Isochronal Maps Research Articles

Multiphase faults activation in the southwest Huizhou Sag, Pearl River Mouth basin: Insights from 3D seismic data

The southwest Huizhou Sag is located in the Zhu I depression in the northern part of Pearl River Mouth Basin, which is influenced by the pre-existing basement fabrics and multiphase rifting, and has complex fault patterns in the Cenozoic. Using 3D seismic data of the southwest Huizhou Sag, we used seismic interpretation, fault pattern analysis from isochron maps, detailed fault throw analysis and structural evolution section analysis to constrain the initial formation timing, active periods and genesis of different striking normal faults, and the influence of basement faults on Cenozoic faults and the evolution progress of the sag was discussed, which significantly improve our understanding on the tectonic evolution of the northern Pearl River Mouth Basin. There are four groups of faults developed in the southwest Huizhou Sag, consisting of NE-SW, ENE-WSW, E-W and WNW-ESE striking, and the boundary faults of the subsag are mostly curved. Selective reactivation of ENE-WSW and WNW-ESW striking basement faults controlled the evolution of fault system during the Cenozoic. The southwest Huizhou Sag experienced multiple phases of extension, and the extension direction rotated clockwise from NW-SE to NNE-SSW. During the Early Eocene (Rift Ia), a large number of NE-SW striking faults were formed, accompanied by reactivation of ENE-WSW and WNW-ESW striking basement faults. These group of faults continued to be active during the Middle Eocene (Rift Ib) and some ENE-WSW striking faults were newly formed. The Late Eocene to Early Oligocene (Rift II) was dominated by E-W striking faults, and the depocenter shifted to the northwestern part of the study area. The Middle-Late Oligocene to Quaternary (Post-rift) was dominated by WNW-ESE striking faults, and the depocenter was not obvious.

Comparison of combined substrate-based mapping techniques to identify critical sites for ventricular tachycardia ablation

Established electroanatomic mapping techniques for substrate mapping for ventricular tachycardia (VT) ablation includes voltage mapping, isochronal late activation mapping (ILAM), and fractionation mapping (FM). Omnipolar mapping (Abbott, Inc.) is a novel, optimized bipolar electrogram creation technique with integrated local conduction velocity annotation. The relative utilities of these mapping techniques are unknown. To evaluate the relative utility of various substrate mapping techniques for identification of critical sites for VT ablation. Electroanatomic substrate maps were created and retrospectively analyzed in 27 patients in whom 33 VT critical sites were identified. Both abnormal bipolar voltage and omnipolar voltage encompassed all critical sites and were observed over a median 66 (IQR: 41.3-86) cm2 and 52 (IQR 37.7-65.5) cm2, respectively. ILAM deceleration was observed over a median 9 (IQR 5.0, 11.1) cm2 and encompassed 22 (67%) critical sites, while abnormal omnipolar conduction velocity (OCV, <1mm/ms) was observed over 10 (IQR 5.3-16.6) cm2 and identified 22(67%) of critical sites, and fractionation mapping was observed over a median 4 (IQR 1.5, 7.6) cm2 and encompassed 20 (61%) critical sites. Mapping yield was greatest for Fractionation + OCV (2.1 critical sites / cm2), and least for bipolar voltage mapping (0.5 critical sites / cm2). OCV identified 100% of the critical sites in areas with a local point density >50 points/ cm2. ILAM, fractionation and omnipolar conduction velocity mapping each identified distinct critical sites and provided a smaller area of interest than voltage mapping alone. Sensitivity of novel mapping modalities improved with greater local point density.

Cycle length oscillation during ventricular tachycardia: What is the mechanism?

