Seiji Fukamizu

Background: Pulsed field ablation (PFA) has emerged as a novel non-thermal ablation modality with preferential myocardial selectivity. However, its effects on adjacent structures, including the sinus node and its arterial supply, remain incompletely understood. Case summary: A 72-year-old woman underwent repeat ablation for recurrent paroxysmal atrial fibrillation. Following pulmonary vein isolation, superior vena cava (SVC) isolation was performed using a PFA system. Sinus rhythm was initially preserved. However, sinus arrest developed several minutes after ablation. High right atrial backup pacing was initiated. Coronary angiography revealed severe spasm of the sinus node artery. Sinus node function gradually recovered after supportive management. Post-procedural voltage mapping confirmed successful SVC isolation. Discussion: This case highlights delayed sinus arrest following SVC isolation using PFA, with angiographic evidence suggesting sinus node artery spasm. While multiple mechanisms may contribute to sinus node dysfunction after PFA, coronary vasospasm should be considered, particularly in cases with delayed onset.

Background: The subcutaneous implantable cardioverter‐defibrillator (S‐ICD) avoids transvenous leads and is a promising option for sudden cardiac death (SCD) prevention in pediatric patients. However, mid‐term outcomes and post‐shock management strategies remain insufficiently characterized. Methods: This multicenter, retrospective observational study included pediatric patients (≤ 18 years) who underwent S‐ICD implantation between February 2016 and July 2021. Clinical characteristics, pre‐implant screening, procedural details, device‐related events, and follow‐up data were analyzed. The incidence and management of appropriate and inappropriate therapies and subsequent recurrence were evaluated. Results: Ninety‐six patients (median age 14.5 years) were enrolled and followed for a median of 70 months (29–75.0 months). Sensing vector suitability remained stable despite somatic growth. Appropriate shocks occurred in 32 patients (33.7%), while inappropriate shocks occurred in 27 (28.4%). After appropriate therapy, intensified pharmacological treatment and catheter ablation prevented recurrent device therapy in 45.5% and 50.0% of cases, respectively, although device shock occurred in 50.9% despite intervention. Following inappropriate therapy, device reprogramming and lifestyle guidance prevented recurrence in 71.4% of patients (15/21). Device‐related infection was rare (2 cases), and no lead fractures were observed. Conclusions: S‐ICD therapy demonstrated favorable mid‐term safety and efficacy in pediatric patients, with durable sensing performance and a low incidence of device‐related infection. Although inappropriate shocks were not uncommon, appropriate post‐shock management effectively reduced recurrence, supporting S‐ICD as a viable option for selected pediatric patients without pacing requirements.

Although slow pathway ablation is an established curative therapy for typical atrioventricular nodal reentrant tachycardia (AVNRT), lesion delivery is constrained by the anatomical proximity to the His bundle, limiting the procedural safety margin. Peak frequency mapping (PFM) is a novel physiology-based method that highlights regions of the slow pathway-related electrograms and may enable safer ablation at more annular sites. To evaluate the reproducibility, procedural safety, and clinical efficacy of PFM-guided slow pathway ablation compared with the conventional anatomical approach. Eighty-one consecutive patients with typical AVNRT were analyzed (39 conventional, 42 PFM-guided). Procedural characteristics, acute success, safety outcomes, and mid-term recurrence were assessed. PFM consistently localized the slow pathway around the 4-5 o'clock region of the tricuspid annulus and enabled effective ablation at significantly greater distances from the His bundle (22.8 ± 5.5 vs. 11.5 ± 3.2 mm, p < 0.0001). Acute success was achieved in all PFM-guided cases and in 97.4% of conventional cases. PFM-guided ablation required fewer RF applications and demonstrated earlier and slower junctional rhythm during energy delivery. During a mean follow-up of 822 ± 362 days, recurrence occurred in 2 conventional patients (5.1%) but in none of the PFM-guided patients. PFM-guided slow pathway ablation enables lesion delivery at annular sites farther from the His bundle while maintaining acute success and mid-term efficacy. By facilitating ablation at sites more distant from the His bundle, this physiology-based strategy may provide a wider procedural safety margin and represents a reproducible refinement of conventional AVNRT ablation.

Aims: The superior vena cava (SVC) is a frequent non‐pulmonary vein trigger in atrial fibrillation (AF). Adjunctive SVC isolation (SVCi) may reduce AF recurrence; however, radiofrequency (RF) ablation carries risks such as phrenic nerve palsy (PNP) and sinus node dysfunction (SND). Pulsed field ablation (PFA) offers myocardial selectivity, but clinical data using a circular PFA catheter guided by spontaneous block lines remain limited. Methods and Results: This single‐centre retrospective study included 85 patients who underwent adjunctive SVCi (RF n = 45, PFA n = 40). RF ablations were performed from August 2023 to December 2024, and PFA was introduced in January 2025. Spontaneous block lines were identified using the EnSite X mapping system and incorporated into ablation planning. SVC isolation was achieved in all patients. First‐pass success was higher with PFA (97.5% vs. 84.4%, p = 0.06). PFA required fewer applications (4.4 ± 2.4 vs. 14.2 ± 6.3, p < 0.01) and a shorter procedural duration (368 ± 350 vs. 847 ± 656 s, p < 0.01), with similar isolation area (14.0 ± 6.9 vs. 14.2 ± 6.3 cm², p = 0.42). Transient PNP occurred in one PFA case and none with RF. Transient SND occurred in four PFA and two RF cases; all resolved spontaneously, and no persistent complications were observed. During follow‐up, atrial fibrillation recurrence rates were low and comparable between groups (7.5% vs. 8.9%, p = 0.81). Among patients undergoing repeat ablation, SVC reconnection was infrequent. Conclusions: Wide‐area SVCi using a circular PFA catheter guided by spontaneous block lines is feasible and efficient. PFA reduced procedure time and ablation burden while maintaining comparable efficacy and low complication rates. This strategy provides an anatomically rational, reproducible approach for adjunctive SVCi in AF ablation workflows.

