BACKGROUND:Electrocardiographic imaging (ECGI) enables noninvasive assessment of 3-dimensional activation and repolarization sequences. Whether ECGI allows to detect repolarization abnormalities in relation to myocardial scar and differentiate arrhythmogenic phenotypes has not been systematically investigated. OBJECTIVE:This study aimed to compare ECGI-derived activation time and activation-recovery interval (ARI) metrics in sinus rhythm in patients with structural heart disease (SHD) and evaluate their relationship to myocardial scar and ventricular tachycardia (VT) status. METHODS:Patients who underwent 252-electrode computed tomography-ECGI and delayed-enhancement magnetic resonance imaging were reviewed and categorized according to the presence of myocardial scar, left ventricular ejection fraction (LVEF), and history of reentrant VT. Reconstructed unipolar activation and repolarization maps and derived ARI maps were coregistered with 3-dimensional magnetic resonance imagin scar models. ARI duration, ARI dispersion, and activation time dispersion were estimated on ventricular and segmental levels and compared across groups and tissue types. RESULTS:71 patients were included: 39 patients with scar+/VT+ (28.3% ischemic, LVEF 41.2% ± 17.5%), 14 patients with scar+/VT- (37.5% ischemic, LVEF 33.3% ± 10.6%), 9 patients with impaired LVEF/VT- (LVEF 21.9% ± 5.6%), and 9 controls (LVEF 59.2% ± 7.1%). In sinus rhythm, ARI duration and dispersion differed significantly between groups and tissue types (all P < .05). Segmental ARI was longest over scar regions and dispersion higher in transmural (22.0 ms [IQR 26.3]) and subepicardial scar (20.6 ms [IQR 22.8]) than subendocardial scar (16.5 ms [IQR 16.1]) and non-scarred myocardium (15.8 ms [IQR 20.3]; P < .001). ARI dispersion within scar regions was significantly higher in the scar+/VT+ than the scar+/VT- cohort (β = -8.4 ms; P = .009). Activation dispersion was significantly increased at sites of scar compared with normal myocardium (β = -5.3 ms; P < .001) but showed only a trend toward distinguishing VT status (P = .059). Severe left ventricular dysfunction, even in the absence of overt myocardial scar, was also associated with significantly prolonged ARI and elevated dispersion metrics compared with controls. CONCLUSION:ECGI-derived ARI alterations in SHD are associated with scar presence, transmurality, and VT history. Segmental ARI dispersion in association with myocardial scar may potentially serve as a complementary non-invasive marker of arrhythmogenic risk.

AF can mediate left ventricular systolic dysfunction (LVSD) through a tachycardia-mediated cardiomyopathic process that may reverse with rate control alone. However, additional mechanisms contribute to AF-induced cardiomyopathy (AIC) that require rhythm control therapies. AIC can currently only be diagnosed retrospectively, as these component mechanisms are difficult to distinguish from each other and from other causes of LVSD prospectively. This narrative review considers the different potential mechanisms through which AF can impair ventricular function: rapid ventricular rate; irregularity of the ventricular rhythm; and impaired atrial contraction. How these features may exploit underlying structural vulnerability are considered and additional imaging-based parameters such as late gadolinium enhancement on cardiac MRI and contractile reserve during stress echocardiography are discussed. The limitations of existing parameters are discussed and a novel, non-parametric marker of ventricular rate with consideration of the inherent irregularity of AF - the Restitution Threshold Index (RTI) - is reviewed. Integrating RTI with these imaging-based measures may enhance clinical decision-making by more accurately identifying patients who would benefit from timely rhythm control. Further prospective validation is essential to develop accessible tools and an open-access RTI calculator has been made available (https://restitutionthreshold.com) to facilitate reproducibility and wider application.