A 55 y/o male with history of inferoapical myocardial infarction presented with symptomatic tolerated ventricular tachycardia (VT) and was referred for catheter ablation. A linear tridecapolar catheter (1-1-1 mm, T3, Access Point Technologies) was positioned along the region of endocardial isochronal crowding on the isochronal late activation map. Stable monomorphic VT with right bundle branch superior axis with V4 transition was induced and exhibited spontaneous variability in tachycardia cycle length (360-415ms). What is the mechanism of oscillation in tachycardia cycle length (TCL)? (Figure 1)

Abnormal Conduction Zone Detected by Isochronal Late Activation Mapping Accurately Identifies the Potential Atrial Substrate and Predicts the Atrial Fibrillation Ablation Outcome After Pulmonary Vein Isolation.

The presence of abnormal substrate of left atrium is a predictor of atrial fibrillation (AF) recurrence after pulmonary vein isolation. We aimed to investigate the isochronal late activation mapping to access the abnormal conduction velocity for predicting AF ablation outcome. Forty-five paroxysmal AF patients (30 males, 57.8±8.7 years old) who underwent pulmonary vein isolation were enrolled. Isochronal late activation mapping was retrospectively constructed with 2 different windows of interest: from onset of P wave to onset of QRS wave on surface electrocardiography (W1) and 74 ms tracking back from the end of P wave (W2). Deceleration zone was defined as regions with 3 isochrones (DZa) or ≥4 isochrones (DZb) within a 1 cm radius on the isochronal late activation mapping, and the estimated conduction velocity (ECV) are 0.27 m/s and <0.20 m/s for DZa and DZb, respectively in W2. The distribution of deceleration zone was compared with the location of low-voltage zone (bipolar voltage ≤0.5 mV). Any recurrence of atrial arrhythmias was defined as the primary end point during follow ups after a 3-month blanking period. Pulmonary vein isolation was performed in all patients, and there were 2 patients (4.4%) received additional extrapulmonary vein ablation. After a mean follow-up of 12.7±4.5 months, recurrence of AF occurred in 14 patients (31.1%). Patients with the presence of DZb in W2 had higher AF recurrence (Kaplan-Meier event rate estimates: HR, 9.41 [95% CI, 2.61-33.90]; log-rank P<0.0001). There were 52.6% of the DZb locations in W2 comparable to the distributions of low-voltage zone and 47.4% DZb were distributed in the area without low-voltage zone. Deceleration zone detected by isochronal late activation mapping represents a critical AF substrate, it accurately predicts the AF recurrence following ablation in patients with paroxysmal AF.

High-density Approaches to Ventricular Tachycardia Substrate Ablation

Ventricular tachycardia (VT) ablation is a challenging procedure with significant clinical benefit for patients. The classic VT ablation approach centers on arrhythmia induction and entrainment of tachycardia to identify the critical components of a VT circuit. In the post-coronary reperfusion era, smaller infarct size and subsequently faster VT cycle lengths have led to an increased occurrence of unstable, unmappable VT cases, making the classic approach untenable. While approaches of signal-based substrate modification have shown clinical efficacy in the past, these approaches are sometimes imprecise and require extensive ablation. With the advancement of high-density (HD) mapping technology and recognition of functional tissue properties requisite for VT initiation and propagation, a more finely targeted VT ablation approach may be pursued. Benefits of HD mapping include better tissue and signal characterization, avoidance of ‘perpendicular blinding’ and better identification of VT putative channels. Functional characterization of tissue, such as isochronal late activation mapping or decremental evoked potential mapping, allow for the identification of functional slowing required for VT reentry. Pre-ablative imaging continues to play an increasing role in substrate characterization and pre-operative planning. Using a comprehensive, tailored, substrate-based functional HD VT ablation strategy can allow for safe and effective ablation of even unstable and unmappable VT.

