Voltage Area Research Articles

Predictive value of clinical risk scores for determination of left atrial low voltage area and arrhythmia recurrences in patients undergoing atrial fibrillation ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Presence of left atrial low voltage area (LVA) is an independent predictor of atrial tachyarhythmia (ATa) recurrences after atrial fibrillation (AF) ablation. Thus identifying patients with LVA by using non-invasive methods is an important endeavour. Purpose In this study; we investigated the predictors of LVA and postablation recurrences especially focusing on clinical risk scores. Methods We enrolled 328 consecutive patients who underwent initial AF ablation procedure using high density mapping. LVAs were assessed and segmental distribution was noted in each patient. CHA2DS2-VASc, HATCH, APPLE and SPEED scores were calculated. Predictive value and arrhythmia recurrences were evaluated. Results Two hundred and twenty one patients (67.37%) were paroxysmal AF and 107 (32.62%) patients were non-paroxysmal AF at the time of ablation. Mean CHA2DS2-VASc score was 1.88±1.66, mean APPLE score was 1.20±1.20, HATCH score was 0.93±1.00 and SPEED score was 1.54±1.27 in the whole study group. LVA was detected in 131 patients (39.93%). Female gender [OR:2.94, CI: 1.34-6.43, p=0.007), non-paroxsymal AF (OR: 2.49 CI:1.13-5.46, p=0.023), APPLE score ≥1 (OR:1.69 CI:1.12-2.55, p=0.012) and SPEED score ≥ 1 (OR: 1.47 CI:1.00-2.14, p=0.045] were independent predictors for the presence of LVA in multivariate analysis. Presence of LVA (OR:1.98; CI:1.13-4.15; p=0.017) and HT (OR:2.00; CI:1.19-3.38; p=0.009) were the independent predictors of recurrences. Conclusion Higher clinical scores are associated with more LVA which is associated with ATa recurrence. However the predictive value of these risk scores is limited. Better risk scoring systems are needed to precisely identify the underlying atrial substrate in this patient group.

Beat to beat P wavelet analysis in addition to standard P wave indices as correlates of left atrial extent of low voltage areas in patients with PAF undergoing catheter ablation

Abstract Funding Acknowledgements Type of funding sources: None. BACKROUND Left atrium (LA) fibrosis has been shown to be an important factor associated with atrial fibrillation recurrence after catheter ablation (CA). Morphological features of the P wave have been related to the extent of atrial fibrosis as identified with electroanatomic mapping (EAM) in patients with paroxysmal atrial fibrillation (PAF) undergoing catheter ablation (CA). The ability to assess, by means of non-invasive markers, the electroanatomical substrate of the LA and the likelihood of PAF recurrence after CA, could be very useful in PAF management, patient selection for CA and improving outcomes. Purpose In the current prospective cohort study we aimed at establishing a pathophysiological basis of beat-to-beat (B2B) P-wave morphological and wavelet analysis, showing that it is associated with areas of considerable fibrosis, as identified with EAM in patients with PAF. Methods 44 patients with symptomatic paroxysmal AF, diagnosed at least 6 months before, were enrolled. 12-lead electrocardiogram (ECG) recordings, as well as 12 min vectorcardiogram (VCG) recordings were obtained from all patients, while EAM of left atrium (LA) was performed in all patients before radiofrequency CA. B2B P-wave morphological and wavelet analysis was performed according to a methodology described in previous publications. Results The 35 patients who were valid for statistical analysis were divided into 2 groups: in Group A the total low-voltage (<0.5 mV in EAM) area was greater than the median value of 5.55% (large low-voltage area), while in Group B the total low-voltage area was <5.55% (small low-voltage area). From the correlation between standard P-wave indices derived from 12-lead ECG and low-voltage areas only P-wave duration was significantly different between the two groups. From orthogonal ECG parameters analysis X axis was the most representative of low-voltage areas. B2B P-wave analysis revealed 3 features which showed a statistically significant difference between the 2 groups and no collinearity (Table 1). Logistic regression analysis of the non correlated variables for the prediction of low-voltage areas is shown in Table 2. It seems that a longer distance between the P-wave peak and the P-wave end, as well as a more «flattened» P-wave (small area with long duration) is associated with larger low-voltage areas and consequently more extensive LA fibrosis. Conclusions In patients with PAF and no overt atrial myopathy, B2B wavelet analysis may be a useful non-invasive tool for the prediction of low-voltage areas, representing fibrosis in the LA. Further studies in larger cohorts of patients are needed in order to confirm these findings and enable the use of B2B wavelet analysis in clinical practice.

Insights into level of pulmonary vein isolation using pulsed-field ablation for atrial fibrillation and unexpected effects in the posterior wall

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Pulse field ablation (PFA) has emerged as an effective, safe and efficient tool for pulmonary vein isolation (PVI). Purpose We studied the extent of PVI, specifically the isolation of PV antrum, carina and left atria’s posterior wall after PFA with an ultrahigh density mapping (UHD). Methods We involved the first patients referred for atrial fibrillation (AF) ablation treated with a PFA multispline catheter. PFA-lesion extension was assessed with a voltage-map UHD mapping performed before and immediately after PVI. Results Sixty-one consecutive patients underwent PVI with PFA (62±10 year old, 23 women, 39 paroxysmal AF). Four out of 61 patients were excluded because their posterior wall was isolated with extra aplications on purpose. Acute results involved a 100% success of PVI and the only safety issue was a pericardial effusion in one patient managed conservatively. Mean procedure and fluoroscopy times were 59±39 min and 16±5 min, respectively. UHD immediately after PVI revealed early reconnection just in one vein (1/228 veins). PFA created wide antral circumferential lesions without electrical activity registered by UHD mapping inside the isolation area. There were no notch-like normal voltage areas at the anterior or posterior side of carinas. As a result of the PVI with this technology, it was observed the existence of a narrow corridor in the posterior wall in 8 patients (14%) and in another 8 cases right and left antral ablation converged at the posterior wall creating an unexpected isolation area. There was a significant relationship between LA posterior inter-carina distance and posterior wall´s level of isolation (77,1±7mm, no affectation; 68,8±7mm narrow corridor; 60,3±1mm posterior wall isolation (fig 1); p=0.036). Finally, it was a significant linear correlation between posterior inter-carina distance and the distance between the ipsilateral, antral levels of isolation at the posterior wall (fig 2, r=0.79, p=0.001) Conclusion(s) PFA creates wide antral circumferential PVI lesions involving the ipsilateral veins carina. Nevertheless, in small left atria it can create an undesired isolation or a narrow corridor in the posterior wall.

