Termination Of Atrial Fibrillation Research Articles

Characteristics of successful termination of atrial fibrillation by atrial antitachycardia pacing in patients with cardiac implantable electronic devices.

Asymptomatic paroxysmal atrial fibrillation (AF) is often found in patients implanted with cardiac implantable electronic devices (CIEDs). Second-generation atrial antitachycardia pacing (A-ATP) is effective in managing AF in patients implanted with CIEDs. The purpose of this study was to evaluate the efficacy and safety of A-ATP in patients implanted with CIEDs. This was a single-center retrospective study involving 91 patients (male 46 patients, mean age 74 ± 9years) implanted with Reactive A-ATP equipped devices (84 patients with pacemakers, 6 with ICDs, and 1 with a CRT-D). The AF burden, rate of AF termination, and details of the activation of the A-ATP were analyzed in each patient. During a mean follow-up period of 21 ± 13months, A-ATP was activated in 45 of 91 patients (49.5%). No patients had adverse events. Although the efficacy of the A-ATP varied among the patients, the median rate of AF termination was 44%. In comparison to the A-ATP start time, "0min" had a higher AF termination rate by the A-ATP (39.4% vs. 24.4%, P = 0.011). The rate of termination by the A-ATP was high for AF with a long cycle length and a relatively regular rhythm. A-ATP successfully terminated AF episodes in some patients implanted with CIEDs. The optimal settings of the A-ATP will be determined in future studies.

Ventricular response as a predictor of the termination of sustained paroxysmal atrial fibrillation.

Atrial fibrillation (AF) is the most common sustained atrial arrhythmia. Accurate detection of the timing and possibility of AF termination is vital for optimizing rhythm and rate control strategies. The present study evaluated whether the ventricular response (VR) in AF offers a distinctive electrocardiographic indicator for predicting AF termination. Patients experiencing sustained paroxysmal AF for more than 3h were observed using 24-h ambulatory Holter monitoring. VR within 5min before AF termination (VR 0-5min, BAFT) was compared with VR observed during the 60th to 65th min (VR 60-65min, BAFT) and the 120th to 125th min (VR 120-125min, BAFT) before AF termination. Maximum and minimum VRs were calculated on the basis of the average of the highest and lowest VRs across 10 consecutive heartbeats. Data from 37 episodes of paroxysmal AF revealed that the minimum VR0-5min, BAFT (64±20bpm) was significantly faster than both the minimum VR120-125min, BAFT (56±15bpm) and the minimum VR60-65min, BAFT(57±16bpm, p<.05). Similarly, the maximum VR0-5min, BAFT (158±49bpm) was significantly faster than the maximum VR120-125min, BAFT (148±45bpm, p<.05). In the daytime, the minimum VR0-5min, BAFT (66±20bpm) was significantly faster than both the minimum VR60-65min, BAFT (58±17bpm) and minimum VR120-125min, BAFT(57±15bpm, p<.05). However, the mean and maximum VR0-5min, BAFT in the daytime were similar to the mean and maximum VR120-125min in the daytime, respectively. At night, the minimum, mean, and maximum VR0-5min, BAFT were similar to the minimum, mean, and maximum VR120-125min, respectively. Elevated VR rates during AF episodes may be predictors for the termination of AF, especially during the daytime and in patients with nondilated left atria. These findings may guide the development of clinical approaches to rhythm control in AF.

Concurrent vs Staged Hybrid Ablation for Long-Standing Persistent Atrial Fibrillation: A Propensity-Matched Cohort Study.

Long-term success rates of catheter ablation (CA) for long-standing persistent atrial fibrillation (LSPAF) are less than satisfactory. Further improvement of ablation methods is crucial for enhancing the treatment of LSPAF. This study sought to compare the outcomes of concurrent vs staged minimally invasive surgical-catheter hybrid ablation for LSPAF. From December 2015 to December 2021, 104 matched patients (concurrent and staged, 1:1) were included in study. In the concurrent group, both left unilateral thoracoscopic epicardial ablation (EA) and CA were performed simultaneously in one procedure. In the staged group, EA was performed at the first hospitalization. If the patients experienced atrial fibrillation (AF) recurrence, CA was performed between 3months and 1 year after EA. In the concurrent group, 4 patients were restored to sinus rhythm after EA, and 41 were patients restored to sinus rhythm during CA; 86.5% (45 of 52) achieved intraprocedural AF termination during concurrent hybrid ablation. In the staged group, all 52 patients underwent staged CA because of the recurrence of AF or atrial tachycardia (AT). Forty-seven (90.4%) patients achieved intraprocedural AF or AT termination during CA. Freedom from AF or AT off antiarrhythmic drugs at 2 years after hybrid ablation was 79.9% ± 5.7% in the concurrent group and 86.0% ± 4.9% in the staged group (P=0.390). Failure of intraprocedural AF termination (HR: 14.378) was an independent risk factor for AF recurrence after hybrid ablation. Both concurrent and staged hybrid ablation could be safely and effectively applied to treat LSPAF. Improving the intraprocedural AF termination rate predicted better outcomes.

