Isochronal Maps Research Articles

DETERMINATION OF TRANSPORT ACCESSIBILITY IN THE FORMATION OF TOURIST ROUTES USING QGIS AND GRASS GIS

The creation of modern tourist products contributes to the attractiveness of our country in the market of tourist services. Transport accessibility is an important aspect for creating tourism products. This study considers the algorithm for determining transport accessibility for the projection of tourist travel routes, based on the use of geographic information technologies. Transport accessibility is determined by collecting and filtering data and subsequent creation of isochron maps, which show the time distance when moving a particular mode of transport along the lines of the road network from points of interest. Attractions of Ternopil region were chosen as such points of interest for tourists. The paper uses open OSM data on tourist facilities and the road network. Data preparation was performed using PostgreSQL software. When performing the study, the QGIS program was used, in which data processing was performed. Spatial analysis is performed in the spatial information processing environment GRASS GIS; data processing modules or GRASS GIS plug-ins are used. The proposed algorithm allows forming a database of tourist facilities, transport routes, to define more accurately existing tourist routes, to create new ones. As a test in the course of the study, the route of the tour of Ternopil was designed, in the construction of which an isochron map was used. Spatial analysis helps to better determine the path of the tourist tour and its duration.

Inhibition of Small-Conductance Calcium-Activated Potassium Current (I K,Ca) Leads to Differential Atrial Electrophysiological Effects in a Horse Model of Persistent Atrial Fibrillation.

BackgroundSmall-conductance Ca2+-activated K+ (KCa2) channels have been proposed as a possible atrial-selective target to pharmacologically terminate atrial fibrillation (AF) and to maintain sinus rhythm. However, it has been hypothesized that the importance of the KCa2 current—and thereby the efficacy of small-conductance Ca2+-activated K+ current (IK,Ca) inhibition—might be negatively related to AF duration and the extent of AF-induced remodeling.Experimental Approach and MethodsTo address the hypothesis of the efficacy of IK,Ca inhibition being dependent on AF duration, the anti-arrhythmic properties of the IK,Ca inhibitor NS8593 (5 mg/kg) and its influence on atrial conduction were studied using epicardial high-density contact mapping in horses with persistent AF. Eleven Standardbred mares with tachypacing-induced persistent AF (42 ± 5 days of AF) were studied in an open-chest experiment. Unipolar AF electrograms were recorded and isochronal high-density maps analyzed to allow for the reconstruction of wave patterns and changes in electrophysiological parameters, such as atrial conduction velocity and AF cycle length. Atrial anti-arrhythmic properties and adverse effects of NS8593 on ventricular electrophysiology were evaluated by continuous surface ECG monitoring.ResultsIK,Ca inhibition by NS8593 administered intravenously had divergent effects on right and left AF complexity and propagation properties in this equine model of persistent AF. Despite global prolongation of AF cycle length, a slowing of conduction in the right atrium led to increased anisotropy and electrical dissociation, thus increasing AF complexity. In contrast, there was no significant change in AF complexity in the LA, and cardioversion of AF was not achieved.ConclusionsIntra-atrial heterogeneity in response to IK,Ca inhibition by NS8593 was observed. The investigated dose of NS8593 increased the AF cycle length but was not sufficient to induce cardioversion. In terms of propagation properties during AF, IK,Ca inhibition by NS8593 led to divergent effects in the right and left atrium. This divergent behavior may have impeded the cardioversion success.

Spatial and transmural properties of the reentrant ventricular tachycardia circuit in arrhythmogenic right ventricular cardiomyopathy: Simultaneous epicardial and endocardial recordings

While advances in the characterization of the structural substrate in arrhythmogenic right ventricular cardiomyopathy (ARVC) have been made, the ventricular tachycardia (VT) circuit remains incompletely described. The purpose of this study was to delineate the reentrant VT circuit with simultaneous epicardial and endocardial mapping (SEEM) in ARVC. Twenty-three consecutive patients with ARVC and VT underwent SEEM at 4 centers between 2014 and 2020. Retrospective analysis was performed on combined isochronal activation maps. Of the 30 VT circuits, 24 were delineated with SEEM (956 [341-1843] endocardial points and 1763 [882-3054] epicardial points). The apex and outflow tract rarely harbored VT circuits, with 50% distributed in the inferior wall and 43% in the free wall. The entire tachycardia cycle length was recorded from the epicardium in 71% of circuits. In all circuits, a large proportion of the tachycardia cycle length was recorded from the epicardium relative to the endocardium. Localized epicardial reentry was observed in 35% of patients (14 mm × 15 mm), which was associated withsmaller endocardial low voltage area (39 cm2 vs 104 cm2; P= .002) and preserved right ventricular ejection fraction (35% vs 25%; P = .046) compared with those with larger circuit dimensions. Seventy percent of termination sites were achieved from the epicardium. High-resolution recordings from both myocardial surfaces confirm a consistent predominance of epicardial participation during reentry in ARVC. Only the perivalvular inflow region of the "triangle of dysplasia" had a strong propensity to harbor VT circuits, with the greatest proportion located in the inferior wall. Localized epicardial reentry may be a manifestation of earlier stage disease with a relative paucity of endocardial substrate.