Development and Emplacement of Ana Slide, Eivissa Channel, Western Mediterranean Sea

AbstractSubmarine landslides can destroy seafloor infrastructures and generate devastating tsunamis. In spite of decades of research into the functioning of submarine landslides there are still numerous open questions, in particular how different phases of sliding influence each other. Here, we re‐analyze Ana Slide—a relatively small (&lt;1 km3) landslide offshore the Balearic Islands, which is unique in the published literature because it is completely imaged by high‐resolution 3D reflection seismic data. Ana Slide comprises three domains: (a) a source area that is almost completely evacuated with evidence of headscarp retrogression, (b) an adjacent downslope translational domain representing a by‐pass zone for the material that was mobilized in the source area, and (c) the deposit formed by the mobilized material, which accumulated downslope in a sink area and deformed slope sediment. Isochron maps show deep chaotic seismic units underneath the thickest deposits. We infer that the rapid deposition of the landslide material deformed the underlying sediments. A thin stratified sediment unit between three lobes suggests that Ana Slide evolved in two failure stages separated by several tens of thousands of years. This illustrates the problem of over‐estimating the volume of mobilized material and under‐estimating the complexity even of relatively simple slope failures without high‐quality 3D reflection seismic data.

Automated conduction velocity estimation based on isochronal activation of heart chambers

BackgroundSpatial differences in conduction velocity (CV) are critical for cardiac arrhythmias induction. We propose a method for an automated CV calculation to identify areas of slower conduction during cardiac arrhythmias and sinus rhythm.MethodsColor-coded representations of the isochronal activation map using data coming from the RHYTHMIA™ Mapping System were reproduced by applying a temporal isochronal window at 20 ms. Geodesic distances of the 3D mesh were calculated using an algorithm selecting the minimum distance pathway (MDP). The CV estimation was performed considering points on the boundary of two spatially and temporally adjacent isochrones. For each of the boundary points of a given isochrone, the nearest boundary point of the consecutive isochrone was chosen, the MDP was evaluated, and a map of CV was created. The proposed method has been applied to a population of 29 patients.ResultsIn all cases of perimitral atrial flutter (16 pts out of 29 (55%)), areas with significantly low CV (< 30 cm/s) were found. Half of the cases present regions with low CV located in the anterior wall. No case with low CV at the so-called LA isthmus was observed. Right atrial maps during common atrial flutters showed low CV areas mainly located in the inferior inter-atrial septum. No areas of low CV were observed in subjects without a history of atrial arrhythmia while pts affected by paroxysmal AF showed areas with a limited extension of low CV.ConclusionsThe proposed software for automated CV estimation allows the identification of low CV areas, potentially helping electrophysiologists to plan the ablation strategy.

Subsurface Imaging of the Fatha Formation Utilizing 3D Seismic Data in Chia Surkh Area, Kurdistan Region, Iraq

The current study aims to detect subsurface geologic features using 3D dense sampling seismic data in the Fatha Formation, in the Chia Surkh area, Kurdistan Region,Iraq. A3D cube seismic data covering 75 Km2 were used to image the Fatha Formation subsurface geologic structures. The seismic data and appropriate information were gathered from Pet Oil Company with the permission of the Ministry of Natural Resources of the Kurdistan Region, Iraq. A cube of seismic data was used to image the three units of the Fatha Formation. In this study, forty seismic sections with the direction of NE-SW and 30 crossline sections of NW-SE direction were used. The map shows the existence of several features such as a three-way dip closure elongated NW-SE and extended through the whole study area. The reflector three of the Fatha isochron map shows TWT ranging from 890 ms to 1720 ms. The depth map of Fatha unit 1 Formation, shows depth with seismic reference datum ranging from 838 m to 2334 m. The study concluded the existence of several structural features; a major anticline trending with Zagros belt trend, and three longitudinal systematic reverse faults on the southwest side of the anticline, leading to the possibility for which the area is considered as a prospective oil reservoir, might work as a good trap, an anticline, evaporites work as a seal and limestone rocks as a reservoir.

Innovations in ventricular tachycardia ablation.

