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.

Redefining the blanking period following pulsed-field ablation in patients with atrial fibrillation.

BACKGROUND: Recurrence during the 3-month blanking period following radiofrequency ablation of atrial fibrillation (AF) is typically not considered as a predictor for late recurrence. OBJECTIVE: We investigated the significance of early recurrence as a risk factor for late recurrence in AF patients receiving pulsed-field ablation (PFA). METHODS: Consecutive patients undergoing PFA were prospectively followed-up for 1 year. All patients received isolation of pulmonary veins. Additional ablations were performed per operator's discretion. Following the procedure all remained on their previously ineffective antiarrhythmic drugs (AAD) during the 2-month blanking period after which the AADs were discontinued. Early recurrence was defined as atrial arrhythmia of > 30 second duration during the 3-mo blanking period and any recurrence beyond 3-mo was considered as late recurrence. RESULTS: A total of 337 patients undergoing PFA for AF were included. Early recurrence was recorded in 53 (15.7%) patients; 10 in the 1st month, 12 in the 2nd month and 31 in the 3rd month. Of the 10 patients having recurrence during the 1st month, 7 (70%) remained in sinus rhythm after cardioversion whereas 3 (30%) underwent redo because of late-recurrence. At 1 year, all patients with recurrence during the 2nd and 3rd month, experienced late-recurrence of which 10/12 and 27/31 underwent redo and the remaining 6 patients were in sinus on-AAD. CONCLUSION: In this consecutive series of AF patients, early-recurrence in the 2nd or 3rd month following the PFA procedure was associated with high risk of late-recurrence. Thus, blanking period could be redefined as 1-month following PFA.

Comparison of Cryoballoon vs. Pulsed Field Ablation in Patients with Symptomatic Paroxysmal Atrial Fibrillation (SINGLE SHOT CHAMPION): Study protocol for a randomized controlled trial.

Background: Single-shot devices are increasingly used for pulmonary vein isolation (PVI) in atrial fibrillation (AF). The Arctic Front cryoballoon is the most frequently used single-shot technology. A recently developed novel pulsed field ablation (PFA) device (FARAPULSE) has been introduced with the aim to improve procedural safety and efficacy. Objective: This study will compare the novel FARAPULSE PFA device and the Arctic Front cryoballoon for first PVI in patients with symptomatic paroxysmal AF. Methods: SINGLE SHOT CHAMPION is a multicenter, randomized controlled trial with blinded endpoint adjudication by an independent clinical events committee. Overall, 210 patients with paroxysmal AF undergoing their PVI are randomized 1:1 between PFA and cryoballoon ablation. Continuous rhythm monitoring with an implantable cardiac monitor is performed in all patients. Results: The primary endpoint is time to first recurrence of any atrial tachyarrhythmia (AF and/or organized atrial tachyarrhythmia) lasting ≥120 seconds and identified by the implantable cardiac monitor within 91 and 365 days postablation. The composite procedural safety endpoint includes cardiac tamponade requiring drainage, persistent phrenic nerve palsy, vascular complications requiring intervention, stroke/transient ischemic attack, atrioesophageal fistula, and death occurring during or up to 30 days after the procedure. Key secondary endpoints include (1) increase in high-sensitivity troponin on day 1 postablation, (2) analysis of postablation 3-dimensional electroanatomic mapping (first 25 patients per study group), (3) AF burden, and (4) quality-of-life changes. Conclusion: SINGLE SHOT CHAMPION will evaluate the efficacy and safety of PVI using the novel FARAPULSE PFA for patients with symptomatic paroxysmal AF.

Electroporation saves the day again: Pulsed-field ablation for phrenic nerve-sparing in right atrial tachycardia.

INTRODUCTION: Pulsed-field ablation (PFA) is a novel nonthermal energy that shows unique features that can be of use beyond pulmonary vein ablation, like tissue selectivity or proximity rather than contact dependency. METHODS AND RESULTS: We report three cases of right focal atrial tachycardias arising from the superior cavoatrial junction and the crista terminalis, in close relationship with the phrenic nerve, effectively ablated using a commercially available PFA catheter designed for pulmonary vein isolation without collateral damage. CONCLUSION: PFA can be useful for treating right atrial tachycardias involving sites near the phrenic nerve, avoiding the need for complex nerve-sparing strategies.

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.

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.

Ventricular tachycardia ablation with pentaspline pulsed field technology in two patients with ischemic cardiomyopathy.