Predicting Major Adverse Events in Patients Undergoing Transcatheter Left Atrial Appendage Occlusion.

The National Cardiovascular Data Registry Left Atrial Appendage Occlusion Registry (LAAO) includes the vast majority of transcatheter LAAO procedures performed in the United States. The objective of this study was to develop a model predicting adverse events among patients undergoing LAAO with Watchman FLX. Data from 41 001 LAAO procedures with Watchman FLX from July 2020 to September 2021 were used to develop and validate a model predicting in-hospital major adverse events. Randomly selected development (70%, n=28 530) and validation (30%, n=12 471) cohorts were analyzed with 1000 bootstrapped samples, using forward stepwise logistic regression to create the final model. A simplified bedside risk score was also developed using this model. Increased age, female sex, low preprocedure hemoglobin, no prior attempt at atrial fibrillation termination, and increased fall risk most strongly predicted in-hospital major adverse events and were included in the final model along with other clinically relevant variables. The median in-hospital risk-standardized adverse event rate was 1.50% (range, 1.03%-2.84%; interquartile range, 1.42%-1.64%). The model demonstrated moderate discrimination (development C-index, 0.67 [95% CI, 0.65-0.70] and validation C-index, 0.66 [95% CI, 0.62-0.70]) with good calibration. The simplified risk score was well calibrated with risk of in-hospital major adverse events ranging from 0.26% to 3.90% for a score of 0 to 8, respectively. A transcatheter LAAO risk model using National Cardiovascular Data Registry and LAAO Registry data can predict in-hospital major adverse events, demonstrated consistency across hospitals and can be used for quality improvement efforts. A simple bedside risk score was similarly predictive and may inform shared decision-making.

First clinical data on artificial intelligence-guided catheter ablation in long-standing persistent atrial fibrillation.

Despite advanced ablation strategies and major technological improvements, treatment of persistent atrial fibrillation (AF) remains challenging and the underlying pathophysiology is not fully understood. This study analyzed the multiple procedure outcome and safety of catheter ablation of spatiotemporal dispersions (DISPERS) detected by artificial intelligence (AI)-guided software in patients with long-standing persistent AF. The Volta VX1 software was used for 50 consecutive patients undergoing catheter ablation for persistent AF. First, high-density mapping (78% biatrial) with a multipolar mapping catheter was performed. In addition to pulmonary vein isolation (PVI), ablation of DISPERS was performed aiming at homogenizing, dissecting, isolating, or connecting DISPERS areas to nonconducting anatomical structures. Follow-up contained regular visits at our outpatient clinic at 1, 3, 6, and 12 months including 7-day Holter electrocardiograms. Patients were mainly suffering from long-standing persistent AF (mean AF duration 50.30 ± 54.28 months). Following PVI, ablation of left atrial and right atrial DISPERS areas led to AF cycle length prolongation (mean of 162.0 ± 16.6to 202.2 ± 21.6 ms after) and AF termination to atrial tachycardia (AT) or sinus rhythm (SR) in 12 patients (24%). No stroke or pericardial effusion occurred; major groin complications (pseudoaneurysm n = 1, atrioventricularfistula n = 1) were detected in two patients. After a blanking period of 6 weeks, recurrence of any atrial arrhythmia was documented in 26 patients (52%). The majority of patients presented with organized AT (n = 15) while AF was present in n = 9 patients and AT/AF was observed in n = 2 patients. Twenty-twopatients underwent reablation. During a mean follow-up of 363.14 ± 187.42 days and after an average of 1.46 ± 0.68 procedures, 82% of patients remained in stable SR. DISPERS-guided ablation using machine learning software (the Volta VX1 software) in addition to PVI in long-standing persistent AF ablation resulted in high long-term success rates regarding AF and AT elimination. Most arrhythmia recurrences were reentrant AT. After a total of 1.46 ± 0.68 procedures, freedom from AF/AT was 82%. Despite prolonged procedure times complication rates were low. Randomized studies are necessary to evaluate long-term efficacy of dispersion-guided ablation using AI.

