Effects of Contact Force on Lesion Size During Pulsed Field Catheter Ablation: Histochemical Characterization of Ventricular Lesion Boundaries

Role of Catheter-Tissue Contact in Pulsed Field Ablation

Pulsed electrical field energy is a highly customizable, minimally thermal energy source associated with a myriad of potential ablation recipes that would hypothetically limit the importance of catheter-tissue contact on lesion formation. However, recent preclinical studies conducted on ventricular swine models suggest that contact force is pivotal in achieving adequate lesion formation even during pulsed field ablation. Despite the accruing preclinical evidence, clinical data on ablation targets beyond pulmonary veins are lacking and vast, and prospective human studies are required to better explore the clinical outcome of patients undergoing contact-force-guided pulsed field ablation for cardiac arrhythmias.

Catheters and Tools with Pulsed Field Ablation: Pentaspline Farawave

Pulsed field ablation (PFA) is an emerging technology in cardiac electrophysiology that uses pulsed electrical fields to precisely target myocardial tissue. Both preclinical and randomized clinical trials have confirmed the safety and efficacy of using the Farawave pentaspline PFA catheter to treat paroxysmal atrial fibrillation (AF). Ongoing clinical trials are exploring its potential for treating patients with persistent AF and other arrhythmias beyond the left atrium. This review summarizes the development of the Farawave pentaspline PFA catheter, evidence for the safety and efficacy in treating AF, and future directions for its use in cardiac electrophysiology.

Catheters and Tools with Pulsed Field Ablation-Pulmonary Vein Isolation with Focal Lattice-Tip Affera Sphere 9

The Affera system features a versatile and large footprint catheter with a lattice-tip design that is capable of delivering both pulsed field and radiofrequency energy. It provides precise mapping and ablation capabilities, demonstrating high acute success rates and durable lesion formation, with excellent safety profile in both radiofrequency and pulsed field ablation modes. Preclinical and clinical studies have shown high lesion durability, reduced procedural time, and promising outcomes in pulmonary vein isolation with minimal complications.

Transient conduction block of the superior vena cava following pulsed field ablation of the right superior pulmonary vein

This case demonstrates that an immediate superior vena cava (SVC) conduction block may occur during pulsed field ablation (PFA) due to anatomical proximity, a positive tissue proximity index, and a narrow SVC diameter. However, lesions not directly influenced by PFA tend to regress and may be reversible, leading to SVC potential reconduction. CS, coronary sinus; d, distal; LAO, left oblique view; LL, left lateral; p, proximal; PA, posteroanterior view; RA, right atrial; RAO, right oblique view; RSPV, right superior pulmonary vein; RV, right ventricular; SUP, superior view.

Pulsed field ablation: The basics relating to effectiveness, durability, and safety

Pulsed field ablation (PFA) represents an innovative energy delivery approach for cardiac arrhythmia treatment, characterized by a favorable safety profile and effective myocardial lesion formation. It has demonstrated high acute pulmonary vein isolation rates with a reduced incidence of injury to adjacent anatomical structures. Nonetheless, procedure-specific complications such as haemolysis, intravascular gas formation, and coronary vasospasm have been observed and warrant further evaluation. Clinical evidence supports efficacy comparable to conventional thermal ablation in terms of arrhythmia recurrence. Ongoing advancements in catheter engineering, pulse modulation, and multimodal energy strategies aim to enhance lesion durability and transmurality. These developments position PFA as a promising technology in the field of cardiac ablation.

Feasibility of reversible electroporation mapping in human atrial flutter

BACKGROUND

Reversible pulsed field ablation (PFREV) can temporarily block conduction and may emerge as a novel clinical mapping tool to accurately identify critical isthmuses before permanent lesions are created.

OBJECTIVE

We aimed to assess the feasibility and performance of PFREV as a mapping tool in humans.

METHODS

PFREV pulses were delivered with a 9-mm lattice-tip ablation catheter in 24 atrial flutters, targeting sites in and outside the circuit. Only nonpropagated PFREV pulses without change in activation sequence were analyzed.

RESULTS

In 21 patients, 100 nonpropagated PFREV pulses were delivered in 24 tachycardias; 74 (74%) pulses were delivered within the circuit (54 at the isthmus and 20 at outer loop sites), and 26 (26%) pulses were delivered outside the circuit. Three responses were observed: termination, tachycardia cycle length (TCL) prolongation, and no effect. Of the PFREV pulses delivered at the isthmus, 9 (16.7%) led to termination, 10 (18.5%) led to TCL prolongation, and the remaining 35 (64.8%) had no effect. None of the PFREV pulses delivered at the outer loop and outside the circuit induced any change. The isthmus was significantly wider when no PFREV effect was observed compared with termination or prolongation (23.2 ± 2.3 mm vs 11.6 ± 2.0 mm; P < .001). When nonpropagated PFREV pulses were delivered at the same site, 85% showed the same type of response, rising to 90% when termination and prolongation were combined.

