Ablation Of Persistent Atrial Fibrillation Research Articles

Single-centre experience with an electrogram-based artificial intelligence software system to identify drivers in pulsed field ablation of persistent atrial fibrillation

Abstract Background Ablation of persistent atrial fibrillation (AF) beyond pulmonary vein isolation (PVI) remains challenging, despite increasing numbers of eligible patients. Previous studies suggest a possible role for non-PVI lesions targeting atrial drivers, but their identification can be difficult and subject to inter-operator variability. Purpose We investigated feasibility for an electrogram-based artificial intelligence software system to assist in the identification of left or right atrial dispersion sites as ablation targets for persistent AF using the penta-spline multi-electrode pulsed-field ablation (PFA) catheter, a recent technique which is more conventionally employed for PVI. Methods This is a single-centre retrospective descriptive study of a cohort of patients with persistent AF, who underwent their first-time ablation from May to November 2023 using the Farawave PFA catheter (Boston Scientific) and the VX1 system (Volta Medical). This system relies on off-line pre-training of multiparametric machine learning algorithms on a database of annotated AF intracardiac electrograms. It connects to cardiac electrophysiology recording systems via a custom data cable to receive analogue data and digitize them through an integrated converter. Its algorithms analyse signals in the cardiac chamber of interest to adjudicate the local presence or absence of dispersion and provides relevant visual cues to operators in order to target energy delivery. Results We identified 16 patients who underwent PFA for persistent AF (long-standing in 5/16, 31.3%), including PVI and further ablation guided by VX1. See table 1 for baseline population characteristics and table 2 for procedural characteristics. All underwent ablation with uninterrupted anticoagulation, general anaesthesia, use of the Rhythmia electroanatomic mapping system and its Orion mapping catheter (Boston Scientific) to feed signals into the VX1 system. VX1-guided electrogram localization and ablation mostly targeted the anterior region of the left atrium (16 segments), followed by its septal region (6 segments) and its lateral region (4 segments); the median number of applications per procedure was 88 [IQR 68-108], including a median of 76 [61-85] in the left atrium and 12 [0-15] applications in the right atrium. The median procedure duration was 123 [114-137] minutes; the median fluoroscopy time was 32 [26-40] minutes and the median radiation dose was 12.5 Gy∙cm2 [10.0-25.8]. Sinus rhythm was restored either during ablation or by electrical cardioversion (see Table 2). Two complications occurred one femoral arteriovenous fistula requiring stenting and one tamponade requiring drainage. At a three-month follow-up, 87.5% did not present AF recurrences. Conclusion Real-time detection and annotation of electrograms to track dispersion using AI-assisted technology to support PFA with a multipolar catheter is feasible. The interest of the approach should be validated by further studies.Table 1.Table 2.

Ablation of persistent atrial fibrillation based on atrial electrogram duration map: methodology and clinical outcomes from the AEDUM pilot study

Abstract Background Catheter ablation of persistent atrial fibrillation (PsAF) represents a challenge for the electrophysiologist and there are still divergences regarding the best ablative approach to adopt. Objectives Create a new map of the duration of atrial bipolar electrograms (Atrial Electrogram DUration Map, AEDUM) to recognize a functional substrate during sinus rhythm and guide a patient-tailored ablative strategy for PsAF. Methods 40 PsAF subjects were assigned in a 1:1 ratio to either for PVI alone (Group B1) or PVI+AEDUM areas ablation (Group B2). A cohort of 15 patients without AF history undergoing left-sided accessory pathway ablation was used as a control group (Group A). In all patients, voltage and AEDUM maps were created during sinus rhythm. The minimum follow-up was 12-months, with rhythm monitoring via 48-h ECG Holter or by implantable cardiac device. Results Electrogram (EGM) duration was higher in Group B than in Group A (49±16.2ms vs 34.2±3.8ms; p-value<0.001). In Group B the mean cumulative AEDUM area was 21.8±8.2cm2; no difference between the two subgroups was observed (22.3±9.1cm2 vs 21.2±7.2cm2; p-value=0.45). The overall bipolar voltage recorded inside the AEDUM areas was lower than in the remaining atrial areas [median:1.30mV (IQR:0.71–2.38mV) vs 1.54mV (IQR:0.79–2.97mV); p-value:<0.001)]. Low voltage areas (<0.5mV) were recorded in three (7.5%) patients in Group B. During the follow-up [median 511 days(376-845days)] patients who underwent PVI-only experienced more AF recurrence than those receiving a tailored approach (65% vs 35%; p-value=0.04). Conclusions All PsAF patients exhibited AEDUM areas. An ablation approach targeting these areas resulted in a more effective strategy compared with PVI only.AEDUM mapAEDUM map and lesion set

Findings at repeat ablation after complex left atrial pulsed field ablation for longstanding persistent atrial fibrillation

Abstract Background There is a limited knowledge on atrial arrhythmias recurring after complex left atrial (LA) pulsed field ablation (PFA) for longstanding persistent atrial fibrillation (LSPAF). Purpose To present recurrent atrial arrhythmias and their sources found at repeat ablation following PFA for LSPAF. Methods and results Of 214 patients with LSPAF (age 65±8, 53 females, continuous AF for 30±27 months) with complex LA PFA (Farapulse) in 10/2021-10/2023, 19 patients (64±8 years, 5 females) underwent repeat ablation for recurrent AF or arial tachycardia (AT) in 20 procedures. First PFA procedure included pulmonary vein isolation (PVI), roof/posterior wall, and mitral isthmus/coronary sinus/Ligament of Marshal region (LOM) ablation. At repeat ablation, 3D activation and entrainment mapping and ablation identified the AF/AT sources; ATs sources were classified as macroreentry (MRAT) (perimitral, roof-dependent, typical flutter) or localized (LOCAT) in case of smaller reentry or ectopic origin. Results The clinical recurrent arrhythmias included paroxysmal AF (n=1), persistent AF (n=2), paroxysmal AT (n=1) or persistent AT (n=16). At the onset of repeat ablation, persistent AF/AT was present (n=15) or had to be induced (n=5). AF was finally present during the procedure in 8 patients, and was terminated by ablation directly into SR (n=3) or into intermediate AT (n=3) (conversion sites included LA ridge/LOM region 2x, RA septum 1x, RA low lateral 2x, CTI 1x), or required DCC (n=2). Primary recurrent or from AF converted AT was present in 15 patients; only MRAT in 6 patients, only LOCAT in 3 patients, and both AT types in 6 (patients). Of MRAT (N. ATs = 16), there were 12 perimitral ATs, 0 roof-dependent AT, and 2 typical flutters. Of LOCATs, sources were located at LA anterior wall 4x, LA septum 2x, LA roof 1x, LA ridge/LOM 1x, persistent left vena cava 1x, and RA – para SA node 1x. Recurrent AF/AT sources were targeted by radiofrequency or PFA in 16 and 4 cases, respectively, all spontaneous and induced AF/AT were finally terminated into SR in 16 cases, subsequent noninducibility by atrial pacing up to 300 bpn was achieved in 13 cases, and recurrent AF/AT occurred in 3 patients. Conclusion At repeat ablation PFA (Farapulse) for LSPAF, recurrent AT dominated over AF, MRAT slightly prevailed over LOCAT, mostly constituted by perimitral AT, while roof-dependent AT recurrence was reduced to zero. A majority of AF/AT sources were located outside prior PFA lesions at the LA anterior wall, septum and the right atrium.

