Catheter ablation remains a cornerstone in the treatment of ventricular tachycardia (VT) in structural heart disease. Part 1 of this review focused on the principles and technical aspects of radiofrequency (RF) ablation. Part 2 explores alternative strategies designed to overcome the limitations of conventional RF, in particular, achieving transmurality in complex or deep intramuscular substrates. We critically evaluate the mechanisms, evidence and clinical applications of bipolar RF ablation, pulsed-field ablation (PFA), ultra-low-temperature cryoablation (ULTC) and venous ethanol and needle ablation. Despite the rapid expansion of the technological armamentarium, current clinical evidence remains limited. The data supporting long-term safety and durability are predominantly based on preclinical and small observational studies. We advocate for continued investigation into these specialised techniques to provide a more tailored, patient-specific approach to VT management.

Catheter ablation is the primary treatment for ventricular tachycardia (VT) in patients with structural heart disease. Unfortunately, its long-term success remains limited. Although mapping techniques have advanced considerably, optimal ablation indices remain essential but less well defined. This two-part comprehensive review bridges the gap between bench and bedside by evaluating methods, technologies, and VT-specific lesion parameters. Here, in part 1, we critically examined conventional and emerging techniques, including radiofrequency (RF), high-power short-duration ablation, temperature-controlled RF. In the accompanying paper, part 2, we focus on bipolar RF ablation, pulsed field ablation and ultra-low-temperature cryoablation, venous ethanol and needle ablation. Despite the growing set of tools available for VT operators, clinical data on the practical and safe creation of lesions remain scarce. The evidence supporting most of the techniques reviewed is limited. We emphasise the need for personalised ablation strategies based on substrate and myocardial anatomy and advocate for the development of future integrated, metric-driven technologies.

AIMS:Accuracy data for non-invasive electrocardiographic imaging (ECGi) in defining the arrhythmogenic substrate for scar-dependent ventricular tachycardia (VT) is lacking. This study evaluated the accuracy of ECGi mapping to localize the arrhythmogenic substrate and assessed the relationship to myocardial scar, isthmus, exit, and successful ablation sites. METHODS AND RESULTS:A total of 48 VTs in 31 patients were mapped with both ECGi (View into Ventricular Onset, VIVO) and electro-anatomical maps (EAM) to define the arrhythmogenic substrate. Myocardial segments were assigned for the VT-exit site region (VT-ESR), isthmus region, successful ablation sites, and cardiac cross-sectional imaging defined scar using the ventricular AHA segment model and underwent blinded analysis.VT-ESR complete match (defined as exact AHA segment concordance between ECGi and EAM) was seen in 67% and partial match (defined as adjacent segments) in 21% of VTs. ECGi VT-ESR was located within or adjacent to cross-sectional imaging defined scar in 85% of VTs. The VT isthmus was within or adjacent to the ECGi VT-ESR in 77% of VTs. Successful ablation sites were within or adjacent to the ECGi VT-ESR in 82% of VTs. VIVO ECGi accuracy was not affected by cardiomyopathy type or VT cycle length. In identifying epicardial VT-ESR for ischaemic cardiomyopathy, VIVO ECGi had a sensitivity and specificity of 71.4% and 92.9%; for non-ischaemic cardiomyopathy 66.7% and 100%, respectively. CONCLUSION:ECGi mapping with VIVO can accurately predict the arrhythmogenic substrate for scar-dependent VT. Incorporation of ECGi mapping to conventional VT ablation workflows may improve procedural efficiency.

BACKGROUND:Functional extra-stimulus (ES) substrate mapping has been shown to reduce the recurrence of ventricular tachycardia (VT) compared with intrinsic rhythm mapping. However, there is no standardized approach to functional ES mapping. OBJECTIVES:This study investigated the accuracy of a range of functional ES mapping methods using S1 and S2 ES, evaluating multiple electrogram (EGM) components. METHODS:A multicenter, international VT ablation cohort was investigated. Offline annotation of stimulus artifact, first deflection, last deflection, and near-field (NF) EGM components enabled construction of 6 functional ES maps. Comprehensive accuracy testing was performed in identifying the critical arrhythmogenic substrate. RESULTS:Nineteen patients (mean age 61.1 ± 14.2 years; mean ejection fraction 31.7% ± 11.3%) were included. The EGM duration-based decremental evoked potential (DeEP) map had the highest area under the receiver-operating characteristic curve (0.804 ± 0.107; P < 0.001), with an optimal decrement threshold of 20 milliseconds (F1 score, P = 0.014) or 30 milliseconds (F1 score, P = 0.029). The inclusion of latency to EGM duration, assessed with a stimulus to the last deflection-based DeEP map, did not improve diagnostic performance (area under the receiver-operating characteristic curve 0.625 ± 0.173). Automated NF EGM annotation did not improve accuracy with or without the inclusion of latency. The EGM duration DeEP map exhibited superior accuracy across almost all left ventricular locations, providing higher precision in lateral/basal regions (Δ average precision, 0.24 ± 0.04; P < 0.001). CONCLUSIONS:Functional ES mapping using EGM duration prolongation DeEP maps yielded the highest accuracy in defining the arrhythmogenic substrate. The inclusion of latency or annotation of NF EGM components does not improve functional substrate mapping accuracy.