CONCLUSION

PFREV mapping of reentrant atrial tachycardia is feasible, with termination and TCL prolongation reproducibly identifying the critical isthmus with 100% specificity. Sensitivity of PFREV mapping is influenced by the isthmus electroanatomic characteristics.

In vivo assessment of catheter-tissue contact using tissue proximity indication and its impact on cardiac lesion formation in pulsed field ablation

BACKGROUND

No evidence exists regarding whether tissue proximity indication (TPI), an impedance-based contact indicator, can improve in vivo lesion formation and durability during pulsed field ablation (PFA).

OBJECTIVE

This in vivo study investigated the relationship between catheter-tissue contact and lesion formation.

METHODS

In 5 porcine subjects, PFA applications were delivered at 35 atrial target sites using the VARIPULSE variable-loop circular catheter with the CARTO 3 mapping system. We compared acute ablative low-voltage zones (LVZs; <0.5 mV), chronic LVZs, and pathologic lesions between no/minimum contact (TPI-negative/flickering TPI-positive status) and consistent tissue contact (consistent TPI-positive status) for typical clinical scenarios and tissue tenting (TPI-positive status with electrodes extensively away from the 3-dimensional mapping surface) for safety margin. Ultrasound imaging also confirmed contact category assessments.

RESULTS

Acute and chronic LVZs were significantly larger with consistent contact compared with no/minimum contact, including pathologic lesion length (36.0 ± 12.5 mm vs 17.4 ± 15.2 mm; P = .002) and maximum width (10.3 ± 2.7 mm vs 5.7 ± 5.1 mm; P = .035); results with tenting (length: 34.6 ± 11.7 mm; width: 11.3 ± 1.9 mm) were comparable to consistent contact. Lesion transmurality was achieved in all lesions with consistent contact or tissue tenting but only in 54.5% with no/minimum contact (P = .001 for each). The TPI-based electrode contact distance, measured as the cumulative length of the multielectrode catheter tip positive for TPI, significantly correlated with lesion length, maximum width, and transmurality.

CONCLUSION

Consistent TPI-based contact during PFA was strongly associated with distinct chronic transmural lesions, emphasizing the importance of tissue contact in optimizing circumferential lesion formation with circular PFA catheters.

Pulsed field ablation for atrial fibrillation

INTRODUCTION

Atrial fibrillation is the most common sustained arrhythmia, associated with substantial morbidity and a reduced quality of life. The current standard of care, transcatheter pulmonary vein isolation using thermal ablation techniques, provides symptom relief but carries a risk of collateral tissue damage. In recent years, pulsed field ablation, a nonthermal technique based on irreversible electroporation, has emerged as a promising alternative to conventional thermal ablation methods.

AREAS COVERED

This review provides an overview of pulsed field ablation, a novel nonthermal ablation technique. We briefly explain its biophysical principles and general technical aspects, describe currently available technologies, and summarize findings from clinical studies. Additionally, we discuss its safety profile, unresolved issues, and limitations, while also exploring future perspectives.

EXPERT OPINION

Pulsed field ablation offers distinct advantages over traditional thermal ablation methods, such as shorter procedure times and a favorable safety profile due to precise tissue targeting. Future improvements in ablation device design, energy delivery settings, integration with mapping systems, workflow efficiency, ablation protocols, and patient selection criteria are expected to further enhance clinical outcomes.

Factors Influencing Contact Force in Robotic Magnetic Navigation Ablation

INTRODUCTION

Stability of catheter-tissue contact in the robotic magnetic navigation (RMN) system is one of the key features that distinguishes this system from manually guided catheters. Numerous studies have shown that contact force (CF) in manually controlled catheters is as crucial for forming an optimal lesion as the duration of application or power. Catheters used in the RMN system lack a quantitative method for intraoperative monitoring of this parameter. Our study aims to partially address this gap in scientific knowledge.

METHODS

We conducted a total of 1200 CF measurements using the RMN system (Stereotaxis, St. Louis, MO, USA), a magnetic-guided 8 Fr RF ablation catheter (THERMOCOOL RMT Catheter, Biosense Webster, Irvine, CA, USA) inserted through a long sheath (SR0, Abbott Cardiovascular, Nathan Lane North, Plymouth, MN, USA), and a precision jewelry scale (IKEME, Guangdong, CN). We analyzed the impact on the obtained CF values of four different magnetic field vectors (transverse, sagittal, caudal, and cranial), two field strengths (0.1T and 0.08T), and three catheter extension configurations from the long sheath (with Position 1 being the least extended and Position 3 the most extended).