Multielectrode catheter-based pulsed field ablation of persistent and long-standing persistent atrial fibrillation

Abstract Background Rhythm control of non-paroxysmal atrial fibrillation (AF) is significantly more challenging, as a result of arrhythmia perpetuation promoting atrial substrate changes and AF maintenance. Purpose We describe a tailored ablation strategy targeting multiple left atrial (LA) sites via the multielectrode FarawaveTM pulsed field ablation (PFA) catheter in patients with persistent AF sustained beyond 6 months (PerAF>6m) and long-standing persistent AF (LSPAF). Methods The ablation protocol included the following stages: pulmonary vein antral and posterior wall isolation plus anterior roof line ablation (Stage 1); electrogram-guided substrate ablation (Stage 2); atrial tachyarrhythmia (AT) regionalization and ablation (Stage 3). Results Seventy-two [age:68±10y, 61.1%males; AF history: 25 (18-45) months] patients with PerAF>6m (52.8%) and LSPAF (47.2%) underwent their first PFA via the FarapulseTM system. LA substrate ablation (Stage 1 and 2) led to AF termination in 95.8% of patients. AF termination occurred while ablating the mitral edge of the postero-lateral ridge (40.3%), the inferior left atrium above the proximal coronary sinus (27.4%), the interatrial septum (22.6%), the superior aspect of the postero-lateral ridge (6.5%), the base of the appendage (3.2%). AF organized into a left-sided atrial flutter (AFlu) in 46 (74.2%) patients. The FarawaveTM catheter was used to identify LA sites showing diastolic, low-voltage electrograms and entrainment from its splines was performed to confirm the pacing site was inside the AFlu circuit (Figure 1). Left AFlu termination was achieved in all cases via PFA delivery. Total procedural and LA dwell times were 112±25min and 59±22 min, respectively. Major complications occurred in 2 (2.8%) patients with pre-existing left ventricular systolic dysfunction (EF<35%) who required inotropic therapy due to acute heart failure. Hemodynamics normalized within 24h and both patients were discharged after 2 and 3 additional hospital days. Transient ST-segment elevation was documented in 4 patients after peri-mitral PFA; timely nitrate administration led to ECG normalization within 10 minutes. Single-procedure success rate was 81.8% after 13.3±1.9 months of follow-up; AF-free survival was 93.1% (Figure 2). A subgroup of 36 patients completed a follow-up transthoracic echocardiography study to assess left atrial mechanical contraction changes after ablation. Median A-wave velocity was 30 (IQR: 20-35) cm/s post-ablation and 50 (IQR: 41-70) cm/s after a mean of 7.3±1.8 months post-ablation. Conclusions In our cohort, PFA-based AF substrate ablation led to AF termination in 95.8% of cases. Very favorable clinical outcomes were observed at one year of follow-up.Entrainment from the PFA Catheter.Kaplan-Meier Analysis.

Outcome after cryoballoon ablation of persistent atrial fibrillation in patients with heart failure with preserved ejection fraction versus tachycardiomyopathy: a propensity score-matched analysis

Abstract Introduction Atrial fibrillation (AF) often coexists with heart failure (HF). The aim of the study was to detect differences in outcome between patients with arrhythmia induced cardiomyopathy (AIC)/tachycardiomyopathy and HFpEF undergoing cryoballoon pulmonary vein isolation (cryo-PVI) using a propensity score-based model. Methods In this retrospective observational study, we analysed persistent AF patients with HFpEF and AIC undergoing cryoballoon ablation between 2014 and 2020. AIC was diagnosed ex juvantibus during the first year after ablation at the 3- and 12-month follow-up when LVEF recovered to > 50% and by more than 10% after ablation and a different aetiology for reduced LVEF was excluded. Propensity score matching was used to pair patients based on their age, sex, CHA2DS2-VASc score and left atrial (LA) area. The primary endpoint was the first documented > 30-s recurrence of atrial arrhythmia after a 3-month blanking period during the one-year follow-up. The secondary endpoints were improvements in NYHA class and reduction of LA area. For identification of independent predictors of atrial arrhythmia recurrence after ablation, univariate and multivariate Cox regression analyses were performed. Results Out of 1293 consecutive patients who underwent cryo-PVI, 148 persistent AF patients with HFpEF and 66 patients with AIC were identified. Propensity score matching yielded 46 patients in each group. HFpEF patients were more symptomatic than AIC patients (NYHA: 2.4 +/- 0.5 vs. 2.0 +/- 0,8; p = 0.002). Other baseline characteristics did not differ between the two groups, except LVEF (57 % [IQR: 52-62%] vs. 41% [QR: 35%-45%]; p= 0.002). Kaplan-Meier curves (Figure 1) demonstrated no difference in recurrence-free survival rate between the groups during the 12-month follow-up (71.7 % vs. 56.5%, log-rank P = 0.16). After the 12-month follow-up, the median LA area decreased significantly in the HFpEF group from 25.8 cm2 (IQR: 23.4-29.5 cm2) to 24.6cm2 (IQR: 22.0-29.6 cm2; p = 0.045) and in the AIC group from 26.6 cm2 (IQR: 22.9-31.1 cm2) to 23.0 cm2 (IQR: 18.3-25.2 cm2; p=0.024). At the 12-month follow-up the median LA-area was significantly higher in the HFpEF than in the AIC cohort (p= 0.007). NYHA class improved significantly in both groups from baseline. At the 1-year follow-up NYHA class was similar between both groups (1.6 +/- 0.8 vs. 1.4 +/- 0,6; p = 0.206). After univariate and multivariate analysis, the following predictors of atrial arrhythmia recurrence were identified: body-mass-index (BMI; HR = 1.082, p = 0.015) and LA area (HR = 1.079, p = 0.003). Conclusions Cryoballoon catheter ablation of persistent AF seems to have similar effectiveness on arrhythmia free survival in patients with HFpEF and AIC. NYHA class and LA enlargement improved after ablation in both groups although LA area in HFpEF was higher than in AIC patients at follow-up. BMI and LA area were identified as predictors of arrhythmia recurrence.

