Reversible Pulsed Electrical Fields as an In Vivo Tool to Study Cardiac Electrophysiology: The Advent of Pulsed Field Mapping

Pulsed Field Ablation Using a Lattice-Tip Catheter for Treatment of Ventricular Tachycardias

The inability to create durable, high-quality lesions in the ventricles has limited ventricular tachycardia (VT) ablation outcomes. With pulsed field ablation (PFA), a new modality offers the potential to overcome limitations of conventional, thermal ablation. The lattice-tip catheter's design makes it a promising and versatile tool for ventricular ablation. Preclinical studies have shown that PFA using this system can penetrate scar and fat, create deep lesions, and address difficult ablation targets. Clinical data are scarce but suggest acute feasibility and safety. More research is necessary to evaluate whether this novel ablation system could take VT ablation to the next level.

Pulsed Field Ablation in Ventricular Arrhythmias

Pulsed field ablation (PFA) is a novel nonthermal energy source for catheter ablation, which is potentially useful also for ablation of ventricular arrhythmias since it mitigates the risk of collateral damage to adjacent tissues and may better penetrate through the scar tissue. Solid-tip PFA within the great cardiac vein appears to be advantageous for arrhythmias originating from the left ventricular summit. The use of a large-footprint catheter that toggles between radiofrequency current and PFA may provide an additional advantage since it allows the development of larger lesions to modify myocardial substrate. More experience is expected in the next few years.

Safety and Efficacy of Pulsed Field Ablation for Cavotricuspid Isthmus-Dependent Flutter: A Systematic Literature Review

Cavotricuspid isthmus ablation (CTI) is a first-line therapy in patients with typical atrial flutter. With the advent of pulsed field (PF) as a new energy source, we sought to evaluate the use of PF for CTI ablation. A systematic literature search was conducted on the use of PF for CTI-flutter up to December 2024. A meta-analysis was performed for studies reporting pooled data, while individual case reports were reviewed and summarized. The mean number of PF applications, acute success rate, and prevalence of coronary vasospasm were evaluated. Eleven studies with pooled data from 155 patients were included. All patients had an acute block of the CTI. The mean number of PFA applications was 7.78 (95% CI 6.53-9.48). The incidence of ST-elevation was 0.04% (95% CI 0-2.23%). Subclinical vasospasm was documented in 45% (95% CI 32%-59%) of patients who underwent periprocedural coronary angiography. Prophylactic use of nitrates showed a trend toward reducing the incidence of subclinical vasospasm (RR 0.24, 95% CI 0.06-1.06, p = 0.059). Twelve cases with patient-level data were included; six reported complications, including ST elevation and conduction disturbances. PFA for CTI flutter demonstrates high acute success; however, evidence regarding the durability of the block is limited. Clinical vasospasm with ST segment elevation is uncommon but can lead to life-threatening complications. The incidence of subclinical vasospasm is high, and nitrates tend toward reducing this phenomenon. To date, the role of PFA for this condition appears to be limited.

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.

Using a Novel Pulsed Field Ablation Technique to Identify the Critical Isthmus Within a Tachycardia Circuit

Pulsed field ablation uses irreversible electroporation to interrupt cellular membranes and induce myocyte apoptosis. Reversible electroporation has been used in other specialties, but its utility in cardiac ablation is unknown. Here, a 69-year-old woman undergoing repeat ablation for atypical atrial flutter presented with extensive scar after cardiac surgery (including MAZE) and previous ablation, leading to a macro re-entry circuit. To minimize superfluous lesions and further arrhythmia, we used a single pulse confirming the isthmus location, with cessation of the arrhythmia. As a conclusion, reversible electroporation may be used to test areas of interest prior to irreversible lesion creation.

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.

A novel focal lattice-tip catheter toggling between pulsed field energy and radiofrequency for atrial arrhythmia ablation: Results from a real-world, multicenter registry

BACKGROUND

A novel focal lattice-tip catheter allowing the delivery of either pulsed field (PF) or radiofrequency (RF) energy has recently received regulatory approval. The technology features a proprietary 3-dimensional electroanatomic mapping system.

OBJECTIVE

We describe the first real-world and multicenter experience.

METHODS

Consecutive AF patients undergoing first-time or redo atrial tachyarrhythmia ablation with the Affera system were prospectively enrolled at 3 different centers. PF was the only energy source allowed when ablating the posterior left atrium; anterior applications were performed with either RF (PF/RF strategy) or PF (PF/PF strategy) on the basis of the operator's preference. The primary efficacy end point included acute electrical isolation of pulmonary veins and posterior wall or bidirectional block in case of linear lesions.

