Low-voltage Areas Research Articles

Peak frequency mapping to differentiate near-field from far-field electrograms for ventricular tachycardia ablation: initial results

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Laboratories Background Ablation of ventricular tachycardia (VT) in patients with structural heart disease is challenging. Localization of the critical isthmus of conduction may be difficult because is commonly located within low voltage (LV) areas where far-field (FF) and near-field (NF) electrograms (EGMs) may be present and merged. The peak frequency (PF) associated with bipolar EGMs is a novel parameter which may serve to distinguish NF from FF EGM components. The potential value of PF to identify the critical isthmus of conduction in this setting has never been evaluated. Purpose To compare the ability of LV vs. LVHF to discriminate the VT termination region Methods Bipolar voltage and activation maps were generated with a 16-pole grid catheter (Advisor HD Grid) during VT. Peak frequency maps were retrospectively computed. VTs were included if acute termination could be achieved through application of a focal RF lesions set restricted to a boundary <1.5cm diameter. The ventricular LV mapped surface was sub-regioned into the termination (T-ZONE) and non-termination (NT-ZONE) zones. The T-ZONE surface was centered about the site of termination and was allowed to extend to a rectangular kernel >0.5cm and <1.5cm across perpendicular axes, with the NT-ZONE encompassing the remainder of the mapped surface area (SA). Sensitivity (SE) and specificity (SP) of discrimination of the T-ZONE vs. NT-ZONE was measured according to the %T-ZONE vs. %NT-ZONE SA occupied at LV thresholds ranging from 0.1-1.0mV in increments of 0.1mV (Panel E). In addition to LV, LVHF at peak frequency cutoffs of 200Hz (LVHF200), 250Hz (LVHF250), 300Hz (LVHF300) and 400Hz (LVHF400) were also assessed for T-ZONE discrimination. Results 8 patients with sustained monomorphic VT and structural heart disease (ischemic and non-ischemic) were enrolled. All of them had VT terminated with limited ablation by focal ablation at a discrete region. All areas of VT termination were located in a LV and high PF zone (figure 1). The best area under the curve to identify them was using the 250 Hz cuttoff (AUC 0.91) which was also better that using omnipolar optimized voltage alone (AUC 0.84) (Figure 2). Conclusion PF mapping apparently identifies slow conduction isthmus and provides complementary information to bipolar voltage mapping which can be displayed with emphasis on the electranatomical map.

Electroanatomical voltage mapping with a force-sensing technology catheter for diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Invasive three-dimensional electroanatomical mapping (EAM) can be helpful to diagnose arrhythmogenic right ventricular cardiomyopathy (ARVC). Contact force sensing catheters (CFSC) represent the gold standard to verify adequate tissue contact during EAM. However, normal reference values for right ventricular (RV) EAM as well as substrate characterization in patients with ARVC using CFSC have not been systematically investigated, which was the aim of this prospective study. Methods EAM of the RV during sinus rhythm was performed with the Thermocool SmartTouch catheter via a long sheath in the CARTO3 system in 11 patients with definite ARVC and 5 age- and gender-matched control subjects without structural heart disease. Only points with a mean contact force of ≥4G were analyzed. To account for differences due to RV anatomy, it was divided into 5 segments: RV outflow tract (RVOT), septum, free wall, sub-tricuspid region and apex. Endocardial bipolar and unipolar voltages, signal characteristics and signal duration were analyzed. The impact of catheter orientation on endocardial signals was also assessed. Results A median of 227 (IQR:120-364) endocardial RV points were analyzed. Median bipolar voltage in healthy controls was 3.8mV (range 3.6-4.6, IQR 2.7-5.4), with lower values in the RVOT and higher values in the RV septum. ARVC patients showed significantly lower bipolar voltages as compared to controls (repeated measures ANOVA; between-subjects effect: F=6.443,p=0.024), showing significantly lower bipolar voltage values in the sub-tricuspid region (1.8±1.9vs.4.6±2.9mV,p=0.031) and in the RV apex (2.9±1.4vs.7.2±5.2mV,p=0.024), Figure 1c. Bipolar voltage values in all RV regions yielded a high sensitivity and specificity for ARVC diagnosis (AUC62-78%,p<0.001 for all), with the highest performance for the sub-tricuspid region (AUC78%,95%CI0.75-0.81,p<0.001). A bipolar voltage value <1.5mV in the sub-tricuspid region yielded a sensitivity of 98% and a specificity of 53% for ARVC diagnosis (Figure 1a-b, showing the typical RV free wall "C-scar" in ARVC and normal values for the RV apex in less advanced disease stages). A positive correlation between bipolar voltage values and an orthogonal catheter orientation (46°-90°: r=0.106,p<0.001) as well as a higher catheter contact force (r=0.054,p=0.008), and a negative correlation between bipolar voltage values and QRS duration (r=-0.370,p<0.001) was found. Conclusions For the first time a systematic analysis of RV endocardial low voltage areas in ARVC patients as compared to controls by using CFSC was performed, and confirmed that RV voltages are generally lower in ARVC as compared to controls, with the sub-tricuspid area showing the lowest values and highest discriminatory power vs controls.