Background Functional substrate mapping techniques are increasingly utilised in clinical practice but can involve protracted mapping and procedure time. Objective We incorporated magnetic resonance imaging (MRI) and computed tomography (CT) derived ventricular scar data into the functional mapping workflow to assess the efficacy and outcome compared to conventional ablation strategies. Methods In this prospective multicenter registry, 166 patients with post-infarct Ventricular Tachycardia (VT) were enrolled into a prospective propensity matched registry. Cardiac MRI/CT scans were performed to target focused regions for functional mapping and ablation (Sense2). This was compared to a group that underwent mapping without image guidance (Sense) and a group that underwent activation/entrainment or substrate guided mapping and ablation without functional mapping or image guidance (Institutional). Results In the Sense2 group (145.8±28.7 mins), the mean procedural time was significantly shorter compared to the Sense group (171.0±51.1 mins) and Institutional group (221.4±73.9 mins), (p<0.0001). Similarly, mapping time was shorter (25.4 ± 7.3mins) compared to Sense (47.2 ± 8.9). Ablation time was significantly reduced in the Sense2 (18.1±11.6 mins) compared to the Sense (21.6±12.7 mins) and to the Institutional (25.9±13.9 mins) (p=0.006). Patients in the Sense2 and Sense had higher freedom from VT (p<0.001 for both) and improved survival (p<0.05 for both) compared to Institutional group. Conclusion Sense2, integrating imaging with functional mapping, reduced the procedural times by enabling focused substrate maps to be performed and improved outcomes in terms of VT freedom compared to Institutional ablation. The improved survival requires corroborating with multi- centre randomized trials.

BACKGROUND:Patients undergoing catheter ablation (CA) for persistent atrial fibrillation (PsAF) experience high rates of AF recurrence. Direct current cardioversion (DCCV) is often performed prior to CA, with variable post-DCCV duration of sinus rhythm (SR). OBJECTIVE:We aimed to determine whether shorter SR duration after DCCV is associated with AF recurrence after subsequent CA. METHODS:We performed an international multicentre retrospective study of patients undergoing first-time CA for PsAF between 2015 and 2024 with a prior DCCV. SR duration after the last DCCV preceding CA was recorded. The primary outcome was freedom from atrial arrhythmia after CA (after a 56-day postablation blanking period). RESULTS:938 patients undergoing first-time CA for PsAF were identified from six centres and categorised by post-DCCV SR duration: <7 days (group 1, n=212); 7-31 days (group 2, n=236); and >31 days (group 3, n=490). Over median post-CA follow-up of 511 days, 512 patients (55%) experienced atrial arrhythmia recurrence. There was no significant between-group difference in freedom from atrial arrhythmia (log-rank p=0.10). When analysed as a continuous variable in a Cox regression model, there was no association between post-DCCV SR duration and time to first recurrence of atrial arrhythmia (HR per 10-day increment 1.00, 95% CI 1.00 to 1.01, p=0.07). In secondary analyses, there were significantly more blanking period arrhythmias in groups 1 and 2 compared with group 3 (both pairwise p<0.001), and presentation for CA in persistent atrial arrhythmia was associated with a time-dependent increased risk of atrial arrhythmia recurrence compared with presentation in SR. CONCLUSION:In this large multicentre cohort, shorter duration of SR after DCCV was associated with blanking period arrhythmia after subsequent CA, but we did not find evidence of an association with long-term AF recurrence. Clinicians should consider these findings when making decisions regarding suitability for CA or predicting long-term CA success.

BACKGROUND:Pulmonary vein isolation (PVI) using thermal energy may exert part of its antiarrhythmic effect via collateral injury to left atrial (LA) ganglionated plexi (GPs). Endocardial pulsed field ablation (PFA) is designed to be cardioselective, but its effect on human GP function is uncertain. OBJECTIVE:This study aimed to systematically evaluate the effect of endocardial PFA on LA GP activity. METHODS:In this prospective cohort study, consecutive patients with persistent atrial fibrillation undergoing first-time PFA were enrolled. Focal high-frequency stimulation during atrial fibrillation identified LA GP sites demonstrating atrioventricular delay (AVD) (AVD-GPs), defined as ≥50% RR prolongation or asystole during high-frequency stimulation. Wide antral PFA was delivered using a pentaspline catheter to achieve PVI with posterior wall ablation. Segments with AVD-GP sites overlying PFA lesions were retested, and active AVD-GP sites were subsequently targeted with radiofrequency (RF) ablation and reassessed. RESULTS:10 patients (age 61.9 ± 7.1 years; 3 female [30%]) were enrolled. At baseline, 118 of 591 sites tested (20.0%) met AVD-GP criteria (11.8 ± 7.8 per patient), including 23 (19.5%) at pulmonary vein ostia. Transient AVD occurred during PFA application in 4 of 10 patients (40%). After PFA, 16 of 21 segments (2.0 ± 1.1 segments/patient) with AVD-GP sites overlying PFA-treated regions demonstrated persistent AVD response. After targeted RF ablation, no previously active AVD-GP sites showed AVD response. CONCLUSION:Endocardial PFA does not consistently abolish LA GP function despite lesion delivery at overlapping sites. RF ablation reliably eliminates GP-mediated AVD. These findings support the cardioselective nature of PFA and provide a mechanistic rationale for the prospective evaluation of adjunctive GP ablation following PFA-based PVI strategies.

