Abstract Background The Variable-Loop Circular Catheter (VLCC) is a bidirectional multi-electrode catheter capable of electroanatomical mapping and pulsed field energy delivery for the treatment of atrial fibrillation (AF). Objective to compare Grid projected annotation (GRID) versus projected Ablation tags (ABLt) in predicting lesion area coverage for Pulmonary Vein Isolation (PVI) with VLCC. Methods Consecutive AF patients undergoing PVI with VLCC were prospectively enrolled in our centre between April 2024 and October 2025. Ablation area was visualized using projected 1 mm³ grid points (GRID) or 2 mm projected ablation tags (ABLt) corresponding to each electrode of the VLCC for every ablation. Bipolar voltage maps were performed with VLCC to quantify the lesion areas per PV segment (10-segment model) after PVI. Anatomical maps with GRID or ABLt annotation without voltage data were used to calculate predicted lesion area. The predictive capability of GRID/ABLt was calculated using the formula GRID or ABLt Area in Low Voltage Area/ Total Low Voltage Area and expressed as a percentage. Results We enrolled 65 patients (64.5 ± 9.5 years, 55.4% males, 15.3% Persistent AF) and a total of 258 PVs. All patients underwent PVI. Median procedural time was 58 min (45-75), dwelling time 30 min (25-50) and fluoroscopy time 4 min (3-7). GRID and ABLt annotation were consistent with PV lesion area resulting in a Pearson’s correlation coefficient of 0.91 (p < 0.0001) and 0.82 (p < 0.0001), respectively. GRID showed a higher predictive capability of overall PV lesion area compared to ABLt (95.8% vs 77.6%; p<0.0001) and also for all PV segments (p<0.01) (Figure 1). GRID annotation demonstrated a lower bias (0.031) and narrow limits of concordance (0.421- -0.344) compared to ABLt demonstrated a higher bias (-0.33) and larger limits of concordance (0.356 - −1.016). Conclusions GRID showed a higher predictive capability of PV lesion area compared to ABLt

Pulsed field ablation (PFA) uses high-intensity electric fields to create myocardial lesions and may potentially interact with cardiac implantable electronic devices (CIEDs). This multicenter study evaluated the effects of different PFA technologies on electrical integrity and device-related complications in patients undergoing left- and right-sided atrial ablation. Consecutive patients with CIEDs undergoing catheter ablation with 4 PFA technologies were included. CIED interrogation was performed at baseline, after ablation, and at ≥ 3-month follow-up. Study endpoints were electrical integrity, defined as changes in sensing, pacing threshold, or impedance, and clinically relevant PFA-related CIED malfunction. Real-time device monitoring was performed in a subgroup to assess electromagnetic interference (EMI). A total of 157 patients were included. PFA was performed using a pentaspline catheter in 110 patients, a lattice-tip catheter in 26, a variable-loop circular catheter in 16, and a circular array catheter in 5. No significant changes in lead parameters were observed immediately after ablation or at 3-month follow-up, including in patients undergoing right atrial PFA. PFA was frequently associated with EMI-related oversensing (93

BACKGROUND:In vivo electroanatomic mapping has enabled functional characterization of the human sinoatrial node (SAN), yet precise localization of SAN exit zones (SAN-EZs) and preferential conduction pathways-particularly along the Bachmann bundle (BB)-remains challenging without direct anatomic validation. OBJECTIVE:This study aimed to establish a translational framework integrating human in vivo peak frequency (PF) mapping with preclinical anatomic and histologic validation of the SAN-BB conduction axis. METHODS:High-density endocardial electroanatomic mapping with PF analysis was performed in patients with inappropriate sinus tachycardia, sick sinus syndrome, and normal SAN function. Emphasis maps combining local activation time and PF were used to identify the SAN-EZ and preferential conduction pathways. To address anatomy, complementary preclinical studies were performed using contrast-enhanced micro-computed tomography, 3-dimensional reconstruction, and histology of donor human hearts, focusing on BB microstructure, insertion sites, and myocyte orientation. Frequency analysis was additionally applied to preclinical hearts to compare the BB with the surrounding right atrial myocardium. RESULTS:In vivo PF mapping reliably identified the SAN-EZ and preferential conduction pathways using a 350-450 Hz frequency band. Patients with sick sinus syndrome exhibited reduced SAN-EZ overlap and fewer superior and septal pathways. Preclinical micro-computed tomography and histology in cadaveric human hearts confirmed the anatomic substrate underlying septal conduction. Frequency analysis of swine hearts revealed higher dominant frequencies within the BB than adjacent right atrial myocardium, supporting in vivo findings. CONCLUSION:By integrating human functional mapping with preclinical anatomic and histologic validation, this study provides a translational framework for PF-based identification of the SAN-EZ and BB-mediated conduction.