Artificial intelligence–adjudicated spatiotemporal dispersion: A patient-unique fingerprint of persistent atrial fibrillation

BackgroundSpatiotemporal dispersion-guided ablation is a tailored approach for patients in persistent atrial fibrillation (PsAF). The characterization of dispersion extent and distribution and its association with common clinical descriptors of PsAF patients has not been studied. ObjectivesArtificial intelligence–adjudicated dispersion extent and distribution (AI-DED) was obtained with a machine/deep learning classifier (VX1 Software, Volta Medical) in PsAF patients undergoing ablation. The purpose of this study was to test the hypothesis that AI-DED is unique to each patient and independent of common procedural and clinical parameters. MethodsIn a subanalysis of the Ev-AIFib study (NCT03434964), spatiotemporal dispersion maps were built with VX1 software in 78 consecutive persistent and long-standing PsAF patients. AI-DED was quantified using 2 distinct approaches (visual regional characterization or automated global quantification of AI-DED). ResultsAI-DED paired-subregion Euclidean distance measurements between 78 patients (average distance 5.07 ± 0.60; min 2.23; max 9.75) demonstrate that AI-DED is a patient-unique characteristic of PsAF. Importantly, both AF type and AF history do not correlate with AI-DED levels (R2 = 0.006, P = .53; and R2 = 0.03, P = .25, respectively). The most extensive AI-DED levels are not associated with poorer procedural (83%, 81%, and 83% of AF termination in low, medium, and high dispersion groups, respectively; P = .954) and long-term (88%, 75%, and 91% of freedom from AF/atrial tachycardia after multiple procedures; P = .517) outcomes. ConclusionThe atrial distribution and extent of multipolar electrogram spatiotemporal dispersion follow a nonrandom, albeit patient-unique, distribution in PsAF patients. AI-DED may represent a procedure-implementable fingerprint of the PsAF substrate.

Acute and long-term outcomes of pulmonary vein isolation and left atrial substrate modification for non-paroxysmal atrial fibrillation: a non-randomized trial.

The long-term success rate of nonparoxysmal atrial fibrillation (AF) treated with pulmonary vein isolation (PVI) alone is not ideal. This may indicate atrial fibrosis as a major cause of recurrence. Therefore, the aim of this study is to investigate the efficacy of left atrial substrate modification (LASM) by targeting low-voltage area. A total of 157 consecutive patients with drug-refractory nonparoxysmal AF who underwent radiofrequency ablation during hospitalization in the Third People's Hospital of Chengdu from April 2017 to August 2021 were prospectively included. Stepwise ablation was performed in two different orders: LASM first (n=53) and PVI first (n=104) group. All patients underwent ablation during AF, and the procedural endpoint was AF termination during ablation. In the LASM first group, LASM was performed first and if AF was terminated, PVI was not performed. Similarly, in the PVI first groups, LASM was performed if AF was not terminated. The primary outcome were AF termination and freedom from AF. The secondary outcome was adverse events. Cox regression analysis was used to define predictors of AF termination, and Kaplan-Meier analysis was used to assess differences between groups in AF freedom. The baseline characteristics of the two groups were similar. At a median follow-up of 16 months, the 112 patients (39 in LASM first group and 73 in PVI first group) with AF termination had a higher success rate than the 45 patients who had no AF termination (78.6% vs. 57.8%; P<0.01). The AF termination rate (24/53, 45.3% vs. 12/104, 11.5%; P<0.01) and AF freedom (20/24, 83.3% vs. 7/12, 58.3%; P=0.13) by LASM alone was higher than PVI alone. There were 3 cases of heart failure and 1 case of stroke (4/53) in the LASM first group, and 1 case of pericardial tamponade, 5 cases of heart failure and 1 case of stroke (7/104) in the LASM first group (7.5% vs. 6.7%; P>0.05). LASM provides higher immediate success and a slightly better long-term success rate compared to PVI. Patients who terminated AF were more likely to have AF freedom than those who did not. AF termination during procedure may improve symptoms and reduce hospitalization.

Optoelectronic control of cardiac rhythm: Toward shock-free ambulatory cardioversion of atrial fibrillation.