RESULTS

The contact force values varied significantly across the different magnetic field vectors, field strengths, and catheter extensions from the vascular sheath. The greatest differences in achieved values were observed across the different magnetic field vectors in the Position 1, ranging from 3.52 ± 0.1 g (caudal plane) to 15.15 ± 0.05 g (cranial plane) at 0.08 Tesla (T) field strength (p < 0.001), and from 4.10 ± 0.06 g (caudal) to 15.01 ± 0.07 g (cranial) at 0.1 T, p < 0.001. Differences in other vectors reached approximately 20%. The highest CF values were obtained in Position 1, intermediate values in Position 2, and the lowest in Position 3. An exception was the transverse vector, where, particularly with a magnetic field of 0.1 T, more similar values were observed across Positions 1-3, with respective values of 8.61 ± 0.14 g, 9.36 ± 0.06 g, and 8.31 ± 0.05 g. A stronger magnetic field (0.1 T compared to 0.08 T) resulted in higher CF values, especially during measurements in the transverse vector. This effect was most pronounced in the most extended catheter from the sheath - Position 3 (with respective values of 4.54 ± 0.09 g vs. 8.31 ± 0.05 g, p < 0.001). In the sagittal, cranial, and caudal vectors, the differences were less noticeable.

CONCLUSION

Different magnetic field vectors, catheter extensions from the sheath, and magnetic field strengths result in varying contact force values. For effective radiofrequency ablation lesions, these factors should be considered alongside power, duration, and other established parameters.

[Guideline to safe and effective atrial fibrillation ablation with pulsed-field ablation using the pentaspline PFA system as an example]

Atrial fibrillation ablation is an established procedure for the treatment of atrial fibrillation, in which Pulsed Field Ablation (PFA) is a novel method alongside radiofrequency and cryoablation. The article explains the technical basics of PFA, describes different types of catheters and gives detailed instructions on how to perform the procedure, from patient selection to sedation strategies and imaging. Important safety aspects and possible complications are also covered. Finally, the further development of PFA technology for the treatment of other arrhythmias and integration into 3D mapping systems is discussed. This work is part of a series of articles on further training in special rhythmology.

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.

Catheter ablation using pulsed-field energy: Advantages and limitations compared with conventional energy

Atrial fibrillation (AF) poses significant risks of heart failure and stroke, emphasizing effective treatment. Catheter ablation using thermal energy sources, such as radiofrequency or cryoballoon ablation, has shown greater success in maintaining sinus rhythm compared with drug therapy. However, thermal ablation (TA) is associated with serious complications, such as atrial-esophageal fistula, phrenic nerve palsy, and pulmonary vein stenosis. Pulsed-field ablation (PFA) is an emerging ablation energy source that uses electroporation to selectively target cardiac tissue while sparing adjacent structures such as nerves and blood vessels. Two randomized controlled trials have demonstrated that PFA is comparable to TA in both efficacy and safety at a 1-year follow-up and had shorter procedure times. A review of six meta-analyses consistently showed shorter procedural times for PFA across all studies. Additionally, three out of the four recent studies with large samples reported lower recurrence rates with PFA. Regarding complication rates, four out of four studies showed lower incidences of phrenic nerve injury with PFA, and two out of three studies reported lower rates of esophageal injury with PFA. However, four out of four studies indicated higher incidences of cardiac tamponade with PFA, highlighting the need for caution among early-career operators. Furthermore, careful monitoring is required considering the possible unforeseen complications specific to PFA and the lack of long-term follow-up data. Despite these concerns, PFA shows promise as a safer, more effective, and efficient alternative to TA for AF, particularly as operator experience and device technology continue to advance.

Effect of Sequential, Colocalized Radiofrequency and Pulsed Field Ablation on Cardiac Lesion Size and Histology

BACKGROUND

Sequential application of radiofrequency with pulsed field (PF) ablation may increase lesion depth while preserving the advantages of PF. The study's aim was to determine lesion dimensions of sequential, colocalized radiofrequency and PF ablation.

METHODS

A preclinical study using swine (n=4) performed lesions in the right/left ventricles. Ablations were performed with a force-sensing 3.5-mm irrigated-tip ablation catheter using a generator delivering both radiofrequency and PF. PF was delivered using unipolar, biphasic pulses at a standard dose (PF index, 300) with 4-mL/min irrigation. Radiofrequency was delivered at 50 W for 10 s (15 mL/min). Lesions were created by applying colocalized radiofrequency followed by sequential application of PF on the same location, PF followed by sequential application of radiofrequency on the same location, PF alone, or radiofrequency alone. Tissue was collected after 2 hours for lesion assessment. Results are mean±SD.