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.

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.

The critical isthmus of left atrial anterior wall flutter is mostly circumscribed into a small area immediately behind the aortic root. Implications for catheter ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial flutters (LAFL) are typically observed in patients with previous ablation lines or surgery in the left atrium (LA). Less frequently, scar-related left atrial anterior wall (LAAW) flutters may occur. Although the presence of low-voltage areas (LVAs, a surrogate of scar) in the LA is considered an arrhythmogenic substrate and a marker of atrial cardiomyopathy, the pathophysiologic factors responsible for its formation remain unclear. We hypothesized that compression of the LAAW by the aortic root could be responsible of LVAs found in the LAAW, and therefore, be the substrate for the development of LAAW flutter. Purpose We aimed to describe: 1) the relationship between the aortic root and the presence of LVAs in the LAAW, which is the substrate for reentry; and 2) the clinical and electrophysiological characteristics of LAAW atrial flutter. Methods Consecutive patients referred for LAFL ablation between April 2019 and September 2022 in a single center were retrospectively collected. Among 55 patients with LAFL, 10 (18%) demonstrated a macroreentrant circuit with a critical isthmus identified in the LAAW, in the absence of previous ablation lines or surgery, and were included in the analysis. Previous pulmonary vein isolation (PVI) was not an exclusion criterion. All patients underwent a multidetector computerized tomography (MDCT) prior to the procedure and the images were analyzed using ADAS 3DTM imaging platform. Activation mapping was performed in all patients using a multielectrode mapping catheter and CARTO 3 navigation system. Results 9 of 10 patients were male (mean age 74,3 ± 6,3 years). LA enlargement was present in all patients (48,3 ± 4,7 mm) and the mean aortic root diameter was 34,8 ± 3,4 mm. The mean LAAW flutter cycle length was 293,4 ± 68,3 ms. In 9 of the patients (90%), the LAAW flutter critical isthmus was just behind the aortic root, separated by < 1 mm according to the LA-aortic root fingerprinted isodistance map (mean fingerprinted isodistance area was 5,8 ± 2,5 cm2). The remaining patient had the critical isthmus just below the aortic root, between the area in contact with the latter and the mitral annulus. Furthermore, in all cases, the critical isthmus was immersed in LVAs. All but 1 LAAW flutter terminated during radiofrequency (RF) energy applications and rendered it non-inducible. After a median follow-up of 13,6 months (IQ range 5,3-21,6), 7 patients (70%) remained without recurrences. Conclusion In patients with LAAW atrial flutter, the presence of LVAs and the critical isthmus of the tachycardia are mostly circumscribed into small areas immediately behind the aortic root. Knowledge of this close relationship and the use of the isodistance map could be useful when mapping and ablating LAAW flutter, helping to straightforward the ablation procedure.