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, progressive in nature, and known to have a negative impact on mortality, morbidity, and quality of life. Patients requiring acute termination of AF to restore sinus rhythm are subjected to electrical cardioversion, which requires sedation and therefore hospitalization due to pain resulting from the electrical shocks. However, considering the progressive nature of AF and its detrimental effects, there is a clear need for acute out-of-hospital (i.e., ambulatory) cardioversion of AF. In the search for shock-free cardioversion methods to realize such ambulatory therapy, a method referred to as optogenetics has been put forward. Optogenetics enables optical control over the electrical activity of cardiomyocytes by targeted expression of light-activated ion channels or pumps and may therefore serve as a means for cardioversion. First proof-of-principle for such light-induced cardioversion came from in vitro studies, proving optogenetic AF termination to be very effective. Later, these results were confirmed in various rodent models of AF using different transgenes, illumination methods, and protocols, whereas computational studies in the human heart provided additional translational insight. Based on these results and fueled by recent advances in molecular biology, gene therapy, and optoelectronic engineering, a basis is now being formed to explore clinical translations of optoelectronic control of cardiac rhythm. In this review, we discuss the current literature regarding optogenetic cardioversion of AF to restore normal rhythm in a shock-free manner. Moreover, key translational steps will be discussed, both from a biological and technological point of view, to outline a path toward realizing acute shock-free ambulatory termination of AF.

Abstract 17861: Separating Patients With Long-Term Success versus Acute Response From Atrial Fibrillation Ablation Using Explainable Machine Learning

Introduction: It is difficult to predict outcomes from atrial fibrillation (AF) ablation. In particular, it is unclear what physiology explains patients with long-term AF elimination yet no acute response, or vice versa. Hypothesis: We hypothesize that different combinations of electrophysiological and clinical features predict long-term outcome or acute response to AF ablation. We tested this hypothesis using machine learning of a large Registry. Methods: We studied N=561 patients at pulmonary vein isolation (65±10 years, 28% female) with rich clinical data (44 elements, ECGs), and 64 pole global electrograms (EGMs). We propensity matched the dataset 70/30 for training/testing (fig A). We extracted (i) 4 EGM features: dominant frequency (DF), similarity over time, rate (CL), and voltage; (ii) 6 ECG features; (iii) 44 clinical features. We compared 6 ML models including logistic regression to predict 1 year and acute outcomes in the test set, then used explainability (e.g. Shapley scores) to explain the top models and contributing features for each outcome. Results: Of 561 patients, N=390 (69.5%) had 1 year success and N=278 (49.6%) had AF termination by ablation. The best ML model predicted acute response (Random Forest), provided AUROC = 0.83 (fig B) with highest predictors of AF type, RR interval, CL, DF, and voltage. Conversely, the best model for long-term success provided AUC of 0.65 (accuracy of LT vs acute: p&lt;0.001 McNemar test), but top features were PR interval, QRS axis, AF duration, and age (shapley Rsq = 0.11, fig C). Predictors for long term outcome poorly predicted acute outcome and vice versa (fig C). Conclusions: Clinical features for long-term and acute response to AF ablation were quite different, applying several classification methods to a well-characterized registry. Confirmation in other registries may reveal novel phenotypes to guide clinical decision making or procedural planning, and shed mechanistic insights.

Abstract 14702: Roles of Atrial Mass Reduction and Gaps on the Anti-Atrial Fibrillatory Effects of Pulmonary Vein Isolation: A Computational Modeling Study

Background: Although pulmonary vein isolation (PVI) is the basis of atrial fibrillation (AF) catheter ablation (AFCA), the conditional changes of an anti-AF effect and the wave-dynamic mechanism are poorly understood. Therefore, we compared the effects of PVI based on the ablation circumference, width, and number or locations of gaps with or without amiodarone at the same condition in realistic computational modeling of human AF. Hypothesis: An anatomical level of PVI and characteristics of the PVI gap would affect the anti-AF effects of the AFCA. Methods: We included 50 patients (76.0% persistent AF) who underwent AFCA. Realistic AF modeling reflecting the computed tomography (CT) and the electroanatomical map was performed on each patient. We compared the AF defragmentation rate (DeFR; change to atrial tachycardia (AT) or termination), termination rate (TnR), and changes in the dominant frequency (DF) and the number of phase singularities (PSs) based on the PVI level (antral vs. ostial), PVI width (single vs. 3х width), number and location of 2-mm PVI gaps with or without amiodarone (10mM). We randomly assigned the number and location of the PVI gaps to the AF models. Results: The antral PVI had a significantly higher DeFR (p for trend &lt;0.001) and TnR (p for trend &lt;0.001) than the ostial PVI, PVI gaps, or baseline AF. However, there was no difference depending on PVI width. Among the PVI gaps, the DeFR (p for trend&lt;0.001) decreased as the gap number increased. Additional amiodarone increased DeFR (p=0.003) and TnR (p=0.034) and reduced DF (p&lt;0.001) and the number of PSs (p&lt;0.001) with PVI-gap, especially with a single PVI-gap. Conclusions: In this realistic computational modeling study with integrated patients’ atrial anatomy and electrophysiology, the atrial mass reduction depending on the anatomical PVI level, number of PVI gaps, and additional antiarrhythmic drug significantly affected the AF maintenance mechanisms.