Acute impact of vein of marshall ethanol infusion combined with anatomical ablation validated by pacing in redo ablation of persistent atrial fibrillation

Abstract Background Catheter ablation with radiofrequency in persistent atrial fibrillation (PeAF) has limited success and a significant proportion of patients requires redo ablation. Several trials showed that addition of vein of Marshall ethanol infusion (Vom-EI) to catheter ablation, compared with catheter ablation alone, increases the possibilities of remaining free of AF. No data are available about the effect on VoM-EI in Pe-AF patients that undergo a redo ablation. Purpose We evaluated acute impact on lesion formation post-VoM-EI and the mitral line block validation after a methodical approach including VoM-EI and check of pulmonary vein isolation (PVI), roof-line, mitral line (ML) and cavo-tricuspid isthmus line in a population of PeAF patients undergone redo ablation. We aimed also the results of a short follow-up. Methods Consecutive patients undergoing redo ablation for PeAF were enrolled. All patients underwent check of PVI, left atrium (LA) roofline and cavotricuspid isthmus line and, if necessary, ablation was completed. In all patients, after a detailed electroanatomical map of the LA (filter at 0.05-0.5 mV if the patient was in sinus rhythm or 0.05-0.3 mV in the case of AF), we proceeded with the VoM-ETHO. LA map was thus repeated to assess the extension of the newly-formed low voltage area (LVA). According to the newly-formed LVAs, the validation of mitral line was obtained by the evidence of bidirectional block. In presence of conduction through the mitral line also after endocardial revision, we proceeded to mapping and ablating in the CS epicardial gaps in the "anchored wall" or in the "free-wall"of the great cardiac vein (GCV). Results Twenty consecutive patients (64±8 years and 65% male) undergone redo ablation for AF with VoM-EI were included in this study. All patients underwent PVI in the previous procedure but only in 11 roof line has been performed. In twenty patients (52%) reconnection of PV was observed (12/20 in right superior pulmonary vein). In 4/11 roof line was not complete. The medium value of basal LA-LVAs was 3.38土5.27 cmq and the newly-formed LVAs after the VoM-EI procedure was 9.21土5.63 cmq. All patients achieved bidirectional block validated across ML: in 8/20 after epicardial gaps ablations into the anchored wall of GCV and in 6/20 after epicardial gaps ablation in the free wall of GCV. The ML procedural time was 18.82土12.79 minutes. The number of radiofrequency irrigation was 20.11土10.56. No major complications occurred. Five patients had VOM dissection without consequences. During a short follow-up period (6土5 months), only one patient had AF recurrences after the blanking period of one month. Conclusions VoM ethanol ablation added to PVI and linear lesions in the context of a methodical and anatomical approach during redo ablation of PeAF patients seems to have promising results and to be safe. Longer follow-up is needed to understand the role of this technique in redo ablation.

Pulsed field ablation versus very high-power short-duration radiofrequency ablation in persistent atrial fibrillation: a single-centre experience

Abstract Background Pulsed Field ablation (PFA) has recently emerged as a treatment strategy for patients with atrial fibrillation (AF) and early studies showed promising procedural data and durable pulmonary vein isolation (PVI). However, Very High-Power Short-Duration ablation (VHPSD) has previously reported good efficiency and mid-term outcomes, and only a few works compared these two procedures, especially in patients with persistent AF. Objective Our aim is to compare these different modalities of transcatheter ablation in patients with persistent AF, focusing mainly on some procedural aspects, safety and efficacy. Methods We performed a retrospective observational study enrolling all consecutive patients with persistent AF from September 2021 to May 2023 undergoing transcatheter ablation with PFA or VHPSD. In the first group, PVI was achieved by 2kV pulses with eight applications to each vein using both catheter configurations, while isolation of the posterior wall of the left atrium was achieved by applications through the only "flower" configuration; additional lesions were then added at the operator's discretion. In the second group, PVI was achieved by delivering 90W radiofrequency pulses for 4 seconds in the posterior portions of the left atrium and 50W pulses in the anterior region of the pulmonary veins; additional lesions were occasionally applied. All patients received general anaesthesia or deep sedation with fentanyl and dexmedetomidine. Results A total of 79 patients were included, n = 24 (30%) in the PFA group and N = 55 (70%) in the VHPSD one: early persistent AF (n= 2 [8,3%]; N = 7 [12,7%]), persistent AF (n= 17 [70,8%]; N = 36 [65,5%]), long-standing persistent AF (n= 5 [20,8%]; N = 12 [21,8%]). The two populations showed similar clinical features: CHA2DS2-VASc (median value 3 [0-6] in PFA vs 2 [0-6] in VHPSD, p = 0,10), indexed left atrial volume (mean value 42,6 ml/m² in PFA vs 42,4 ml/m² in VHPSD, p = 0,07) and EF (mean value 55,4% in PFA vs 54,8% in VHPSD, p = 0,33). PVI was successfully achieved in all patients. Nevertheless, the PFA group was associated with shorter procedural duration (92,1 ± 36,9 vs 134,2 ± 36,1 minutes, p = 0,00001) but longer fluoroscopy time (25,5 ± 9,3 vs 17,4 ± 11,5 minutes, p = 0,001); it also showed a lower rate of minor complications (n = 1 [4,2%] vs N = 3 [5,5%], p = 0,057), even though serious complications were not observed in either group. After a median follow-up of 14 (9-26) months, n = 19 [79.2%] in the PFA and N = 43 [78.2%] in the VHPSD population were free of any atrial arrhythmia (p = 0,92). Conclusion PFA allows faster procedures, representing a major advantage for the operator and the patient, who is at lower risk of peri-procedural complications. On the other hand, VHPSD correlates with shorter fluoroscopy times, reducing exposure to ionizing radiation. Finally, the two procedures show similar mid-term efficacy in terms of recurrence-free time.