Aims: Catheter ablation for premature ventricular contractions (PVCs) triggering ventricular fibrillation (VF) after acute myocardial infarction (AMI) has proven effective, with Purkinje potentials often serving as the target. However, the electrophysiological features of Purkinje potentials and their relationship with the conduction system in VF-triggering PVCs remain unclear. Methods: This multicentre retrospective study analysed patients who underwent catheter ablation for VF-triggering PVCs during the acute or subacute phase of AMI. Characteristics of Purkinje potentials, including retrograde conduction from the Purkinje network and subsequent anterograde conduction to the right bundle branch (RB), were evaluated for PVC morphology. Results: Fifty-three patients (mean age 66±11 years; 13% female) with 67 VF-triggering PVCs were analysed. The mean PVC width was 157 ± 42 ms, with 87% showing RB branch block morphology. Purkinje potentials preceded 72% of PVCs (mean interval 68 ± 42 ms). PVCs with preceding Purkinje potentials had narrower QRS duration (145 ± 26 ms vs. 198 ± 57 ms, P < 0.0001). The coupling interval from the preceding sinus beat was inversely correlated with the interval from Purkinje potential to PVC onset (P < 0.0001). Retrograde Purkinje conduction with subsequent anterograde RB conduction was identified in 9%. In these cases, the coupling interval from the preceding sinus beat was longer (391 ± 12 ms vs. 467 ± 34 ms, P = 0.041). Conclusion: Purkinje potentials show distinct properties that influence both QRS duration and PVC timing. The presence of preceding Purkinje potentials together with QRS duration may help guide ablation strategies. In rare cases, Purkinje activity conducts retrogradely from the left bundle and anterogradely through the RB, modifying PVC morphology.

Background: Superior vena cava (SVC)–right atrium (RA) spontaneous conduction block occurs in some patients. We demonstrated a novel approach for SVC isolation using visualization of the SVC–RA conduction block line as a white line with the extended early meets‐late (EEML) tool of the CARTO system. The long‐term durability of SVC isolation using white line has not been investigated. Methods: Overall, 200 patients who underwent SVC isolation as atrial fibrillation therapy or additional procedures between May 2015 and April 2024 were included. We created an activation map of sinus rhythm, adjusted the EEML settings, and confirmed the white line. In the presence of a white line, we performed SVC isolation using the white line (block group); in its absence, we conducted encircling SVC isolation (nonblock group). If additional procedures were needed at follow‐up, repeat sessions were performed to identify the treatment targets, and SVC–RA mapping was performed. SVC–RA block line durability was defined as the SVC isolated area by voltage map at the additional session, including the white line of the first session. The SVC reconduction number between the two groups was compared, and SVC–RA spontaneous block line durability was confirmed in the block group. Results: Thirty‐one of 200 patients underwent additional procedures and follow‐up SVC–RA mapping. The chronic SVC reconduction ratio did not differ significantly between the two groups. SVC–RA spontaneous block line durability was maintained in all patients in the block line group (block group 12/12 [100%]). Conclusion: SVC–RA spontaneous block visualized by using the white‐line approach of EEML tools had durability in the chronic phase.

Aims: Catheter ablation (CA) of idiopathic ventricular arrhythmias (VAs) from the epicardial left ventricular summit is challenging. The endocardial approach targets two sites: the endocardial closest site (ECS) to the epicardial earliest activation site (epi-EAS) and the endocardial earliest activation site (endo-EAS). We aimed to differentiate between cases where CA at the ECS was effective and where CA at the endo-EAS yielded success. Methods and results: Fifty-eight patients (47 men; age 60 ± 13 years) were analysed with VAs in which the EAS was observed in the coronary venous system (CVS). Overall, VAs were successfully eliminated in 42 (72%) patients: 8 in the CVS, 8 where the ECS matched with the endo-EAS, 11 at the ECS, and 15 at the endo-EAS. A successful ECS ablation was associated with a shorter epi-EAS–ECS distance (10.2 ± 4.7 vs. 18.8 ± 5.3 mm; P < 0.001) and shorter epi-EAS–left main coronary trunk (LMT) ostial distance (20.3 ± 7.6 vs. 30.3 ± 8.4 mm; P = 0.005), with optimal cut-off values of ≤12.6 and ≤24.0 mm, respectively. A successful endo-EAS ablation was associated with an earlier electrogram at the endo-EAS [23 (8, 36) vs. 15 (0, 19) ms preceding the QRS; P < 0.001] and shorter epi-EAS–endo-EAS interval [6 (1, 8) vs. 22 (12, 25) ms; P < 0.001], with optimal cut-off values of ≥18 and ≤9 ms, respectively. Conclusion: Shorter anatomical distances between the epi-EAS and ECS, and between the epi-EAS and LMT ostium, predict a successful ECS ablation. The prematurity of the endo-EAS electrogram and a shorter interval between the epi-EAS and endo-EAS predicted a successful endo-EAS ablation.