Background Characterising mid-myocardial substrate during ventricular tachycardia (VT) ablation is challenging. Objective We evaluated how electrode spacing, multipolar signal annotation, and functional mapping affect the identification of conduction delay over endocardial and mid-myocardial substrate. Methods 18 patients with ischaemic cardiomyopathy underwent VT ablation with co-registered MRI scar models. Substrate was mapped in sinus rhythm (SR) and after a single sensed extra-stimulus (SE) from the right ventricle. Twelve patients (bipolar [BP] group) were mapped with both short-spline (Oct-S) and long-spline (Oct-L) Octaray catheters. Six patients (multipolar [MP] group) were mapped with both Oct-S and the OPTRELL catheter (OPT). Points within 1cm geodesic distance of MRI conduction corridors were analysed for late potentials (LPs), conduction velocity (CV), and anisotropic ratio (AR). Results Over endocardial substrate, SE mapping increased LP density versus SR for all catheters (Oct-L 6→14%, Oct-S 1→32%, OPT 21→45%; p<0.001). MP annotation identified more LPs than BP over endocardial (27% vs 9%, p<0.001) and mid-myocardial (41% vs 12%, p<0.001) corridors. With BP annotation, median LAT and CV were similar when stratified by corridor depth (p>0.1). With MP annotation, LAT delayed 12 ms per 10% increase in depth in SR and by 7 ms with SE (p<0.001), and CV slowed over mid-myocardial corridors (18cm/s vs 39cm/s, p<0.001). Substrate-adjacent conduction vector heterogeneity was greatest with functional MP mapping (AR: 0.59) and smallest with SR BP mapping (AR: 0.76, p<0.001). Conclusion Functional mapping improved identification of delayed conduction for all catheters, and MP annotation enhanced the delineation of intramural conduction corridors via the endocardial surface.

ICDs are implanted to treat sudden arrhythmic death by treating episodes of ventricular arrhythmia (VA). Despite this primary function, patients can still die with a functioning ICD due to untreated VA. The purpose of this review is to examine the causes and implications of ICD failures in detection and therapy delivery during VA and assess post-mortem interrogation practices and literature. The literature, adverse event reports, and the authors’ own internal data were reviewed to identify causes of ICD non-therapy. Signal-related, functional, algorithmic and myocardial undersensing were identified as contributors, along with episodes of failed defibrillation/cardioversion. Contemporary ICD programming prioritises specificity but may compromise sensitivity. Post-mortem interrogation is rare, under-utilised and has no standardisation, despite reports of ICD failure being the cause of death in up to 25% of cases. To conclude, failure to interrogate ICDs after death risks missing fatal undersensing. Systematic post-mortem analysis is proposed as the cardiac equivalent of aviation’s black box, which is critical for learning and sudden arrhythmic death prevention.

BACKGROUND:Conventional follow-up after atrial fibrillation (AF) catheter ablation relies on physician-led interval monitoring and often fails to characterize paroxysmal symptoms. An increasing number of patients use smartwatch-based ECG devices for rhythm monitoring, but their structured integration into clinical workflows and the handling of the resultant data are not well described. OBJECTIVES:To describe the design, operationalization, data pipeline, and user engagement of a patient-led smartwatch ECG follow-up strategy after AF ablation within a randomized clinical trial. METHODS:A prospective, randomized controlled trial of adults undergoing first-time AF ablation was conducted. Participants were randomized to an Apple Watch-based protocol (daily and symptom-triggered ECGs) or standard follow-up. A prespecified audit of the smartwatch-derived rhythm classification was conducted. User engagement, symptom annotation, and downstream resource use were quantified. Primary clinical outcomes are reported in a companion Brief Report. RESULTS:Of the 168 enrolled participants (mean age 60.5 ± 9.9 years, 52 (31.0%) female, 84 (50.0%) persistent AF), Active-arm participants recorded a median of 170 (IQR 93-380) ECGs over 12 months and transmitted a median of 1.9% (0.0-8.3) for review. Symptom-annotated ECGs were more likely to show AF compared with unannotated ECGs (OR 16.1, 95% CI 13.0-19.9, P < 0.001) Watch-derived AF and sinus rhythm labels had positive predictive values of 0.96 and 0.95 respectively, although one-third of ECGs were unclassified. CONCLUSIONS:A structured, patient-led smartwatch ECG workflow can be embedded into routine post-ablation care with high engagement, modest staff workload, and accurate device-level rhythm classification. This implementation framework provides a practical template for integrating patient-generated wearable data into AF follow-up pathways and future digitally enabled trials.