Pulsed field ablation for complex resistant atrial tachycardia recurring after radiofrequency ablation of persistent atrial fibrillation

Abstract Background There is a limited knowledge on immediate and long-term efficacy of pulsed field ablation (PFA) for residual atrial tachycardia (AT) recurring after persistent atrial fibrillation ablation (AF). Purpose To present immediate and medium-term outcome of PFA (Farapulse) for complex AT recurring after ≥1 radiofrequency ablation (RFA) of primary (longstanding) persistent AF. Methods In 5/2022-10/2023, 81 patients (64±8 years, 19 females) underwent PFA for complex AT in 83 PFA procedures after prior RFA procedure(s); in first (n=21), second (n=33), third (n=23), fourth (n=5), or fifth (n=1) repeat ablation procedure, respectively. Mapping/ablation strategy was directed by the CS activation/entrainment to: 1) no 3D mapping and direct PFA in left atrium (n=67); 2) PFA directly after 3D LA mapping (n=9); 3) PFA following RFA after 3D LA mapping (n=7). AT sources were classified as macroreentry (MRAT) (perimitral, roof-dependent, typical flutter) or localized (LOCAT) in case of smaller reentry or ectopic origin. Results At the procedure onset, persistent AT was present in 58 patients, in the remaining cases AT (n=21) or AF (n=4) were induced. AF eventually occurred at some time of procedure in another 10 patients and was terminated by ablation at LA ridge/CS/LOM region 8x, LA posterior wall 3x, LUPV 1x, RUPV 1x, and RA low lateral wall 1x. Only MRAT, only LOCAT, or both AT types were found at 34 (41%), 35 (42%), and 14 (17%) procedures, respectively. A total of 125 ATs was identified (1, 2, and 3 ATs in 52, 20, and 11 patients). MRAT (n=60) included 32 perimitral ATs, 20 roof-dependent ATs, and 8 typical flutters. LOCAT (n=65) included RUPV source (n=1), LA extraPV sources (n=59), and RA sources (n=5). SR was restored with a 5±7 PFA applications at the site of AF source, total of PFA deliveries was 71±27, and procedure and fluoroscopy times were and 89±37 and 9±5 minutes, respectively. In the 7 patients with initial ineffective 6, 6, 11, 5, 18, 10, and 2 minutes of RFA, the AT was converted into SR by subsequent 1, 4, 1, 13, 4, 24, and 20 PFA applications. All ATs were terminated and noninducibility was achieved in 82 (99%) and 74 (89%) procedures, respectively. In 52 patients with >3 month follow-up, 46 (88%) patients remain in stable SR (41 / 79%) off AAD); 3 and 3 patients have paroxysmal or persistent AT. Conclusion PFA with catheter Farapulse can affect complex/epicardial AT sources resistant to RFA in prior or present ablation procedure; however, there is a certain discrepancy between high efficacy in AT terminating and medium-term clinical outcome.

Identifying patients with reduced risk of recurrences after ablation for persistent atrial fibrillation

Abstract Background Catheter ablation (CA) is a well-established treatment option for recurrent atrial fibrillation (AF), and has shown to outperform antiarrhythmic drugs in prevention of AF recurrences in numerous studies. However, up to 50% of patients with persistent AF (peAF) will experience recurrences after first-time CA. Improving treatment for these patients involves, choosing the right patients for the ablation procedure, optimizing the timing of the procedure, and using the most effective ablation strategy. This will benefit not only the patients, but also target recourse use in the healthcare system. Purpose To identify characteristics and comorbidities of patients with peAF associated with a reduced risk of recurrence after CA. Additionally, to investigate the optimal timing and ablation strategy. Methods This observational cohort study was conducted using real-life data from the Danish healthcare registries. All patients with peAF, >18 years of age, who were assigned to first-time AF ablation, were included within the study period from January 1st 2010 to December 31st 2018. A composite endpoint for AF recurrences was defined as either AF admission, electric cardioversion, use of antiarrhythmic drugs or re-ablation after a 3-month blanking period. We followed the patients in the registries for up to 5 years. A Cox proportional hazards analysis was performed to identify specific patient characteristics, comorbidities, timing of ablation and ablation strategy associated with reduced risk of AF recurrences after ablation. Results The study cohort consisted of 2,123 patients with peAF undergoing first-time CA. Median age was 63 years [IQR: 56.10;68.90], 77.7% were male, and mean BMI was 28.40 (SD: 4.97). Mean diagnosis-to-ablation-time (DAT) was 3.56 years (SD: 4.25) and mean follow-up time was 928.3 days (SD: 829.62). Most prevalent co-morbidities were hypertension (59.1%), ischemic heart disease (16.9%), and heart failure (HF) (27.7%) (Table 1). Patients characterized by male sex (HR: 0.80, 95% CI 0.69-0.93), age 60-70 (HR: 0.79, 95% CI 0.67-0.93), and absence of co-morbidities such as HF (HR: 0.81, 95% CI 0.70-0.94) and chronic obstructive pulmonary disease (COPD) (HR: 0.58, 95% CI 0.44-0-75), were observed with a significantly reduced relative risk of recurrent AF. Short DAT(<1 year) was associated with a 24% lower risk of recurrence compared to longer (>2 years). Furthermore, PVI Plus (additional ablation to PVI) was not significantly associated with a reduced risk of recurrences (HR: 1.10, 95% CI 0,92-1.31) (Figure 1). Conclusion To obtain rhythm control for patients with peAF is a great challenge. This observational study with more than 2,000 patients, identifies patients most likely to benefit from CA. Lower recurrence rates were observed in younger patients (<70 years), absence of especially HF and COPD, and early ablation (<1 year). Notably, PVI plus did not reduce the risk of recurrences.