Predicting spontaneous termination of atrial fibrillation based on dual path network and feature selection

The termination mechanism of Atrial Fibrillation (AF) is still unclear. In order to avoid the potential incomprehensiveness in feature extraction via manual techniques, a Dual Path Network-SVM (DPNet-SVM) was constructed in this study for predicting the spontaneous termination of AF. The dual paths of the network extracted time and time–frequency domain features, respectively. Different sizes of depthwise separable convolution (DS-Conv) were used in both paths, which enhanced feature extraction via exploration of different sensory fields. Then four methods were used for feature selection. Finally, SVM was employed for AF termination prediction. After validating the model performance based on 1-min fragments, we conducted experiments on 10-second fragments. On the AFTDB public dataset, the accuracy, sensitivity and specificity of 95.6%, 93.3% and 91.8% were obtained, respectively. On the clinical data from Shandong Provincial Hospital (SPHD), the three metrics were 94.3%, 92.9% and 95.4%, respectively. The subsequent cross-database experiment proved the model's good generalization capability, and also substantiated its feasibility in practical applications involving wearable ECG data.

Percolation theory as a conceptual framework to explain spontaneous atrial fibrillation termination: a pilot study.

Atrial fibrillation (AF) strikingly possesses the ability to abruptly transition into more organized electrical activity and spontaneously terminate, even after persisting for long periods. Despite being central to the clinical behavior and treatment of AF, these phenomena remain incompletely understood. In this paper, we hypothesized that the spontaneous termination of AF may represent a type of percolation phase transition, which is more likely to occur when a domain spanning cluster of refractory sites in the atrium are connected (called a 'percolation cluster'). This was assessed in n=50 computational simulations of AF developed using the Aliev-Panfilov (APV) 2-dimensional cell model. In self-terminating simulations of AF, it was found that the average refractory cluster size, χ(p) (median: 647.7), and the largest refractory cluster size, M1 (median: 1702.3), abruptly increased just prior to AF spontaneously terminating, indicating the onset of the formation of a domain spanning percolation cluster. In contrast, simulations of sustained AF did not demonstrate an increase in χ(p) (median: 463.0) and M1 (median: 1448.2). Self-terminating AF simulations also demonstrated hallmark properties characteristic of a percolation phase transition, such as an abrupt increase in χ(p) at the critical occupation probability pc. The cluster size distribution was also shown to obey a power law for various occupation probabilities p, also indicative of a percolation phase transition. Collectively, these properties suggests that the spontaneous termination of AF could be a form of percolation phase transition, which could provide new insights for AF treatment.

Distributions and number of drivers on real-time phase mapping associated with successful atrial fibrillation termination during catheter ablation for non-paroxysmal atrial fibrillation.

Real-time phase mapping (ExTRa™) is useful in determining the strategy of catheter ablation for non-paroxysmal atrial fibrillation (AF). This study aimed to investigate the features of drivers of AF associated with its termination during ablation. Thirty-six patients who underwent catheter ablation for non-paroxysmal AF using online real-time phase mapping (ExTRa™) were enrolled. A significant AF driver was defined as an area with a non-passively activated ratio of ≥ 50% on mapping analysis in the left atrium (LA). All drivers were simultaneously evaluated using a low-voltage area, complex fractionated atrial electrogram (CFAE), and rotational activity by unipolar electrogram analysis. The electrical characteristics of drivers were compared between patients with and without AF termination during the procedure. Twelve patients achieved AF termination during the procedure. The total number of drivers detected on the mapping was significantly lower (4.4 ± 1.6 vs. 7.4 ± 3.8, p = 0.007), and the drivers were more concentrated in limited LA regions (2.8 ± 0.9 vs. 3.9 ± 1.4, p = 0.009) in the termination group than in the non-termination group. The presence of drivers 2-6 with limited (≤ 3) LA regions showed a tenfold increase in the likelihood of AF termination, with 83% specificity and 67% sensitivity. Among 231 AF drivers, the drivers related to termination exhibited a greater overlap of CFAE (56.8 ± 34.1% vs. 39.5 ± 30.4%, p = 0.004) than the non-related drivers. The termination group showed a trend toward a lower recurrence rate after ablation (p = 0.163). Rotors responsible for AF maintenance may be characterized in cases with concentrated regions and fewer drivers on mapping.