RESULTS

Forty-five lesions were analyzed. The lesion depth of radiofrequency alone was 4.9±0.8 mm. The mean lesion depth and width for PF alone were 3.5±0.6 and 5.1±1.8 mm. Lesion depths for combined applications were significantly greater versus PF alone (6.2±1.8 mm radiofrequency followed by sequential application of PF on the same location; 5.7±1.3 mm PF followed by sequential application of radiofrequency on the same location; P<0.0001 for both). Lesion widths were also significantly greater with combined therapy versus PF alone (8.6±1.8 mm radiofrequency followed by sequential application of PF on the same location; 8.9±2.1 mm PF followed by sequential application of radiofrequency on the same location; P<0.0001 for both). Histology for both combined lesions showed central thermal necrosis surrounded by a hemorrhagic and transitional PF zone.

CONCLUSIONS

Combined, colocalized radiofrequency and PF, irrespective of order, show significantly increased lesion size compared with the same dose of PF or radiofrequency alone.

Lesion Formation in Cardiac Pulsed-Field Ablation: Acute to Chronic Cellular Level Changes

As pulsed-field ablation (PFA) emerges as a promising therapy for atrial arrhythmias, an understanding of the cellular injury to cardiac tissue is critical to evaluating and interpreting results for each PFA system. This review aims to detail the mechanism of cell death for PFA, compare the cell death mechanism to thermal ablation modalities, clarify common histology markers, detail the progression of PFA lesions from the acute, to subacute, to chronic maturation states, and discuss clinical indicators of PFA lesions.

Clinical importance of tissue proximity indication during pulsed field ablation for atrial fibrillation: insights from initial experience

BACKGROUND

Pulsed field ablation (PFA) for paroxysmal atrial fibrillation (AF) has been gaining worldwide acceptance because of its efficacy and safety. A variable loop circular catheter (VLCC, VARIPULSE, Biosense Webster, Inc) for PFA recently launched in Japan, includes a tissue proximity indication (TPI) feature to monitor catheter-tissue contact via impedance. However, the role of TPI during pulmonary vein isolation (PVI) is unclear.

OBJECTIVE

This study aims to evaluate TPI feasibility during PVI and its relationship with acute pulmonary vein (PV) reconnection.

METHODS

Twenty-one patients with paroxysmal AF underwent PFA (at least 4 ablations per PV) using the VLCC. We evaluated the association between TPI-positive site percentages, voltage, left atrial wall thickness on ADAS 3D software (Adas3D Medical SL, Barcelona Spain), and acute PVI failure sites.

RESULTS

Four of 21 patients (8 failure sites) experienced PVI failure after primary PFA. Failure sites had significantly lower TPI-positive site percentages (0 ± 0% vs 63 ± 27%, P < .001) and higher voltage (3.57 ± 1.35 mV vs 2.06 ± 1.42 mV, P = .003) but not PV wall thickness. We found that a left atrial bipolar voltage amplitude ≥2.24 mV was determinants of PV gaps with an area under the curve of 0.83 calculating receiver operating characteristic curves. TPI-positive site percentages increased significantly (58 ± 29% to 64 ± 26%, P = .009), whereas PV gaps decreased from 3 of 28 PVs (11%) to 2 of 54 PVs (4%, P = .332) between the first 7 and last 14 cases.

CONCLUSION

Acute PVI failure was significantly associated with poor tissue contact and higher voltage. However, acute PVI failure can be prevented with improved TPI-based contact information.

Biophysics and electrophysiology of pulsed field ablation in normal and infarcted porcine cardiac ventricular tissue

Pulsed Field Ablation (PFA) is a new ablation method being rapidly adopted for treatment of atrial fibrillation, which shows advantages in safety and efficiency over radiofrequency and cryo-ablation. In this study, we used an in vivo swine model (10 healthy and 5 with chronic myocardial infarct) for ventricular PFA, collecting intracardiac electrograms, electro-anatomical maps, native T1-weighted and late gadolinium enhancement MRI, gross pathology, and histology. We used 1000-1500 V pulses, with 1-16 pulse trains to vary PFA dose. Lesions were assessed at 24 h, 7 days, and 6 weeks in healthy and at 48 h in infarcted ventricles. Comparisons of lesion sizes using a numerical model enabled us to determine lethal electric field thresholds for cardiac tissue and its dependence on the number of pulse trains. Similar thresholds were found in normal and infarcted hearts. Numerical modeling and temperature-sensitive MRI confirmed the nonthermal nature of PFA, with less than 2% of a lesion's volume at the highest dose used being attributed to thermal damage. Longitudinal cardiac MRI and histology provide a comprehensive description of lesion maturation. Lesions shrink between 24 h and 7 days post-ablation and then remain stable out to 6 weeks post-ablation. Periprocedural electrograms analysis yields good correlation with lesion durability and size.

