Posterior Left Atrial Research Articles

Unipolar electroanatomical mapping outperforms bipolar voltage in detecting LGE areas in the left atrium

Abstract Introduction In atrial fibrillation (AF) management, understanding left atrial substrate is crucial. While both electroanatomical mapping (EAM) and late gadolinium enhancement MRI (LGE MRI) are reliable methods in assessing atrial substrate and are associated with the ablation outcome, recent findings have highlighted significant discrepancies between bipolar low voltage areas (LVA) in EAM and LGE areas. Objective Explore the relationship between LGE areas and unipolar LVAs by utilizing multipolar high-density (HD) mapping. Methods Nineteen patients scheduled for AF ablation underwent pre-ablation LGE-MRI. Left atrial (LA) segmentation was conducted using a convolutional neural network, which subsequently generated a 3D mesh integrating the LGE data. HD-EAM was performed in sinus rhythm for each patient, capturing at least 4000 points. The EAM map and LGE MRI mesh were co-registered. LVA areas were defined using voltage cut-offs of 0.5 mV for bipolar and 2.5 mV for unipolar measurements. Correspondence between LGE areas and LVAs on the anterior and posterior LA wall was analyzed. Results Both bipolar and unipolar LVA demonstrated high precision in detecting LGE areas (100% and 88% respectively). However, unipolar LVA exhibited a remarkable accuracy of 81% for detecting LGE areas specifically, whereas bipolar LVA displayed a significantly lower accuracy of 28%. These findings were consistent across the different atrial walls. Conclusion Incorporating unipolar voltage data into electroanatomical mapping in the atrium may bridge the observed gap between LGE areas and bipolar LVAs. Our findings highlight the significance of unipolar voltage in evaluating the left atrial substrate, potentially offering a more comprehensive insight into the different layers of atrial walls, and opening the door for new approaches in AF therapy.

Additional left atrial plication improves postoperative cardiovascular events in atrial functional mitral regurgitation.

Left atrial (LA) plication is a procedure used to correct an LA that expands posteriorly due to remodeling. This study aimed to determine the efficacy of additional LA plication in reducing postoperative cardiovascular events (CVEs) after mitral valve (MV) repair in atrial functional mitral regurgitation (MR) patients. Between October 2008 and August 2023, MV repair with or without LA plication in 74 patients was studied. This study examined the efficacy of concomitant LA plication during MV repair. All patients underwent mitral annuloplasty. Of these, 26 underwent additional LA plication. In the mid-term periods, protruding posterior LA length in patients with LA plication was shorter than those without LA plication (2.8±0.49 vs. 3.3±0.72 cm, P=0.01). The percentage change in aortomitral angle from preoperative to mid-term periods in patients with LA plication was bigger than those without LA plication (1.04°±0.102° vs. 0.98°±0.084°, P=0.01). Posterior leaflet coaptation angle in patients with LA plication was smaller than those without LA plication (42°±15° vs. 76°±30°, P<0.001). A postoperative posterior leaflet coaptation angle of 101° had the maximum sum of sensitivity and specificity in predicting postoperative CVEs (96.9% and 76.9%, respectively). Patients with a postoperative posterior leaflet coaptation angle of 101° or higher had a poorer prognosis than those with an angle less than 101°, with an event-free rate of 18% vs. 80% at 7 years after surgery (P<0.0001). Additional LA plication might be useful in reducing postoperative CVEs in atrial functional MR patients.

Characterisation of ablation strategies at redo catheter ablation for atrial fibrillation and predictors of arrhythmia recurrence: results from the AFREDO registry

Abstract Background Patients who have undergone prior pulmonary vein isolation (PVI) for atrial fibrillation (AF) often require a repeat ablation for AF recurrence. The optimal ablative strategy for the redo procedure and predictors of AF recurrence thereafter remain largely unknown. Purpose We aimed to characterise the ablation strategies applied at re-PVI and identify possible predictors of AF recurrence. Methods Our single-centre, retrospective study included all consecutive patients who underwent first redo PVI at our centre from 2017 to 2022. Inclusion criteria required at least one available follow-up visit within the first 12 months after the redo procedure. Ablation strategies of the initial and redo procedure were captured. Kaplan-Meier curves were used to illustrate time of AF recurrence, as classified by predictors of outcome determined by multivariable regression analyses. Results We included 215 patients (39.1% female) with a median age of 66.6 years (IQR 58.6-73.2) at the time of redo procedure. The initial PVI was cryoablation in 39.9%, RFA in 57.7% and surgical ablation in 2.4%. After the initial procedure, 55.8% had paroxysmal AF and 44.2% had persistent AF. At the redo procedure, 25.1% of patients were found to have no PV reconnection, whereas 20.5% had a single reconnected PV, and 54.4% had two or more reconnected PVs. A left-sided flutter ablation was performed in 18.8%, a left atrial (LA) roof line in 16.9%, a posterior mitral isthmus line in 5.2%, an anterior mitral isthmus line in 27.9%, and a posterior box lesion in 8.4%. Overall, 34.4% of patients showed areas of low-voltages in the redo procedure. Patients with areas of low voltages were less likely to have any reconnected PVs in the redo-procedure (p&amp;lt;0.001). After the second ablation procedure, 54.0% experienced AF recurrence. Univariable regression analysis revealed moderate (p=0.006) or severe (p= 0.015) LA dilatation, persistent AF (p=0.005), and posterior LA low voltage areas (p=0.011) as significant predictors of AF recurrence after the redo procedure. The number of reconnected PVs at the re-PVI did not predict AF recurrence (p=0.1090). As illustrated in Fig. 1 and 2, patients with paroxysmal AF experienced less AF recurrence compared to those with persistent AF (log-rank p=0.0025). Moreover, moderate or severe LA dilatation at baseline was associated with more frequent AF recurrences (log-rank p=0.0279). Conclusion A significant proportion of patients undergoing re-PVI experienced AF recurrence. We found that persistent AF and moderate or severe LA enlargement emerged as significant predictors of AF recurrence after the redo procedure. Although PV reconnection was observed in more than two thirds of patients at the re-PVI, it did not predict AF recurrence thereafter. However, patients without PV reconnection had significantly more low-voltage areas, which may be indicative of a different AF recurrence mechanism in this subgroup.Figure 1:Type of AFFigure 2:LA dilatation