Long-term recurrence-free survival following second-generation cryoballoon ablation for persistent atrial fibrillation: role of the autonomic nervous system

Abstract Background The cardiac autonomic nervous system (ANS) plays a pivotal role in the regulation of atrial fibrillation (AF). Cryoballon (CB)-guided pulmonary vein isolation (PVI) is an established treatment for AF. Purpose In our present study we evaluated the impact of vagal reactions (VRs), as a surrogate parameter for ANS modulation, on the long-term outcome of CB-ablation in patients with persistent AF (PERS AF). Methods Data from consecutive PERS AF patients undergoing primary CB-guided PVI for symptomatic drug refractory AF between 2013-2023 were analysed. VRs were defined as bradycardia < 40 beats/min, asystole or higher-degree atrioventricular block. Long-term follow-up data were assessed. AF-recurrence was defined as AF lasting > 30 seconds beyond a 3-month blanking period. Results A total of 250 consecutive patients (mean age 63.9±10.0 years, 30% female) were included. VRs were recorded in 61 patients (24%, mean age 64.2±13.0 years, 30% female). The mean follow-up duration amounted to 84±14 months. Within this observation period 101 patients (40%) developed AF-recurrence. Re-ablation procedures were performed in 61 patients (60%). Patients with PVI-associated VRs presented with a significantly higher estimated AF-free survival rate (log-rank p-value < 0.001) (Figure 1) and a significantly longer median AF-free survival time (75 months, interquartile range (IR) 63-92 months) compared to those without (69 months, IR 13-79 months) (p=0.002). Beyond that Kaplan-Meier plot analyses revealed significant gender differences (Figure 1). Multivariate cox regression analyses confirmed VRs (Confidence interval (CI) 0.294-0.838, Hazard Ratio (HR) 0.497, p=0.009) and male gender (CI 0.352-0.781, HR, 524, p=0.001) as independent predictors (IPs) for AF-free-survival. Conclusion CB-ablation procedure associated VRs and male gender seem to be associated with a favorable long-term outcome in PERS AF. Further studies are warranted to verify our observations.Kaplan Meier plot on long-term AF-free s

Higher recurrence rate after ablation of persistent atrial fibrillation in patients with prolonged P-wave negativity in lead V1

Abstract Background Several ECG P-wave parameters, such as duration, amplitude and morphology reflect the electromechanical condition of the atria. P-wave features mainly served to identify patients prone to atrial fibrillation (AF) or to predict recurrence of paroxysmal AF after ablation. Purpose We sought to investigate which specific features derived from the P-wave might help identify patients with persistent atrial fibrillation (peAF) unresponsive to wide circumferential pulmonary veins isolation (WPVI). Methods 41 patients (63±10 y) with peAF (sustained duration 11±7 months) underwent a de-novo WPVI. A second WPVI was performed in patients with recurrent AF in order to provide complete PV disconnection. We defined "success" as patients who remained in sinus rhythm (SR) after one or two procedures, and "failure" otherwise. The average duration and amplitude of the P-waves on ECG lead II, and the duration and amplitude of positive and negative deflections on ECG lead V1 were extracted during SR after cardioversion at the end of the index WPVI. P-wave terminal force in V1 (PTFV1) was computed as the product of negative amplitude and duration in lead V1. Results Over a mean follow-up of 32±9 months, 24 patients remained free from AF (success group), while 11 patients had AF recurrence after 2 WPVIs (failure group). Six patients were lost to follow-up or declined the second WPVI. 45% (5/11) were ON antiarrhythmic drugs (AAD) during follow-up in the failure group, while 0.04% (1/24) were ON AAD in the success group (p<0.05). Other clinical characteristics (e.g. age, body mass index, left atrial volume or duration in sustained AF) were similar. The figure displays P-wave metrics of patients ON and OFF AAD during follow-up. No significant differences were found in P-wave duration (lead II; Panel A1), in PTFV1 (Panel A2), and in duration of V1 positive deflection (Panel A3). Interestingly, the failure group displayed longer duration of the negative deflection in V1 (76±17ms) than that of the success group (68±18ms, p<0.05; Panel A4). Panel B shows that the differences remained after exclusion of patients ON AAD during follow-up. No differences were found in P-wave amplitude in lead II or in amplitude of positive and negative deflections in lead V1 (data not shown). Conclusion Our results show that prolonged negativity in lead V1, which is indicative of left atrial electromechanical remodeling, is associated with failure to restore long-term sinus rhythm after WPVI of peAF.

Preliminary real-world experience on mitral isthmus ablation with a novel catheter that toggles between radiofrequency and pulsed field ablation

Abstract Background The mitral isthmus (MI) is frequently targeted during the ablation of persistent atrial fibrillation (AF). Nevertheless, achieving a complete bidirectional MI block using radiofrequency (RF) is often technically challenging and time-consuming1,2. Previously, we described a fluoroscopy-guided technique to achieve MI block using a penta-spline pulsed field ablation (PFA) catheter3. Recently, a new catheter was introduced, which toggles between RF and PFA and is integrated into a 3D mapping system, thus supposedly facilitating its use for the ablation of extra-pulmonary vein structures4. Purpose To describe the acute efficacy and procedural features of the first cases of posterior MI ablation performed with the toggling catheter at two centers. Methods We collected and reviewed demographic, clinical and procedural features of all patients who underwent ablation of the posterior MI at our centers between September and October 2023. Ablation of the MI was performed with either RF or PFA according to operator’s discretion. Bidirectional MI block was validated through activation mapping and differential pacing. Results During the study period, 44 patients were treated with the toggling catheter. Out of them, 16 patients (aged 68.3±10.1 years; 29% females) underwent posterior MI ablation for persistent AF, in addition to PVI and posterior wall isolation. Mean history of AF was 29.8±34.5 months and mean LA volume 135.6±54.9 ml. Skin-to-skin procedural time (93 minutes, IQR 64-112), LA mapping time (9.0 min, IQR 7.3-12.1) and time required for MI ablation (4.0 min, IQR 3.3-6.5) were remarkably short. In PFA-treated patients (10 cases), first-pass MI block was achieved in 8 (80%), with 16 (IQR 12-22) applications; none of these patients required RF touch-up. In the remaining 6 RF-treated patients, first-pass MI block was achieved in 3 (50%) patients with 8 (IQR 6-13) applications. Additional PFA applications (median 3, IQR 2-5) on the most venous portion of the MI were required in all RF-treated patients. In the 5 patients in whom bidirectional block could not be achieved at first-pass, remapping and touch-up application time were 2.6 (IQR 2.6- 6.3) and 2.0 (IQR 0.8-5.2) minutes, respectively. Eventually, bidirectional MI block was achieved in 16/16 (100%) patients by the end of the procedure. Importantly, no patients in the entire cohort experienced complications such as coronary artery spasm or clinically significant pericardial effusion. Conclusions Several observations can be made on this first real-world experience on posterior MI ablation with the toggling catheter: first, acute safety and efficacy in achieving a bidirectional MI block are high with both PFA and RF; secondly, patients undergoing RF ablation often require additional PFA applications on the venous segment of the MI; lastly, the time required to achieve MI block is remarkably short even when remapping and touch-up applications are needed.Figure 1Figure 2

Efficacy and safety of very high-power short-duration posterior wall ablation in persistent atrial fibrillation: a propensity score-matched comparison with standard power long-duration ablation