Catheter Ablation for Ventricular Tachycardias: Current Status and Future Perspectives

Catheter ablation for ventricular tachycardia (VT) in patients with systolic heart failure remains a critical yet challenging area of non-pharmacological therapy. Despite positive outcomes in atrial fibrillation, evidence for the efficacy of VT ablation in reducing cardiac mortality is inconclusive due to the absence of standardized ablation strategies. The primary challenges include difficulties in identifying suitable ablation targets and their deep locations within myocardial tissue. Current techniques, such as voltage mapping, provide valuable insights; however, they are limited by the presence of numerous bystander areas and the occurrence of incomplete transmural scarring. Recent advancements in functional substrate mapping have focused on identifying critical isthmuses without requiring hemodynamic stabilization during VT, thereby shifting the emphasis to the analysis of potentials during baseline rhythm. While methods like isochronal late activation mapping have improved target identification, they primarily address conduction abnormalities without adequately considering repolarization heterogeneity. This review highlights emerging technologies that utilize unipolar potentials to assess repolarization heterogeneities and identify VT isthmuses. Furthermore, novel ablation sources such as pulsed-field ablation, bipolar ablation, and ultra-low temperature cryoablation are being explored to create deeper and more durable lesions, addressing the limitations of traditional radiofrequency ablation. These advancements aim to reduce VT recurrence and improve overall treatment efficacy. Ultimately, understanding these innovative strategies is expected to optimize procedural outcomes and significantly enhance the management of patients with scar-related VT.

Mapping and ablation of ventricular tachycardia using dual-energy lattice-tip focal catheter: early feasibility and safety study

AIMS

Catheter ablation is an effective treatment method for recurrent ventricular tachycardias (VTs). However, at least in part, procedural and clinical outcomes are limited by challenges in generating an adequate lesion size in the ventricular myocardium. We investigated procedural and clinical outcomes of VT ablation using a novel 'large-footprint' catheter that allows the creation of larger lesions either by radiofrequency (RF) or by pulsed field (PF) energy.

METHODS AND RESULTS

In prospectively collected case series, we describe our initial experience with VT ablation using a lattice-tip, dual-energy catheter (Sphere-9, Medtronic), and a compatible proprietary electroanatomical mapping system (Affera, Medtronic). The study population consisted of 18 patients (aged 55 ± 15 years, one woman, structural heart disease: 94%, ischaemic heart disease: 56%, left ventricular ejection fraction: 34 ± 10%, electrical storm: 22%) with recurrent sustained VTs and ≥1 previously failed endocardial RF ablation with conventional irrigated-tip catheter in 66% of patients. On average, 12 ± 7 RF and 8 ± 9 PF applications were delivered per patient. In three-fourths of patients undergoing percutaneous epicardial ablation, spasms in coronary angiography were observed after PF applications. All resolved after intracoronary administration of nitrates. No acute phrenic nerve palsy was noted. One patient suffered from a stroke that resolved without sequelae. Post-ablation non-inducibility of VT was achieved in 89% of patients. Ventricular-arrhythmia-free survival at three months was 78%.

CONCLUSION

VT ablation using a dual-energy lattice-tip catheter and a novel electroanatomical mapping system is feasible. It allows rapid mapping and effective substrate modification with good outcomes during short-term follow-up.

Focal monopolar pulsed field ablation from within the great cardiac vein for idiopathic premature ventricular contractions after failed radiofrequency ablation

BACKGROUND

Idiopathic epicardial premature ventricular contractions (PVCs) originating from the left ventricular summit are difficult to eliminate.

OBJECTIVE

The purpose of this study was to describe the feasibility and procedural safety of monopolar biphasic focal pulsed field ablation (F-PFA) from within the great cardiac vein (GCV) for treatment of idiopathic epicardial PVCs.

METHODS

In 4 pigs, F-PFA (Centauri, CardioFocus) was applied from within the GCV followed by macroscopic gross analysis. In 4 patients with previously failed radiofrequency ablation, electroanatomic mapping was used to guide F-PFA from within the GCV and the ventricular outflow tracts. Coronary angiography and optical coherence tomography (OCT) were performed in 2 patients.

RESULTS

In pigs, F-PFA from within the GCV (5 mm away from the coronary arteries) resulted in myocardial lesions with a maximal depth of 4 mm, which was associated with nonobstructive transient coronary spasms. In patients, sequential delivery of F-PFA in the ventricular outflow tracts and from within the GCV eliminated the PVCs. During F-PFA delivery from within the GCV with prophylactic nitroglycerin application, coronary angiography showed no coronary spasm when F-PFA was delivered >5 mm away from the coronary artery and a transient coronary spasm without changes in a subsequent OCT, when F-PFA was delivered directly on the coronary artery. Intracardiac echocardiography and computed tomography integration was used to monitor F-PFA delivery from within the GCV. There were no immediate or short-term complications.

CONCLUSION

Sequential mapping-guided F-PFA from endocardial ventricular outflow tracts and from within the GCV is feasible with a favorable procedural safety profile for treatment of epicardial PVCs.