Seismic Sequence Stratigraphic Sub-Division Using Well Logs and Seismic Data of Taranaki Basin, New Zealand

This study focuses on the sequence stratigraphy and the dominated seismic facies in the Central Taranaki basin. Four regional seismic sequences namely SEQ4 to SEQ1 from bottom to top and four boundaries representing unconformities namely H4 to H1 from bottom to top have been traced based on the reflection terminations. This was validated using well logs information. An onlapping feature on the seismic section indicates a new perspective surface separated between the upper and lower Giant formation, which indicates a period of seawater encroachment. This study focused extensively on deposition units from SEQ4 to SEQ1. The seismic facies, isochron map, and depositional environment were determined, and the system tract was established. This study was also able to propose a new perspective sequence stratigraphy framework of the basin and probable hydrocarbon accumulations and from the general geological aspect, SA-Middle Giant Formation (SEQ3) could act as potential traps.

Seismic record of a cyclic turbidite-contourite system in the Northern Campos Basin, SE Brazil

A new mixed turbidite-contourite system is described in the northern Campos Basin, southeastern Brazilian margin. This system is developed in a middle slope setting, and was formed through non-synchronous interaction between the turbidity current and a contour current in the same stratigraphic interval (Miocene). Depositional cycles were differentiated based on diagnostic seismic features. Seismic attributes, seismic facies, and isochron maps were used to identify alternating cycles of downslope and alongslope processes in the study area, along with the intermediate stage with features from both processes (mixed system). Seismic units were then associated with the dominant type of current. Alongslope current activity can be distinguished from the downslope current based on its acoustic characteristics (mainly low root-mean-square (RMS) amplitude values), internal architecture (clinoforms), and external geometry pattern (alongslope trend).On the other hand, downslope gravity currents develop deposits with high-amplitude or chaotic seismic facies, usually higher values of RMS amplitude, channel or channel-lobe features, erosive surfaces, and a basinward depositional trend. The first and oldest seismic unit (S1) was interpreted as a dominantly alongslope system, with vertical aggrading sigmoidal clinoforms and high-frequency, low-amplitude reflections commonly associated with fine-grained sedimentary deposits, typical of a plastered drift, along with a basinward mass transport deposit (MTD) from previous drift instability. Seismic unit S2 represents the intermediate stage where both gravity-driven and along-slope currents act asynchronously. Its is refered to as a mixed turbidite-contourite sequence that shows high-amplitude sediment waves migrating upslope and a moat feature that is carved in its upslope front. The interfingering between high- and low-amplitude reflectors, distal chaotic facies, together with sediment waves and a channel moat, points to a sand-rich deposit reworked by northward-flowing contour currents. Seismic units S3 and S4 show downslope features with chaotic facies (S3) and paleochannels with coarse basal lag deposits (high RMS amplitude values) (S4). In S4, a series of long-lived submarine channels formed. Last, seismic unit S5, referred to as the second plastered drift sequence, is marked by low-amplitude clinoforms that thin basinward. At the seafloor, submarine channel banks (formed at S4) covered by fine sediment deposits (from S5) show asymmetrical features with a slight northward depositional trend, indicating a northward-flowing bottom current, as the deposits are known to pile up in a downcurrent trend. Important information on the paleocurrents' direction was also made based on the final deposits display (e.g. terraces, sediment waves, paleochannels). Research on alternating dominant processes and transitional stages or mixed depositional systems, with both turbidites and contour currents, may provide a better understanding of deep-water depositional processes. Because these processes do not always fit previous depositional models that are mainly described for synchronous systems, new insights on cyclic non-synchronous mixed systems can improve our understanding of how mixed systems are organized through time and space. Being able to determine which were the dominant processes that controlled the sedimentation by indicating periods where the margin was mostly submitted to sediment transfer from continent to the basin and periods where the oceanic currents prevailed by redistributing sediments along the isobaths and replacing the axis of downslope transfer conduits. Setting new models on cyclic deposits and intermediate stages can have a future economic impact on potential hydrocarbon reservoir architecture.

Towards Dynamic Isochrone Mapping Accounting for Uncertainty

Isochrone Mapping has been used since the late 19th century as a planning and visualization tool in various domains, such as transport planning and hydrology. In the past, isochrone calculation was based mainly on static properties and therefore also yielded static maps. This resulted in a potentially significant — and at the same time unquantifiable — degree of uncertainty. Today however, advances both in information technology and in the availability of input data allow much more nuanced views on the subject. This paper gives an overview of work on dynamic factors that contribute to uncertainty in isochrone calculation and mapping. Various application scenarios and their constraints are discussed, and open research challenges and possibilities identified. Finally, we present preliminary results from a practical approach to quantifying uncertainties in isochrone calculation for motorized individual transport based on Monte Carlo simulations and data from open routing APIs.

