFA) is a promising ablation technique for pulmonary vein isolation (PVI) with appealing advantages over radiofrequency (RF) including speed, tissue selectivity, and the promise of enhanced durability. In this study, we determine the procedural performance, efficacy, safety, and durability of PFA and compare its performance with a dataset of optimized RF ablation.

Methods and results

After propensity score matching, we compared 161 patients who received optimized RF-guided PVI in the PowerPlus study (CLOSE protocol) with 161 patients undergoing PFA-guided PVI for paroxysmal or persistent atrial fibrillation (AF; pentaspline basket catheter). The median age was 65 years with 78% paroxysmal AF in the PFA group (comparable characteristics in the RF group). Pulsed field ablation-guided PVI was obtained in all patients with a procedure time of 47 min (vs. 71 min in RF, P < 0.0001) and a fluoroscopy time of 15 min (vs. 11 min in RF, P < 0.0001). One serious adverse event [transient ischaemic attack] occurred in a patient with thrombocytosis (0.6 vs. 0% in RF). During the 6-month follow-up, 24 and 27 patients experienced a recurrence with 20 and 11 repeat procedures in the PFA and the RF groups, respectively (P = 0.6 and 0.09). High-density mapping revealed a status of 4 isolated veins in 7/20 patients in the PFA group and in 2/11 patients in the RF group (35 vs. 18%, P = 0.3).

Conclusion

Pulsed field ablation fulfils the promise of offering a short and safe PVI procedure, even when compared with optimized RF in experienced hands. Pulmonary vein reconnection is the dominant cause of recurrence and tempers the expectation of a high durability rate with PFA.

Impact of pulsed field ablation on intraluminal esophageal temperature

INTRODUCTION

Atrio-esophageal fistula after esophageal thermal injury (ETI) is one of the most devastating complications of available energy sources for atrial fibrillation (AF) ablation. Pulsed field ablation (PFA) uses electroporation as a new energy source for catheter ablation with promising periprocedural safety advantages over existing methods due to its unique myocardial tissue sensitivity. In preclinical animal studies, a dose-dependent esophageal temperature rise has been reported. In the TESO-PFA registry intraluminal esophageal temperature (TESO) changes in a clinical setting are evaluated.

METHODS

Consecutive symptomatic AF patients (62 years, 67% male, 61% paroxysmal AF, CHA2 DS2 Vasc Score 2) underwent first-time PFA and were prospectively enrolled into our registry. Eight pulse trains (2 kV/2.5 s, bipolar, biphasic, x4 basket/flower configuration each) were delivered to each pulmonary vein (PV). Two extra pulse trains per PV in flower configuration were added for wide antral circumferential ablation. Continuous intraluminal esophageal temperature (TESO) was monitored with a 12-pole temperature probe.

RESULTS

Median TESO change was statistically significant and increased by 0.8 ± 0.6°C, p < .001. A TESO increase ≥ 1°C was observed in 10/43 (23%) patients. The highest TESO measured was 40.3°C. The largest TESO difference (∆TESO) was 3.7°C. All patients remained asymptomatic considering possible ETI. No atrio-esophageal fistula was reported on follow-up.

CONCLUSION

A small but significant intraluminal esophageal temperature rise can be observed in most patients during PFA. TESO rise over 40°C is rare. The clinical implications of the observed findings need to be further evaluated.

The Safety and Feasibility of Pulsed-Field Ablation in Atrioventricular Nodal Re-Entrant Tachycardia: First-in-Human Pilot Trial

BACKGROUND

The incidence of atrioventricular conduction system damage during the catheter ablation procedure has long been a safety concern in patients with atrioventricular nodal re-entrant tachycardia (AVNRT). Pulsed-field ablation (PFA) with high tissue selectivity is a promising technique to address this problem in patients with AVNRT.

OBJECTIVES

This study aimed to evaluate the safety and feasibility of PFA in patients with AVNRT.

METHODS

This was an investigator-initiated, single-center, single-arm, prospective study performed in West China Hospital, Sichuan University. Patients diagnosed with AVNRT by electrophysiological examination were included and treated using PFA. The primary outcome was the ability to achieve acute ablation success. The secondary outcomes were ablation success after 6 months and safety incidents reported.

RESULTS

A total of 30 patients with AVNRT with a mean age of 47.9 ± 13.9 years were included and underwent PFA. Acute ablation success was achieved in all patients. The skin-to-skin procedure time was 109.1 ± 32.1 minutes, and fluoroscopy time was 4.1 ± 0.9 minutes. A median of 8 (range: 6.5 to 11.0) PFA applications were delivered. The average distance of the closest ablation site to the His bundle was 6.5 ± 2.5 mm, with a minimum distance of 2.0 mm. All patients maintained sinus rhythm after 6 months. No adverse events occurred in any patient during the ablation or the 6-month follow-up.