Pulsed Field Ablation of Atrial Fibrillation: A Novel Technology for Safer and Faster Ablation

Atrial fibrillation (AF), the most common arrhythmia, is associated with increased morbidity, mortality, and healthcare costs. Evidence indicates that rhythm control offers superior cardiovascular outcomes compared to rate control, especially when initiated early after the diagnosis of AF. Catheter ablation remains the single best therapy for AF; however, it is not free from severe complications and only a small percentage of AF patients in the Western world ultimately receive ablation. Ensuring that AF ablation is safe, effective, and efficient is essential to make it accessible to all patients. With the limitations of traditional thermal ablative energies, pulsed field ablation (PFA) has emerged as a novel non-thermal energy source. PFA targets irreversible electroporation of cardiomyocytes to achieve cell death without damaging adjacent structures. Through its capability to create rapid, selective lesions in myocytes, PFA presents a promising alternative, offering enhanced safety, reduced procedural times, and comparable, if not superior, efficacy to thermal energies. The surge of new evidence makes it challenging to stay updated and understand the possibilities and challenges of PFA. This review aims to summarize the most significant advantages of PFA and how this has translated to the clinical arena, where four different catheters have received CE-market approval for AF ablation. Further research is needed to explore whether adding new ablation targets, previously avoided due to risks associated with thermal energies, to pulmonary vein isolation can improve the efficacy of AF ablation. It also remains to see whether a class effect exists or if different PFA technologies can yield distinct clinical outcomes given that the optimization of PFA parameters has largely been empirical.

The use of Intracardiac Echocardiography in Catheter Ablation of Atrial Fibrillation

PURPOSE OF THE REVIEW

Intracardiac echocardiography (ICE) provides real-time, fluoroless imaging of cardiac structures, allowing optimal catheter positioning and energy delivery during ablation procedures. This review summarizes the use of ICE in catheter ablation of atrial fibrillation (AF).

RECENT FINDINGS

Growing evidence suggests that the use of ICE improves procedural safety and facilitates radiofrequency and cryoballoon AF ablation. ICE-guided catheter ablation is associated with reduced procedural duration and fluoroscopy use. Recent studies have examined the role of ICE in guiding novel ablation techniques, such as pulsed field ablation. Finally, the use of ICE allows for early detection and timely management of potentially serious procedural complications. Intracardiac echocardiography offers significant advantages during AF ablation procedures and its use should be encouraged to improve procedural safety and efficacy.

Pulsed-field- vs. cryoballoon-based pulmonary vein isolation: lessons from repeat procedures

AIMS

Pulsed-field ablation (PFA) is an emerging technology to perform pulmonary vein isolation (PVI). Initial data demonstrated high safety and efficacy. Data on long-term PVI durability and reconduction patterns in comparison to established energy sources for PVI are scarce. We compare findings in repeat ablation procedures after a first PFA to findings in repeat ablation procedures after a first cryoballoon ablation (CBA) based PVI.

METHODS AND RESULT

A total of 550 consecutively enrolled patients underwent PFA or CBA index PVI. Repeat ablations in patients with symptomatic atrial arrhythmia recurrences were analysed. A total of 22/191 (12%) patients after index PFA-PVI and 44/359 (12%) after CBA-PVI underwent repeat ablation. Reconduction of any pulmonary vein (PV) was detected by multipolar spiral mapping catheter at each PV with careful evaluation of PV potentials and by 3D-mapping in 16/22 patients (73%) after PFA-PVI and in 33/44 (75%) after CBA-PVI (P = 1.000). Of 82 initially isolated PVs after PFA-PVI, 31 (38%) were reconducting; of 169 isolated PVs after CBA-PVI, 63 (37%) were reconducting (P = 0.936). Clinical atrial tachycardia occurred similarly in patients after PFA (5/22; 23%) and CBA (7/44; 16%; P = 0.515). Roof lines were set more often after PFA- (8/22; 36%) compared with CBA-PVI (5/44; 11%; P = 0.023). Repeat procedure duration [PFA: 87 (76, 123) min; CBA: 93 (75, 128) min; P = 0.446] was similar and fluoroscopy time [PFA: 11 (9, 14) min; CBA: 11 (8, 14) min; P = 0.739] equal between groups at repeat ablation.

CONCLUSION

During repeat ablation after previous PFA- or CBA-based PVI, electrical PV-reconduction rates and patterns were similar.

Ablation Strategies for Persistent Atrial Fibrillation: Beyond the Pulmonary Veins

Despite advances in ablative therapies, outcomes remain less favorable for persistent atrial fibrillation often due to presence of non-pulmonary vein triggers and abnormal atrial substrates. This review highlights advances in ablation technologies and notable scientific literature on clinical outcomes associated with pursuing adjunctive ablation targets and substrate modification during persistent atrial fibrillation ablation, while also highlighting notable future directions.