BACKGROUND:Reversible pulsed field ablation (PFREV) can temporarily block cardiomyocyte conduction, potentially identifying critical target sites before creating definitive lesions. However, PFREV local capture might interfere with the tachycardia mechanism. The aim of the study was to characterize the responses of nontriggered PFREV pulses to serve as a novel clinical mapping tool in reentrant atrial flutter. METHODS:PFREV pulses were delivered in and outside of the circuit using a 9-mm lattice-tip catheter in 30 reentrant atrial tachycardias in 26 patients. The presence of local capture and responses to PFREV pulses was characterized. RESULTS:Out of 163 PFREV pulses analyzed, 56 (34.4%) showed atrial capture and propagation. Propagated versus Nonpropagated PFREV cohorts were compared. The coupling interval of propagated PFREV pulses was significantly longer (195.3±69.2 msec versus 98.9±77.2 msec; P<0.001). Globally, 4 responses were observed: tachycardia termination (11.0%), stable tachycardia cycle length (TCL) prolongation (9.8%), transient irregular TCL variations (3.1%), and no change in activation sequence and TCL (76.1%). Propagation was only associated with irregular TCL variations (8.9% versus 0%, P=0.002). Tachycardia termination or TCL prolongation occurred only when PFREV was delivered in the reentry circuit (100% specificity). Termination occurred exclusively in the critical isthmus (100% specificity regardless of propagation), and stable TCL prolongation occurred in 93.8% and 6.2% of the cases in the isthmus and outer loop, respectively (100% specificity for nonpropagated and 83.3% specificity for propagated PFREV to localize the isthmus). Sensitivity of termination or stable TCL prolongation for identifying the critical isthmus was moderate (38.8%) and influenced by isthmus width (11.7±1.7 mm versus 22.9±2.1 mm; P<0.001). Reproducibility of PFREV pulses, determined by consecutive pulses delivered at the same site producing identical responses, was high (82.9%). CONCLUSIONS:PFREV mapping is a novel, feasible, and reproducible tool for identifying critical sites in reentrant atrial tachycardia with narrow isthmuses that may be improved through optimized triggering and dose titration.

Physiological pacing of the atrium, specifically targeting the Bachmann bundle area (BBA), has been associated with improved interatrial conduction and reduced atrial arrhythmia risk. The Bachmann bundle (BB) is the principal interatrial conduction tract, yet its electrophysiological definition in humans remains incompletely characterized. This study aimed to describe the electrogram features of the BBA using 3D electroanatomical-mapping (EAM) with peak-frequency (PF) analysis during atrial lead implantation. All patients undergoing dual-chamber pacemaker implantation with the atrial lead positioned in the BBA were included. Right atrial mapping was performed using either a quadripolar or the HD Grid catheter. PF maps were created and PFs at the targeted site were measured before and after lead positioning. Procedural parameters, P-wave duration (PWD) and pacing thresholds were analyzed. Twelve consecutive patients undergoing dual-chamber pacemaker implantation with the atrial lead positioned in the (BBA) were prospectively studied. The optimal PF band for BBA localization was 400–500 Hz (AUC = 0.83, sensitivity 87