Using computed tomogram atrial myocardial thickness maps in high-power short-duration radiofrequency pulmonary vein isolation: UTMOST AF.

High-power short-duration (HPSD) ablation creates wide, shallow lesions using radiofrequency (RF) heating. It is uncertain if adjusting RF energy based on atrial wall thickness provides extra benefits. We studied the safety and effectiveness of tailored HPSD energy based on left atrial (LA) wall thickness (LAWT) for circumferential pulmonary vein isolation (CPVI) in patients with paroxysmal atrial fibrillation (PAF). We enrolled 212 patients (68.4% male, mean age: 59.5 ± 11.0 years) and randomly assigned them to two groups: LAWT-guided CPVI (WT, n = 108) and conventional CPVI (control, n = 104). Both groups used an open irrigated-tip deflectable catheter to apply 50 W for 10 s to the posterior LA, while controls used 60 W for 15 s on other LA regions. RF delivery time in WT was titrated (15 s at LAWT > 2.1 mm, 13 s at 1.4-2.1 mm, and 11 s at <1.4 mm) according to the computed tomogram-myocardial thickness color map. After a mean follow-up of 13.4 ± 7.0 months, the WT and control groups showed no significant difference regarding clinical recurrence rate (13.9% vs. 5.8%, respectively; p = .061) and major complication rate (4.6% vs. 3.8%, respectively; p > .999). The total procedure time, cardioversion rate, and post-procedural AAD prescription rates did not significantly differ between the groups. The LAWT-guided energy titration strategy did not result in improved procedural safety and efficacy compared to the conventional 50-60 W-HPSD CPVI in patients with PAF.

Posterior left atrial isolation is associated with a lower incidence of atrial tachycardia in patients with persistent atrial fibrillation.

Patients may develop atrial tachycardia (AT) after left atrial (LA) ablation of persistent atrial fibrillation (AF). The population consisted of 101 consecutive patients (age = 64.3 ± 8.7years, 70 males (69%), LA = 4.6 ± 0.8cm, ejection fraction = 48.5 ± 16%) undergoing their initial procedure for persistent AF. After pulmonary vein isolation, patients either underwent posterior LA isolation (n = 50; study group) or linear ablation at the LA roof with verification of conduction block (n = 51; control group). A repeat procedure was performed in 17 (34%) and 28 (55%) patients in the study and control groups, respectively (p = 0.02). Patients in the study group were less likely to develop AT (9/50 [18%] vs. 18/51 [35%]; p = 0.02), roof-dependent (1/50 [2%] vs. 8/51 [16%]; p = 0.008), and multi-loop AT (6/50 [12%] vs. 14/51 [27%]; p = 0.03) as compared to controls. Among various factors, only posterior LA isolation was associated with a lower likelihood of AT recurrence and roof tachycardia at redo procedure (OR, 0.37; 95% CI, 0.1 to 1.00, p = 0.05, and OR, 0.1, 95% CI, 0.01 to 0.96; p < 0.05, respectively). In patients with persistent AF, posterior LA isolation is associated with a lower risk of a redo procedure, roof-dependent macro-reentry, and post-ablation AT in general as compared to controls who only received roof ablation. Posterior LA isolation also obviates the need for pacing maneuvers, and may be a more definitive endpoint than linear ablation at the LA roof.

Hybrid convergent ablation: an evaluation of left atrial electroanatomical voltage maps

Abstract Background Hybrid convergent ablation is an effective, emerging treatment for persistent atrial fibrillation (AF) (1). Minimally invasive surgical epicardial left atrial (LA) ablation is performed via a subxiphoid incision to ablate the posterior wall, within the limits of the pericardial reflections, before endocardial catheter ablation is performed primarily to complete pulmonary vein isolation. The overall aim is to create durable, transmural posterior wall ablation to target potential drivers that may sustain persistent AF. Purpose We evaluated electroanatomical maps obtained during endocardial ablation to determine the site and extent of LA posterior wall scar following epicardial ablation and whether this determines outcome in patients undergoing convergent ablation. Methods Patients who underwent Convergent ablation at a single UK cardiac centre (2012-2019) using CARTO-3 mapping system for endocardial ablation were included. Patients who had previous AF ablation were excluded. Low-voltage areas (LVAs) were manually measured using the CARTO-3 system and defined as areas &amp;lt;0.5mV on bipolar voltage maps (pulmonary veins were excluded). Scar location was classified by evaluating for presence and amount of LVA in each quadrant of the posterior LA wall. AF recurrence was evaluated at 12 months post-procedure. SPSS (v. 27) was used for statistical analysis. Results Of the 32 patients included, 7 patients experienced AF recurrence within 12 months post-procedure (21.9%). The average amount of posterior wall LVA following convergent ablation was 54.1% of posterior wall area and 5.8% of total left atrial area, neither of which were associated with 12-month AF recurrence (see Table 1). The presence and extent of LVAs in the upper quadrants were heterogeneous amongst patients and did not relate to AF recurrence. All patients displayed LVAs in the lower quadrants post-epicardial ablation, with the majority having LVAs occupying more than 50% of these quadrants. 96.8% had LVA on the inferior LA surface. In total, 75% of patients had a significant amount of LVA (defined as LVA occupying &amp;gt;50% of the quadrant area) in both lower posterior wall quadrants (see Figure 1) and this feature was associated with lower AF recurrence on multivariable Cox regression analysis (see Table 1). Conclusions Extensive scar was observed in the LA posterior wall in patients following epicardial convergent ablation. The presence of such scar, particularly in the lower regions of the posterior wall, may influence outcomes and be associated with reduced AF recurrence.Table 1Figure 1