RESULTS

The study included 130 patients (mean age, 67 ± 10 years; 63.8% [n = 83] male; 61.5% [n = 80] nonparoxysmal AF; 55.4% first-time AF ablation). First-time pulmonary vein isolation was performed in 72 patients: RF/PF in 13 (18.1%) patients and PF/PF in the remaining 59 (81.9%); first-pass isolation for pulmonary vein and posterior wall was achieved in 100% of cases. A total of 289 ablation lines were performed (roof line, 91 patients; inferior line, 83 patients; anterior mitral line, 32 patients; posterior mitral line, 45 patients; cavotricuspid isthmus line, 38 patients). First-pass isolation and primary efficacy end point were 96.2% (roof line, 100%; inferior line, 100%; anterior mitral line, 96.9%; posterior mitral line, 84.4%; cavotricuspid isthmus, 92.1%) and 100%, respectively. We had 2 (1.5%) major complications: 1 ST-segment elevation at the inferolateral leads requiring intracoronary administration of nitrate and 1 complete atrioventricular block.

CONCLUSION

Catheter ablation with a novel 9-mm lattice-tip catheter confirmed high efficacy and safety in a real-world scenario.

Lesion Morphometry of the Pentaspline Pulsed Field Ablation Catheter: Understanding Catheter Pose, Rotation, and Dosing

BACKGROUND

The pentaspline pulsed field ablation catheter achieves pulmonary vein isolation using 8 stacked, pose-specific applications with rotation. The morphology of pose-specific, single or double applications has not been described.

METHODS

One or 2 applications were delivered to select veins and discrete atrial and ventricular sites in 9 swine. General anesthesia with neuromuscular paralysis ensured a stable position. Preablation, postablation, and serial intraprocedural mappings were performed to characterize electrical vein isolation and dynamic voltage changes. Upon euthanize at 2 days (7 of 9 swine), hearts were subject to pathological examination.

RESULTS

Six superior vena cavae received single or double applications in basket pose without rotation. Despite incomplete dosing, acute electrical isolation occurred in 4 of 6 veins. None recovered conduction over 40 minutes, but all 3 isolated veins that were remapped at 2 days had reconnected. Lesions were linear (15-16 mm) with gaps and significantly wider with double versus single applications (8.2±2.8 versus 6.1±2.0 mm; P=0.02). Similar lesions, with acute isolation and subsequent reconnection, were observed in 3 of 4 ablated pulmonary veins. Double flower pose applications to the posterior atrium created wide (≈40×30 mm) confluent lesions, whereas single applications resulted in curvilinear lesions with variable gaps. Flower pose lesions (single or double) in the right ventricle were flower-shaped, linear with gaps, and with depths up to ≈5 mm.

CONCLUSIONS

The pentaspline catheter in the basket pose creates perivenous linear lesions with gaps. Single applications in flower pose generate narrow linear lesions with variable gaps, whereas double applications result in wide, confluent lesions.

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.

Unexpected transient atrioventricular block and slow junctional rhythm using pulsed field ablation for slow pathway modification: Excited or cautious for ablators

BACKGROUND

Data regarding the effects of pulsed field ablation (PFA) on atrioventricular nodal reentrant tachycardia (AVNRT) are limited.

OBJECTIVE

This study was undertaken to evaluate the outcomes of PFA for AVNRT and its impact on dual-pathway electrophysiology.

METHODS

A larger cohort of patients with typical AVNRT underwent slow pathway (SP) modification (SPM) using a focal PFA catheter in a biphasic/bipolar manner. The primary endpoints were the efficacy and safety of PFA during the procedure and at 6-month follow-up.