Identification of the fossa ovalis by voltage mapping using a high-density mapping catheter

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Transseptal puncture (TP) is routinely performed under fluoroscopy and/or echocardiography guidance. Additional methods to localize the fossa ovalis (FO) may decrease radiation exposure, as well as periprocedural risk. In the recent years, high-density mapping (HDM) catheters have been used for mapping and ablation of left atrial (LA) arrhythmias. Purpose The aim of this study is to determine whether a HDM catheter can reliably identify the specific FO electrogram (EGM) patterns. Methods During atrial fibrillation (AF) ablation, a voltage map of the right-sided atrial septum was created using a HDM catheter (Pentaray, Biosense Webster, USA, spacing 2-6-2 mm). The location of the FO was identified by transesophageal echocardiogram and fluoroscopy guidance prior to TP. At the end of the procedure, a 3D phantom was created during catheter retrieval from the left to the right atrium through the TP. Post ablation analysis was done to evaluate whether the HDM catheter was able to record EGM characteristics of the FO. Results Fifteen patients were included (male 63%, mean age 61.2±11.7 y. o.); 80% of the cases were in sinus rhythm, 53% had a normal LA size, and the mean CHADS2-VA2SC score was 1.5 ± 1.6. One patent fossa ovalis and one septal pouch of the left atrium were seen. In all patients, an area of low voltage could be identified in the vicinity of the transseptal puncture. In 74%, the location of transseptal puncture was inside of the area of low voltage. The mean voltage value of this area was 0.6 ± 0.3 mV, whereas the mean voltage value of the myocardium surrounding the "low voltage area" was 4.3 ± 2.1 mV (P<0.01). The surface of the low voltage could be best demarcated using a scale from 0.05 -1.5 mV with an area measured at 3.8 ± 2.6 cm2 [Figure 1]. At other voltage scales, the FO surface demonstrated smaller areas of low voltage (scale/surface [mV/cm2] : 0.05-0.5/ 0.8 ± 1.3; 0.05-1.0/2.2 ± 1.8; 0.5-1.0/2.3±1.6). In 63%, fractionated potentials were recorded in the area of the FO [Figure 1]. Conclusions Based on its EGM characteristics, the fossa ovalis can be accurately localized with a high-density mapping catheter. This finding will certainly help to implement radiation free procedure particularly when echocardiographic modalities are not available. Figure 1: Mapping of the region of the fossa ovalis with a high density mapping catheter revealed an area of low voltage with fractionnated electrogram. Fossa ovalis was identified by transseptal puncture. TP: phantom of the catheters, CS: coronary sinus, H: His, IVC: inferior vena cava, SVC: superior vena cava, * fractionnated electrogram

A novel method to define critical isthmus of left atrial tachycardia; late potential mapping during sinus rhythm

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial tachycardia (AT) is a commonly encountered rhythm disorder in patients with underlying atrial scar. The role of late potential (LP) based mapping in the detection of AT critical isthmus has yet to be systematically evaluated. Purpose We aimed to investigate the relationship between the atrial LPs (ALP) localization in sinus rhythm and the critical isthmus of re-entrant ATs in patients with underlying atrial low-voltage areas. Methods Thirty-five symptomatic patients [mean age: 62 ±9, gender: 25 (71.4%) female] with left AT, who had undergone catheter ablation, were enrolled. Voltage and LP mapping were performed in sinus rhythm in both atriums. Low voltage areas and signals with continuous-fragmented morphology were tagged. Isochronal late activation mapping (ILAM) was also performed in all procedures. After induction of AT, activation mapping was performed during tachycardia in all patients to detect critical sites of the tachycardia. Results Activation mapping indicated single re-entry in 30 patients and ≥1 re-entry in 5 patients. Localized re-entry was observed in 20 (51.2%) patients, macro re-entry in 18 (46.1%), and biatrial re-entry in 1(2.5%). The mean fractionated electrogram duration in the AT termination site was calculated at 134.3±46.7 ms and the mean bipolar voltage at 0.17±0.12 mV. The ALPs were tagged in 25 (64.1%) patients on the anterior wall, 12 (34.3%) on the roof, 5 (12.8%) on the septal wall and 2 (5.7%) in the Bachmann’s Bundle region. All ALPs were in the latest activated zones of ILAM in patients with localized re-entry and predicted successful ablation sites to terminate the AT. Freedom from atrial tachyarrhythmias (ATAs) was 78.7% at six months during a mean follow-up duration of 338 ±226 days. Conclusion Our findings demonstrated the utility of ALPs during sinus rhythm to predict the successful termination sites for left ATs. These areas displayed continuous-fragmented signal morphology during sinus/paced rhythm in correlation with the critical isthmus of AT detected during activation mapping.