Abstract Background Catheter ablation (CA) with pulmonary vein isolation (PVI) is an optimal treatment option in patients with paroxysmal atrial fibrillation (AF). PVI alone in patients with persistent AF has proved to have suboptimal results. Ablation of additional atrial structures, such as posterior wall (PW) and left atrial appendage has been investigated as a tool to improve procedural efficacy. Recently very high-power short-duration (vHPSD) ablation was developed to allow rapid PVI, limiting complication through the maximization of resistive heating, and minimization of conductive heating. Objectives Compare PVI plus PWI using vHPSD versus standard-power (SP) ablation index-guided CA among consecutive patients with persistent AF Methods Forty consecutive patients underwent PVI plus PW isolation using vHPSD, compared to 40 controls underwent standard power (SP) PVI plus PW isolation. The primary efficacy endpoint outcome was recurrence of atrial tachyarrhythmias after a 3-month blanking period. The primary safety outcome was a composite of major complications within 30 days of CA. Results Treated patients have a median age of 62.8±9 years, 68 (85%) are male. Median left atrial volume is 42.4 (36-50) ml/m2. 61 (78.8%) patients had never undergone catheter ablation before. There are no statistically significant differences between groups. PW isolation was obtained more commonly in the vHPSD compared to the SP group (98% vs. 75%, p=0.007), despite shorter procedure and fluoroscopy times (p<0.001). Survival free from recurrent atrial tachyarrhythmias at 18 months was 68% in the vHPSD and 47% in SP groups, respectively (log-rank p=0.071), without major adverse events. The vHPSD approach was significantly associated with reduced risk of recurrent AF at multivariable analysis (HR, 0.39, p=0.030). Conclusions The results show feasibility and safety of posterior wall vHPSD ablation for persistent AF using this new temperature-controlled catheter without intraprocedural and periprocedural major complications at follow-up. vHPSD ablation for PW isolation may be more effective in term of atrial tachyarrhythmias recurrences with a trend for superior efficacy. However, this remains a single center experience in a small group of patients. Comparative trials involving greater number of patients with long-term follow-up are necessary to definitive results.

Pulsed-field ablation of atrial fibrillation in elderly and frail patients: procedural efficacy and safety from a single-center experience

Abstract Introduction The demographic data shows a growing population, mostly elderly and with multiple comorbidities, therefore becoming increasingly frail. In this context Atrial fibrillation (AF) is the predominant sustained arrhythmia, and over the years trans-catheter isolation of pulmonary veins (PVI) has become a crucial approach in AF treatment. Among the technologies and energy resources employed through the years to perform atrial fibrillation transcatheter ablation, a novel technique has recently begun to gain ground, specifically pulsed-field ablation (PFA). PFA employs sequential brief and high amplitude electrical pulses to induce selective and irreversible electroporation of the myocardium, leading to cell death. The high selectivity of the lesion, ensured by the lower electroporation threshold of myocardial tissue compared to adjacent anatomic structures, allows for a decrease in potential complications associated with conventional thermal ablation. Purpose To assess the efficacy and safety in the use of pulsed field ablation in a selected population of elderly and frail patients undergoing atrial fibrillation ablation. Method We conducted a retrospective study focusing on elderly and frail patients admitted to our centre for paroxysmal or persistent AF ablation. The inclusion criteria were: age greater than 75 years and a Clinical Frailty Scale ≥ 5. The study population consisted of 26 patients [male gender 18, mean age 78 ± 3 years] including 8 who were affected by an oncological or haematological disease at the time of admission. The majority of patients were affected by paroxysmal AF while two of them presented persistent AF (9%). The primary ablation endpoint was the pulmonary vein isolation (PVI) that was achieved by delivering an energy of 2 kV over 8 applications, employing an alternating approach between the two configurations of the basket and flower catheter for each individual vein. Results The short-term success, represented by the complete and verified electrical isolation of the veins was achieved in all 26 patients without any periprocedural complications. First-pass pulmonary vein isolation (FPI) was universally achieved among the patient in study, with a mean skin-to-skin procedural time of 70 ± 30 minutes. From the procedural data perspective, ablation was achieved using an average fluoroscopy time of 22 ± 8.4 minutes and an average dose area product (DAP) of 1320 cGy×cm2. Conclusions In elderly and frail patients, we assessed the efficacy and safety of ablative procedures using the PFA technique. Successful electrical PVI was achieved without additional touch-ups, thanks to a high FPI rate. This results in lower procedural times and shorter intra-operative radiation exposure. These data confer an augmented value within the elderly-frail population, wherein shorter procedural times contribute to a better postoperative course, characterized by reduced bed rest and shorter intra-hospitalization periods.

Objective randomised blinded investigation of therapeutic ablation versus cardioversion for persistent atrial fibrillation- outcomes of the feasibility

Abstract Background Patients with persistent atrial fibrillation (pers.AF) commonly undergo catheter ablation (CA) for symptom relief and improved quality of life(QoL). However,the benefits of CA compared to DC cardioversion (DCCV) or medical therapy lack substantial evidence from blinded randomized trials. Purpose Conducting such a large-scale trial presents substantial challenges in terms of recruitment, maintaining blinding, and implementation.To address this, we conducted a pilot study prior to a definitive larger study. Methods This feasibility trial is a single-centre, prospective, randomised, double-blinded placebo control study. Patients with early pers AF (<2 years) eligible for pulmonary vein isolation (PVI) or DCCV were enrolled. Twenty patients were recruited, accounting for 10% of the proposed larger trial based on power calculation. The intervention arm (PVI + DCCV) and placebo arm (Placebo + DCCV) were randomised in a 1:1 manner after ultrasound-guided vascular access with local anaesthetic and deep sedation (Midazolam + opioid). All procedures were performed as day cases on uninterrupted oral anticoagulation. Phrenic nerve pacing was performed in the Placebo group, mimicking lab interactions and fluoroscopy system movements. Implantable loop monitors were inserted immediately after heparin reversal and groin sheath removal. A 6-week(wk) blanking period was observed post-procedure. Blinding was assessed using Bang's blinding index (BI) for both patients and medical staff and a successful blinding is considered BI between -0.2 to 0.2. Health-related quality of life (HRQoL) was evaluated using SF12, EQ5D-5L, and AF PROMS. The study obtained ethical approval (REC ref 19/LO/0775),adhered to the principles of the Declaration of Helsinki,and obtained written informed consent from all participants. Results A remarkable 92% of patients approached, expressed a willingness to participate in the study. Procedure time and time to discharge were similar between groups. The study successfully achieved blinding among the patients at day0 (BI = PVI-0.2 vs placebo- 0) and was maintained throughout the 6-wk and 3M follow-up, among the patients as well as clinical staff. HRQoL improved in the active group in terms of AF PROMS [Improved difference from baseline PVI 23 (±22); vs Placebo 2 (±10), p=<0.001 and SF-12 mental component (MCS) at 12M (PVI 11.8 (±11) vs placebo 8.54(±11.5), p= 0.017). Over a follow up period of 12M, there was a trend towards greater recurrence (60% vs 30%; p=0.07) and repeat procedures (70% vs 40%; p=0.4) in the placebo group. Conclusion: Performing a blinded placebo-controlled interventional study to assess the efficacy of PVI is feasible and high recruitment rates are achievable. CA appears to result in better arrhythmic and QoL outcomes;a full-scale follow-on study will assess the true efficacy of CA in patients with early pers.AF and allow consideration of whether there is a role for DCCV in many patients.