CONCLUSIONS

PFA showed favorable feasibility and safety in patients with AVNRT in this pilot study. Further study with larger population and longer follow-up time is warranted to verify the results.

Catheter-Based Electroporation: A Novel Technique for Catheter Ablation of Cardiac Arrhythmias

Catheter ablation of arrhythmias is now standard of care in invasive electrophysiology. Current ablation strategies are based on the use of thermal energy. With continuous efforts to optimize thermal energy delivery, effectiveness has greatly improved; however, safety concerns persist. This review focuses on a novel ablation technology, irreversible electroporation (IRE), also known as pulsed-field ablation which may be a safer alternative for arrhythmia management. Pulsed-field ablation is thought to be a nonthermal ablation that applies short-duration high-voltage electrical fields to ablate myocardial tissue with high selectivity and durability while sparing important neighboring structures such as the esophagus and phrenic nerves. There are multiple ongoing studies investigating the potential superior outcomes of IRE compared to radiofrequency ablation in treating patients with atrial and ventricular arrhythmias. In this review, we describe the current evidence of preclinical and clinical trials that have shown promising results of catheter-based IRE.

Deep sedation protocol during atrial fibrillation ablation using a novel variable-loop biphasic pulsed field ablation catheter

BACKGROUND

Pulsed field ablation (PFA) is a novel, largely nonthermal ablative modality that, by virtue of its putative preferential action on myocardial tissue through the process of irreversible electroporation (IRE), may replace conventional thermal ablation for atrial fibrillation (AF). The recent inspIRE study confirmed safety and effectiveness of a fully integrated biphasic PFA system with a variable loop circular catheter for the treatment of paroxysmal AF. The majority of PFA procedures were performed using general anesthesia. However, due to the risks of general anesthesia we report the data regarding our sedation protocol used during inspIRE study.

METHODS

A total of 29 patients (mean age 55±9 years; 72% male) were enrolled as part of this analysis within the inspIRE trial. The sedation protocol is reported in the manuscript. The Richmond Agitation-Sedation Scale (RASS), the Visual Analogue Scale (VAS) and the Patient State Index were collected during sedation. Each patient was monitored using the Masimo Sedline. At the end of ablation, the Likert Scale Questionnaire (LSQ) was used to assess the patients' satisfaction with intraoperative analgesia-sedation.

RESULTS

No procedural complications were documented. Sufficient oxygen saturation was maintained in all patients during procedure. Non-invasive ventilation or tracheal intubation were not required for any patient. The RAAS score between -1 to -5 was obtained in 27 patients (93%) while the value 0 was obtained in 2 patients (7%). The VAS score between 0 to 2 was obtained in 24 patients (83%); the VAS score 3 in 3 patients (10%) and the VAS score 4 in 2 patients (7%). The PSI score <50 was achieved in 16 patients (55%) while the PSI between 50 and 70 was achieved in 9 patients (31%). Positive answers to LSQ were obtained in most patients.

CONCLUSION

During PFA ablation procedures with the variable-loop circular catheter and its accompanying biphasic pulse, our deep sedation protocol is a valid alternative to general anesthesia.

Determinants of acute irreversible electroporation lesion characteristics after pulsed field ablation: the role of voltage, contact, and adipose interference

AIMS

Pulsed field ablation (PFA) is a non-thermal ablative approach in which cardiomyocyte death is obtained through irreversible electroporation (IRE). Data correlating the biophysical characteristics of IRE and lesion characteristics are limited. The aim of this study was to assess the effect of different procedural parameters [voltage, number of cycles (NoCs), and contact] on lesion characteristics in a vegetal and animal model for IRE.

METHODS AND RESULTS

Two hundred and four Russet potatoes were used. Pulsed field ablation lesions were delivered on 3 cm cored potato specimens using a multi-electrode circular catheter with its dedicated IRE generator. Different voltage (from 300 to 1200 V) and NoC (from 1 to 5×) protocols were used. The impact of 0.5 and 1 mm catheter-to-specimen distances was tested. A swine animal model was then used to validate the results observed in the vegetable model. The association between voltage, the NoCs, distance, and lesion depth was assessed through linear regression. An almost perfect linear association between lesion depth and voltage was observed (R2 = 0.95; P < 0.001). A similarly linear relationship was observed between the NoCs and the lesion depth (R2 = 0.73; P < 0.001). Compared with controls at full contact, a significant dampening on lesion depth was observed at 0.5 mm distance (1000 V 2×: 2.11 ± 0.12 vs. 0.36 ± 0.04, P < 0.001; 2.63 ± 0.10 vs. 0.43 ± 0.08, P < 0.001). No lesions were observed at 1.0 mm distance.