BACKGROUND:Atrial fibrillation (AF) significantly affects patients' health-related quality of life (HRQoL), influencing physical, psychological, and social wellbeing. Despite existing tools, there is a notable lack of AF-specific instruments that comprehensively assess HRQoL and are developed in collaboration with patients from the outset. OBJECTIVE:This study aimed to develop and validate the AF specific Patient Reported Outcome Measures questionnaire (AF-PROMs), a novel, patient-centered tool designed to measure HRQoL in patients with AF. METHODS:A prospective, observational study was conducted across 2 centers in the United Kingdom, enrolling 856 participants (265 in the pilot phase, 550 in the field-validation phase). Item generation and domain selection were guided by extensive patient and public involvement (PPI), through focus groups and qualitative interviews with patients, ensuring content validity. Psychometric evaluations included exploratory (EFA) and confirmatory factor analyses (CFA), along with assessments of reliability, responsiveness, and known-group validity. RESULTS:The AF-PROMs tool demonstrated excellent internal consistency across all domains (Cronbach's alpha ≥0.89) and strong test-retest reliability (intraclass correlation coefficient [ICC] >0.97), highlighting its stability. The tool showed robust responsiveness to clinical changes, particularly post-catheter ablation, with moderate to large effect sizes (Cohen's d ≥1.0 for overall score), underscoring its sensitivity to meaningful treatment effects. The 3-factor model achieved a satisfactory fit. Known-group validity was confirmed by significant score differences (P < .01) between healthy volunteers and patients with AF across all domains. CONCLUSION:AF-PROMs is a validated, patient-centered instrument, developed with the largest participant group to date, offering a comprehensive assessment of HRQoL in patients with AF. Its unique strengths include extensive patient involvement, high reliability, and sensitivity to clinical interventions, making it a valuable tool for both clinical practice and research in enhancing the measurement of HRQoL in AF.

BACKGROUND:The sympathetic autonomic nervous system plays a major role in arrhythmia development and maintenance. Historical preclinical studies describe preferential increases in cardiac sympathetic tone upon selective stimulation of the subclavian ansae (SA), a nerve cord encircling the subclavian artery. OBJECTIVES:This study sought to define, for the first time, the functional anatomy and physiology of the SA in humans using a percutaneous approach. METHODS:The authors prospectively recruited patients undergoing catheter ablation for paroxysmal atrial fibrillation (AF) under general anesthesia. SA stimulation (SAS) was performed on the left and/or the right (L/SAS and/or R/SAS, respectively) within the subclavian artery using an ablation catheter introduced via a femoral arterial sheath. Stimulation involved up to 70 V, 10 Hz, and a 2- to 4-millisecond pulse width for 15 to 30 seconds. Invasive blood pressure (BP), heart rate, and electrophysiological parameters were recorded. A positive response was a ≥10% increase in BP or heart rate from baseline. RESULTS:Seventeen patients (median age 60 years [Q1-Q3: 58-67 years];11 male subjects; paroxysmal AF duration 24 months [Q1-Q3: 10-60 months) underwent the stimulation protocol before their clinical AF ablation procedure. A positive hemodynamic response was observed in 11 patients; of these, arrhythmia was inducible in 5 patients. The median sinus cycle length decreased after stimulation, and there was a larger decrease with R/SAS (L/SAS 1,008 milliseconds to 926 milliseconds [P = 0.037] vs R/SAS 1,029.5 milliseconds to 917 milliseconds [P = 0.005]). Both L/SAS and R/SAS led to a notable increase in median systolic BP (L/SAS 81 to 128 mm Hg [P = 0.005] vs R/SAS 85 to 104 mm Hg [P = 0.007]) and a similar trend in diastolic BP. In addition, there was a demonstrable decrease in interatrial conduction time and increase in P-wave dispersion. CONCLUSIONS:This study represents the first successful application of selective SAS in humans. The SA is a potentially important site for targeted autonomic neuromodulation therapy.