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.

Arrhythmogenic Right Ventricular Cardiomyopathy With Extensive Abnormal Substrate: Is Isolation Possible?

BackgroundIn arrhythmogenic right ventricular cardiomyopathy (ARVC) patients with extensive right ventricular free wall (RVFW) abnormal substrate, large-area homogenization with combined epicardial and endocardial approach is time consuming and often inadequate for modification. ObjectivesThis study aimed to explore the feasibility and efficacy of RVFW abnormal substrate isolation in such patients to control ventricular tachycardia (VT). MethodsEight consecutive ARVC patients with VT who had extensive abnormal RVFW substrate were included. VT induction was performed before substrate mapping and modification. Detailed voltage mapping was done during sinus rhythm. A circumferential linear lesion was deployed along the border zone of low-voltage area on the RVFW to achieve electrical isolation. Other small areas with fractionated or late potentials were further homogenized. ResultsAll 8 patients had RVFW endocardial low-voltage area. The entire RV low-voltage area was 113.8 ± 84.1 cm2 (49.6% ± 29.8%) and the dense scar was 59.6 ± 39.8 cm2 (25.0% ± 14.1%). Electrical isolation of abnormal substrate was achieved in 5 of 8 (62.5%) patients via endocardial approach alone and 3 of 8 (37.5%) patients via a combination of endocardial and epicardial approach. Electrical isolation was verified by slow automaticity (5 of 8, 62.5%) or RV noncapture (3 of 8, 37.5%) during high-output pacing inside the encircled area. VTs were induced in 6 patients before ablation, and all patients were rendered noninducible after ablation. During a median follow-up of 43 months (range: 24-53 months), 7 of 8 (87.5%) patients remained free of sustained VT. ConclusionsElectrical isolation of RVFW is feasible and can be the option in ARVC patients with extensive abnormal substrate.

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.

Low atrial natriuretic peptide to brain natriuretic peptide ratio is associated with left atrial remodeling.

Atrial natriuretic peptide (ANP) deficiency is thought to be one of the causes of heart failure induced by atrial fibrillation (AF). Although ANP deficiency is thought to occur as a result of atrial remodeling, data to explain this mechanism are limited. The purpose of this study was to investigate the association between ANP and left atrial remodeling or prognosis of heart failure in patients with AF ablation. In total, 373 consecutive patients who underwent initial ablation for persistent AF [age, 67 ± 10 years; female, 97 (26%)] were retrospectively enrolled. ANP and brain natriuretic peptide (BNP) were measured before the procedure and the ANP/BNP ratio was calculated. Left atrial volume index, left atrial appendage emptying velocity, and left atrial low-voltage areas (LVAs) were used as left atrial-remodeling parameters. The primary outcome of heart failure was defined as the composite of all-cause death or hospitalization due to worsening heart failure. The median ANP level was 116 (71-178) pg/ml and the median ANP/BNP ratio was 0.65 (0.46-1.00). The ANP/BNP ratio decreased with increasing left atrial volume index or LVAs and with decreasing left atrial appendage emptying velocity. During the 5-year follow-up, freedom from the primary outcome was significantly lower in patients with ANP/BNP ratio ≤0.65 than in those with ANP/BNP ratio >0.65 (84.6% versus 95.6%, P < 0.01). Secretion of ANP relative to BNP decreased with progression of left atrial remodeling in patients with AF ablation. Furthermore, prognosis of heart failure was poor in patients with a low ANP/BNP ratio.