Impact of sleep apnea on left atrial remodeling and stroke risk factors

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Obstructive sleep apnea (OSA) is associated with left atrial (LA) remodeling, which increases the thromboembolic risk of atrial fibrillation (AF) and recurrence of atrial fibrillation after catheter ablation of AF. This study aimed to assess the association between severity of OSA and LA remodeling. Method In 126 patients with AF who underwent catheter ablation for AF (male 78.4% male, 58.0 ± 10 years old, persistent AF 27%), LA voltage distribution were analyzed during atrial pacing. All the subjects underwent polysomnography for screening of OSA. We categorized the subjects into 4 groups based on the severity of OSA which was determined by the respiratory disturbance index (RDI; RDI <5: normal, 5≤RDI<15: Mild, 15≤RDI<30: moderate, 30≤RDI: severe). The presence of stroke risk factors (left atrial appendage [LAA] pulse wave velocity < 20cm/sec, NT pro BNP >1,250 ng/l, presence of spontaneous echo contrast [SEC] and LA volume index >32 ml/m3) were evaluated. Result The LA low voltage area was significantly greater (p=0.007) and LA volume measured by cardiac magnetic resonance imaging (MRI) was significantly larger with the severity of OSA (p=0.004). The presence of SEC (3.2% vs. 13.6%; p=0.201) and LAA pulse wave velocity < 20cm/sec (3.2% vs. 9.6%; p=0.454) were higher in patients with moderate to severe OSA but it did not reach statistical significance. In the multivariate regression analysis, the total number of the stoke risk factors other than CHA2DS2-VASc was significantly associated with RDI (β=0.191; p=0.037). Conclusion The severity of OSA has significant relationship with stroke risk factors.

The relationship between high dominant frequency and low voltage areas in patients with atrial fibrillation: digital twin study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): a grant [2022R1I1A1A0106342211] from the Basic Science Research Program run by the National Research Foundation of Korea (NRF) which is funded by the Ministry of Science, ICT & Future Planning (MSIP) Background It has been suggested that the high dominant frequency (DF) site plays an atrial fibrillation (AF) driver, but its relationship with the atrial substrate voltage map (Vm) in the entire chamber AF map has yet to be studied. We explored the relationship between the DF site during AF and Vm in the entire chamber maps by applying the human left atrial (LA) electroanatomical map (EAM) to the digital twin AF map. Methods We acquired LA substrate Vm (at sinus rhythm, >800 points bipolar electrograms) of 110 patients with persistent AF (male 72.7%, 58.7±9.8 years old) who underwent AF catheter ablation. We applied EAM to digital twins (0.4 million nodes), reflecting anatomy, histology, and electrophysiology. We evaluated the highest 10% DF areas for 6 sec after inducing virtual AF. The correlation between the highest 10% DF and the low Vm areas (<0.2mV) was evaluated in the LA region of 10 segments. Results The mean voltage of the entire LA area was 1.96±0.85 mV (2.19±0.82 mV extra-PV area, 1.33±0.93 mV PV area) in 110 patients. The correlation between low Vm and high DF areas was not significant in the entire LA (r=0.106, p<0.001), extra-PV (r=0.157, p<0.001), and PV (r=0.079, p=0.097) areas. In the LA 10 segment regional analysis, 72 patients (65.5%) showed the co-localization of the highest DF in the region with the lowest Vm, and 14 patients (12.7%) had the lowest Vm segment in the region with the highest DF. The mean voltage where high DF appeared was 0.69±1.35 mV, and the mean voltage of the region where high DF did not appear was 0.59±1.15 mV (p=0.171). Conclusion High DF site, a parameter representing a localized focal source, had statistically significant but very poor correlations with LA extra-PV voltage substrate in patients with persistent AF.

Atrial myocardial substrate has a significant influence on local impedance data - clinical experience from high power short duration and standard radio frequency ablations

Abstract Funding Acknowledgements Type of funding sources: None. Background Local impedance is a new clinically used RF ablation parameter used to predict RF lesion creation. By now, data about the influence of atrial substrate on local impedance is still scarce. The aim of this study was to investigate local impedance data of different atrial tissues (healthy myocardium vs. Low Voltage areas) and the importance of local impedance drops during HPSD and standard RF ablation in atrial tissue. Methods A total of n=1319 clinical RF applications in n=51 clinical left atrial ablation procedures were analyzed regarding underlying RF ablation parameters (RF power, duration, contact force, global and local impedance data). 3D mapping data were used to differentiate RF ablations in low voltage areas (<=1.0mv) from those in healthy atrial myocardium (>1.0mV). Local and global impedance baseline values and drops, RF electrogram amplitude attenuation, as well as RF data were calculated and registered for statistical analysis. Results Local impedance drops were significantly higher during RF application in healthy myocardium when compared to low voltage areas (18,6 vs. 16,6 Ohm, p<0.01). Baseline local impedance was significantly higher in healthy atrial myocardium when compared to low voltage areas (105,4 vs. 99,1 Ohm, p<0.01). There was no significant difference in global impedance values between low voltage areas and healthy atrial myocardium (p=0.34). These findings were confirmed in HPSD (60W, 10s) as well as in standard (30-40W, 30-60s) RF applications. Impedance drops were significantly larger in HPSD when comapred to standard RF ablation (p<0.01). Detailed boxplot results are presented in the Figure. Conclusions Local impedance drop is a good predictor of RF lesion creation in HPSD as well standard RF ablations. Interestingly, different local impedance but not global impedance values were observed in healthy and low voltage areas. In clinical practice, local impedance may be a useful parameter to identify atrial substrate.