Incidence and impact on arrhythmia recurreces of atrial fibrillation termination during linear radiofrequency ablation in the left atrium

Abstract Atrial Fibrillation Termination During Linear Radiofrequency Ablation in the Left Atrium: Incidence and Impact on Arrhythmia Recurrences Background Termination of atrial fibrillation (AF) during persistent atrial fibrillation (peAF) ablation is infrequent and has shown no clear association with reduced recurrences during follow-up. Linear ablation, often considered to have minimal impact on efficacy, has been primarily explored through creating ablation lines from the mitral annulus to the inferior pulmonary vein or by isolating the posterior wall. Purpose This study aims to assess the incidence of AF termination using an alternative linear ablation approach and its correlation with arrhythmia recurrence during follow-up. Methods Patients enrolled in the PowerFast III trial (a multicenter randomized trial comparing high- power short-duration radiofrequency (RF) application to conventional RF application) with peAF and undergoing linear ablation were included in this sub-study. Conventional pulmonary vein isolation (PVI) was performed using two different RF settings along with a set of RF lines, including anteroseptal (AS), anterolateral (AL), posterior wall isolation between the pulmonary veins, and between the two anterior lines. Patients were categorized into two groups based on AF termination or flutter organization (Group 1) or no AF termination (Group 2) during RF application. All patients were monitored with EKG transmission for one year. Results Fifty-one consecutive patients (mean age 61 years, male 39) were included. AF terminated in 21 patients (41%) during RF application (9 converting to AF and 12 to atrial flutter). AF did not terminate during RF application for PVI, except for one patient during right PV ablation following left PVI. AF termination occurred by posterior wall lines in three patients, roof line in three, and anterior line in two. AF converted into atrial flutter during ablation by a roof line in 5 patients and by an anterior line in 7. No significant differences in atrial arrhythmia recurrence were observed between the two groups (three patients in Group 1 vs. eleven in Group 2, P = 0.11). However, Group 1 exhibited fewer AF recurrences (zero patients) than Group 2 (eight patients, P = 0.015). Conclusions Extensive linear RF ablation resulted in a substantial proportion of patients experiencing AF termination or conversion into atrial flutter. AF termination or conversion did not appear to be correlated with atrial arrhythmia freedom during follow-up but was associated with fewer AF recurrences.Any arrhythmia recurrenceAF recurrence

A straightforward assessment of anterior mitral isthmus lines block

Abstract Background Complex atrial fibrillation (AF) and left atrial flutter (LAFL) ablation procedures often involve creating lines on the anterior wall of the left atrium, such as the anterior septal and lateral mitral isthmus lines. Purpose This study aims to evaluate the role of a simplified criteria to demonstrate the achievement of conduction block across the anterior wall of the left atrium ("anterior mitral isthmus") after linear ablation (LA). Methods Patients scheduled for persistent AF or LAFT ablation were prospectively recruited. The procedure employed a homogeneous LA strategy that included the anteromedial, anterolateral and roof lines. The following intervals were measured before and after LA, placing a multipolar catheter in the left atrial appendage (LAA) in order to register the earliest egm in a reproducible position: 1) P-LAA: conduction time from the sinus P wave onset to the LAA, 2) IASp-LAA: conduction time pacing at CL 500 ms from the interatrial septum to the LAA, 3) CSp-LAA: conduction time pacing at CL 500 ms from the distal CS to the LAA, 4) LAA-QRS onset. Patients with linear ablation were further divided according to the presence or block (BG) or non-block group (NBG) in the anterior at the end of the procedure, demonstrated with a high-density activation map. A parallel control group (CG) of patients with paroxysmal AF without LA was also included for comparison. Statistical analysis involved the Kruskal-Wallis and Mann-Whitney test with Bonferroni correction. Results 21 patients were enrolled in the study: mean age 66.67 years (± 8.48), 80% male sex. Among them, 16 had AF and AFL and underwent LA, while the remaining 5 constitute the CG. Baseline measures before LA did not exhibit significant differences compared to the CG with mean values for P-LAA at 93±20 ms (P=2.35), IASs-LAA at 82±27 ms (P=1.94), CSs-LAA at 52±17 ms (P=0.91), and LAA-QRS at 80±27 ms (P=1.82). However, upon comparing the BG and NBG, significant differences emerged in P-LAA (82±10 ms vs. 11±5 ms (P=0.002) and IAS-LAA (83±17 ms vs. 27±24 ms (P=0.004), while no significant differences were observed in the remaining intervals. In comparisons between the BG and the CG, significant differences were noted in P-LAA (82±10 ms vs. 16±10 ms (P=0.01) and IAS-LAA (83±17 ms vs. 1.2±17 ms (P=0.01), without differences in the other intervals. Conversely, when comparing NB to the CG, no significant differences were observed in any of the intervals. Finally, P-LAA >70 ms and the IASp-LAA >55 ms showed a sensitivity of 100 % and specifitity of 100 vs. 87% respectively to discriminate anterior wall block. Conclusion The simple measurement of the P-LAA and IAS-LAA interval proves highly valuable in evaluating anterior mitral isthmus lines block, serving as a complementary approach to conventional maneuvers. P-LAA >70 ms and IASp-LAA > 55 ms could be usefull to discriminate anterior wall block.Anterior linear ablation with block