AIMS:Persistent atrial fibrillation (AF) ablation success rates remain limited. The aim was to evaluate the impact of ganglionated plexi (GP) ablation on AF mechanisms and outcomes in patients with low scar burden. METHODS AND RESULTS:Patients undergoing persistent AF ablation were included. Patients that had <30% low voltage zones (LVZs) in the left atrium underwent pulmonary vein isolation and GP ablation. Dominant frequency (DF), coronary sinus (CS) electrogram characteristics, and AF inducibility score were assessed pre- and post-GP ablation. Ganglionated plexi ablation response was determined. One hundred twenty patients were included, of which 84 (70.0%) patients had <30% LVZs and underwent GP ablation. An ablation response was seen in all patients [AF termination (66.7%) and CL slowing of ≥30 ms (33.3%)]. The average DF, CS cycle length variability (CLV), and CS activation pattern stability (APS) pre-GP ablation were predictive of AF termination. Ganglionated plexi ablation resulted in a significant change in the DF (6.3 ± 1.2 Hz pre-GP ablation vs. 5.1 ± 1.0 Hz; P < 0.001), CS CLV (40.2 ± 6.5 ms vs. 28.2 ± 6.8%; P < 0.001), and CS APS (25.2 ± 5.8% vs. 35.2 ± 6.5%; P < 0.001). Atrial fibrillation inducibility was harder post-GP ablation than pre-GP ablation (3.8 ± 1.2 AF inducibility score pre-ablation vs. 1.3 ± 1.8 AF inducibility score post-ablation; P < 0.001). Seventy-eight out of the 84 (92.9%) patients were free from AF/atrial tachycardia (AT) off anti-arrhythmic drugs at 12-months. CONCLUSION:Ganglionated plexi ablation results in a mechanistic impact in AF with an ablation response, changes in DF, CS electrogram characteristics, and AF inducibility score. Pulmonary vein isolation and GP ablation in patients with minimal LVZs results in a high freedom from AF/AT.

BACKGROUND:Catheter ablation for atrial fibrillation (AF) in left ventricular systolic dysfunction (LVSD) improves outcomes, yet left ventricular ejection fraction (LVEF) response is difficult to prospectively predict. OBJECTIVE:This study aimed to identify preprocedural predictors of LVEF response after AF ablation in patients with LVSD and develop a pragmatic score to stratify patients. METHODS:This multicenter cohort study included patients with AF and an LVEF of <50% undergoing index ablation. The primary endpoint was responder status defined as ≥10% increase in LVEF or improvement to ≥50% on follow-up echocardiography after the final ablation. Multivariable logistic regression modeling, stratified by follow-up rhythm, was used to identify predictors and derive a simplified scoring tool. RESULTS:Among 366 patients (aged 64.4 ± 10.6 years; 82% male), 70.8% were left ventricular responders at follow-up. Predictors of nonresponse in the sinus rhythm subgroup included heart failure etiology, QRS duration of >105 ms, paroxysmal AF, and type 2 diabetes. These were incorporated into the PACED score, which stratified response (score <2, 87% probability of response; score ≥3, 71% of nonresponse) with good discrimination (c-statistic 0.83; 95% confidence interval 0.77-0.89). In the largest contemporary multicenter cardiac magnetic resonance subcohort, late gadolinium enhancement was more frequent among nonresponders (84.6% vs 53.6%; P < .001). Guideline-directed medical therapy at baseline was not independently associated with recovery. CONCLUSION:LVEF response post-AF ablation in patients with LVSD can be accurately predicted precatheter ablation with a bedside score. Left ventricular response depends primarily on substrate and conduction characteristics rather than pharmacotherapy in a guideline-directed medical therapy-optimized cohort. Late gadolinium enhancement on cardiac magnetic resonance is associated with an increased chance of being a nonresponder to ablation.