Predictors of pacemaker implantation within three months after catheter ablation of atrial fibrillation.

It is inevitable for patients to have a temporary or permanent pacemaker implanted during or after radiofrequency catheter ablation (RFCA) for treatment of atrial fibrillation (AF) in some cases. The aim of our study was to evaluate the incidence of pacemaker implantation (PMI) during or within 3 months of RFCA for AF and to identify the risk factors that were associated with PMI. We performed a retrospective analysis of consecutive AF patients who underwent RFCA between August 2018 and October 2020 at our center. The incidence of PMI within 3 months during or after RFCA were assessed. A multivariate logistic regression model was performed to identify predictors of PMI. One thousand and five patients (mean age, 60.2±10.3 years; 37.6% women) were included in this analysis. PVI was performed in all patients. A total of 23 (2.3%) patients had a pacemaker implanted within 3 months during or after ablation. Multivariable logistic regression analysis revealed that older age (OR: 1.08 [95% CI 1.03-1.13], p=.003), female sex (OR: 3.08 [95% CI 1.28-7.45], p=.012), paroxysmal AF (OR: 4.71 [95% CI 1.09-20.45], p=.038) and repeated ablation (OR: 2.78 [95% CI 1.04-7.40], p=.041) were the independent predictors for PMI. Older age, female sex, paroxysmal AF and repeated ablation were identified as predictive risk factors for PMI after RFCA in patients with AF. A "watch and wait" strategy could be taken for patients with temporary PMI after ablation, especially for those with prolonged sinus pause after AF termination.

Mild elevation of extracellular potassium greatly potentiates the effect of sodium channel block to cardiovert atrial fibrillation: The Lankenau approach

Cardioversion of atrial fibrillation (AF) is a common clinical necessity and there is a need for more effective and safe options for acute cardioversion of AF. To test the hypothesis that the efficacy and time course of AF cardioversion by sodium channel current (INa) block can be improved by mild elevation of extracellular potassium ([K+]0). Using a canine acetylcholine (ACh)-mediated AF model (isolated coronary-perfused right atrial preparations with a rim of right ventricle), we evaluated the ability of flecainide to suppress AF in the presence of [K+]0 ranging from 3 to 8 mM. At [K+]0 of 4 mM (baseline), persistent AF (>1 hour) was induced in 5/5 atria in the presence of 0.5 μM ACh. Flecainide alone (1.5 μM) cardioverted 3/6 atria at 4 mM [K+]0, 1/6 atria at 3 mM [K+]0, 5/5 atria at 5 mM and 6 mM [K+]0, and 4/4 atria at 8 mM [K+]0. In the absence of flecainide, an increase in [K+]0 from 4 to 5, 6 and 8 mM terminated AF in 0/5, 2/6, and 4/4 atria. The time to conversion was also abbreviated by elevation of [K+]0. Following AF termination with flecainide plus elevated [K+]0, AF was either not inducible or brief (< 100 sec). Combined flecainide and elevated [K+]0 (6 mM) caused an atrial preferential depression of excitability. Our findings suggest that a combination of INa block accompanied by mild elevation of serum potassium may be a novel approach to more effectively, rapidly, and safely cardiovert AF and prevent its recurrence in the short term.

The spatiotemporal electrogram dispersion ablation targeting rotors is more effective for elderly patients than non-elderly population.

Modulating atrial fibrillation (AF) drivers has been proposed as one of the effective ablation strategies for non-paroxysmal AF (non-PAF). However, the optimal non-PAF ablation strategy is still under debate because the exact mechanisms of AF persistence including focal activity and/or rotational activity, are not well-understood. Recently, spatiotemporal electrogram dispersion (STED) assumed to indicate rotors in the form of rotational activity is proposed as an effective target for non-PAF ablation. We aimed to clarify the effectiveness of STED ablation for modulating AF drivers. STED ablation plus pulmonary vein isolation was applied in 161 consecutive non-PAF patients not undergoing previous ablation. STED areas within the entire left and right atria were identified and ablated during AF. After the procedures, the STED ablation's acute and long-term outcomes were investigated. (1) Despite a more effective acute outcome of the STED ablation for both AF termination and non-inducibility of atrial tachyarrhythmias (ATAs), Kaplan-Meier curves showed that the 24-month freedom ratio from ATAs was 49%, which resulted from the higher recurrence ratio of atrial tachycardia (AT) rather than AF. (2) A multivariate analysis showed that the determinant of ATA recurrences was only a non-elderly age, not long-standing persistent AF, and an enlarged left atrium, which were conventionally considered as key factors. STED ablation targeting rotors was effective in elderly non-PAF patients. Therefore, the main mechanism of AF persistency and the component of the fibrillatory conduction might vary between elders and non-elders. However, we should be careful about post-ablation ATs following substrate modification.