Noninvasive ECG imaging of the intrinsic atrial pacemaker and atrial activation in surgically repaired or palliated congenital heart disease.

Sinus node location, function, and atrial activation are often abnormal in patients with congenital heart disease (CHD),due to anatomical, surgical, and acquired factors. We aimed to perform noninvasive electrocardiographic imaging (ECGI)of the intrinsic atrial pacemaker and atrial activation in patients with surgically repaired or palliated CHD, compared with control patients with structurally normal hearts. Atrial ECGI was performed in eightCHD patients with prespecified diagnoses (Fontan circulation, dextro transposition of the great arteries post Mustard/Senning, tetralogy of Fallot), and three controls. Activation and propagation maps were constructed in presenting rhythm. Wavefront propagation was analyzed to identify (1) intrinsic atrial pacemaker breakout site, (2) morphological right atrial (RA) activation pattern, (3) morphological left atrial (LA) breakout sites (i.e., interatrial connections), (4) LA activation pattern, and (5) putative lines of block. Physiologically appropriate atrial activation and propagation maps were able to be constructed. In the majority of patients, atrial breakouts were in keeping with the sinus node, observed in a crescent-shaped distribution from the anterior superior vena cava to the posterior RA. Ectopic atrial pacemaker sites were demonstrated in the atriopulmonary (AP) Fontan patient (very diffuse posterolateral RA) and Mustard patient (very posterior RA competing with a low RA focus). RA propagation was laminar in controls, but suggested either a line of block or conduction slowing consistent with an atriotomy scar in the tetralogy of Fallot (TOF) patients. Putative lines of block were more complex and RA propagation more abnormal in the atrial switch and AP Fontan patients, compared with the TOF patients. RA activation in the extracardiac Fontan patients was relatively laminar. Earliest LA breakout was most commonly observed in the region of Bachmann's Bundle in both controls and CHD patients, except for posterior LA breakouts in two patients. LA activation was typically more homogeneous than RA activation in CHD patients. ECGI can be utilized to create a noninvasive mapping model of atrial activation in postsurgical CHD, demonstrating atrial pacemaker location, putative lines of block and interatrial connections. Once validated invasively, this may have clinical implications in predicting risk of sinus node dysfunction and atrial arrhythmias, or in guiding catheter ablation.

Wide antral circumferential vs. ostial pulmonary vein isolation using pulsed field ablation-the butterfly effect.

Wide antral circumferential ablation (WACA) in comparison to ostial pulmonary vein (PV) isolation (PVI) has been attributed with improved rhythm outcome. We investigated the feasibility, lesion formation, and rhythm outcome of WACA-PVI in comparison to ostial-PVI using pulsed field ablation (PFA). Symptomatic atrial fibrillation (AF) patients (69 years, 67% male; 67% paroxysmal AF) were prospectively enrolled into our single-center registry and underwent first-time ostial-PFA or WACA-PFA, N = 15 each. In all patients, eight pulse trains (2 kV/2.5 s, bipolar, biphasic, 4× basket/flower configuration each) were delivered to each PV. In WACA-PFA, two extra pulse trains in a flower configuration were added to the anterior and posterior antrum of the PVs. For comparison of PFA lesion size, pre- and post-ablation left atrial (LA) voltage maps were acquired using a multipolar spiral catheter together with a three-dimensional electroanatomic mapping system. WACA-PFA resulted in a significant larger lesion formation than ostial-PFA (45.5 vs. 35.1 cm2, p = 0.001) with bilateral overlapping butterfly shape-like lesions and concomitant posterior LA wall isolation in 73% of patients. This was not associated with increased procedure time, sedation dosage, or exposure to radiation. One-year freedom from AF recurrence was numerically higher after WACA-PFA than ostial-PFA (94% vs. 87%) but not statistically significant (p = 0.68). No organized atrial tachycardias (ATs) were observed. Ostial-PFA patients more often underwent re-ablation due to recurrent AF episodes. WACA-PFA is feasible and resulted in significantly wider lesion sets than ostial-PFA. Concomitant posterior LA wall isolation occurred as an epiphenomenon in the majority of patients. The WACA approach was associated with neither increased procedure and fluoroscopy times nor statistically significant differences in 1-year rhythm outcome. ATs were absent.

Lesion formation following pulsed field ablation for pulmonary vein and posterior wall isolation.