AIMS:A dual-energy ablation system was developed to optimize targeted energy delivery via a flexible-tip, contact-force sensing catheter with electroanatomic mapping integration. This is the first report of long-term safety and effectiveness results of this system for ablation of paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS:The FOCALFLEX study is a prospective, multicentre study. Patients with PAF were enrolled between August 2024 and January 2025, with 144 patients (62.0 ± 10.0 years, 62.6% male) undergoing ablation with the TactiFlex PFA System at 21 sites worldwide. Primary safety and effectiveness endpoints were the rate of pre-defined serious adverse events within 7 days and the 6-month freedom from documented AF/AFL/AT episodes >30 s after a 90-day blanking period.Pulmonary vein isolation (PVI) was performed in each case with pulsed field required for posterior left atrium (LA) ablation and radiofrequency (RF) for cavotricuspid isthmus or near coronary arteries. Non-PV targets and modality were at physician's discretion. Acute effectiveness was confirmed via entrance block and post-ablation LA voltage map after a 20-min waiting period and was achieved in 99.6% (566/568) of treated PVs with 95.5 ± 37.1 pulsed field ablation (PFA) applications/patients. Procedure, fluoroscopy, LA dwell, and PV ablation times were 112.2 ± 29.5, 7.6 ± 5.7, 81.1 ± 19.7, and 47.4 ± 16.4 min, respectively. There were two (1.4%) primary safety events. At 6 months, 81.0% of subjects were free from documented arrhythmia recurrence and the protocol-defined primary effectiveness rate was 79.6%. There was one repeat ablation (0.7%) after the blanking period through 6 months. CONCLUSION:The FOCALFLEX study results demonstrate safety and effectiveness of a novel dual-mode RF/PFA system through 6 months of follow-up to treat symptomatic, recurrent PAF. CLINICAL TRIAL REGISTRATION:ClinicalTrials.gov Identifier: NCT06271967.

Ventricular arrhythmias represent a diverse spectrum of cardiac rhythm disorders, ranging from clinically silent premature ventricular contractions (PVCs) to life-threatening events such as ventricular tachycardia and ventricular fibrillation. These arrhythmias are a primary driver of morbidity and remain a leading cause of sudden cardiac death across a variety of structural and inherited cardiac conditions. Clinical presentation varies significantly, encompassing incidental findings on routine screening, symptomatic palpitations, syncope, haemodynamic collapse or sudden cardiac arrest. A structured clinical approach is mandatory for effective management, requiring a detailed history, 12-lead electrocardiogram interpretation, ambulatory monitoring and advanced imaging, most notably cardiac magnetic resonance imaging, which is essential for substrate characterization. Management strategies are multifaceted, involving the correction of reversible triggers, optimization of heart failure therapy, antiarrhythmic medications, implantable cardioverter–defibrillators and catheter ablation.

Background: Cardiac sarcoidosis (CS) is associated with potentially serious complications, including heart failure and life-threatening arrhythmias. The diagnosis and management of CS is multifaceted, requiring a multi-disciplinary team (MDT)-based approach. A new regional CS clinical service was established in Sussex County (UK) in January 2025. This service is based on a core of cardiologists working with a wider MDT, including specialists in pulmonary sarcoidosis, nuclear medicine and cardiac electrophysiology. This study assessed the clinical performance of this new service. Methods: Patients with suspected CS referred to the Sussex CS Service between January and December 2025 were included, as compared to a control cohort of patients referred for CS assessment before the service was conceived. Results: Of the 51 CS service referrals, 13 patients fulfilled the Heart Rhythm Society (HRS) criteria, all of whom were correctly diagnosed with CS, whilst only two out of seven HRS-positive control patients were correctly diagnosed. In the 38 HRS-negative CS service referrals, 8 patients (21%) were still given a clinical CS diagnosis compared to none in the HRS-negative controls. Of the 21 patients diagnosed with CS, 7 (33%) had active myocardial inflammation and 8 (38%) had LV systolic dysfunction. Where indicated, immunosuppressive and heart failure therapies were initiated in all patients. Eight CS patients (38%) underwent implantable cardioverter defibrillator implantation. No deaths or heart failure hospitalisations occurred within the first 11 months. Conclusions: An MDT-based CS service model can provide multi-faceted care to patients, without major short-term adverse outcomes. The service model replicability and long-term outcomes require further assessment.

Background Current data are limited regarding how electrophysiologists are integrating emerging technologies and updated atrial fibrillation (AF) guidelines into clinical practice. Objective This survey aimed to analyze the periprocedural management of patients undergoing AF ablation across Europe. Methods An online-based questionnaire was conducted between September and November 2024. An additional set of questions was sent to all participants 6 months later. Results A total of 203 physicians from 23 European countries participated; 53% had > 10 years of experience as electrophysiologists, 58% worked in university hospitals, and 63% worked in centers performing more than 400 procedures annually. Preprocedural imaging is routinely used by 53%, with computed tomography being the most common modality (47.7%). General anesthesia is used by 42.4%, and 29.6% of physicians do not interrupt anticoagulants before the procedure. In paroxysmal AF ablation, pulmonary vein isolation is the main strategy (93%). Point-by-point radiofrequency (RF) was the predominant energy source (68%), with 65% of physicians performing RF adopting a high-power strategy (> 50 W). For persistent AF ablation, high-density mapping catheters are used by 82.8%, and 66.4% perform additional lesions beyond pulmonary vein isolation, most commonly targeting low-voltage areas and aiming at posterior wall isolation. Between the 2 phases of the survey, half of the physicians switched from RF or cryoballoon to pulsed field ablation. Intermittent use of 24-hour Holter is the primary strategy in 44.3% of cases for monitoring AF recurrence. Conclusion This survey highlights some discrepancies between the routine clinical practice of European physicians performing AF ablation and European guidelines, emphasizing the need for better integration of emerging technologies and greater adherence to updated protocols across Europe.