Voltage and propagation mapping: new tools to improve successful ablation of atrioventricular nodal reentry tachycardia

Abstract Funding Acknowledgements Type of funding sources: None. Background Ablation of atrioventricular nodal reentry tachycardia (AVNRT) has become the treatment of choice for AVNRT due to high success and low complication rate. A 3-D reconstruction of the atrial endocardial anatomy created by mapping system is useful because anatomic variances or unusual slow pathway locations may affect the effectiveness of classical anatomical approach. Voltage mapping is useful to identify a low voltage area in the Koch triangle (KT) called low-voltage-bridge (LVB); propagation mapping identifies the collision point (CP) of atrial wavefront convergence. These technique may be helpful to improve the localization of the slow pathway. Purpose Our purpose is to conduct a prospective study to evaluate the relationship of the propagation map to voltage mapping and successful site of ablation; moreover we would identify a cut-off value of LVB able to standardized the procedure. Methods Voltage maps of KT (at least 150 points) were obtained through the ablation catheter. Voltage values were adjusted until LVB was observed and classified in two types (Pic 1): Type I is a clear, large area; Type II is a narrow corridor or small areas. The collision point is the area in which the atrial wavefront during sinus rhythm collided on the propagation map indicating the area of slow pathway conduction. Ablation site was selected by LVB position or collision point, confirmed on anatomic position or AV ratio. Ablation of the slow pathway was performed using radio-frequency (RF) or cryotherapy. Results Eighteen consecutive patients were included; one patient was excluded because of inadequate voltage map. Ten patients were female. The median age was 51. In all patients inducible typical AVNRT was present. In 8 patients RF energy was used. Mean procedure time was 109 minutes; mean fluoroscopy time was 3,4 seconds (zero-fluoro procedure in 13 patients). Procedure success (no inducible AVNRT and no more than a single AV node echo beat) was achieved in all patient. No procedural complications were observed. No recurrence at 1 year follow up. The LVB was present in all patients; 9 patients had a type 1 LVB. Voltage map was created adjusting voltage high and low ranges in order to visualize LVB. Limited of LVB visualization is the leak of standard range of value for map creation. Post procedural evaluation identified standard cut-off of 0.3-1mv useful for LVB identification (only one patient had lower voltage range). The collision point was present in all patients. A correlation between LVB and CP was observed in 17/18 patients (Pic 2). In 16 patients successful ablation site was within 5mm of the wave collision. Conclusion In our prospective study, we found correlation between LVB and CP and the site of effective slow pathway ablation in most patients, and we identified a voltage range useful for standardized LVB identification during voltage mapping. Moreover, these techniques are useful to identify ablation site and minimize radiation exposure.

Voltage characterization of abnormal conduction zones in patients affected by atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background In case of persistent atrial fibrillation (AF), atrial substrate assumes a dominant role in sustaining the arrhythmia. Recent studies prove that low voltage areas (LVA, Voltage Amplitude < 0,5 mV) represent an additional target for ablation of AF patients. Purpose The purpose of this study is to analyse whether structural atrial conduction abnormalities (i.e., pivot sites and slow conduction corridors) may occur outside low voltage areas. Methods The study is based on the retrospective analysis of 31 consecutive maps of patients undergoing AF ablation (16 paroxysmal and 15 persistent cases). The clinical procedures have been performed with the support of a mapping system. Sinus rhythm activation maps and bipolar maps used for this analysis have been created with a multipolar mapping catheter. Map points were only acquired when the electrode was in contact with the endocardial tissue to avoid misleading voltage amplitude information. Slow conduction corridors and pivot sites have been analysed. At these sites, EGMs characterization included voltage amplitude (mV), signal duration (ms) and fractionation. Results The average value of EGMs amplitude reported at pivot sites and slow conduction zones, respectively, amounted to 2,08 ± 0,63 mV and 2,1 ± 0,66 mV in paroxysmal cases. In persistent cases, there were slight decreased values to 1,95 ± 0,93 mV and 1,89 ± 0,89 mV. Characterization at pivot sites documented a mean duration value of 45,4 ± 4,64 ms and 49,93 ± 5,51 ms in paroxysmal and persistent patients, respectively, while in slow conduction zones 41,53 ± 7,94 ms and 49,04 ± 6,41 ms have been reported. As for fractionation, more than five deflections per signal have been identified in all abnormal conduction areas. Conclusion Our study proves that functional electrophysiological phenomena can occur outside low voltage areas, even in persistent cases. According to this analysis, not all LVA represent the correct target for catheter ablation, encouraging the development of further methods for investigation of atrial substrate.

Refinement of voltage-based atrial scar assessment using pacing thresholds and local impedance