Pulsed field ablation (PFA) results in unique lesion formation, but there is lack of in-vivo validation in terms of scar formation following atrial fibrillation (AF) ablation. We aimed to access atrial lesion formation based on late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (CMR) following PFA for pulmonary vein (PV) and posterior wall isolation (PWI). AF ablation was performed in 10 patients using a 31mm pentaspline PFA catheter. After pulmonary vein isolation (PVI; n=8 PFA-applications/ PV; n=4 in basket and n=4 in flower configuration), another eight applications in flower configuration were conducted for concomitant PWI. Patients underwent LGE CMR 3 months after ablation aiming for quantification of left atrial (LA) scar. Acute procedural success was achieved in all patients. Mean procedure duration was 62±7min. and mean LA dwell time of the PFA catheter was 13±2min. Mean post ablation total LA scar burden was 8.1±2.1% and mean scar width was 12.8±2.1mm. At the posterior LA, 22.6±2.2% of the anatomical segment resulted in chronic scar tissue, concentrated at the PW. Postablation CMR found no evidence for PV stenosis or collateral damage of adjacent structures. At 7 months of follow-up, 9/10 patients (90%) were free from arrhythmia recurrence. PFA for AF resulted in durable and transmural atrial scar tissue at the PVs and PW. LGE CMR found a very homogeneous and contiguous lesion pattern with no signs for collateral damage.

Abstract 14874: Electrical Isolation of the Posterior Left Atrium is Associated With a Lower Incidence of Atrial Tachycardia in Patients With Persistent Atrial Fibrillation

Introduction: Patients may develop atrial tachycardia (AT) after left atrial (LA) ablation of persistent atrial fibrillation (AF). Hypothesis: We hypothesized that patients with persistent AF undergoing electrical isolation of the posterior wall of the LA would be less likely to experience AT, and specifically, roof-dependent tachycardia as compared to historical controls who only received linear ablation at the LA roof. Methods: The population consisted of 101 consecutive patients (age= 64.3±8.7 years, 70 males (69%), LA=4.6±0.8 cm, ejection fraction=48.5±16%) undergoing their initial procedure for persistent AF. After pulmonary vein isolation, patients either underwent posterior LA isolation (n=50; study group) or linear ablation at the LA roof with verification of conduction block by established pacing maneuvers (n=51; control group) Results: During the initial procedure for AF, electrical isolation of the posterior LA or linear block at the LA roof were achieved in all patients in the study or control groups, respectively. During follow-up, patients in the study group were less likely to develop AT (9/50 [18%] vs. 18/51 [35%]; p=0.02), roof-dependent (1/50 [2%] vs. 8/51 [16%]; p=0.008), and multi-loop AT (6/50 [12%] vs. 14/51 [27%]; p=0.03) as compared to controls. A repeat procedure was performed in 18 (34%) and 28 (55%) patients in the study and control groups, respectively (p=0.03). After a mean follow-up of 25.3 ± 13, and 50.3 ± 27.3 months, 45 of the 50 study (90%), and 44 of the 51 control patients (86%) remained in sinus rhythm (p=0.72), with 12 and 13 patients taking antiarrhythmic medications, respectively (p=0.43) Conclusions: In patients with persistent AF, posterior LA isolation is associated with a lower risk of a redo procedure, roof-dependent macro-reentry, and post-ablation AT in general as compared to controls who only received linear ablation of the left atrial roof. Posterior LA isolation also obviates pacing maneuvers, the results of which might be equivocal, and may be a more definitive endpoint of linear ablation at the LA roof

Validating left atrial fractionation and low-voltage substrate during atrial fibrillation and sinus rhythm-A high-density mapping study in persistent atrial fibrillation.

Low-voltage-substrate (LVS)-guided ablation for persistent atrial fibrillation (AF) has been described either in sinus rhythm (SR) or AF. Prolonged fractionated potentials (PFPs) may represent arrhythmogenic slow conduction substrate and potentially co-localize with LVS. We assess the spatial correlation of PFP identified in AF (PFP-AF) to those mapped in SR (PFP-SR). We further report the relationship between LVS and PFPs when mapped in AF or SR. Thirty-eight patients with ablation naïve persistent AF underwent left atrial (LA) high-density mapping in AF and SR prior to catheter ablation. Areas presenting PFP-AF and PFP-SR were annotated during mapping on the LA geometry. Low-voltage areas (LVA) were quantified using a bipolar threshold of 0.5 mV during both AF and SR mapping. Concordance of fractionated potentials (CFP) (defined as the presence of PFPs in both rhythms within a radius of 6 mm) was quantified. Spatial distribution and correlation of PFP and CFP with LVA were assessed. The predictors for CFP were determined. PFPs displayed low voltages both during AF (median 0.30 mV (Q1-Q3: 0.20-0.50 mV) and SR (median 0.35 mV (Q1-Q3: 0.20-0.56 mV). The duration of PFP-SR was measured at 61 ms (Q1-Q3: 51-76 ms). During SR, most PFP-SRs (89.4 and 97.2%) were located within LVA (<0.5 mV and <1.0 mV, respectively). Areas presenting PFP occurred more frequently in AF than in SR (median: 9.5 vs. 8.0, p = 0.005). Both PFP-AF and PFP-SR were predominantly located at anterior LA (>40%), followed by posterior LA (>20%) and septal LA (>15%). The extent of LVA < 0.5 mV was more extensive in AF (median: 25.2% of LA surface, Q1-Q3:16.6-50.5%) than in SR (median: 12.3%, Q1-Q3: 4.7-29.4%, p = 0.001). CFP in both rhythms occurred in 80% of PFP-SR and 59% of PFP-AF (p = 0.008). Notably, CFP was positively correlated to the extent of LVA in SR (p = 0.004), but not with LVA in AF (p = 0.226). Additionally, the extent of LVA < 0.5 mV in SR was the only significant predictor for CFP, with an optimal threshold of 16% predicting high (>80%) fractionation concordance in AF and SR. Substrate mapping in SR vs. AF reveals smaller areas of low voltage and fewer sites with PFP. PFP-SR are located within low-voltage areas in SR. There is a high degree of spatial agreement (80%) between PFP-AF and PFP-SR in patients with moderate LVA in SR (>16% of LA surface). These findings should be considered when substrate-based ablation strategies are applied in patients with the left atrial low-voltage substrate with recurrent persistent AF.