INTRODUCTION: Due to its unique features, pulsed field ablation (PFA) could potentially overcome some limitations of current radiofrequency (RF) ventricular tachycardia (VT) ablation. However, data on the use of PFA in this setting are currently scarce. METHODS: Two patients with ischemic cardiomyopathy and previously failed RF VT ablations were treated with PFA. RESULTS: A total of 18 bipolar applications (case1) and seven bipolar applications (case2) were delivered to the infero-lateral and infero-septal areas (case1) and to the apical lateral left ventricular (LV) wall (case2), placing the catheter adjacent to the LV wall in the flower configuration. A rapid cessation of VT and restoration of sinus rhythm were observed during PFA delivery in both cases. Further applications were delivered to achieve complete elimination of late potentials. In case 1, during the in-hospital stay, ECG monitoring did not show VT recurrences. Six-month follow-up was uneventful, with no VT recurrences at ICD interrogation. In case 2, due to postdischarge VT recurrences, a second RF procedure was scheduled 1 month later. The voltage map performed in sinus rhythm showed a low-voltage zone located at the anterolateral wall, near the previous ablation site. Numerous late potentials were recorded. At the 6-month follow-up, no further VT recurrences were documented after RF redo ablation. CONCLUSION: While the speed of application and potential transmural effect can facilitate the ablation of large diseased endocardial areas, early loss of contact due to difficult pentaspline catheter manipulation in the LV could lead to insufficient contact force and, consequently, inadequate energy penetration.

Evaluation of pulsed field ablation lesion characteristics using an in vitro vegetable model.

BACKGROUND: In vitro models to evaluate cardiac pulsed field ablation (PFA) have not been well established. We sought to create a standardized vegetable model and staining protocol for assessing unipolar PFA using a surface electrode. METHODS: We exposed potato slabs to unipolar PFA in a saline bath using a 3.5 mm electrode catheter and grounding pad connected to a custom-built high-voltage generator. Lesions were clearly visualized after staining with 2,3,5-triphenyltetrazolium chloride (TTC) using a timed protocol to reveal a necrotic center and a periphery of electroporated cells with intact mitochondria. RESULTS: Lesion volume increased linearly with increasing voltage and logarithmically with repetitive PFA applications. CONCLUSION: The findings observed in this vegetable model using a TTC staining protocol are consistent with findings observed with cardiomyocytes.

Significant hemolysis is present during irreversible electroporation of cardiomyocytes in vitro.

BACKGROUND: Pulsed-field ablation (PFA) of atrial fibrillation (AF) is a new method in clinical practice. Despite a favorable safety profile of PFA in AF ablation, rare cases of renal failure, probably due to hemolysis, have been recently reported. OBJECTIVE: The aim of this study was to determine the rate of hemolysis and cardiac cell death during in vitro PFA with different electric field intensities. METHODS: Blood samples from healthy volunteers and mouse HL-1 cardiomyocyte cell lines were subjected to in vitro irreversible electroporation (IRE) using 216 bipolar pulses, each lasting 2 µs with 5 µs intervals, repeated 20 times at a frequency of 1 Hz. These pulses varied in from 500 to 1500 V. Cell-free hemoglobin levels were assessed spectrophotometrically, and red blood cell microparticles (RBCµ) were evaluated using flow cytometry. Cardiomyocyte death was quantified using propidium iodide. RESULTS: PF energy (1000 V/cm, 1250 V/cm, and 1500 V/cm) was associated with a significant increase in cell-free hemoglobin (0.31 ± 0.16 g/l, 2.33 ± 0.90 g/l, and 5.7 ± 0.20 g/l, p< 0.05), and similar increase in the concentration of RBCµ. Significant rates of cardiomyocyte death were observed at electric field strengths of 750 V/cm, 1000 V/cm, 1250 V/cm and 1500 V/cm (26.5 ± 5.9%, 44.3 ± 6.2%, 55.5 ± 6.9% and 74.5 ± 17.8% of cardiomyocytes, p < 0.05). CONCLUSION: The most effective induction of cell death in vitro was observed at 1500 V/cm. This intensity was also associated with a significant degree of hemolysis.

Application Repetition and Electrode-Tissue-Contact Results in Deeper Lesions Using a Pulsed-Field Ablation Circular Variable Loop Catheter.