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific Background Common cut-offs for dense scar and ‘low-voltage areas’ on atrial 3D electroanatomical mapping are 0.05mV and 0.50mV respectively. These are not physiologically validated and may not fully represent underlying scar compared with unipolar readings or the novel parameter local impedance (LI). Objectives Investigate the relationship of bipolar voltage, unipolar voltage and LI with pacing threshold (PT). Establish cut-offs for electrically inert (EI), partially active (PA) and electrically active (EA) atrial tissue based upon pacing capture. Methods Patients undergoing AF ablation were recruited. 3D electroanatomical maps were created. PTs were assessed using the MiFi and Stablepoint (SP) ablation catheters between the tip and first ring electrodes. PTs were assessed with a 2ms pulse duration commencing at 5mA and moved up or down accordingly. LI was referenced against a blood pool reading (LIr). EI sites were defined as no pacing capture, PA capture between 5-20mA and EA less than 5mA. Results 292 PTs and LI readings were recorded in 40 patients (Male: 21/40; Age: 66.7 ± 8.8; Paroxysmal AF: 10, Persistent AF: 30, De novo 21, Redo 19). A weak correlation exists between SR voltages and PT (Spearman's Rho - Bipolar: -0.35, Unipolar: -0.26, both p <0.0005). Weak correlations exist between LI and PT, (Spearman's Rho - MiFi = -0.35, SP = - 0.33, both p < 0.0005), but moderate-strong correlations exists between LIr and PT (Rho - MiFi = -0.52, SP = -0.57, both p <0.0005, [Figure 1]). For the EI-PA cut-off, the ability to distinguish capture / no capture for bipolar voltages was fair (AUROC = 0.74), but poor for unipolar, (AUROC = 0.68). The lowest tissue voltage values with capture were 0.03mV and 0.31mV respectively. In contrast, LIr had excellent discriminatory ability (AUROC – MiFi = 0.87, SP = 0.90, lowest value with tissue capture = 1Ω for both MiFi and SP). For the PA-EA cut-off, the ability to distinguish PT above/below 5mA for bipolar voltages was fair (AUROC = 0.69, optimal cut-off 1.29mV), and poor for unipolar voltages, (AUROC = 0.63). In contrast, LIr had good discrimination, (AUROC - MiFi = 0.82, optimal cut-off 12.5Ω, SP = 0.89, optimal cut-off 10.5Ω). Using these cut-offs, there was a significant difference between PTs between EI, PA and EA, for bipolar voltage, (EI: 20mV, PA 6.0 ± 6.3mV, EA: 2.6 ± 2.6mV, p < 0.0005) and LIr, (MiFi: EI: 20mV, PA 7.8 ± 7.5mV, EA: 2.8 ± 2.8mV. SP: EI 20mV, PA: 4.0 ± 2.5mV, EA: 2.2 ± 0.9mV, both p < 0.0005, [Figure 2]). Conclusions PTs suggest conventional voltage cut-offs could be improved. LIr shows potential as a novel parameter in assessing tissue health complimentary to bipolar voltages. Based on pacing capture data, what has previously been labelled dense scar is not electrically inert and should be ablated if clinically indicated. Values of 0.03mV and 1.31mV, and for potential future LIr mapping, 0.5Ω and 10.5Ω are suggested as dense scar and low voltage area thresholds.

Electrophysiological findings in HFpEF patients presenting for AF ablation

Abstract Funding Acknowledgements Type of funding sources: None. Aims The prevalence of atrial fibrillation (AF) in heart failure with preserved ejection fraction (HFpEF) patients is high. Impaired left atrial (LA) function is a major determinant in HFpEF. The extent of arrhythmogenic left atrial tissue degeneration in HFpEF patients is unknown. Methods and results We prospectively enrolled consecutive patients presenting for first time AF ablation. Each patient underwent baseline laboratory and transthoracic echocardiography assessment. The HFA-PEFF score was utilized to identify HFpEF patients. Bipolar high density voltage mapping [1213 (825 to 1606) mapping points] was created in sinus rhythm prior to PVI to evaluate the general LA bipolar voltage and quantify areas of low voltage, a well known surrogate for fibrosis and arrhythmogenesis. 160 patients were enrolled (55 % male). 42 patients (26 %) suffered from HFpEF. Low voltage areas (LVAs) were present in 84 patients (53 %). HFpEF was associated with generally decreased LA bipolar voltage (0.95 ± 0.45 mV vs. 1.59 ± 0.91 mV respectively; p < 0.001) (Fig. 1) and predictive for the existence of low voltage areas (81 % vs. 45 % low voltage area positive, respectively; p = 0.006). The HFA-PEFF score inversely correlated with LA bipolar voltage (r = - 0.380; p < 0.001) (Fig. 1). Furthermore, the HFA-PEFF score closely correlated to the extent of LVAs (r = 0.275; p = 0.001) and to the low voltage amplitude of atrial myocardium excluding areas of low voltage (r = - 0.403; p < 0.001). Conclusion HFpEF is highly predictive for generally decreased LA bipolar voltage and for the existence of fibrotic and arrhythmogenic left atrial tissue degeneration.

Characterization of right ventricular low voltage areas in patients with arrhythmogenic right ventricular cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: None. Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by fibrofatty replacement in the myocardium progressing from the epicardium towards the endocardium and affecting primarily the right ventricle (RV). Little data is available on the distribution of RV electrical abnormalities at the era of epicardial and high-resolution mapping. Purpose To evaluate the extent and distribution of RV epicardial and endocardial low voltage areas and their relationship with ECG abnormalities in ARVC patients. Methods Patients with a definite ARVC diagnosis according to the 2020 Task Force Criteria, who underwent ventricular tachycardia ablation between 2016 and 2022 with a high-density RV 3-dimensional electroanatomic mapping, were included. A custom RV segmentation dividing the RV into 10 segments from endocardial maps was used: anterior and lateral right ventricular outflow tract (RVOT); basal and mid inferior wall; apex; septum; basal anterolateral, basal inferolateral, mid anterolateral and mid inferolateral RV free wall (Figure). A standard definition of electrical scar was used (bipolar voltage ≤0.5 mV), and scar areas were manually delineated. Percentage of scar was defined by the ratio between scar area and the total segment area. ECG abnormal findings, such as epsilon wave and T-wave inversion in precordial leads, were measured before ablation procedure. Results Twenty-nine consecutive definite ARVC patients were included, among whose 24 had epicardial mapping in addition to endocardial mapping. When considering all segments, the epicardial scar (median:70%, interquartile range [IQR] 37-97%) was larger (p<0.0001) than the endocardial scar (9% [IQR] 0-32%). The higher percentage of epicardial scar was found in the basal inferolateral (100% [IQR] 73-100%), basal anterolateral (94% [IQR] 67-100%), RV free wall and lateral RVOT (89% [IQR] 48-100%) segments (Table). Transmural scar was observed mostly in basal inferolateral RV free wall (10 patients, 41%) and basal inferior wall (8 patients, 33%). Patients with major depolarization criteria had a higher percentage of epicardial and endocardial scar as compared to those with no or minor depolarization criteria (respectively 93% [IQR] 59-100% versus 62% [IQR] 28-89%, p<0.0001 and 17% [IQR] 0-42% versus 4% [IQR] 0-23%, p=0.001). There was no significant difference of the percentage of epicardial or endocardial scar in patients with and without major repolarization criteria (respectively 90% [IQR] 49-98% versus 84% [IQR] 43-100%, p=0.91 and 14% [IQR] 11-35% versus 16% [IQR] 0-41%, p=0.73). Conclusion In ARVC, the electrical abnormalities predominate in the basal epicardium. Patients with major depolarization criteria had a higher extent of epicardial and endocardial scar, but there was an association between scar extent and repolarization abnormalities.