Background:In patients with symptomatic permanent atrial fibrillation (AF) who are not candidates for rhythm control, atrioventricular node (AVN) ablation followed by ventricular pacing "ablate-and-pace" offers reliable rate control and symptom relief. Conventional transvenous systems are effective but associated with lead- and pocket-related complications. Leadless pacemakers represent a promising alternative, yet comparative data in this setting remain scarce. The aim is to compare clinical outcomes of leadless vs. transvenous single-chamber pacemakers in patients undergoing AVN ablation for permanent AF. Methods:We conducted a retrospective, multicenter study (LEAD-AP) of 168 consecutive patients undergoing ablate-and-pace between 2,017 and 2024 across four European centers. Patients received either a leadless pacemaker (n = 56) or a conventional transvenous VVI pacemaker (n = 112). The primary efficacy endpoint was the composite of all-cause mortality, cardiovascular mortality, AF-related hospitalizations, unplanned visits and device-related hospitalizations or reinterventions. The secondary efficacy endpoint was device-related hospitalizations or reinterventions. The primary safety endpoint was acute complications within 30 days. Results:Patients in the leadless group more frequently underwent a single-step ablate-and-pace strategy (96.4% vs. 10.9%, p < 0.001), resulting in shorter hospitalization (1.1 days ± 3.1 vs. 5.7 days ± 2.2, p = 0.008). At 24 months of follow-up, there was no statistically significant difference between patients with leadless pacemaker vs. standard single-chamber VVI pacemaker in the event-free survival for the clinical efficacy endpoint (82.1% vs. 80.4% Log-Rank p = 0.29). Conclusions:Leadless pacemakers provide comparable safety and efficacy to transvenous systems in ablate-and-pace patients, while enabling shorter hospitalization through a streamlined single-step approach.

BACKGROUND:Understanding the mechanisms and anatomical substrates underlying postablation atrial tachycardia (AT) is essential for guiding targeted mapping and successful re-ablation strategies. OBJECTIVE:This study analyzed patients referred for repeat ablation for AT after first-time atrial fibrillation ablation with a pentaspline pulsed field ablation (PFA) catheter. METHODS:High-density electroanatomical mapping was performed to identify the mechanism of post-PFA ATs and assess lesion durability. Re-entrant circuits were analyzed according to the principles of topology (paired rotations, identification of critical boundaries, and ablation strategies). RESULTS:Among 4,144 patients, 236 underwent repeat ablation (160 for atrial fibrillation [3.9%] and 76 for AT [1.8%]), and this constituted the final cohort. A total of 87 ATs were mapped: 21 in the right atrium (4 focal and 17 peri-tricuspid valve re-entry) and 66 in the left atrium (1 focal and 65 re-entry). Pulmonary vein and posterior wall isolation durability were 84% and 89%, respectively. Left atrial (LA) re-entry mechanisms comprised single-loop (n = 9) and predominantly dual-loop (n = 56) re-entry, including circuits defined by anatomical boundaries (n = 32) or involving an anterior scar (n = 24). In all cases of LA re-entrant AT, sinus rhythm was restored when ablation connected the 2 critical boundaries. Topological principles accurately explained the observed activation patterns and responses to ablation. CONCLUSIONS:The incidence of repeat ablation for AT after pentaspline PFA was low, likely reflecting the high durability of the index lesion sets. Most post-PFA ATs manifested as dual-loop LA re-entry. Retrospective application of the topological framework provided coherent mechanistic interpretations of AT behavior and accurately predicted the response to direct and indirect critical boundary-targeted ablation.