PO-02-065 CATHETER ABLATION WITH TERMINATION OF PERSISTENT ATRIAL FIBRILLATION USING SPATIOTEMPORAL DISPERSION

Several strategies of electrogram (EGM) guided catheter ablation of atrial fibrillation (AF) have been previously described. A spatiotemporal dispersion (SD) ablation strategy targeting AF drivers with very high termination rates has been reported; however, these sites have not been well characterized. The purpose of this study is to validate the prior experience with SD ablation in the persistent AF cohort and further characterize the regions of AF termination. Consecutive patients with persistent AF undergoing radiofrequency catheter ablation were included. Electroanatomic mapping of SD areas was performed during AF. Ablation was delivered initially at sites of continuous SD, followed by pulmonary vein isolation in all patients. If AF did not terminate, additional regions of intermittent SD were ablated. If AF terminated to atrial tachycardia or flutter, additional electroanatomic mapping and ablation was performed to achieve sinus rhythm. Representative EGMs at sites of continuous SD, intermittent SD, and no SD are shown in Figures 1A, 1B, and 1C, respectively. Left atrial (LA) volume and surface area, termination sites, and procedural characteristics are reported. A total of 20 consecutive patients (13 male, 67 ± 9 years) with persistent AF (median time from diagnosis 5 years) undergoing ablation were included in the study. The majority of continuous SD was seen on the anterior wall (18/20 patients) and septum (15/20 patients) and occasionally on the posterior wall (8/20 patients). 17/20 (85%) patients successfully terminated to sinus rhythm during the procedure. The majority of the termination sites were on the septum and anterior wall (12/17) with none on the posterior wall. LA volume by echocardiography was smaller in the termination group (84 vs. 105 mL, p < 0.01) and fluoroscopy use was less in the termination group (2.3 vs. 4.8 min, p = 0.03). There was no difference in ejection fraction, LA surface area, radiofrequency time, or procedure time (p = NS). A very high termination rate of persistent AF was achievable with ablation of SD regions. These regions likely represent drivers of AF and seem to localize predominantly on the septum and anterior wall of the LA, and rarely on the posterior wall. Ablation incorporating SD mapping may allow for patient-tailored approach to AF ablation.

PO-02-207 PREDICTION OF CORRELATION LENGTH FROM THE SURFACE ELECTROCARDIOGRAM IN ATRIAL FIBRILLATION

Correlation length in atrial fibrillation (AF) can be calculated from intracardiac electrograms (EGMs) and conceptualized as the distance over which electrical signals remain synchronized. Emerging data shows correlation length predicts AF termination and is associated with outcomes after AF ablation. The capacity to estimate correlation length non-invasively would be a major advance for its applicability to clinical care. Association with non-invasive electrocardiographic (ECG) measurements is currently unknown. We sought to determine if correlation length, measured from EGMs at the time of AF ablation, can be predicted non-invasively from the surface ECG in AF. We conducted a prospective, multicentre, observational study, with a published and registered protocol (ACTRN12619001172190p) of participants undergoing clinically indicated AF ablation. Data collected included (1) detailed clinical phenotyping of participants pre-procedurally, (2) intraprocedural mapping of spontaneous or induced AF with a HD Grid catheter, recording 1-minute EGM segments in 6 right atrial and 10 left atrial anatomic locations, sampled at 2000Hz, with simultaneously acquired ECG. Correlation length is a measure of the distance over which EGMs remain synchronized, measured by calculating the cross-correlation of nearby EGMs as a function of distance. Predictors of correlation length were modelled with a multilevel mixed-effects gamma generalised linear regression. The study recruited n=42 participants. Correlation length could be predicted by surface ECG metrics, including ECG dominant frequency (DF) (coefficient -0.0509, 95% CI -0.0881- -0.0136, p=0.007), Hursts exponent (coefficient -11.66, 95% CI -20.90 - -2.42, p=0.013), Kurtosis (coefficient -0.0034, 95%CI -0.0059 - -0.0009, p=0.007), and Shannon entropy (coefficient -0.1701, 95% CI -0.3319- -0.0083, p=0.039) (see figure 1). The directionality of these findings is biologically plausible. ECG features which did not predict the invasive correlation length included ECG standard deviation (p=0.466), ECG skewness (p=0.332), ECG period (p=0.314) and ECG mean (p=0.261). Intracardiac correlation length is associated with surface ECG features. Importantly, ECG features are measurable non-invasively, meaning this approach could be expanded to patients not undergoing AF ablation, or prior to AF ablation. Given correlation length associates with clinical parameters and outcomes, this metric may help to personalize AF therapy in the future.