A proposed index of myocardial staining for vein of marshall ethanol infusion

Abstract Background Mitral isthmus(MI) conduction block is a fundamental step in anatomical approach treatment for persistent atrial fibrillation(PeAF). However, MI block is hardly achievable with endocardial ablation only. Retrograde ethanol infusion(EI) into the vein of Marshall(VOM) facilitates MI block. Fluorographic myocardial staining(MS) during VOM-EI could be helpful in predicting procedural alcoholization outcome even if its role is qualitatively assessed in the routine. Purpose The aim was to quantitatively assess MS during VOM-EI and to evaluate its association with MI block achievement. Methods Consecutive patients undergoing catheter ablation for PeAF at our Institution from February 2022 to May 2023 were considered. Patients with identifiable VOM were included. A proposed index of MS(MSI) was retrospectively calculated in each included patient. Correlation of MSI with low voltage zones(LVZ) extension after VOM-EI and its association with MI block achievement were assessed. Results 42 patients out of 49 (85.8%) had an identifiable VOM. MI block was successfully achieved in 35 patients out of 42 (83.3%). MSI was significantly associated with the occurrence of MI block (OR 1.24 (1.03 – 1.48); p = 0.022). A higher MSI resulted in reduced ablation time (p = 0.014) and reduced radiofrequency applications (p = 0.002) to obtain MI block. MSI was also associated with MI block obtained by endocardial ablation only (OR 1.07 (1.02 – 1.13); p = 0.002). MSI was highly correlated with newly formed LVZ extension (r = 0.776; p = 0.001). Conclusion In our study cohort, optimal MSI predicts MI block and facilitates its achievement with endocardial ablation only.Myocardial stainingSpline plots

Posterior wall isolation with pulsed field ablation or radiofrequency ablation with vein of marshall ethanol ablation for the treatment of atrial fibrillation

Abstract Background In patients undergoing repeat catheter ablation for atrial fibrillation (AF) two ablation strategies beyond pulmonary vein isolation (PVI) have recently gained increased interest: posterior wall isolation (PWI) using pulsed field ablation (PFA) and Vein of Marshall (VoM) ethanol ablation combined with radiofrequency energy ablation (RFA). However, a direct comparison is lacking. Purpose To compare prospectively enrolled patients undergoing repeat catheter ablation for persistent AF using PVI and PWI with PFA (PFA group) vs. PVI and VoM ethanol ablation using RFA (VoM group) regarding procedural characteristics, safety, myocardial injury and outcomes. Methods Patients undergoing redo PFA-PVI with PWI and VoM ethanol ablation with RFA were included. Isolation and bidirectional block were checked using a multipolar mapping catheter. High-sensitivity cardiac troponin T (hs-cTnT) was measured after 24h of ablation. Results A total of 84 patients were included (age 69 [interquartile range (IQR) 63-75] years; ejection fraction 56% [IQR 48-60%]; left atrial size 42 [IQR 37-47] mm), baseline characteristics did not differ significantly between groups. Of these, 54 patients (64%) were in the PFA group and 30 (36%) in the VoM group. The procedure duration (65 [IQR 56-73] minutes vs 116 [IQR 103-142] minutes; p < .001) and fluoroscopic times (11 [IQR 8–14] minutes vs 14 [IQR 12-19] minutes; p < .001) were significantly shorter for the PFA group than for the VoM group. No major complications were observed except for a probable allergic reaction in the VoM group and a transient AV-block in the PFA group. High-sensitivity cardiac troponin levels post ablation were similar between the PFA group and the VoM group with 886 [IQR 627–1260] ng/L and 793 [IQR 543-1199] ng/L, p=0.28, respectively. During follow-up (median duration 230 [IQR 117-370] days), AF recurrence was observed in 15% in the PFA group and in 40% in the VOM group (p ≤ 0.01). Conclusion In patients undergoing repeat catheter ablation for AF, PVI and PWI using PFA is associated with shorter procedure and fluoroscopic times, similar high-sensitivity cardiac troponin levels and a reduced recurrence rate compared to PVI using RFA with additional VoM ethanol ablation.Central Illustration

Effects of different types of fibrotic remodelling in areas of low voltage on atrial fibrillation dynamics: an in-silico study

Abstract Background Personalized computational models include the effects of personalised anatomy and atrial fibrillation (AF) remodelling in a framework that can be used to investigate patient-specific AF mechanisms and test treatment response, but modelling fibrosis remains an unresolved matter. The interpretation of regions exhibiting low voltage in electroanatomic mapping data at different pacing rates also remain unclear. However, these occurrences are correlated with fibrotic remodelling. We aimed to use patient-specific simulations to investigate the effects of fibrosis type on AF properties by modelling conduction velocity slowing, changes in ionic channels, and replacement fibrosis, incorporated in regions of low voltage identified through omnipolar mapping at different pacing rates. Methods Local activation times (LATs) voltage and geometry data were obtained from patients undergoing ablation for persistent AF. LATs were collected in sinus rhythm with coronary sinus pacing at pacing interval (PIs) of 250ms and 600ms. For a total of 10 cases, personalised anatomical models were constructed for electrophysiology simulations, and analysed using an automated pipeline in python. For conductivity models, areas with peak omnipolar voltage (OV) below 0.5mV were assigned low conduction velocity. To incorporate ionic changes, the ionic properties were altered in fibrotic regions (peak OV < 0.5mV). In the simulations where replacement fibrosis was included through a probabilistic percolation method, percolation was modelled by using random number generator to probabilistically remove elements of low voltage. Pulmonary vein isolation was simulated in each model after 5s of AF, and wavefront propagation patterns were analysed to quantify the number of rotational areas or areas of wavefront break-up in 7 anatomical segments. Results The models with conductivity fibrotic remodelling demonstrated rotational drivers in more than two LA anatomical segments for both CS250ms pacing rate and CS600ms pacing rate across all 10 cases. The anterior wall exhibited the largest degree of rotational activity in 7 out of 10 cases for CS250ms pacing rate and in 9 out of 10 cases for CS600ms pacing rate (Figure A). The combination of percolation and conductivity remodelling also exhibited rotational activity on the anterior wall in 9 out of 10 cases at CS250ms pacing rate, and 7 out of 10 cases for CS600ms pacing rate. For the simulations where replacement fibrosis was included (percolation), both the roof and anterior wall exhibited the largest degree of rotational activity in 5 out of 10 cases at CS250ms pacing rate; while at CS600ms pacing rate, the posterior walled exhibited the majority of rotational activity in 7 cases (Figure B). All fibrosis models containing ionic changes terminated in more than half of the 10 cases for both pacing rates (CS250ms and 600). Conclusion The impact of low voltage on fibrotic remodelling causes complex effects on AF dynamics.