Catheter ablation of ventricular arrhythmias (VAs) has evolved significantly over the past decade and is currently a well-established therapeutic option. Technological advances and improved understanding of VA mechanisms have led to tremendous innovations in VA ablation. The purpose of this review article is to provide an overview of current innovations in VA ablation. Mapping techniques, such as ultra-high density mapping, isochronal late activation mapping, and ripple mapping, have provided improved arrhythmogenic substrate delineation and potential procedural success while limiting duration of ablation procedure and potential hemodynamic compromise. Besides, more advanced mapping and ablation techniques such as epicardial and intramyocardial ablation approaches have allowed operators to more precisely target arrhythmogenic substrate. Moreover, advances in alternate energy sources, such as electroporation, as well as stereotactic radiation therapy have been proposed to be effective and safe. New catheters, such as the lattice and the saline-enhanced radiofrequency catheters, have been designed to provide deeper and more durable tissue ablation lesions compared to conventional catheters. Contact force optimization and baseline impedance modulation are important tools to optimize VT radiofrequency ablation and improve procedural success. Furthermore, advances in cardiac imaging, specifically cardiac MRI, have great potential in identifying arrhythmogenic substrate and evaluating ablation success. Overall, VA ablation has undergone significant advances over the past years. Innovations in VA mapping techniques, alternate energy source, new catheters, and utilization of cardiac imaging have great potential to improve overall procedural safety, hemodynamic stability, and procedural success.

Identification of Metropolitan Area Boundaries Based on Comprehensive Spatial Linkages of Cities: A Case Study of the Beijing–Tianjin–Hebei Region

As a regional management unit to solve "urban diseases,” metropolitan areas are gradually attracting widespread attention. How to objectively and accurately delineate the boundaries of a metropolitan area is the primary prerequisite for carrying out targeted studies and precisely formulating regional planning measures. However, the existing methods for delineating metropolitan area boundaries have problems, such as high data acquisition costs, subjectivity, and a single perspective of urban linkage. To address the above problems, we propose a “bottom-up” approach to metropolitan area boundary delineation based on urban comprehensive spatial linkages. We used only publicly available data to construct a directionally weighted network of urban spatial linkages, and applied community detection algorithms to delineate metropolitan area boundaries. Taking the Beijing–Tianjin–Hebei region as a case study area, the method’s validity was confirmed. The results showed the following: (1) Eight metropolitan areas were delineated within the region, with two types of metropolitan areas: “Inter-municipal” and “single-city”. (2) The overall accuracy of the delineation results reached 83.41%, which is highly consistent with their corresponding isochrone maps. (3) Most metropolitan areas were observed to have an obvious “central–peripheral” structure, with only the JingJinLang metropolitan area being a polycentric mature metropolitan area, whereas the other metropolitan areas remained in the initial stage of development, with Zhangjiakou and Chengde not yet having formed metropolitan areas. This study’s methodology highlights the basic criteria of “inter-city spatial linkage” as the foundation for boundary delineation, avoiding the inaccuracy caused by the subjective selection of boundary thresholds, and can also accurately determine the developmental stage and internal spatial structure of metropolitan areas. Our method can provide new perspectives for regional boundary delineation and spatial planning policy formulation.

Effects of different dosages esketamine on cardiac conduction and heterogeneity of Cx43: the epicardial mapping in guinea pigs.