Uric acid significantly correlates with the presence of low-voltage areas at the endocardial mapping in patients with non-valvular atrial fibrillation

Background and aimsInterest in the role of atrial substrate in maintaining Atrial Fibrillation (AF) is growing. Fibrosis is the culprit in the electrical derangement of the myocytes. Many cardiovascular risk factors are known to be linked to atrial scarring; among them Uric Acid (UA) is emerging. The purpose of our study is to find whether UA is associated with Left Atrium (LA) with pathological substrate. Methods and results81 patients who underwent radiofrequency transcatheter ablation for nonvalvular AF at the cardiological department of the Niguarda Hospital were enrolled in an observational, cross-sectional, single-center study. UA levels were analysed before the procedure. High density electroanatomic mapping of the LA was performed and patients were divided according to the presence or not of areas of pathological substrate (bipolar voltage <0.5 mV in sinus rhythm). 19 patients showed a LA with pathological substrate. These subjects showed a significant higher prevalence of persistent phenotype of AF (84.2 vs. 25.8%, p < 0.001). UA levels were significantly higher in the group of patients with LA with pathological substrate (6.8 ± 1.9 vs 5.3 ± 1.4 mg/dL, p < 0.001) as well as the prevalence of hyperuricemia (26.5 vs. 6.5%, p = 0.021). The association between uric acid LA with pathological substrate remains significant even after correction for confounding factors (age, left ventricular dysfunction, valvular disease, arrythmia phenotype and furosemide use) and also when the ratio UA/creatinine was evaluated. ConclusionsIn a population of patients who underwent AF ablation, higher UA levels were significantly associated with pathological LA substrate at electro-anatomical mapping.

Consumer-feeder relationship identification method for low-voltage distribution station area considering feature fusion of voltage variation and spatial distribution

Consumer-feeder relationship is an important basis for the fault location, outage management, load adjustment and power quality management in low-voltage distribution station area (LVDSA). The current identification method of the consumer-feeder relationship based on electrical characteristics analysis is single and lack of reliability. Besides, the consumers of different feeders which locate near the bus at the low voltage side of distribution transformer have high voltage variation similarity, which makes it difficult to distinguish reliably. The spatial distribution of consumers can directly reflects the feeder trend. Therefore, a consumer-feeder relationship identification method for LVDSA considering feature fusion of voltage variation and spatial distribution is proposed in this paper. Firstly, the electrical characteristics based on voltage variation and spatial distribution characteristics based on geographical location are analyzed, and the correlation between the characteristics above and consumer-feeder relationship is explained. Secondly, a semi-supervised spectral clustering (SSC) algorithm based on the feature of voltage variation and spatial distribution is proposed to identify the consumer-feeder relationship. Finally, the proposed method is tested with the real data of LVDSAs in China. The results indicate that the feature fusion of voltage variation and spatial distribution can effectively improve the identification accuracy of consumer-feeder relationship.

AB-452665-4 ATRIAL SCAR: GENDER DIFFERENCE IN PREVALENCE AND PROGNOSIS OF ADDITIONAL SUBSTRATE MODIFICATION IN PATIENTS WITH ATRIAL FIBRILLATION RESULTS FROM STABLE-SR-III TRIAL

Female gender has long been recognized to present a higher burden of low-voltage area (LVA), and tend to have an increased atrial fibrillation (AF) recurrence rate than male after circumferential pulmonary vein isolation (CPVI). However, benefits of additional LVA modification in female patients with AF remain unknown. This study was to describe the prevalence of LVA and outcomes of additional substrate modification according to sex at entry STABLE-SR-III trial. Patients aged 65-80 years were randomly assigned to either CPVI plus LVA modification during sinus rhythm (STABLE-SR) group or “golden-standard” CPVI alone group. The primary outcome was freedom from atrial arrhythmias lasting for ≥30 s after a single ablation procedure. Of 414 patients included in the STABLE-SR-III, 204 (49.3%) were female, mean age was 70.5±4.7 years. Females demonstrated significant higher LVA prevalence (51.5% vs. 32.9%, P=0.000) and burden [6.5% (2.7-12.4) vs. 2.9% (1.9-5.9), P=0.000] than males. Female sex, age and large left atrial diameter were independent predictors of LVA. For the primary outcome, additional LVA ablation was associated with a 65% reduction in atrial arrhythmias recurrence for females (hazard ratio 0.35; 95% CI 0.19-0.65, P=0.002). Females with LVA who received CPVI alone had significantly higher recurrence rate than those females without LVA and those females with LVA receiving substrate modification (P=0.003). Female sex was found to have a higher LVA prevalence, LVA burden, and greater benefit of additional LVA modification than male. Addictive LVA ablation has emerged as a promising solution to improve the success rate in this population.