Electrophysiological insights into left atrial conduction times and regional velocities in atrial fibrillation patients with and without fibrotic atrial cardiomyopathy

Abstract Background Although considerable progress has been made in understanding the process of arrhythmogenesis in atrial fibrillation (AF) patients and the role of atrial substrate, little is known about atrial conduction characteristics in different grades of fibrotic atrial cardiomyopathy (FACM) and specific left atrial (LA) regions. Purpose The aim of this study was to evaluate left atrial conduction times (LACT) and -velocities (CV) in electroanatomical high density maps during sinus rhythm in AF patients with and without signs of atrial fibrosis. Methods Before radiofrequency catheter ablation electroanatomical high density mapping was performed in 41 AF patients (n=38 persistent, n=3 paroxysmal) using a 10-polar circular mapping catheter and the CARTO3 V7 navigation system (Biosense Webster, Diamond Bar, CA). We evaluated the size of low voltage areas (LVA ≤0.5mV), LACTs and local CVs at the anterior and posterior wall in low voltage areas and normal voltage areas (NVA ≥1.5mV). The latter were specifically calculated in the direction of wave-front propagation (coherent algorithm) by using 3-dimensional coordinates and local activation times of triads of sites. Results 20 FACM and 21 non-FACM maps were analysed (1823±1031 points, n=16 low grade FACM I+II, n=4 high grade FACM III+IV, EF 57.24±6,18%, LAVI 43.01±15,63 ml/m2). The mean total size of LVA in FACM patients was 12.06 cm2 (anterior wall 9.51 cm2, posterior wall 2.55 cm2). LACT was 109.15±25.30 ms in our AF population, whereby LACT was shown to be longer (118.79ms, +18%) in FACM patients compared to patients without substrate (100.40 ms, p=0.01), particularly pronounced in high grade FACM (III–IV) (146 ms, +46%, p=0.001). The extension of LVA fairly strong correlated with LACT duration (Spearman ρ= 0.76). Conduction velocities in LVA revealed significantly lower (−55%) than those in NVA (0.61±0.11m/s vs. 1.34±0.30m/s, p=0.000). When comparing the anterior to the posterior wall, anterior conduction appeared slower than posterior conduction, which was significant in NVA (−12%, 1.02 vs. 1.16 m/s, p=0.0053) and failed to reach statistical significance in LVA (−11.6%, 0.61 vs. 0.069 m/s, p=0.39). See Figure 1 and Table 1 for more clinical and electrophysiological characteristics in FACM vs. non FACM patients. Conclusion Total LACT is significantly prolonged in FACM patients and seems to correlate with LVA size. Compared to areas with a normal bipolar voltage (≥1.5mV) LVAs (≤0.5mV) show a 55% CV reduction. Furthermore, regional CVs were shown to differ between the anterior and the posterior LA wall. Those findings might have an impact on developing substrate-based ablation strategies in catheter ablation of FACM patients. Funding Acknowledgement Type of funding sources: None.

Impact of very wide antral pulmonary vein isolation on esophageal temperature changes during pulsed field ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Esophageal thermal injury (ETI) is a serious drawback of available energy sources for atrial fibrillation (AF) ablation, especially on the posterior left atrial (LA) wall. Pulsed field ablation (PFA) is a novel non-thermal energy source with promising safety advantages over existing methods due to its unique myocardial tissue specificity sparing the esophagus. Objective To evaluate esophageal temperature changes during very wide antral pulmonary vein isolation (PVI) using the PFA system. Methods Thirteen consecutive AF patients (62% with paroxysmal AF; age: 61 years; 70% male) underwent first-time PFA under deep sedation. Eight pulse trains (2kV/2.5 sec, bipolar, biphasic, 4x basket/flower configuration each) were delivered to each pulmonary vein (PV). Extra pulse trains in the flower configuration were added for very wide antral circumferential ablation (vWACA). Continuous intraluminal esophageal temperature (TESO) was monitored with an S-shaped esophageal temperature probe. Results A median of 32 (IQR 32;32) and 8 (IQR 8;9) pulse trains for PVI and vWACA with a procedural time and catheter dwell time of 67 min (IQR 61-69) and 17 min (IQR 16-18) were applied. PFA with vWACA resulted in consecutive posterior LA wall isolation in 11/13 patients. Fluoroscopically, the esophagus coursed near the right PVs in 2/13, left PVs in 8/13 and mid-posterior wall position in 3/13 patients. Maximum TESO increase from baseline was 0.8 ±0.9 °C. However, no clinically relevant TESO changes occurred (Table 1). On short-term, all patients remained asymptomatic for sore throat, cough, or other symptoms potentially related to ETI. No esophago-duodenoscopy was necessary. Conclusion PFA of the PVs and lesion extension to the posterior LA wall demonstrated clinically non-significant TESO changes and has the potential to eliminate the risk of a thermal damage to the esophagus.