BACKGROUND: Pulsed field ablation (PFA) is a novel, myocardial-selective, non-thermal ablation modality used to target cardiac arrhythmias. Although prompt EGM signal disappearance is observed immediately after PFA application in the pulmonary veins, whether this finding results in adequate transmural lesions is unknown. STUDY AIM: If application repetition and catheter-tissue contact impact on lesion formation during PFA. METHODS: A circular loop PFA catheter was used to deliver repeated energy applications with various levels of contact-force. A benchtop vegetal potato model and a beating heart ventricular myocardial model were utilized to evaluate the impact of application repetition, contact force, and catheter repositioning on contiguity and lesion depth. Lesion development occurred over 18 hours in the vegetal model and over 6 hours in the porcine model. RESULTS: Lesion formation was found to be dependent on application repetition and contact. In porcine ventricles, single and multiple stacked applications led to a lesion depth of 3.5 ± 0.7 mm and 4.4 ± 1.3 mm, respectively (p =0.002). Furthermore, the greater the catheter-tissue contact, the more contiguous and deeper the lesions in the vegetal model (1.0±0.9 mm with no contact Vs. 5.4±1.4 mm with 30 g of force; p=.0001). CONCLUSION: PFA delivered via a circular catheter showed that both repetition and catheter contact led independently to deeper lesion formation. These findings indicate that endpoints for effective PFA ablation are more related to PFA biophysics than mere EGM attenuation.

The importance of electrode-tissue proximity in creating pulsed field ablation lesions: insights from a sub-acute preclinical model.

BACKGROUND: We sought to evaluate the anatomic and functional lesion development over time at different atrial sites immediately following delivery of pulsed field ablation (PFA). METHODS: Using a porcine model, PFA ablations were performed in the superior vena cava (SVC), right atrial lateral wall (RA), left atrial appendage (LAA), and right superior pulmonary vein (RSPV) using four different PFA profiles. Mapping was done sequentially in 5-20-min increments up to 280-min post lesion delivery for low voltage area (LVA) assessment and conduction velocity. Lesion characteristics were noted with voltage mapping immediately post ablation and at the serial time points. RESULTS: In 9 animals, 33 sites were ablated. None of the four different profiles across all sites showed any statistical difference on acute lesion formation or persistence. Higher tissue contact was observed in the SVC and RSPV and lower tissue contact was observed in the LAA and RA locations. Higher contact areas were noted to have higher density electroanatomic low voltage area (LVA) (12/14 vs 5/18, p = 0.01) and larger lesions on gross pathology (2 /14 vs 6/16, p = 0.01) compared to lower contact areas. Lesion regression occurred in 16/33 sites. Sustained lesions were significantly more prevalent in higher versus lower contact sites (65% vs 38%, p = 0.037). CONCLUSION: The development of significant and durable lesions for PFA in a porcine model appears to be dependent on tissue proximity and contact.

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.

Hybrid-Convergent Procedure or Pulsed Field Ablation in Long-Standing Persistent Atrial Fibrillation.

BACKGROUND: Hybrid-convergent radiofrequency (RF) ablation targeting pulmonary veins (PVs) and left atrial posterior wall (LAPW) has shown better arrhythmic outcomes than an endocardial-only RF strategy, despite higher rates of complications. Comparisons with extensive pulsed field ablation (PFA) are currently lacking. OBJECTIVES: This study aimed to compare the efficacy and safety of the hybrid-convergent RF vs PFA of PVs and LAPW in long-standing persistent atrial fibrillation (LSPAF). METHODS: Ninety-three consecutive LSPAF patients, treated with 2-step hybrid-convergent RF ablation (hybrid group, n = 49) or with PFA of PVs and LAPW (PFA group, n = 44) were enrolled. Primary efficacy endpoint was defined as any atrial tachyarrhythmias (ATA) recurrence after the 3-month blanking period, over a follow-up time of 12 months. Periprocedural adverse events and late complications during follow-up were deemed primary safety outcomes. RESULTS: The hybrid and PFA groups had similar baseline characteristics; mean age was hybrid 63.8 ± 10.6 years vs PFA 66.0 ± 7.4 years; P = 0.105. PV and LAPW ablation were acutely successful in all patients. Step 1 hybrid-epicardial procedures were longer than PFA (166 [Q1-Q3: 140-205] minutes vs 107.5 [Q1-Q3: 82.5-12] minutes; P < 0.01). At 12-month follow-up, there was no difference in ATA recurrences between groups (hybrid 36.7% vs PFA 40.9%; P = 0.680; log-rank at survival analysis P = 0.539). After adjusting for confounders, a larger left atrial volume and recurrences during the blanking-period were predictors of ATA recurrences after ablation, regardless of procedural technique employed. PFA showed a better safety profile with a lower rate of major periprocedural complications compared with hybrid ablation (12% vs 0%; P = 0.028). CONCLUSIONS: Hybrid-convergent and PFA share comparable arrhythmic outcomes in LSPAF, but hybrid-convergent ablation carries higher periprocedural risks.