AB-452663-1 THE IMPACT OF LOW POSTERIOR LEFT ATRIAL WALL VOLTAGE ON THE OUTCOMES OF CATHETER ABLATION FOR PERSISTENT ATRIAL FIBRILLATION: A CAPLA RANDOMIZED CLINICAL TRIAL SUBSTUDY

Pulmonary vein isolation(PVI) is less effective in patients with persistent atrial fibrillation(PsAF). Adjunctive ablation targeting low voltage areas(LVA) had demonstrated improved arrhythmia outcomes. To compare the outcomes of adding posterior wall isolation(PWI) to PVI, versus PVI alone, in PsAF patients with posterior wall LVA. The CAPLA study was a multi-centre, randomized trial involving PsAF patients randomized 1:1 to either PVI alone or PVI with PWI. Voltage mapping performed during pacing pre-ablation was reviewed offline, with LVA defined as bipolar voltage of <0.5mV. The primary endpoint was freedom from any documented atrial arrhythmia of >30 seconds off anti-arrhythmic medication (AAD) at 12 months, after a single ablation procedure in patients with posterior LVA. 210 patients (average 64.6+/-9.2years,73.3% males)underwent multipolar LA mapping. Posterior LVA was present in 32.9%(median surface area 0.6cm2), and associated with larger left atrial diameter(4.8cm vs 4.4cm, p<0.01). The addition of PWI to PVI did not significantly improve freedom from atrial arrhythmia recurrence over PVI alone(PVI with PWI 44.8% vs PVI 41.9%, HR0.95, 95%CI0.51-1.79; p=0.95). Compared to no posterior LVA, patients with posterior LVA were more likely to have LVA in other atrial regions(91.7% vs 57.1%, p<0.01), and significantly increased risk of atrial arrhythmia recurrence at 12 months (LVA 78.2% vs no LVA 44.2%; HR1.51, 95%CI 1.01-2.27, p=0.04). In patients with PsAF undergoing catheter ablation, posterior LVA was associated with a significant increase in atrial arrhythmia recurrence. However, the addition of PWI in those with posterior LVA did not reduce atrial arrhythmia recurrence over PVI alone.

PO-02-208 CHARACTERIZATION OF ATRIAL ELECTROPHYSIOLOGICAL PROPERTIES IN PATIENTS WITH HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY

Atrial fibrillation (AF) occurs frequently in patients with hypertrophic obstructive cardiomyopathy (HOCM) and the success rate of pulmonary vein isolation in these patients is less effective compared to other populations. This may be explained by the presence of an extensive arrhythmogenic substrate in both atria due to a primary atrial myopathy, but electrophysiological properties of the right (RA) and left atrium (LA) have never been investigated. The aim of this study is to 1) quantify atrial electrophysiological properties during sinus rhythm and 2) to determine whether atrial electrogram morphology and conduction disorders differ between the RA and LA in patients with HOCM. Intra-operative epicardial mapping of both atria was performed in HOCM patients undergoing surgical myectomy. Conduction delay and/or block (CD, CB), unipolar electrograms characteristics (unipolar voltages, potential fractionation) and low voltage areas (LVA) were quantified during sinus rhythm. Fifteen patients (mean age: 50± 12 years) were included. Conduction disorders were found in both atria in all patients, but did not differ between the RA and LA (CD: 2.9 [1.9-3.6] % versus 2.6 [2.1-6.4] %, p=0.541; CB: 1.7 [0.9-3.1] % versus 1.5 [0.5-2.8] %, p=0.600; respectively). Though unipolar voltages histograms differed significantly between the RA and LA (Table 1), LVA were equally present in both RA and LA (RA: 4.7 % [1.6-7.7] % versus LA: 2.9 % [2.1-7.1] %, p=0.793). The magnitude of unipolar voltages of single- and complex fractionated potentials (SP, CFP) were higher in the LA compared to the RA (SP: P75 10.9 mV versus 7.3 mV, respectively; CFP: P75 3.7 mV versus 2.0 mV, respectively).(Table 1) CFP corresponded to LVA in only 18% of all LA sites compared to 36% of all RA sites. In patients with HOCM, the magnitude of unipolar voltages is considerably higher in the LA compared to the RA. Remarkably, fractionated potentials in both atria mainly contained high voltage deflections. Therefore, substrate modification strategies, consisting of low voltage or other electrogram morphology guided AF ablation strategies, should be disease-tailored in this population. The observed equal amount of conduction disorders and LVA in both atria support the concept of a primary atrial myopathy with a bi-atrial substrate in HOCM patients.

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-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.

PO-04-150 ATRIAL TACHYCARDIA IN PATIENTS WITH REPAIRED TETRALOGY OF FALLOT: ITS CHARACTERISTICS AND THE EFFICACY OF CATHETER ABLATION

With advanced surgical techniques and patient care, many patients with repaired tetralogy of Fallot (TOF) have extended life expectancy. However, longevity is often complicated by tachyarrhythmias. In this study, we focused on atrial tachycardias (AT), its characteristics, and the effectiveness of catheter ablation. Seventy-seven patients with repaired TOF, who are treated and followed at the University of Tsukuba Hospital, were included. The patients were divided into patients with AT and without. Various clinical parameters were evaluated and compared between the two groups. Electrophysiological and electro-anatomic data were studied in patients who had AT and underwent catheter ablation. The mean age was 34± 12 years old, and 55% were females. Twenty-three patients had AT (30%). The patients with AT were older than those without AT (40± 12 vs 31± 11; P= 0.003), the left ventricular ejection fraction was lower (58± 6 vs 62± 5; P=0.006), the right atrial (RA) area (cm2) was larger (29± 14 vs 15± 5; P<0.001), the left atrial (LA) area (cm2) was also larger (19± 3 vs 16± 4; P<0.001), the RA to LA ratio was higher (1.5 vs 1; P<0.001), had a lower tricuspid annular plane systolic excursion (16± 4 vs 18± 4; P= 0.032), and a higher prevalence of restrictive physiology (35% vs 9%; P= 0.007), respectively. These parameters were obtained during maintained sinus rhythm in all patients. Twenty patients underwent catheter ablation, in which 30 AT were ablated. Low voltage area in RA was recognized in all patients using 3D electro-anatomic mappings. The mechanism of AT was intra-atrial reentrant tachycardia revolving around RA atriotomy scar from the previous surgery in 13 AT (43%), cavotricuspid isthmus dependent in 12 AT (40%), and focal activity in the remaining 5 AT (17%). After a median follow-up of 27 months, only three patients had AT recurrence. However, in one patient, the recurrent AT could not be suppressed by endocardial ablation and was successfully treated by surgical cryoablation done during pulmonary valve replacement. The patients with AT had biventricular dysfunction and larger bi-atrial size compared with those without AT. Additionally, regardless of AT mechanism, catheter ablation was an effective treatment modality in the majority of the patients.