Performance of the ablation index during pulmonary vein isolation: periprocedural data from a multicenter registry.

PurposeOur study aimed to assess the achievement of target ablation index (AI) values and their impact on first-pass pulmonary vein isolation (FPI) as well as to identify FPI predictors.MethodsAtrial fibrillation (AF) ablation was performed according to the local practice, and target AIs were evaluated. The actual AI was calculated as the median value of all ablation points for the anterior and posterior left atrial (LA) walls.ResultsA total of 450 patients from nine centers were enrolled. Patients with first-time ablation (n = 408) were divided into the FPI and non-FPI groups. In the FPI group, a higher median target AI was reported for both the anterior and posterior LA walls than those in the non-FPI group. A higher actual AI was observed for the anterior LA wall in the FPI group. The actual AI was equal to or higher than the target AI for the posterior, anterior, and both LA walls in 54%, 47%, and 35% (n = 158) cases, respectively. Parameters such as hypertension, stroke, ablation power, actual AI value on the anterior wall, target AI values on both LA walls, AI achievement on the posterior wall, carina ablation, and operator experience were all associated with FPI in a univariate logistic regression model; only carina ablation was an independent predictor of FPI.ConclusionsAccording to our multicenter study, FPI and a target AI were not achieved in a significant proportion of AF ablation procedures. Higher actual and target AI values were associated with FPI, but only carina ablation can independently predict FPI.

B-PO04-107 INCIDENCE AND CHARACTERISTICS OF CARINAL ABLATION IN PULMONARY VEIN ISOLATION

Radiofrequency ablation (RFA) of the intervenous carinae may be needed for pulmonary vein isolation (PVI) during catheter ablation of atrial fibrillation (AF), possibly due to epicardial connections. We sought to evaluate incidence and characteristics of carinal RFA needed to achieve PVI. A retrospective analysis of 200 AF RFA cases at the Ohio State University Hospital using CARTO 3 (Biosense Webster, Inc.[BSW]), a contact force catheter, real-time lesion quality assessment tool (Ablation Index [AI]) was performed using case data stored on cloud-based storage (CARTONET™, BSW). Each lesion was automatically annotated and regionally assigned to one of the 10 left atrial (LA) anatomical segments (anterior, posterior, inferior, roof, and carina on each side). A total of 22013 lesions were analyzed, including 1302 right and 671 left carinal lesions. PVI was achieved in all 200 patients (50% paroxysmal [PAF] and 50% persistent AF [PersAF]). Carinal RFA was performed only if PVI was not initially achieved after wide area circumferential ablation (WACA) of the PV antra. Ipsilateral only carinal RFA was required in 65 (32.5%) right and 32 (16%) left WACA’s respectively, while 48 (24%) required bilateral carinal RFA and no carinal RFA was required in 55 (27.5%). The right carina required significantly more RFA’s than the left carina (6.5 ± 8.3 vs. 3.4 ± 5.8 [p< 0.001]). There was no difference between the right and left carinae in the contact force (14.2 ± 5.6 g vs 12.5 ± 5.4 g), power (32.2 ± 7.8 W vs. 32.3 ± 7.1 W) or AI (336.8 ±57.4 vs. 327.1 ± 63.1). PersAF required significantly more carinal RFA lesions than PAF (12.3 ± 10.1 vs. 7.45 ± 11.3 [p=0.002]). In 134 patients with carinal RFA and complete AI data, the anterior LA, posterior LA, and the carinae received significantly different levels of AI (429.1 ± 84.8 vs 315.1 ± 48.7 vs. 222.2 ± 79.9 respectively [p< 0.001)]. Carinal RFA was frequently needed for PVI. More RFA in the carinae were needed in right than left PVs consistent with known prevalence of epicardial connections. Interestingly, more carinal RFA was needed in PersAF than PAF. The mean AI in the carinae was significantly lower than AI in anterior and posterior LA. These data may allow more efficient planning of lesion delivery.

B-PO03-090 ABLATION SCAR CAUSES A DECREASE IN PULMONARY VEIN DIAMETER IN ATRIAL FIBRILLATION PATIENTS AND IN HEALTHY SHEEP

A decrease in pulmonary vein (PV) diameter and in left atrial (LA) volume is observed in atrial fibrillation (AF) patients after PV isolation (PVI) ablation. It is unknown whether the changes are due to a direct effect of the ablation scar or to a reverse remodeling initiated by successful ablation. To evaluate PVI-induced changes in 1) PV dimensions in AF patients with successful ablation and in healthy sheep and, 2) atrial contractility in the patients. An increase in contractile force is compatible with reverse remodeling. We retrospectively studied 21 paroxysmal AF patients with functional cardiac magnetic resonance (CMR) before and 3 months after successful PVI (absence of AF during CMR and re-catheterization 3 months post-ablation). PV-LA conduction was observed in all patients upon re-catheterization indicating an incomplete PVI. We therefore studied healthy sheep (n=12) 3 months after incomplete PVI of the right PV. Local LA contractility was measured with a feature-tracking algorithm. The maximal diameter of all PVs decreased after ablation in the patients (19±5 (overall mean±SD) vs. 17±5mm, pre- vs. post-ablation, p=0.019). The PV diameter of the ablated right PV in sheep was also smaller after ablation (14±3 vs. 12±2mm, pre vs. post, p=0.024), whereas the control left PVs were unchanged. The percentage decrease of the ablated PV diameter was similar (11±17% and 9±11% in patients and sheep, respectively, p=0.725). In patients, the maximal LA volume decreased from 103±38 to 92±31ml after ablation (p=0.006). The ablation induced a decrease in the active LA emptying fraction from 27±11 to 22±11% (p=0.031). Moreover, maximal radial strain (defined as motion fraction towards the LA center) during the atrial contractile phase decreased in the posterior LA wall from 8 (11)% (median (IQR)) to 5 (7)% after ablation (p=0.016). The diameter of ablated PVs decreased similarly in AF patients and healthy sheep without AF and was therefore caused by the ablation scar and not by reverse remodeling. Moreover, the atrial contractility decreased after successful ablation in patients, which is incompatible with reverse remodeling. Therefore, the reduction in LA volume was likely also caused by the ablation scar.