Pulsed-field ablation for atrial fibrillation without the use of fluoroscopy

INTRODUCTION

Pulsed-field ablation (PFA) and fluoroless ablation (FA) are emerging techniques in contemporary in electrophysiology. With widespread use of 3D electroanatomic mapping systems and advanced intracardiac echo (ICE) imaging, fluoroless ablation has become more widely adopted. However, with the importance of tissue contact for lesion durability, initial PFA has been used with fluoroscopic guidance, but both ICE and electroanatomic mapping make fluoroless PFA feasible. The objective of this study is to demonstrate that PFA can be done safely and effectively without fluoroscopy.

METHODS

At a single center, consecutive patients undergoing ablation with a pentaspline PFA catheter using a fluoroless approach are described. The standard 3D anatomic map settings were adjusted with changes in interior and exterior projection, respiratory compensation, and interpolation. In addition, projection map lesions were used to confirm adequate circumferential ablation lesions. ICE was used extensively for wire guidance and evaluation of contact with tissue.

RESULTS

Beginning on March 15, 2024, 50 consecutive subjects (19 female/31 male) aged 68.0 (± 13.7) underwent PFA ablation. The average CHA2DS2-VA2Sc score was 3.0 (± 1.9). The average LVEF was 57.3% (± 10.0) and the average LA size was 3.9 cm (± 1.2). Projection lesions were placed with every application of PFA. An average of 41.7 (± 8.5) PFA applications were placed. In 100% (50/50) of subjects, acute isolation of the pulmonary veins was achieved. Eighteen subjects also underwent concomitant posterior wall isolation and in 100% of these subjects, posterior isolation was achieved. There were zero complications in this cohort. In 50/50 subjects (100%), fluoroscopy was not used. In comparison to the control cohort, the LA dwell time of the ablation catheter was similar (p = 0.34).

CONCLUSION

In comparison to the traditional PFA with fluoroscopy, this proof-of-concept study shows fluoroless PFA ablation can be performed safely and with similar acute success rates as with use of fluoroscopy.

In Vitro Assay Development to Study Pulse Field Ablation Outcome Using Solanum Tuberosum

Exposing cells to intense and brief electric field pulses can modulate cell permeability, a phenomenon termed electroporation. When applied in medical treatments of diseases like cancer and cardiac arrhythmias, depending on level of cellular destruction, it is also referred to as irreversible electroporation (IRE) or Pulsed Field Ablation (PFA). For ablation device testing, several pulse parameters need to be characterized in a comprehensive manner to assess lesion boundary and efficacy. Overly aggressive voltages and application numbers increase animal burden. The potato tuber is a widely used initial model for the early testing of electroporation. The aim of this study is to characterize and refine bench testing for the ablation outcomes of PFA in this simplistic vegetal model. For in vitro assays, several pulse parameters like voltage, duration, and frequency were modulated to study effects not only on 2D ablation area but also 3D depth and volume. As PFA is a relatively new technology with minimal thermal effects, we also measured temperature changes before, during, and after ablation. Data from experiments were supplemented with in silico modeling to examine E-field distribution. We have estimated the irreversible electroporation threshold in Solanum Tuberosum to be at 240 V/cm. This bench testing platform can screen several pulse recipes at early stages of PFA device development in a rapid and high-throughput manner before proceeding to laborious trials for IRE medical devices.

Ablation of accessory pathways in different anatomic locations using focal pulsed field ablation

BACKGROUND

Ablation of accessory pathways (APs) is the cornerstone for treatment of patients with Wolff-Parkinson-White syndrome and manifestation of atrioventricular reentrant tachycardia. Pulsed field ablation (PFA) is a new type of nonthermal energy source delivered to the underlying tissue via the ablation catheter and used for ablation of arrhythmic substrates.

OBJECTIVE

The purpose of this study was to determine the efficiency and long-term outcome of ablation of APs of different localizations using a focal pulsed electrical field.

METHODS

Electrophysiological study was performed in patients with indication for AP ablation. An ablation catheter was used to map the position of AP insertion. Pulsed electric field was delivered through a standard ablation catheter. In left-sided APs, the first ablation attempt was within the coronary sinus (CS). Patient follow-up was scheduled 1-3 months after the ablation. Additional check-up was performed after 6 and 12 months.

RESULTS

Fourteen 14 patients (3 pediatric) were treated. Termination of AP conduction was achieved in all procedures. The cohort consisted of 3 right free wall, 3 posteroseptal, and 8 left-sided APs. Ablation through CS was successfully used in 7 of 8 patients with left-sided APs. No complications were reported. Median follow-up was 5.5 months. Conduction recurrence through AP was documented in 1 patient.

CONCLUSION

Focal PFA for AP shows promising results in terms of efficacy and safety. A high rate of successful termination of left-sided APs by ablation within CS may represent a new standard approach. The safety and efficacy profile of PFA seems to be transferable to the pediatric population.