PO-02-160 NOVEL APPLICATION OF THE WAVE DYNAMICS USING HIGH DENSITY VECTOR FIELD MAPPING FOR PERSISTENT ATRIAL FIBRILLATION

Catheter ablation for persistent atrial fibrillation (AF) has shown limited success. The vector field (VF) mapping illustrates the stationary waveform propagating during AF, can compute the global propagation patterns to demonstrate the mechanism of AF maintenance. This study aimed to visualize the global wavefront pattern during AF by using VF mapping and investigate the ablation outcome based on different pattern. In phase 1 study, we applied a cellular automation technique to simulate the electrical wave propagation to improve the VF mapping algorithm, involving analysis of high similarity electrogram vectors to to display the stable wave propagation of AF. In the phase 2 study, patients with persistent AF underwent catheter ablation were prospectively enrolled. (Group 1 [N=35]: AF drivers emanating from 1 or more PVs; Group 2 [N=30]: No AF drivers emanating from 1 or more PVs). VF mapping and PRISM-guided PVI was performed in all patients. The patient characteristics and procedural data were extracted for analysis. We evaluated the single-procedure freedom from AF after first ablation procedure. We identified an average of 2.7±2.0 VF regions per patients. These regions (N=177) involved PV (N=100) and left atrium (N=77). A higher procedural AF termination rate (43%vs. 17%, P=0.03) was achieved in Gp-1 than Gp-2. Gp-1 patients had a significant reduction in all arrhythmia recurrence compared to Gp-2. After multivariate analysis, the behavior of driver emanating from PV (Hazards ratio [HR] 0.426, 95% confidence interval [CI]: 0.187-0.968, P =0.042) and the left atrial diameter (HR 1.092, 95% CI: 1.021-1.169, P = 0.011) independently predicted the recurrence. VF mapping of persistent AF revealed the waveform dynamic of the entire atrial chamber and revealed the spatially stable AF drivers with sink-to-source phenomenon to the rest of the atrium. The arrhythmogenic drivers within PVs/antra are predictive of the successful PV isolation in patients with persistent AF.

Multi-centre, prospective randomized comparison of three different substrate ablation strategies for persistent atrial fibrillation.

The optimal strategy for persistent atrial fibrillation (PerAF) is poorly defined. We conducted a multicentre, randomized, prospective trial to compare the outcomes of different ablation strategies for PerAF. We enrolled 450 patients and randomly assigned them in a 1:1:1 ratio to undergo pulmonary vein isolation and subsequently undergo the following three different ablation strategies: anatomical guided ablation (ANAT group, n = 150), electrogram guided ablation (EGM group, n = 150), and extensive electro-anatomical guided ablation (EXT group, n = 150). The primary endpoint was freedom from atrial fibrillation (AF) lasting longer than 30 s at 12 months after a single ablation procedure. After 12 months of follow-up, 72% (108) of patients in the EXT group were free from AF recurrence, as compared with the 64% (96) in the EGM group (P = 0.116), and 54% (81) in the ANAT group (P = 0.002). The EXT group showed less AF/atrial tachycardia recurrence than the EGM group (60% vs. 50%, P = 0.064) and the ANAT group (60% vs. 37.3%, P < 0.001). The EXT group showed the highest rate of AF termination (66.7%), followed by 56.7% in the EGM group, and 20.7% in the ANAT group. The AF termination signified less AF recurrence at 12 months compared to patients without AF termination (30.1% vs. 42.7%, P = 0.008). Safety endpoints did not differ significantly between the three groups (P = 0.924). Electro-anatomical guided ablation achieved the most favourable outcomes among the three ablation strategies. The AF termination is a reliable ablation endpoint.