Background:We conducted a multicenter study to compare procedural and 1-year outcomes of pulmonary vein isolation (PVI) using lattice-tip (LT) vs pentaspline (PS) pulsed field ablation catheters in patients with paroxysmal atrial fibrillation. Objective:This study aimed to compare procedural metrics and arrhythmia-free survival during the 1-year follow-up. Methods:Procedures were performed between August 2023 and December 2024. A propensity score matching technique was adopted (LT-to-PS ratio 1:2). Results:Among 447 patients with paroxysmal atrial fibrillation undergoing first-time PVI with either an LT (n = 74) or a PS catheter (n = 391), propensity score matching yielded 50 (LT group) and 100 patients (PS group), respectively. No differences were reported for first-pass isolation per patient (96% [LT group] vs 97% [PS group]; P = .75) and per pulmonary vein (98.9% [LT group] vs 99.2% [PS group]; P = .75). The LT group showed longer procedural (56 vs 50; P < .0001) and dwelling times (40 vs 30; P < .0001) but reduced fluoroscopy times (5 vs 10; P < .0001). No differences were reported for overall (2% vs 2%; P = 1.0) and major complications (0% vs 0%; P = 1.0). At 1-year follow-up, similar freedom from atrial tachyarrhythmia (86.2% [LT group] vs 83% [PS group]; P = .59) and atrial fibrillation (90.7% [LT group] vs 85.8% [PS group]; P = .41) was observed. Conclusion:First-time PVI using an LT or a PS pulsed field ablation catheter showed high efficacy and 1-year freedom from atrial tachyarrhythmias, without differences between groups. The LT catheter yielded longer procedural and dwelling times, but a significant reduction in fluoroscopy time.

BACKGROUND:Several sinus rhythm substrate mapping strategies have been described for ventricular tachycardia (VT) ablation. OBJECTIVES:The aim of this study was to evaluate a novel sinus rhythm mapping method for identifying critical isthmus sites based on both repolarization and activation mapping (repolarization depolarization mapping [REDEEM]). METHODS:Patients undergoing VT ablation at 2 centers were retrospectively analyzed. The local activation time (LAT) map was performed with the LAT set to the last deflection (LATlatest) method. Each LAT map was divided into 8 isochrones. Deceleration zones (DZs) were defined as >3 isochrones within 10 mm. Unipolar repolarization mapping was performed by using the Wyatt method. A steep repolarization heterogeneity was defined as a "repolarization cliff" if 2 contiguous areas within 1 cm distance showed a difference in repolarization time >100 milliseconds. RESULTS:A total of 20 patients with 20 mapped VTs were included. The VT exit site or any boundary of the diastolic channel overlapped with a repolarization cliff in 20 VTs (100.0%) and with a DZ in 14 VTs (70.0%). The VT entrance site was found to overlap with a repolarization cliff in 2 VTs (10.0%) and with a DZ in 18 VTs (90.0%). The mid-isthmus was found in an area connecting a DZ with a repolarization cliff in 19 VTs (95.0%). The positive predictive value of a repolarization cliff for any isthmus site was 63.2%, and the positive predictive value of a DZ for any isthmus site was 40.1%. CONCLUSIONS:The REDEEM method is feasible and shows anatomical associations with VT isthmus sites. This hypothesis-generating study provides mechanistic insights that warrant prospective validation.

BACKGROUND:Vagal responses (VR) are frequently observed during pulmonary vein isolation (PVI) with pulsed field ablation (PFA). OBJECTIVES:The aim of this study was to compare the effectiveness of 2 different anticholinergic (AC) medications, namely glycopyrrolate (GLY) or atropine (ATP), for VR prophylaxis in patients undergoing PVI via a pentaspline PFA catheter. METHODS:Consecutive patients with atrial fibrillation undergoing first-time PVI with PFA were prospectively enrolled at 4 centers between April 2023 and March 2024. Intravenous GLY 0.2 mg (Group GLY) or ATP 1 mg (Group ATP) were administered prophylactically before transseptal access. Clinically relevant VRs included sinus bradycardia (<40 beats/min), asystole (>6 seconds), atrioventricular block, and the need for temporary backup pacing. The incidence of periprocedural VRs was compared with that of patients without prophylactic AC drug administration (Group noAC). Drug-related adverse events were compared between the 2 AC drugs. RESULTS:We enrolled 240 patients (age 61 ± 12 years, 60.0% male) (GLY: n = 80; ATP: n = 80; noAC: n = 80). Intraprocedural VRs were observed in 65 patients (27.1%). GLY and ATP effectively reduced overall VRs (GLY: 7.5% vs ATP: 11.3% vs noAC: 62.5%; P < 0.001), asystole (GLY: 1.3% vs ATP: 2.5% vs noAC: 33.8%; P < 0.001), and need for temporary backup pacing (GLY: 1.3% vs ATP: 5.0% vs noAC: 23.8%; P < 0.001). The risk of overall drug-related adverse events (8.8% vs 0%; P = 0.007) and drug-induced atrial fibrillation (5% vs 0%; P = 0.043) was significantly higher with ATP. CONCLUSIONS:Prophylactic AC drug administration effectively prevented clinically relevant VRs in patients undergoing PVI with PFA. Both AC drugs were equally highly effective, but ATP showed a significantly higher rate of drug-induced adverse events.