BackgroundEsketamine is favored in clinical settings. Relative to other anesthetics it preserves protective airway reflexes, maintains spontaneous respiration, stabilizes hemodynamics, and alleviates neuropathic pain. This study sought to evaluate the cardiac safety of esketamine at 3 sub-anesthetic gradient concentrations.MethodsWe examined the cardiac electrophysiological effects of esketamine with infusion rates of 0.125, 0.25, and 0.5 mg·kg−1·h−1. Short-term studies were performed in ventricular myocytes using patch-clamp techniques and optically mapped Langendorff-perfused guinea-pig hearts. Long-term studies were performed using Langendorff-perfused guinea-pig hearts and electrically mapping the receipt of the infusion for 3 hours.ResultsEsketamine changed the action potential (AP) morphology of cardiomyocytes. Notably, it increased the resting membrane potential (RMP), attenuated the amplitude of action potential (APA), reduced the maximum upstroke velocity (Vmax), and shortened the action potential duration (APD) at 30% to 70%, which led to relatively prolonged monophasic action potentials (MAP) triangulation in G0.25 and G0.5. All the effects were partially eluted. Optical mapping demonstrated almost equal and heterogeneous conduction. G0.125 resulted in an increased heart rate (HR) accompanied by a shortened APD. No detectable arrhythmia was observed at the cycle lengths (CLs) used. Long-term electrical mapping demonstrated the dose-dependent deceleration of the Vmax and APA, but only prolonged the AP parameters in G0.5. Left-ventricular isochronal conduction maps revealed the conduction heterogeneities at G0.5, and conduction velocity (CV) was increased in G0.125 and G0.25. None of these effects were reversed on drug washout. Electrocardiogram (ECG) traces revealed an accelerated HR with the associated curtailment of QT intervals in G0.125; HRs were decreased in G0.25 and G0.5; the PR intervals and QRS duration differed between G0.125 and G0.25, G0.5, which elicited electrical alternans. Connexin43 (Cx43) expression were significantly decreased in G0.125, G0.25 and G0.5.ConclusionsThese data provide a basic electrophysiology for esketamine. Specifically, we found that (I) various methods of esketamine infusion had different effects on cardiac conduction at different dosages; (II) the heterogeneous expression of Cx43 is associated with spatially dispersed conduction; and (III) potential cardiac risks should be considered for high-risk patients receiving continuous esketamine infusions of high dosages.

Concurrent 17. Presentation for: Stratigraphic framework and structural architecture of the Upper Cretaceous in the deep-water Otway Basin – implications for frontier hydrocarbon prospectivity

Presented on Wednesday 18 May: Session 17 Geoscience Australia has undertaken a regional seismic mapping study that extends into the frontier deep-water region of the offshore Otway Basin. This work builds on seismic mapping and petroleum systems modelling published in the 2021 Otway Basin Regional Study. Seismic interpretation spans over 18 000 line-km of new and reprocessed data collected in the 2020 Otway Basin seismic program and over 40 000 line-km of legacy 2D seismic data. Fault mapping has resulted in refinement and reinterpretation of regional structural elements, particularly in the deep-water areas. Structure surfaces and isochron maps highlight Shipwreck (Turonian–Santonian) and Sherbrook (Campanian–Maastrichtian) supersequence depocentres across the deep-water part of the basin. These observations will inform the characterisation of petroleum systems within the Upper Cretaceous succession, especially in the underexplored deep-water region. To access the presentation click the link on the right. To read the full paper click here

Geoscience Poster G5: Stratigraphic framework and structural architecture of the Upper Cretaceous in the deep-water Otway Basin – implications for frontier hydrocarbon prospectivity

Poster G5 Geoscience Australia has undertaken a regional seismic mapping study that extends into the frontier deep-water region of the offshore Otway Basin. This work builds on seismic mapping and petroleum systems modelling published in the 2021 Otway Basin Regional Study. Seismic interpretation spans over 18 000 line-km of new and reprocessed data collected in the 2020 Otway Basin seismic program and over 40 000 line-km of legacy 2D seismic data. Fault mapping has resulted in refinement and reinterpretation of regional structural elements, particularly in the deep-water areas. Structure surfaces and isochron maps highlight Shipwreck (Turonian–Santonian) and Sherbrook (Campanian–Maastrichtian) supersequence depocentres across the deep-water part of the basin. These observations will inform the characterisation of petroleum systems within the Upper Cretaceous succession, especially in the underexplored deep-water region. To access the poster click the link on the right. To read the full paper click here

Assessment of wave front activation duration and speed across the right ventricular outflow tract using electrocardiographic imaging as predictors of the origin of the premature ventricular contractions: A validation study