PO-01-189 IMPACT OF CORONARY SINUS BALLOON UTILIZATION ON IDENTIFICATION OF THE VEIN OF MARSHALL FOR ADJUNCTIVE ETHANOL ABLATION FOR ATRIAL FIBRILLATION

Retrograde ethanol infusion into the vein of Marshall (EI-VOM) as an adjunct to pulmonary vein isolation (PVI) has been reported to improve success of atrial fibrillation (AF) ablation. However, identification and cannulation of the VOM remains technically challenging. It has been proposed that balloon occlusion of the coronary sinus (CS) allows for improved contrast opacification and facilitates identification of the VOM as well as differentiation of other branching veins. This study sought to assess the impact of CS balloon use on the success rate of VOM identification and time to VOM identification during adjunctive VOM ethanol ablation for AF. All patients undergoing PVI with EI-VOM at The Ohio State University Wexner Medical Center from January 2021 to November 2022 with known use or non-use of CS balloon were included. The primary endpoint was success rate of VOM identification and time to identification of VOM. The secondary endpoints were fluoroscopy time, procedure time, successful VOM cannulation, successful scar formation as defined by development of a characteristic low voltage area around the left inferior pulmonary vein on high-density electroanatomical mapping after ethanol infusion, and procedural complications. 106 patients underwent VOM ethanol ablation, 36 (34%) with and 68 (66%) without CS balloon use respectively. There was a significantly increased success rate in identification of VOM with CS balloon use (balloon 32 (89%) vs no balloon 50 (71%) patients, p=0.042). There was no significant difference in time to VOM identification. Notably, overall procedure time was significantly longer with CS balloon use (balloon 210.4 ± 51.7 vs no balloon 181.4 ± 37.1 minutes, p=0.004). There was no significant difference with balloon use in terms of fluoroscopy time, successful VOM cannulation, or successful scar formation (Table I). Notably, there were 3 (4%) cases of CS or VOM dissection in patients without balloon use as compared to 0 (0%) cases with balloon use, but this difference did not meet statistical significance. Figure 1 demonstrates the use of CS balloon during EI-VOM to facilitate identification of the VOM as well as atrial branches. CS balloon use is associated with significantly improved success in identification of the VOM during adjunctive ethanol ablation for AF. However, this is balanced by an associated increased procedure time.Tabled 1Table I: Procedural characteristicsProcedural characteristicsCoronary Sinus Balloon Used (N=36)Coronary Sinus Balloon Not Used (N=70)Total (N=106)P valueTimingTime to VOM identification, mins43.2 ± 15.546.1 ± 14.445.1 ± 14.80.419Fluoroscopy time, mins33.4 ± 10.031.4 ± 11.532.1 ± 11.00.374Procedure time, mins210.4 ± 51.7181.4 ± 37.1191.3 ± 44.60.004Key Procedural StepsCS cannulated36 (100%)68 (97%)104 (98%)0.547VOM identified32 (89%)50 (71%)82 (77%)0.042VOM cannulated29 (81%)46 (66%)75 (71%)0.112Able to advance balloon to VOM29 (81%)46 (66%)75 (71%)0.112Ethanol infused into VOM29 (81%)46 (66%)75 (71%)0.112OutcomeSuccessful formation of characteristic scar / low voltage area on high-density EAM15 (42%)35 (50%)50 (47%)0.853ComplicationsCS or VOM dissection0 (0%)3 (4%)3 (3%)0.549Values presented as mean ± 1 standard deviation for continuous variables and n (%) for categorical variables. Abbreviations: CS = coronary sinus, EAM = electroanatomical map, VOM = Vein of Marshall. Open table in a new tab