CONCLUSION

In a vegetal and animal model for IRE assessment, PFA lesion characteristics were found to be strongly dependent on voltage settings and the NoCs, with a quasi-linear relationship. The lack of catheter contact was associated with a dampening in lesion depth.

EUropean real-world outcomes with Pulsed field ablatiOn in patients with symptomatic atRIAl fibrillation: lessons from the multi-centre EU-PORIA registry

AIMS

Pulsed field ablation (PFA) is a new, non-thermal ablation modality for pulmonary vein (PV) isolation in patients with atrial fibrillation (AF). The multi-centre EUropean Real World Outcomes with Pulsed Field AblatiOn in Patients with Symptomatic AtRIAl Fibrillation (EU-PORIA) registry sought to determine the safety, efficacy, and learning curve characteristics for the pentaspline, multi-electrode PFA catheter.

METHODS AND RESULTS

All-comer AF patients from seven high-volume centres were consecutively enrolled. Procedural and follow-up data were collected. Learning curve effects were analysed by operator ablation experience and primary ablation modality. In total, 1233 patients (61% male, mean age 66 ± 11years, 60% paroxysmal AF) were treated by 42 operators. In 169 patients (14%), additional lesions outside the PVs were performed, most commonly at the posterior wall (n = 127). Median procedure and fluoroscopy times were 58 (interquartile range: 40-87) and 14 (9-21) min, respectively, with no differences due to operator experience. Major complications occurred in 21/1233 procedures (1.7%) including pericardial tamponade (14; 1.1%) and transient ischaemic attack or stroke (n = 7; 0.6%), of which one was fatal. Prior cryoballoon users had less complication. At a median follow-up of 365 (323-386) days, the Kaplan-Meier estimate of arrhythmia-free survival was 74% (80% for paroxysmal and 66% for persistent AF). Freedom from arrhythmia was not influenced by operator experience. In 149 (12%) patients, a repeat procedure was performed due to AF recurrence and 418/584 (72%) PVs were durably isolated.

CONCLUSION

The EU-PORIA registry demonstrates a high single-procedure success rate with an excellent safety profile and short procedure times in a real-world, all-comer AF patient population.

Pulsed field ablation using focal contact force-sensing catheters for treatment of atrial fibrillation: acute and 90-day invasive remapping results

AIMS

Pulsed field ablation (PFA) has emerged as a promising alternative to thermal ablation for treatment of atrial fibrillation (AF). We report performance and safety using the CENTAURI™ System (Galvanize Therapeutics) with three commercial, focal ablation catheters.

METHODS AND RESULTS

ECLIPSE AF (NCT04523545) was a prospective, single-arm, multi-centre study evaluating safety and acute and chronic pulmonary vein isolation (PVI) durability using the CENTAURI System in conjunction with the TactiCath SE, StablePoint, and ThermoCool ST ablation catheters. Patients with paroxysmal or persistent AF were treated at two centres. Patients were analysed in five cohorts based upon ablation settings, catheter, and mapping system. Pulsed field ablation was performed in 82 patients (74% male, 42 paroxysmal AF). Pulmonary vein isolation was achieved in 100% of pulmonary veins (322/322) with first-pass isolation in 92.2% (297/322). There were four serious adverse events of interest (three vascular access complications and one lacunar stroke). Eighty patients (98%) underwent invasive remapping. Pulsed field ablation development Cohorts 1 and 2 showed a per-patient isolation rate of 38% and 26% and a per-PV isolation rate of 47% and 53%, respectively. Optimized PFA Cohorts 3-5 showed a per-patient isolation rate of 60%, 73%, and 81% and a per-PV isolation rate of 84%, 90%, and 92%, respectively.

CONCLUSION

ECLIPSE AF demonstrated that optimized PFA using the CENTAURI System with three commercial, contact force-sensing, solid-tip focal ablation catheters resulted in transmural lesion formation and high proportion of durable PVI with a favourable safety profile, thus providing a viable treatment option for AF that integrates with contemporary focal ablation workflows.