AimsEvaluate right ventricular outflow tract (RVOT) activation duration (AD) and speed, invasively and with the electrocardiographic imaging (ECGI), as predictors of the origin of the PVCs, validating the ECGI. Methods18 consecutive patients, 8 males, median age 55 (35–63) years that underwent ablation of PVCs with inferior axis and had ECGI performed before ablation. Isochronal activation maps of the RVOT in PVC were obtained with the ECGI and invasively. Total RVOT AD was measured as the time between earliest and latest activated region, and propagation speed by measuring the area of the first 10 ms of activation. Cut-off values for AD, activation speed and number of 10 ms isochrones to predict the origin of the PVCs, were obtained with the ROC curve analysis. Agreement between methods was done with Pearson correlation test and Bland-Altman plot. ResultsPVCs originated from the RVOT in 11 (61%) patients. The stronger predictor of PVC origin was the AD. The median AD in PVCs from RVOT was significantly longer than from outside the RVOT, both with ECGI and invasively, respectively 62 (58–73) vs 37 (33–40) ms, p < 0.0001 and 68 (60–75) vs 35 (29–41) ms, p < 0.0001. Agreement between the two methods was good (r = 0.864, p < 0.0001). The cut-off value of 43 ms for AD measured with ECGI predicted the origin of the PVCs with a sensitivity and specificity of 100%. ConclusionsWe found good agreement between ECGI and invasive map. The AD measured with ECGI was the best predictor of the origin of the PVCs.

Accuracy of noninvasive electrocardiographic imaging using isopotential versus isochronal map for identifying the site of origin of ventricular arrhythmias

Abstract Funding Acknowledgements Type of funding sources: Private hospital(s). Main funding source(s): Learning Health Background and aim Previous studies reporting the results of noninvasive electrocardiographic imaging (ECGI) used both isopotential map and isochronal map to assess the site of origin (SOO) of premature ventricular contractions (PVCs). The aim of this study was to evaluate the accuracy of both methods globally, and according to the location of the arrhythmia: from the right ventricular outflow tract (RVOT) or other locations (non-RVOT). Methods We studied with ECGI 35 consecutive patients with frequent (&amp;gt;10.000/24 h) PVCs. Patients were excluded if the ablation was not performed (7 patients) or was unsuccessful (7 patients). The study group consisted of 21 patients, 11 male, median age of 56 (44-71) years. The ECGI was performed with the epi-endocardial system Amycard. Two noninvasive maps were obtained: isopotential map based on the analysis of the shape and amplitude of the unipolar electrogram (FND method) and an isochronal map obtained using the activation direction method (ADM) (Figure). The invasive activation map was obtained with the Carto or the Ensite system and radiofrequency was applied at the earliest activation site with QS morphology on the unipolar electrogram and a pace match of at least 11/12. The SOO of the PVCs was considered the site where the PVCs were abolished. We assessed the accuracy of the ECGI to identify the SOO of the PVCs using both methods. A perfect match was defined as a predicted location by the ECGI within the same anatomic segment of the actual SOO of the PVCs, whereas a near match as a predicted location within the same segment or a contiguous one. Values are presented as median (Q1-Q3) Results PVCs originated in the RVOT in 11 (52%) patients. The percentage of near matches was not significantly different between FND and ADM methods (95% vs 86%, p=0.50), however the percentage of perfect matches was significantly higher with the FND than with the ADM technique (95% vs 67 %, p=0.031). We found no significant differences in accuracy according to the location of the PVCs, in the RVOT or outside (Table). Conclusions We found a good agreement between ECGI and invasive maps, however the FND technique showed a better accuracy regardless the site of the PVCs.

Assessment of activation duration across the right ventricular outflow tract in patients with premature ventricular contractions using noninvasive electrocardiographic mapping: a validation study