PO-01-231 IDENTIFICATION OF ATRIAL ENDO-EPICARDIAL ASYNCHRONY USING SIGNAL FINGERPRINTING

Atrial three-dimensional (3D) dissociation in conduction facilitates the development of atrial fibrillation (AF). Previous mapping studies revealed that patients with persistent AF have more endo-epicardial asynchrony (EEA) during SR than those without AF. Areas of EEA can be accurately identified by using unipolar electrograms (EGM). Alterations in endo-epicardial unipolar EGM features within EEA areas may provide novel insight into the electrical substrate of AF. To develop a novel method for estimating the degree of EEA by using unipolar EGM characteristics recorded from either the endo- and/or epicardium. During SR, intra-operative simultaneous endo-epicardial mapping (256 electrodes, 2 mm interelectrode distance) of the right atrium was performed in 86 patients. EEA was defined as an endo-epicardial dissociation exceeding 15 ms. EGM features, including voltages, low voltage areas (LVAs, <1.0 mV), potential types (single, short/long double and fractionated potentials) and fractionation duration (FD) were analyzed and correlated to EEA areas. The Asynchrony Fingerprinting Score (AFS) was developed based on uni- and multivariable logistic regression analyses. Three AFSs (Epi-AFS, Endo-AFS and EE-AFS) were established and assessed. EEA areas were characterized by a decrease in potential voltages, an increase in the number of long double potentials (LDPs) and fractionated potentials (FPs) and prolongation of double potentials (DPs) and FPs compared to non-EEA areas. Epi-AFS contained epicardial median voltage and the proportion of LDP, whereas the Endo-AFS contained the endocardial proportion of LVAs and single potentials (SPs). The EE-AFS, containing the proportion of endocardial LVAs, and the FD of epicardial DPs, showed the highest predictive value (AUC: 0.913) in determining the degree of EEA, although both Epi- and Endo-AFS also showed good predictive value with AUCs of 0.830 and 0.901 respectively. EEA is characterized by increased amounts of LVAs, LDPs and FPs, as well as an increase in the duration of both DPs and FPs. Epi-, Endo- and EE-AFS all showed good accuracy in identifying EEA areas. Therefore, AFS, as a novel approach utilizing integrated data from endo- or/and epicardium, may enable precise identification of EEA degree, including potentially arrhythmogenic substrates.

PO-04-030 PREDICTORS OF LOW VOLTAGE IN POSTERIOR WALL AND ASSOCIATION WITH ABLATION OUTCOMES

Areas of low voltage electrograms (<0.5 mV) (LVA) are known to correlate with areas of atrial fibrosis and are related to clinical outcomes after ablation for atrial fibrillation (AF). To identify predictors of posterior wall (PW) LVA and associate PW LVA with ablation outcomes. Patients with AF who underwent PW and PVI ablation were included. Pre-ablation voltage map data was obtained from CARTO and LVA was recorded. Patients were considered to have LVA if there was any voltage <0.5 mV in the PW. Patient characteristics and outcomes were also recorded. Time to ablation was defined as time from AF diagnosis to ablation. Recurrence <1 year was noted if AF was detected between 3 months and 1 year, to allow for 3-month blanking period. A total of 80 patients were included: 38 (47.5%) had PW LVA with a mean area of 3.54 + 5.76 cm2 (median 1.1, IQR .5-3.6), 42 (52.5%) had no PW LVA. Duration of AF was associated with presence of PW LVA: 18.42% of patients with paroxysmal AF had low voltage area, 21.05% for persistent AF, 60.53% for longstanding persistent (p = 0.036). Predictors of PW LVA are included in figure 2. Patients who sought ablation greater than 1 year after diagnosis of AF had larger PW LVA (2.2 + 5.19 cm2 vs 0.67 + 1.2, p = 0.13). Seventy-five patients had 1-year follow up at 366.52 + 69.23 days after ablation. Mean follow up was 899.98 + 453.72 days. Recurrence rates were higher in those with PW LVA compared to those without PW LVA at both <1 year (26.32% vs 9.52%, p = 0.048) and >1 year (42.11% vs 23.81%, p = 0.08). Respective odds ratios for recurrence at <1 year and >1 year based on presence of PW LVA was 3.39 (p = 0.05) and 2.32 (p = 0.08). Patients without PW LVA had higher incidence of atrial flutter before 1-year follow up (21.43% vs 5.26%, p = 0.036). CHADS2-VAsc score, vascular disease and duration of AF are positive predictors of PW LVA. Presence of PW LVA is associated with higher recurrence rates after ablation, however lower incidence of atrial flutter.