Cardiac tamponade complicating ventricular arrhythmia ablation: Real life data on incidence, management, and outcome

BACKGROUND AND OBJECTIVE

Cardiac tamponade during ablation procedures is a life-threatening complication. While the incidence and management of tamponade in atrial fibrillation ablation have been extensively described, the data on tamponade during ventricular ablations are very limited. The purpose of this study is to shed light on the incidence, typical perforation sites, and optimal management as observed through real-life data in a tertiary referral center for ventricular ablation.

METHODS AND RESULTS

Consecutive patients with structural heart disease undergoing ventricular tachycardia ablation from 2008-2020 were analyzed. Of the 1078 patients undergoing 1287 ventricular ablation procedures, 20 procedures (1.5%) were complicated by cardiac tamponade. In all but one patient, the tamponade was treated with emergent pericardial drainage, while nine patients eventually underwent surgical repair. The perforation occurred during transseptal or subxiphoid puncture in six patients, during ventricle mapping in two patients, and during ablation in five patients (predominantly basal left ventricle). Steam pop as definite perforation cause could only be established in two patients. Regardless of the management of the complication, all patients survived to discharge.

CONCLUSION

Cardiac tamponade during ventricular ablation occurred in 1.5% of the procedures. In nine patients cardiac repair was necessary. Perforation was mostly associated with subxiphoid puncture or ablation of the basal left ventricle.

Human cardiomyocytes are more susceptible to irreversible electroporation by pulsed electric field than human esophageal cells

Pulse electric field-based (PEF) ablation is a technique whereby short high-intensity electric fields inducing irreversible electroporation (IRE) are applied to various tissues. Here, we implemented a standardized in vitro model to compare the effects of biphasic symmetrical pulses (100 pulses, 1-10 μs phase duration (d), 10-1000 Hz pulse repetition rate (f)) using two different human cellular models: human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and human esophageal smooth muscle cells (hESMCs) cultured in monolayer format. We report the PEF-induced irreversibly electroporated cell monolayer areas and the corresponding electric field thresholds (EFTs) for both cardiac and esophageal cultures. Our results suggest marked cell type specificity with EFT estimated to be 2-2.5 times lower in hiPSC-CMs than in hESMCs when subjected to identical PEF treatments (e.g., 0.90 vs 1.85 kV/cm for the treatment of 100 pulses with d = 5 μs, f = 10 Hz, and 0.65 vs 1.67 kV/cm for the treatment of 100 pulses with d = 10 μs, f = 10 Hz). PEF treatment can result in increased temperature around the stimulating electrodes and lead to unanticipated thermal tissue damage that is proportional to the peak temperature rise and to the duration of the PEF-induced elevated temperatures. In our study, temperature increases ranged from less than 1°C to as high as 30°C, however, all temperature changes were transient and quickly returned to baseline and the highest observed ∆T returned to 50% of its maximum recorded temperature in tens of seconds.

Effect of Anisotropic Electrical Conductivity Induced by Fiber Orientation on Ablation Characteristics of Pulsed Field Ablation in Atrial Fibrillation Treatment: A Computational Study

Pulsed field ablation (PFA) is a promising new ablation modality for the treatment of atrial fibrillation (AF); however, the effect of fiber orientation on the ablation characteristics of PFA in AF treatment is still unclear, which is likely an essential factor in influencing the ablation characteristics. This study constructed an anatomy-based left atrium (LA) model incorporating fiber orientation and selected various electrical conductivity and ablation targets to investigate the effect of anisotropic electrical conductivity (AC), compared with isotropic electrical conductivity (IC), on the ablation characteristics of PFA in AF treatment. The results show that the percentage differences in the size of the surface ablation area between AC and IC are greater than 73.71%; the maximum difference in the size of the ablation isosurface between AC and IC at different locations in the atrial wall is 3.65 mm (X-axis), 3.65 mm (Z-axis), and 4.03 mm (X-axis), respectively; and the percentage differences in the size of the ablation volume are greater than 6.9%. Under the condition of the pulse, the amplitude is 1000 V, the total PFA duration is 1 s, and the pulse train interval is 198.4 ms; the differences in the temperature increase between AC and IC in LA are less than 2.46 °C. Hence, this study suggests that in further exploration of the computational study of PFA in AF treatment using the same or similar conditions as those used here (myocardial electrical conductivity, pulse parameters, and electric field intensity damage threshold), to obtain more accurate computational results, it is necessary to adopt AC rather than IC to investigate the size of the surface ablation area, the size of the ablation isosurface, or the size of the ablation volume generated by PFA in LA. Moreover, if only investigating the temperature increase generated by PFA in LA, adopting IC instead of AC for simplifying the model construction process is reasonable.