Abstract Funding Acknowledgements Type of funding sources: Private hospital(s). Main funding source(s): Learning Health Introduction Previous studies have reported that wavefront propagation speed across the right ventricular outflow tract (RVOT) can distinguish premature ventricular contractions (PVCs) with a RVOT origin from PVCs with a left ventricular outflow tract (LVOT) origin. Aim Validate the non-invasive electrocardiographic mapping (ECGI) for assessment of RVOT activation duration (AD) during PVCs and assess its value as a predictor of the origin of the PVCs. Methods We studied 18 consecutive patients, 8 males, median age 55 (35-63) years that underwent ablation of frequent (&amp;gt; 10.000 per 24 h) idiopathic PVCs with inferior axis, that had and an ECGI performed before ablation and the RVOT mapped in PVC. The ECGI was performed with the Amycard system, and invasive mapping was performed with the Carto or Ensite system. Isochronal activation maps of the RVOT in PVC were obtained with the activation direction method (ADM) of the ECGI, and with the Carto and Ensite systems. Total RVOT AD was measured as the time interval between the earliest and the latest activated region. Agreement between the two methods was performed using a Bland-Altman plot and linear regression . The cutoff value of AD to predict PVC origin was calculated with ROC curve. Results PVCs originated from the RVOT in 11 (61%) patients. The median (Q1-Q3) RVOT AD measured with ECGI was 54 (39-68) ms and with invasive map 57 (36-70) ms. The agreement between both methods was good with an R2 of 0.747, p&amp;lt;0.0001. Figure displays the Bland-Altman plot (panel A), the linear regression plot (panel B). and two examples of the ECGI isochronal map (panel C). The AD was significantly higher in PVCs from the RVOT vs LVOT, both with ECGI and Carto, respectively 62 (58-73) vs 37 (33-40) ms, p&amp;lt;0.0001 and 68 (60-75) vs 34 (30-40) ms, p&amp;lt;0.0001. The cutoff value of 43 ms for AD measured with ECGI, predicted the origin of the PVCs with a sensitivity and specificity of 100%. Conclusions We found good agreement between ECGI and Carto. The AD obtained with ECGI was accurate to predict the origin of the PVCs.

Isthmus characteristics in operated congenital heart disease with atrial tachycardias

Abstract Funding Acknowledgements Type of funding sources: None. Background Patients with surgically repaired congenital heart disease (RCHD) present a high prevalence of atrial tachycardias (ATs). Although typical circuits dependent on the cavotricuspid isthmus (CTI-AFL) are the most frequent, intra-atrial re-entrant tachycardias (IART) are also common and a significant cause of recurrence. Purpose The aim of this observational study was to describe the characteristics of incisional isthmuses identified with ultrahigh-density electroanatomical mapping in patients with RCHD and to investigate their clinical significance. Methods The present investigation ambispectively examined 23 patients with RCHD. Mapping of index, induced and recurrent ATs was performed using a multipolar basket catheter and an ultra-high density mapping system. The conduction velocities (CV) and isthmus widths were calculated on isochronal and activation maps (Figure 1). Results Overall, 33 ATs in 23 patients were mapped in their entirety. 8 patients had no IART as index AT and no other zones of slow conduction. In the remaining 15 patients, 22 ATs were mapped (9 CTI-AFL/13 IART) and 27 zones of slow conduction were identified. All identified critical and/or potential incisional isthmuses had a CV≤0.625 m/sec. By trichotomizing the predictor of CV, all isthmuses (9/9) of the middle third (CV 0.075-0.133 m/sec) were critical for an IART (either index or induced) and they were significantly more frequently associated with an IART (100%) compared with the isthmuses of the upper (44.4%) and lower third (66.7%) (p=0.034). Width of critical isthmuses was significantly narrower compared to width of non-critical isthmuses (10.1±3.1 mm versus 16.3±7.3 mm, p=0.049). Among 9 induced/recurrent IARTs, critical incisional isthmus was visible at the activation map of the index AT in 6 patients (66.7%) and concealed (presented as line of block and/or collision of the wavefronts) in the remaining (33.3%). Index ATs with concealed isthmuses were significantly slower from index ATs without (U=6, p=0.047). During index ATs with cycle length &amp;lt;270 msec all critical isthmuses were visible (sensitivity 100%) (AUC=0.860, p=0.050). Conclusions The majority of isthmuses related to IARTs can be identified using ultrahigh-density activation mapping in patients with RCHD. A proportion can be overlooked due to functional block, especially during a slow index AT. CV and width of incisional isthmuses can be easily measured using novel mapping tools. Mid-range slow CV and narrow isthmus width may be predisposing factors of IART. Whether these features should promote ablation irrespective of stimulation protocol for AT induction needs further investigation. Figure 1. Isthmus CV calculation using isochronal activation mapping. Figure 2. An incisional isthmus, critical for an induced IART, was identified during a typical flutter. This isthmus had a narrow width (9.0 mm) and a mid-range slow CV (0.11 m/sec), features that may be predisposing factors for IARTs.