RESULTS

The acute success of SPM was achieved in all 40 patients. The total ablation time was 7.9 ± 3.8 seconds for 6.4 ± 2.2 ablation sites (ASs). Slow junctional rhythm (SJR) was induced in 32 (80%) patients, lasting 28.9 ± 10.3 seconds in 3.0 ± 1.1 ASs per patient. SP was located 11.1 ± 1.2 mm from the largest His activation (LHA). At 9 ASs, SJR could be reinduced after an increase of contact force (CF) from 1.3 ± 0.5g to 6.4 ± 1.3 g (P < .0001). Transient atrioventricular block (AVB) was recorded in 7 (17.5%) patients (1 second-degree and 6 third-degree AVB) lasting 435.3 ± 227.4 seconds, with a shorter AS-LHA distance than patients without AVB (7.7 ± 0.6 mm vs. 11.3 ± 1 mm; P < .0001). PFA-related delayed atrial-His (n = 6) and His-atrial (n = 1) conduction preceded transient AVB with a constant His-ventricular interval. Normal PR interval was restored within 24 hours. All patients maintained sinus rhythm without any significant adverse events during 6-month follow-up.

CONCLUSION

Despite the high efficiency of PFA for SPM, the notable incidence of transient AVB warranted caution when applying it near the His bundle. SJR frequently occurred during SPM and was dependent on moderate CF.

Efficacy and safety of pulsed field ablation for accessory pathways: a pilot study

AIMS

Radiofrequency ablation is used as a first-line therapy for accessory pathways (APs). However, data regarding the effects of pulsed field ablation (PFA) on APs are limited. We sought to evaluate the acute procedural and 6-month success and safety of PFA in a cohort of patients with APs.

METHODS AND RESULTS

A focal contact force-sensing PFA catheter was used for patients with APs. Pulsed field ablation generator generated a bipolar and biphasic waveform (±1000 V) with a duration of 100 ms from the tip of the PFA catheter. A 100% acute procedural success was achieved in 10 conscious patients with APs (7 left anterolateral, 2 left inferolateral, and 1 right posteroseptal APs) including 6 (60%) patients after an initial application. The average total ablation time was 6.3 ± 4.9 s for 4.7 ± 1.8 ablation sites (ASs), including 3.1 ± 2.4 s at targets and 3.2 ± 2.9 s at 3.2 ± 2 bolus ASs. The mean skin-to-skin time was 59.3 ± 15.5 min, and PFA catheter dwell time was 29.4 ± 7.8 min. One patient encountered transient sinus arrest during PFA due to parasympathetic overexcitation. Sinus rhythm was restored in all patients without any significant adverse events during the short-term follow-up.

CONCLUSION

Pulsed field ablation of APs was feasible, effective, and safe. Its efficiency was remarkable for its ultrarapid termination of AP conduction. Further studies are warranted to prove whether utilization of PFA with current parameters can extend to manifold AP ablation.

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.

A real-world case-control study on the efficacy and safety of pulsed field ablation for atrial fibrillation

OBJECTIVE

The primary objective of this study was to evaluate the efficacy and safety of pulsed field ablation in individuals diagnosed with atrial fibrillation.

METHODS

A total of 36 patients diagnosed with atrial fibrillation were enrolled in the pulsed field ablation group, while another 36 patients diagnosed with atrial fibrillation were included in the radiofrequency ablation group. Among the study participants, 15 patients in the pulsed field ablation group and 17 patients in the radiofrequency ablation group had persistent atrial fibrillation. Comprehensive comparisons were made between the two groups, including baseline data, underlying diseases, medication usage, intraoperative parameters, and atrial fibrillation recurrence rates at 1, 3, and 6 months during the postoperative follow-up period.

RESULTS

(1) There were no significant differences observed between the two groups concerning baseline data and antiarrhythmic drug usage (P > 0.05); (2) the effective ablation time for both left and right pulmonary veins in the pulsed field ablation group was markedly shorter compared to the radiofrequency ablation group (P < 0.001 for each vein); (3) within the pulsed field ablation group, the number of discharges, catheter operation time, and effective ablation time for the left pulmonary vein were significantly higher than those for the right pulmonary vein (P < 0.05). Conversely, in the radiofrequency ablation group, the number of discharges for the left pulmonary vein was significantly higher than that for the right pulmonary vein (P < 0.05); and (4) when comparing sinus rhythm maintenance at 1, 3, and 6 months postoperatively, no statistically significant differences were noted between the two groups for paroxysmal, persistent, and paroxysmal + persistent atrial fibrillation cases (P > 0.05).

CONCLUSION

During the 6-month follow-up period, pulsed field ablation demonstrated comparable efficacy to radiofrequency ablation with respect to recurrence rates for both paroxysmal and persistent atrial fibrillation. Moreover, pulsed field ablation exhibited high safety levels, excellent surgical efficiency, and a notably brief learning curve, affirming its viability as a therapeutic option for these conditions.