BACKGROUND Left bundle branch area pacing is currently the procedure of choice for various indications including atrioventricular block and is considered a physiological modality of pacing compared with right ventricular apex pacing especially in young adults. OBJECTIVES This study aimed to increase the precision of left bundle branch area pacing (LBBAP) lead placement by developing a novel implantation technique using electrocardiographic imaging (ECGI). METHODS This is a single-center prospective study. 10 consecutive patients who underwent an LBBAP device implantation under real-time ECGI guidance have been included in the study. Lead positioning was initially performed using fluoroscopy and a pacemaker analyzer only; then electrocardiographic (ECG) and ECGI analyses were performed in real time during the implantation at each lead position before and after fixation. ECG and ECGI parameters were measured as previously described. A directional activation map has been created for each attempt before lead fixation to ensure the final position. Correlation analysis between 12-lead ECG and ECGI values has been performed to analyze redundancy. RESULTS LBBAP implantation was successful in all patients. ECGI has been shown to be a fast and visual way to assess interventricular activation at every stage of conduction system pacing lead implantation. Inferoposterior sheath positions are associated with long total ventricular activation time using ECGI and higher interventricular dyssynchrony than anterosuperior septal sheath positions. All procedures were performed with only 1 screwing attempt. Screwing depth is mostly characterized by total ventricular activation time and left ventricular activation time using ECGI reduction during the screwing process. Previously described discordance between classic ECG parameters and ECGI analysis was confirmed, and redundancy of certain parameters was confirmed. Correlation analysis confirmed the importance of ECGI measurement of right ventricular activation in general and total activation time and left ventricular activation time for patients with an intrinsic QRS duration of >130 ms. CONCLUSION ECGI can bring significant value to conduction system device implantation. ECGI allows direct visualization of every procedural step, and its values confirm correct lead positioning and physiological ventricular activation. This might be very helpful in clinical practice by reducing the number of fixation attempts and proper activation assessment during the implantation, especially for patients with difficult cardiac and noncardiac anatomy.

Background Effective balloon positionnking during pulmonary vein isolation (PVI) with a radiofrequency balloon (RFB) is crucial for optimal energy delivery, maximising lesion formation, and preventing gaps. Traditionally, fluoroscopy is used to guide pulmonary vein (PV) occlusion, however, this method exposes patients to radiation. Recently, RFBs equipped with 3D electroanatomical mapping (EAM) offer an alternative approach, potentially achieving the same results with reduced radiation exposure. Our main aim was to evaluate procedural characteristics, such as acute isolation and time-to-isolation (TTI), when the RFB is positioned based only on fluoroscopy feedback vs. fluoroscopy and a 3D-EAM. The secondary objective was to assess PVI durability through mandated remapping in asymptomatic patients from both groups. Methods A total of 60 patients were enrolled and underwent either a fluoroscopy-guided (FLUO, 30 patients) or fluoroscopy + 3D-EAM (3D-MAP, 30 patients) ablation. In each group, 15 patients without any documented recurrence underwent protocol-mandated repeat 3D-EAM six months after the index ablation. Procedural outcomes, lesion metrics, and safety profiles were assessed and compared between groups. Results At a median follow-up of 579 days, freedom from any atrial tachyarrhythmias (ATAs) was 89.7% in the FLUO group and 92.3% in the 3D-EAM group (P > 0.05). The latter was associated with significantly reduced fluoroscopy exposure (median 10.5 vs. 7.0 min, P < 0.005). Procedure time and efficacy metrics, including single-shot isolation rates and TTI, were comparable between groups. Durable PVI on a per PV basis was present in 54/60 (90%) vs. 57/60 (94%) of PVs in the FLUO and 3D-EAM groups, respectively (P = 0.9). Conclusion Radiofrequency balloon led to a high rate of durable PVI whether its guided by fluoroscopy only or 3D mapping. The latter allowed avoiding dye comsuption and a reduction of fluoroscopic times.