The role of a difference between target and actual ablation index values for first-pass point-by-point pulmonary vein isolation: results from a multicenter prospective registry

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Ministry of Science and Higher Education grant (Russian Federation President Grant) Background/Introduction. Pulmonary vein electrical isolation (PVI) is a cornerstone of atrial fibrillation (AF) ablation. The Ablation Index (AI) aims to improve the efficacy and safety of radiofrequency (RF) PVI. First-pass isolation (FPI) is an indicator of PVI acute success. Target AI is being calculated for every operator as a mean value (usually, differently for anterior and posterior left atrial (LA) segments) following several "ideal" first-pass PVI procedures. However, adherence to target values, as well as its clinical importance, are unknown. Purpose. The aim of the present study was to evaluate the difference between the target and actual AI in the real practice. Methods. This work represents data from the Prospective Multicenter AF Ablation Registry. Data were collected using a web-based system. PVI procedures were performed according to the local practice, and RF ablation settings depended on operators’ preferences. Between January 2019 and December 2020, a total of 446 patients were enrolled from 7 centers, 407 of them underwent first-time AF ablation and were included into the analysis (mean age 61 ± 9 years old; 226 (55%) males; 313 (76%) with paroxysmal AF). FPI was determined as PVI achieved after circular ablation around PVs without additional applications plus persistence of bidirectional block over a 20-minute waiting period. Therefore, patients were divided in two groups: Group 1 (FPI, n = 242) and Group 2 (non-FPI, n = 165). Results. There was a significant difference between target (the mean target AI for the anterior LA segments was 438 ± 58 and 390 ± 27 for the posterior segments) and actually achieved mean AI (406 ± 33 for anterior segments and 389 ± 34 for posterior segments) with a greater difference for anterior segments (Δ 26 (95% CI [19; 32], p = 0,0001) than for posterior (Δ 4 (95% CI [0,2; 8], p = 0,042). The number of patients with a mean actual AI lower than a target value on the anterior and posterior LA walls was 219 (54%) and 171 (42%), respectively. In the FPI group higher mean values of target AI were present (FPI 444 ± 52 for anterior and 393 ± 27 for posterior LA segments vs non-FPI 432 ± 51 (p = 0,04) and 387 ± 23 (p = 0,01), respectively). The FPI group was characterized by higher mean actual AIs on anterior segments (FPI 410 ± 36 vs non-FPI 399 ± 25, p = 0,0001). There was no difference between groups in actual AI on the posterior wall (391 ± 27 vs 386 ± 41, p = 0,1). The non-FPI group was characterized by a higher proportion of subjects with hypertension (87% vs 69%, p = 0,0001) and a lower number of subjects with central obesity (body mass index≥30 in 48% vs 57%, p = 0,04). Conclusion(s). According to our prospective multicenter data, target AI is not achieved in a significant proportion of patients during PVI. This is associated with acute PV electrical reconduction and the necessity in additional ablations. FPI can be achieved more frequently when a higher mean AI value is achieved.

The role of marshall bundle epicardial connections in atrial tachycardias after atrial fibrillation ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial tachycardias (ATs) are often seen in the context of AF ablation. Objectives We evaluated the role of the Marshall bundle (MB) network in left atrial (LA) ATs using high-density high-spatial resolution 3D mapping. Methods 199 post-AF ablation LA tachycardias were mapped in 140 consecutive patients (112 (80%) males, mean age: 61.8 years); 133 (66.8%) were macro-reentrant and 66 (33.2%) were scar-related re-entry. MB-dependent perimitral AT (PMAT) was diagnosed where the difference between the post pacing interval and the tachycardia cycle length (PPI-TCL) was &amp;lt;20ms in parts of the expected MB-dependent perimitral circuit (within the VOM, the ridge between the left pulmonary veins and LA appendage (LAA), the anterior LA and between 6- and 11-o’clock of the mitral annulus) and the PPI-TCL was &amp;gt;20ms in areas bypassed by the VOM (the distal coronary sinus (CS), the posterior LA and the mitral isthmus). MB-related re-entry was diagnosed by PPI-TCL &amp;lt;20ms at the left lateral ridge, posterior base of LAA, inferolateral LA or VOM ostium; and PPI-TCL &amp;gt;20ms in the septal annulus. Typically, in MB-dependent localized re-entry, the earliest activation was found along the MB-LA endocardial connection or MB-CS epicardial connection. Results The MB network was found to participate in 60 (30.2%) re-entrant ATs, 31 PMATs and 29 localized re-entries. High-frequency multiphasic fragmented electrograms with long duration were often recorded endocardially or epicardially at the MB-LA or MB-CS connections. The amplitude and duration of these signals were 0.5 ± 0.79 mV and 65 ± 40 ms for MB-PMATs and 0.26 ± 0.28mV and 122 ± 67 ms for MB-localized re-entries. Unipolar EGMs at the site of endocardial-epicardial breakthrough had a rS pattern in all MB-related ATs. Of 60 MB-related ATs, 49 (81.6%) terminated with RF ablation, 44 (73.3%) at the MB-LA junction and 5 (8.3%) at the MB-CS junction, while 9 (15%) terminated after 2.5-5 cc of alcohol infusion inside the vein of Marshall (VOM). Of the 31 MB-related macroreentrant ATs, 17 (54.8%) terminated at the MB-LA junction, 5 (16.1%) at the MB-CS junction and 7 (22.6%) with alcohol infusion inside the VOM. Two macroreentries (6.5%) using the MB did not terminate with RF energy either endocardially at the MB-LA junction or epicardially at the MB-CS junction, and we were unable to identify or cannulate the VOM for ethanol infusion. Of the 29 localized re-entrant ATs using the MB, 27 (93.1%) terminated at the MB-LA junction, none terminated at the MB-CS junction and 2 (6.9%) terminated after alcohol infusion. After a mean follow up of 12 months, only 4 patients (6.7%) had AT recurrence. Conclusions MB re-entrant ATs accounted for up to 29% of the left ATs after AF ablation. Ablation of the MB-LA or CS-MB connections or alcohol infusion inside the VOM is required to treat these arrhythmias. Abstract Figure.