P61 VIP–AF. CORRELATION BETWEEN VOLTAGE AND IMPEDANCE MAPPING IN PATIENTS AFFECTED BY ATRIAL FIBRILLATION: A FURTHER STEP TOWARDS SUBSTRATE CHARACTERIZATION

Abstract Background Pulmonary veins isolation (PVI) represents the main strategy for paroxysmal atrial fibrillation (AF) treatment. Due to the poor clinical outcomes of PVI in case of non–paroxysmal AF, significant efforts have been made to develop new ablative strategies to modify the atrial substrate. Up to now, in order to characterise atrial substrate, only bipolar voltage maps have been used and impedance mapping has never been evaluated. Purpose Our aim is to demonstrate the potential correspondence among atrial wall thickness, bipolar voltage and impedance. Atrial impedance mapping could represent an additional tool for atrial substrate characterization, providing further information on tissue conductive properties and confirming bipolar substrate analysis. Methods The study includes the retrospective analysis of 60 electro–anatomical (EA) maps of patients with paroxysmal (40 patients) and persistent (20 patients) AF admitted to our institution for treatment. The clinical procedures have been performed with the support of CARTO3 mapping system. Map points have been collected with Navistar RMT Thermocool ablation catheter in order to enable the evaluation of atrial impedance values. To perform the correspondence analysis between the voltage map and impedance map, the atrial endocardial surface has been divided in six sections. Before ablation, for all patients a computed tomography has been performed in order to evaluate atrial endocardial thickness. Parameters of interest that have been evaluated in this study are EGMs voltage amplitude (mV) and fractionation (> five deflections per signal) and the corresponding impedance value (Ohm) at the considered acquisition point. Results In all PAF cases no voltages lower than 0.5 mV have been reported. The corresponding impedance values ranged from 140.6 to 169.9 Ohm, with an average value of 151.5 ± 5.4 Ohm. In PsAF cases, instead, voltage values inferior to 0.05 mV have been reported in the posterior wall, anterior wall and roof in 19/20 patients. In these low voltage areas, long duration fractionated signals have been reported and the average impedance value dropped to 129.1 ± 3.8 Ohm, ranging from 110.2 Ohm to 139.6 Ohm. Conclusion Our study supports the association between left atrial thickness, voltage amplitude and impedance values. This allows the correct substrate evaluation in case of uncertain bipolar values thanks to additional information provided by impedance mapping.

P57 VOLTAGE CHARACTERIZATION OF ABNORMAL CONDUCTION ZONES IN PATIENTS AFFECTED BY ATRIAL FIBRIALLATION

Abstract Background In case of persistent atrial fibrillation (AF), atrial substrate assumes a dominant role in sustaining the arrhythmia. Recent studies prove that low voltage areas (LVA, Voltage Amplitude < 0,5 mV) represent an additional target for ablation of AF patients. Purpose. The purpose of this study is to analyse whether structural atrial conduction abnormalities (i.e., pivot sites and slow conduction corridors) may occur outside low voltage areas. Methods The study is based on the retrospective analysis of 31 consecutive maps of patients undergoing AF ablation (16 paroxysmal and 15 persistent cases). The clinical procedures have been performed with the support of a mapping system. Sinus rhythm activation maps and bipolar maps used for this analysis have been created with a multipolar mapping catheter. Map points were only acquired when the electrode was in contact with the endocardial tissue to avoid misleading voltage amplitude information. Slow conduction corridors and pivot sites have been analysed. At these sites, EGMs characterization included voltage amplitude (mV), signal duration (ms) and fractionation. Results The average value of EGMs amplitude reported at pivot sites and slow conduction zones, respectively, amounted to 2,08 ± 0,63 mV and 2,1 ± 0,66 mV in paroxysmal cases. In persistent cases, there were slight decreased values to 1,95 ± 0,93 mV and 1,89 ± 0,89 mV. Characterization at pivot sites documented a mean duration value of 45,4 ± 4,64 ms and 49,93 ± 5,51 ms in paroxysmal and persistent patients, respectively, while in slow conduction zones 41,53 ± 7,94 ms and 49,04 ± 6,41 ms have been reported. As for fractionation, more than five deflections per signal have been identified in all abnormal conduction areas. Conclusion Our study proves that functional electrophysiological phenomena can occur outside low voltage areas, even in persistent cases. According to this analysis, not all LVA represent the correct target for catheter ablation, encouraging the development of further methods for investigation of atrial substrate.