Stratigraphic framework and structural architecture of the Upper Cretaceous in the deep-water Otway Basin – implications for frontier hydrocarbon prospectivity

Geoscience Australia has undertaken a regional seismic mapping study that extends into the frontier deep-water region of the offshore Otway Basin. This work builds on seismic mapping and petroleum systems modelling published in the 2021 Otway Basin Regional Study. Seismic interpretation spans over 18 000 line-km of new and reprocessed data collected in the 2020 Otway Basin seismic program and over 40 000 line-km of legacy 2D seismic data. Fault mapping has resulted in refinement and reinterpretation of regional structural elements, particularly in the deep-water areas. Structure surfaces and isochron maps highlight Shipwreck (Turonian–Santonian) and Sherbrook (Campanian–Maastrichtian) supersequence depocentres across the deep-water part of the basin. These observations will inform the characterisation of petroleum systems within the Upper Cretaceous succession, especially in the underexplored deep-water region.

PO-622-06 RELATIVE UTILITY OF OMNIPOLAR SUBSTRATE MAPPING FOR VENTRICULAR TACHYCARDIA ABLATION

EnSite Omnipolar mapping (Abbott, Abbott Park, IL, USA.) is a novel method of directionally optimized, high density, bipolar electrogram creation with integrated local conduction velocity annotation. Established electroanatomic mapping techniques for substrate mapping for ventricular tachycardia (VT) ablation includes voltage mapping, isochronal late activation mapping (ILAM), and fractionation mapping. The relative utilities of these mapping techniques is unknown.

PO-637-08 A COMPARISON BETWEEN DECELERATION ZONES ON ISOCHRONAL LATE ACTIVATION MAPPING AND SUBSTRATE FOR VENTRICULAR TACHYCARDIA USING CT LATE IODINATED CONTRAST ENHANCEMENT AND WALL THINNING

Isochronal late activation mapping (ILAM) is an important tool for identification of targets for ablation without requiring induction of ventricular tachycardia. Computed tomography is also a promising a non-invasive method of identification of scar. Late iodinated contrast enhancement and wall thinning with acquisition of sub-1mm slice thickness are used, which are surrogates for ablation targets. The relationship of deceleration zones observed on ILAM with substrate observed on CT imaging is unknown. To assess the correlation between deceleration zones seen on ILAM with CT substrate. Consecutive patients who underwent VT ablation during a 2-year period using the NAVX (St. Jude Medical, Minneapolis, MN) electroanatomic mapping system and underwent CT imaging (InHeart, Bordeaux, France) were retrospectively reviewed. Patients with incomplete maps, low density maps, or incomplete imaging were excluded (n=15). After CT image integration into the EA map, the presence of DZs was assessed and the presence of underlying substrate on imaging defined. All maps and images following integration were evaluated by 3 independent reviewers who were blinded to ablation lesion sets and clinical outcomes. The DZ was identified and demarcated and then the superimposed substrate on imaging was evaluated. There were 20 patients in the final analysis. The cohort was 80% male with mean age of 68 years with a left ventricular ejection fraction of 34%. Ischemic heart disease was present in 55% of subjects. In 17 of the 20 patients (85%) wall thinning of 1-3mm superimposed on the DZ sites was observed. Dense scar was present in only 7 patients (35%) at DZ sites. DZs observed on ILAM area are highly associated with areas of wall thinning from 1-3 mm on CT. Dense scar was less frequently noted with DZs. These findings may serve as a basis for imaging guided VT ablation in future studies.