Spatial and quantitative assessment of the correlation between sinus rhythm and atrial fibrillation voltage mapping to identify low voltage substrate in persistent atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG) through DO637/22-3 Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg through the Research Seed Capital (RiSC) program. Introduction Presence of left atrial (LA) fibrotic low voltage substrate (LVS) is associated with high risk for arrhythmia recurrences in patients undergoing pulmonary vein isolation (PVI) for atrial fibrillation (AF). PVI and additional ablation of LVS - as identified by mapping in sinus rhythm (SR) or AF - has been reported to improve SR maintenance rates, despite differences of the extent and distribution of LA-LVS in SR versus AF. Aims To study the relationship between SR and AF voltage maps, we sought to identify the optimal AF voltage threshold providing the highest concordance in the extent and distribution of LVS when comparing voltage maps in SR vs. AF. Methods Using the statistical shape modelling software Scalismo, the voltage information from the SR and AF maps (acquired prior to PVI) from 28 patients (66 ± 7 years, 46% male, 82% persistent AF) was projected onto a representative LA-geometry. Sensitivity and specificity of LVS identification were calculated for varying thresholds during AF and the correlation between the SR (threshold 0.5mV) and AF maps was assessed and areas of agreeing LVS classification (SR &amp; AF) were identified for each patient. The data of all 28 patients were combined to a spatial histogram of agreement between SR and AF low voltage maps. Results The correlation between SR and AF maps was high across all patients, with agreement at 60-95% of all mapped sites (Figure A: each red triangle represents one patient and the respective agreement of LVS classification and substrate extent). The optimal AF threshold - to identify LA-LVS &amp;lt;0.5 mV in SR - was 0.29 mV (Q1-3: 0.20-0.37 mV) and was independent of the underlying extent of LVS during SR (Figure A: each blue asterisk represents one patient and the corresponding AF threshold and substrate extent). Agreement between LVS in AF vs. SR was high across most (&amp;gt;90) patients on the anterior LA, lateral LA and the left atrial appendage. Lower agreement (60% of patients) was observed in the posterior wall (Figure B). Conclusions SR and AF voltage maps reveal high spatial concordance in low voltage substrate at the anterior LA, lateral LA and LA appendage, however significant discordances in LVS are found in 40% of patients at the posterior LA. Further studies on an extended patient cohort should assess if regional voltage-thresholds would result in an improved substrate concordance between AF and SR substrate maps. Abstract Figure.

Toll-like receptor 4 activation modulates pericardium-myocardium interactions in lipopolysaccharide-induced atrial arrhythmogenesis.

Inflammation plays a role in the pathogenesis of atrial fibrillation (AF). Pericarditis enhanced atrial arrhythmogenesis, but the role of the pericardium remains unclear in AF. Activation of the toll-like receptor 4 (TLR4) by binding to lipopolysaccharide (LPS) promotes cardiac electrical remodelling. In this study, we hypothesized that pericarditis may induce atrial arrhythmogenesis via pericardium-myocardium interactions by TLR4 signalling. Pericarditis was induced in rabbits by injecting LPS (1-2 mg/kg) into the pericardium. Conventional microelectrodes were used to record the action potentials of left atrial (LA) posterior walls (LAPWs) and LA appendages (LAAs) with and without attached pericardium in the control or pericarditis-induced rabbits. Cytokine array was used to measure the expression levels of proinflammatory cytokines in control and LPS-treated pericardium. Compared with the controls, the LPS-treated pericardium had higher expressions of IL-1α, IL-8, and MIP-1β. Rapid atrial pacing-induced burst firing in LPS-treated LAPWs and LAAs, and in control LAPWs (but not in LAAs). The incidence of pacing-induced spontaneous activity and burst firing was increased by LPS-treated pericardium but was attenuated by the control pericardium. Moreover, burst firing induced by LPS-treated pericardium was blocked upon administration of the TLR4 inhibitor, TAK-242 (100 ng/mL), ryanodine receptor inhibitor (ryanodine, 3 μM), or calmodulin kinase II inhibitor (KN-93, 1 μM). Healthy and inflamed pericardium differently modulate LPS-induced atrial arrhythmogenesis. Targeting pericardium via TLR4 signalling may be a novel therapeutic strategy for AF.