Three-Terminal Lines Fault Location Using Two Main Terminals Data in the Presence of Renewable Energy Sources

Penetration of renewable energy sources (RESs) in power systems is increased considerably and fault location algorithms face considerable problems with the presence of RESs. Also, the third terminal of three-terminal lines is expanded as a cost-effective solution to energize the remote areas of medium voltage (MV) systems, while its data may not be measured and easily available. In addition, in cases where this data is obtainable, due to the excessive harmonics of the inverter-based resources (IBRs) in that terminal, the measured data includes high error. Therefore, providing a method for fault location in three-terminal lines in the presence of RESs is challenging. This paper proposes an accurate method to identify the fault location on these lines incorporating RESs without requiring the third terminal data. Due to current transformers saturation and transient response of capacitive voltage transformers, the fault location based on the faulted phase data contains significant errors. The proposed method combines both the faulty and healthy phases data to improve the accuracy of fault location. Its performance is evaluated on a MV system for different scenarios including various fault resistances, locations and types, and third terminal integration of RESs. The obtained results confirm superiority of the proposed method.

PO-04-228 DIFFERENTIATION OF HIGH FREQUENCY NEAR FIELD VS. FAR-FIELD POTENTIALS IN LOW VOLTAGE ZONES DURING SINUS RHYTHM IMPROVES DISCRIMINATION OF LOCAL SITES OF TERMINATION DURING VT

Ventricular tachycardia (VT) in patients with structural heart disease (SHD) is often poorly tolerated or presents with several inducible morphologies. These factors support mapping the arrhythmic substrate during sinus rhythm (SR). However, poor discrimination between near-field (NF) and far-field (FF) electrogram (EGM) components in low voltage (LV) areas is the main limitation. The peak frequency (PF) associated with bipolar EGMs may distinguish NF from FF EGMs (Panel D). To evaluate if PF combined with voltage mapping during SR enhances discrimination of the region of VT termination by radiofrequency application (RFa). Bipolar activation and voltage maps were generated with a 16-pole grid catheter (HD Grid) during SR (Panel B). PF maps were retrospectively computed (Panel C). The maps were only analysed if acute termination was achieved by focal RFa within a boundary diameter<1.5cm (panel A). The mapped surface area (SA) was sub-regioned into the termination (T-ZONE) and non-termination (NT-ZONE) zones. The T-ZONE surface was centered about the termination site and was allowed to extend to a rectangular kernel >0.5cm and <1.5cm across perpendicular axes, with the NT-ZONE encompassing the remainder mapped SA. Sensitivity (SE) and specificity (SP) of discrimination of the T-ZONE vs. NT-ZONE were measured according to the %SA covered at different LV thresholds (0.1-1.0mV in increments of 0.1mV - Panel F). LV high PF (LVHF) areas at different PF cutoffs from 150Hz (LVHF150) to 300Hz (LVHF300) were also assessed. 15 patients with SHD and sustained monomorphic VT were enrolled. Four (60-74 years, all male, 3 ischemic) of them had 5 VT’s terminated by 1.4±0.9 focal RF lesions. All termination sites were located in a LVHF region mapped during SR (Panels B,C,E). The T-ZONE occupied 0.41±0.33cm2/92.75±13.31cm2 global SA, and consisted of 15±10 EGM points/1432±337 global points. T-ZONE voltage during SR (0.50±0.32mV) was significantly lower vs. global voltage (2.01±0.69mV, P<0.001), while T-ZONE PF was higher (324±51Hz) vs. global (270±37Hz, P<0.001). ROC discrimination of the T-ZONE yielded AUC’s of 0.79-LV alone, 0.87-LVHF150, 0.91-LVHF200 (Delta +12.2% vs LV alone, Panel F), 0.85-LVHF250 and 0.77-LVHF300. At a 0.7mV cutoff, LVHF200 yielded a balanced SE/SP of 0.89/0.87 vs. LV alone (0.90/0.63). Assessment of regions with LV and high PF during SR improves specificity for discrimination of sites of VT termination compared to LV alone.

PO-02-205 ELECTROGRAPHIC FLOW CONSISTENCY CORRELATES WITH HIGH-DENSITY BIPOLAR VOLTAGE MAPS IN SINUS RHYTHM AND ATRIAL FIBRILLATION

In patients with atrial fibrillation (AF), left atrial scar revealed by low voltage areas on 3D electroanatomic mapping have been correlated with scar on late gadolinium enhanced cardiac magnetic resonance imaging, which is recognized as a surrogate for fibrosis. Electrographic Flow (EGF) mapping reconstructs global atrial wavefront propagations in near real-time. Electrographic flow consistency (EGFC) quantifies concordance of observed wavefront patterns and may provide insight into the nature of atrial substrate where diseased substrate shows more chaotic wavefront propagation and lower FC. Correlate EGFC with regional bipolar voltage values in patients during AF and sinus rhythm (SR). FLOW EVAL-AF is a single-center, prospective study of 10 AF patients who underwent concomitant high-density bipolar voltage mapping with HD Grid and EGF mapping with 64-pole basket catheter. Biatrial voltage maps and 1-minute EGF maps from 2-3 standard basket positions per atria were made prior to any induction or ablation. Atrial surface area with voltage >0.5 mV was computed from 2D voltage map projections. EGF fields computed per 2-sec segment of recording. Overall EGFC per atrium computed as average of the modulus of individual EGF vectors, where vector length represents consistency of flow patterns in arbitrary units. We compared % atrial surface area with normal voltage v. mean EGFC across EGF recordings per atria in a given rhythm. Data from 8 patients (2 AF; 6 SR) was analyzed; 2 excluded for non-comparable voltage map acquisition parameters. Mean age 70±11 years; 1 female; mean LA size 4.5±0.35 cm. Surface area % with voltage >0.5 mV was 0.24±0.08 in AF v. 0.36±0.05 in SR. Mean EGFC in AF 0.74±0.14 and in SR 1.0±0.11. Intraprocedural rhythm change occurred in 5 (3 induced into AF; 2 converted to SR post-PVI), and all had higher voltage values overall and higher mean EGFC in SR v. AF. Pooling data from all pre-procedure voltage maps and EGF maps revealed overall correlation between EGFC and bipolar voltage from both atria and in both rhythms (r=0.67, p=4.8x10-3). Both EGFC and bipolar voltage values were higher in SR v. AF. EGFC correlated with voltage across both atria and in both SR and AF. Global EGFC can be obtained with 1-minute recordings in 2-3 basket positions per atria and may provide another measure of the degree of atrial myopathy similar to the information gained from high-density bipolar voltage mapping.