Efficacy and safety of focal pulsed-field ablation for ventricular arrhythmias: two-centre experience

AIMS

A pulsed electric field (PF) energy source is a novel potential option for catheter ablation of ventricular arrhythmias (VAs) as it can create deeper lesions, particularly in scarred tissue. However, very limited data exist on its efficacy and safety. This prospective observational study reports the initial experience with VA ablation using focal PF.

METHODS AND RESULTS

The study population consisted of 44 patients (16 women, aged 61 ± 14years) with either frequent ventricular premature complexes (VPCs, 48%) or scar-related ventricular tachycardia (VT, 52%). Ablation was performed using an irrigated 4 mm tip catheter and a commercially available PF generator. On average, 16 ± 15 PF applications (25 A) were delivered per patient. Acute success was achieved in 84% of patients as assessed by elimination of VPC or reaching non-inducibility of VT. In three cases (7%), a transient conduction system block was observed during PF applications remotely from the septum. Root analysis revealed that this event was caused by current leakage from the proximal shaft electrodes in contact with the basal interventricular septum. Acute elimination of VPC was achieved in 81% patients and non-inducibility of VT in 83% patients. At the 3-month follow-up, persistent suppression of the VPC was confirmed on Holter monitoring in 81% patients. In the VT group, the mean follow-up was 116 ± 75 days and a total of 52% patients remained free of any VA.

CONCLUSION

Pulsed electric field catheter ablation of a broad spectrum of VA is feasible with acute high efficacy; however, the short-term follow-up is less satisfactory for patients with scar-related VT.

Sequential Unipolar Biventricular Pulsed Field Ablation for Refractory Intramural Septal Ventricular Tachycardia

Catheter ablation of septal ventricular tachycardia (VT) is challenging. Pulsed field ablation is a promising technology, potentially reaching deep substrates. We report the first sequential unipolar biventricular pulsed field ablation targeting refractory septal VT. Besides, we illustrate the importance of searching underlying cardiomyopathy in patients with recurrent multiple morphology VTs and normal magnetic resonance imaging.

State-of-the-art pulsed field ablation for cardiac arrhythmias: ongoing evolution and future perspective

Pulsed field ablation (PFA) is an innovative approach in the field of cardiac electrophysiology aimed at treating cardiac arrhythmias. Unlike traditional catheter ablation energies, which use radiofrequency or cryothermal energy to create lesions in the heart, PFA utilizes pulsed electric fields to induce irreversible electroporation, leading to targeted tissue destruction. This state-of-the-art review summarizes biophysical principles and clinical applications of PFA, highlighting its potential advantages over conventional ablation methods. Clinical data of contemporary PFA devices are discussed, which combine predictable procedural outcomes and a reduced risk of thermal collateral damage. Overall, these technological developments have propelled the rapid evolution of contemporary PFA catheters, with future advancements potentially impacting patient care.

Initial clinical experience with the balloon-in-basket pulsed field ablation system: acute results of the VOLT CE mark feasibility study

AIMS

Pulsed field ablation (PFA) for the treatment of atrial fibrillation (AF) potentially offers improved safety and procedural efficiencies compared with thermal ablation. Opportunities remain to improve effective circumferential lesion delivery, safety, and workflow of first-generation PFA systems. In this study, we aim to evaluate the initial clinical experience with a balloon-in-basket, 3D integrated PFA system with a purpose-built form factor for pulmonary vein (PV) isolation.

METHODS AND RESULTS

The VOLT CE Mark Study is a pre-market, prospective, multi-centre, single-arm study to evaluate the safety and effectiveness of the Volt™ PFA system for the treatment of paroxysmal (PAF) or persistent AF (PersAF). Feasibility sub-study subjects underwent phrenic nerve evaluation, endoscopy, chest computed tomography, and cerebral magnetic resonance imaging. Study endpoints were the rate of primary serious adverse event within 7 days and acute procedural effectiveness. A total of 32 subjects (age 61.6 ± 9.6 years, 65.6% male, 84.4% PAF) were enrolled and treated in the feasibility sub-study and completed a 30-day follow-up. Acute effectiveness was achieved in 99.2% (127/128) of treated PVs (96.9% of subjects, 31/32) with 23.8 ± 4.2 PFA applications/subject. Procedure, fluoroscopy, LA dwell, and transpired ablation times were 124.6 ± 28.1, 19.8 ± 8.9, 53.0 ± 21.0, and 48.0 ± 19.9 min, respectively. Systematic assessments of initial safety revealed no phrenic nerve injury, pulmonary vein stenosis, or oesophageal lesions causally related to the PFA system and three subjects with silent cerebral lesions (9.4%). There were no primary serious adverse events.

CONCLUSION

The initial clinical use of the Volt PFA System demonstrates acute safety and effectiveness in the treatment of symptomatic, drug refractory AF.