Background Automatic digital photogrammetry produces digital reproductions of objects using photographs. The aim of this study is to analyze feasibility of photogrammetry for electroanatomic map (EAM) reconstruction from different mapping systems. Furthermore, the possibility to import the reconstructed EAMs in a common working space is evaluated. Methods All consecutive patients undergoing EAM with one of the following EAM systems were screened for the study: (1) CARTO™; (2) Ensite™ X; (3) Rhythmia™; (4) Affera™ PRISM-3. All patient geometries were reconstructed from a video acquisition within the source EAM software. The video obtained was processed with Zephyr software and a dense point cloud was obtained. An image or sequence of images was selected to build a 3D mesh. At the end, the mesh was imported in the 3D graphics software Blender. Result A total of 24 EAMs from 24 patients were included in the study. All EAMs were reconstructed with success using photogrammetry from all 4 mapping systems assessed. The process time was ≈ 25 min. In particular, EAMs were as follows: left atrium (2 Carto; 2 Ensite; 5 Rhythmia; 2 Affera), right atrium (1 Carto; 6 Ensite; 3 Affera) and left ventricles (1 Carto; 2 Ensite). All the reconstructed EAMs were imported in Blender with success. They could be visualized in Blender and all the operations were allowed including moving EAMs in a common working space and EAMs overlap. Conclusion This study demonstrated for the first time the possibility of realizing 3-D objects from digital video formats of different EAMs.

BACKGROUND:The human sinoatrial node (SAN) pacemaker is a complex structure located at the right atrium (RA)-superior vena cava (SVC) junction. OBJECTIVE:This study aimed to perform in vivo endocardial and epicardial electroanatomic mapping of human SAN in inappropriate sinus node tachycardia (IST) and to correlate electrical findings with anatomic observations from thoracoscopy during hybrid SAN-sparing IST ablation. METHODS:All consecutive patients with diagnosis of symptomatic IST, refractory to or intolerant of drugs, and endocardial and epicardial mapping of SAN during hybrid ablation were included. Local activation time was defined by steepest -dV/dT on unipolar electrogram (EGM). Exit zone (EZ) was defined as the earliest activation site on endocardial and epicardial maps. Endo-epicardial delay was the time difference between the first endo-epicardial activations. Bipolar EGM morphology and SVC sleeve extension were analyzed. RESULTS:A total of 61 patients were included. The SAN-EZ area was 1.4 ± 0.6 cm2; it was located in the superior anterior region of the RA in 46 (75.4%) patients and in the mid RA in 15 (24.6%) patients. The earliest activation occurred on epicardial SAN-EZ in all patients. The local activation time of the epicardial vs endocardial SAN-EZ was -30.8 ms vs -12.4 ms (P < .001). Endo-epicardial delay was 19.7 ms. Bipolar EGM reversed polarity at SAN-EZs was observed in 43 (70.5%) patients. SVC sleeve extension was 31.2 mm and inversely correlated with age. CONCLUSION:The earliest SAN-EZ was found in the epicardium. Bipolar EGM reversed polarity is a novel electrophysiologic marker for SAN-EZs.