PO-05-100 DETECTION OF THE CRITICAL SUBSTRATE FOR VENTRICULAR TACHYCARDIA ABLATION WITH THE COMBINED IMAGE OF TC-99M SCINTIGRAM AND LATE IODINE ENHANCEMENT CT

Late potentials (LPs) are the important target for ventricular tachycardia(VT) abltion. However, LPs sometimes cannot be observed sufficiently because of intramural localization of VT substrates. Efficacy of CT for prediction of VT substrates even in intramural layer has been reported. On the other hand, Tc-99m scintigram has been reported to determine the viability of myocardium. The uptake of Tc-99m scintigram could quantify the viability of VT substrates and predict the localization of critical VT substrates such as LPs. Moreover, combination of CT and Tc-99m scintigram could show intramural VT substrates. We evaluated the relationship between the localization of LPs and uptake rate of Tc-99m scintigram. Moreover, we evaluated VT substrates with combined image of scintigram and CT. In eight patients (age, 67.5±8.6 years ; left ventricular(LV) ejection fraction, 26.0±8.7%) with ischemic cardiomyopathy and VT, electroanatomical map (EAM) and Tc-99m scintigrafic image of LV were obtained and were divided into twenty segments. LPs were determined as isolated potentials after QRS and were evaluated in EAM. The relationship between LPs and scintigrafic characteristics was evaluated in total of 160 segments. Electrocardiogram gated CT was performed and late iodine enhancement(LIE) was recorded 8 minutes after administration of contrast media. LPs were recorded in 59 segments. According to the Tc-99m uptake rate, cut off value 35% was set for the prediction of the location of LPs with ROC curve. LPs were observed in the lower scintigram perfusion segments with ≤35% uptake rate (n=61) more than the segments with >35% uptake rate (n=99) with statistical significance (78.6% vs 11.1% p<0.0001). With this cutoff value, we performed another VT ablation with intramural substrate. EAM revealed the exit site of VT circuit from endocardium and the existence of intramural substrate (Fig.A). Low Tc-99m uptake area observed around the apical aneurysm and made the borderline between the basal normal voltage area (Fig.B). LIE showed the transmural damaged tissue on the apical aneurysm and the intramural damaged tissue of mid anterior wall(Fig.C). This border zone of Tc-99m uptake and intramural LIE was similar to the exit site of VT circuit. Long cauterization on this area terminated VT. Lower perfusion area of Tc-99m scintigram could be utilized to predict VT substrates in ICM patients and combination of LIE of CT could add the information of the depth of the VT substrate.

PO-04-054 FIRST REPORTED HUMAN CASE OF ELECTRICAL STORM TREATED WITH THE NEW HIGH-POWER-SHORT-DURATION TACTIFLEXTMABLATION CATHETER.

In the last decade, standard-power-long-duration radiofrequency delivery systems were the standard care to treat ventricular arrhythmias. Recently, high-power-short-duration radiofrequency delivery systems are available and TactiFlexTM Ablation Catheter is the most recent one. we present the first worldwide case of electrical storm catheter ablation using the new TactiFlexTM. N/A A 78 years old female was admitted to the emergency department because of arrhythmic storm. Thirty days earlier she had been hospitalized for acute coronary syndrome. On initial assessment, she appeared soporous, arterial blood pressure was 80/50 mmHg and ECG revealed sustained monomorphic ventricular tachycardia, regular cycle length, left bundle branch morphology, negative concordance in precordial lead. Patient therapy included metoprolol, mexiletine and cordarone; intravenous lidocaine and procainamide were added, with poor results in controlling arrhythmia; then, we decide to perform VT catheter ablation. Left ventricle mapping was performed with TactiFlexTM and AdvisorTM HDGrid Mapping Catether supported by the new EnsiteX V2 electro-anatomical mapping system and Omnipolar Technology. During voltage substrate mapping we found a central necrotic core area surrounded by a low voltage area in the mild-apical posterior-lateral wall. During late potential mapping the same area showed late and multi-fragmented potentials. Clinical tachycardia was easily induced during programmed ventricular pacing. VT activation map was performed and no meso-diastolic potentials or "early meets late" areas were found, probably signifying a possible epicardial regions involvement in the VT circuitry: it was not possible to reconstruct the entire arrhythmia circuit. Activation velocity map was performed and VT slowed in the same regions of low voltage and fragmented potentials. High-power radiofrequency energy (35W-25seconds or 40W-20seconds pulses) was delivered in the mid-basal posterior-septal wall obtaining VT termination. Subsequently, substrate homogenization, which include late and fragmented potentials elimination, was performed. No ventricle arrhythmias were inducible during programmed ventricular pacing. No procedure-related complications occurred. TactiFlexTM appears safe and effective to control left VT. Further reports and studies are needed to evaluate the most appropriate Watts and seconds to perform effective and safe human left ventricle injuries.