Testing the limitations of buffer zones and Urban atlas population data in urban green space provision analyses through the case study of Szeged, Hungary

A liveable city requires urban green spaces (UGS) in many locations, since such spaces have a direct impact on the quality of life and overall well-being of city dwellers. UGS provision analyses therefore have been attracting a number of researchers, practitioners and decision makers for recent years using various methodologies. In this study, we conduct reference UGS provision analysis using accurate input data, calculating the population with access to a UGS within fifteen minutes of walking, with a one-minute resolution. These results are employed as reference for quantifying the spatial accuracy of buffer zone-based isochrone maps and the overall (thematic and scale) accuracy of the European Environmental Agency’s Urban Atlas population database in UGS provision estimation. The estimated differences between the Urban Atlas and the reference data in UGS provision assessment are 11.8 % (6861 people) within 10 min and 11.8 % (7050 people) within 15 min of walking. The difference between estimates from buffer zone-based isochrone maps and the reference is 2.1 % (1479 people) within 10 min and 0.1 % (77 people) within 15 min of walking. Further statistical analyses reveal that the spatial accuracy (correlation coefficient with reference = 0.7878) of the buffer zone-based map’s impact on the result of UGS provision estimation is more than the overall accuracy of the Urban Atlas’ population database (correlation coefficient with reference = 0.9798). These results may potentially enhance the knowledge about the limitations, usefulness and reliability of the buffer zone-based isochrone maps and the European-scale land cover and population dataset in spatial analyses of UGS provision. The results of this study can be used for improving the accuracy of buffer zone- and Urban Atlas-based UGS provision mapping estimates at local and regional scales.

Abstract 13669: Slow Conduction Zone of Left Atrium is a Precursor to Low Voltage Area in Patients With Atrial Fibrillation

Introduction: The slow conduction zone (SCZ) in the left atrium (LA) has attracted attention as an arrhythmia substrate of atrial fibrillation (AF). However, the occurrence mechanism of SCZ remains unclear. Hypothesis: The SCZ is related to the low voltage area (LVA) or the LA anatomical contact areas (CoAs) with other organs in patients with AF. Methods: We studied 100 patients (49 non-paroxysmal AF, 66 males, 67.9 ± 9.9 years) who received catheter ablation for AF. High-density LA mapping during right atrial appendage pacing at a rate of 100 bpm after pulmonary vein isolation were constructed. Isochronal activation maps were created at 5-ms interval setting, and the SCZ was identified on the activation map by finding a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s (Figure). The LVA was defined as the following; mild (<1.3 mV), moderate (<1.0 mV), and severe LVA (<0.5 mV). The CoAs (ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using computed tomography. Results: The SCZ was distributed linearly (Figure), and observed in 95 of 100 patients (95%). The SCZ was most frequently observed in the anterior wall region (77%). A longer SCZ was significantly associated with a larger LA size and a prevalence of non-PAF. The 51.2±36.2% of SCZ overlapped with mild LVA, 32.9±32.8% of SCZ with moderate LVA, and 14.6±22.0% of SCZ with severe LVA. In contrast, only 25.6±28.0 % of SCZ matched with the CoAs. Conclusion: The slow conduction zone reflects LA electrical remodeling and may be a precursor finding of the low voltage zone, not LA contact areas in patients with atrial fibrillation.

Characteristics and outcomes of pace mapping for ablation of premature ventricular complexes

Abstract Background/Introduction Activation mapping is the “gold standard” for localisation of the site of origin during mapping and ablation of symptomatic premature ventricular complexes (PVC). In case of suppression of PVCs during the procedure, the origin of the PVC can be located using a pace mapping technique. The PASO module is an addition in the CARTO3 mapping system that calculates the correlation between the induced and observed 12-lead ECG PVC morphology, and visualises this correlation on an isochronal 3D colour map. Purpose The aim of this study was to compare the follow-up success rate of pace mapping using the PASO module and activation mapping and to determine cut-off values for clinical success. Methods Seventy-six consecutive ablation procedures of symptomatic PVCs were included in this single-center retrospective study. Mapping and ablation parameters were derived from the CARTO3 mapping system. Ablation success was defined as a ≥95% reduction in PVC burden on 24-hour Holter recordings or absence of the clinical PVC on multiple ECGs in case of multiple PVC morphologies. Logistic regression analysis was performed to evaluate the relationship between applied mapping methods and ablation parameters. Optimal cut-off values of ablation characteristics for successful ablation were determined using ROC curves. Results Thirty-five (46%) patients were male and 39 (51%) patients had a reduced left ventricular ejection fraction. Pace mapping was used in 36 (47%) patients. Baseline PVC burden was lower in patients when pace mapping was applied (18% vs. 28%, p<0.001). The use of either mapping technique was influenced by PVC localisation (p=0.004). Pace mapping was used predominantly in the right ventricular outflow tract (n=21/31) whereas activation mapping was used predominantly in the left ventricle (n=14/22) and left ventricular outflow tract (n=7/7). Ablation success did not differ between activation mapping (77.5%) and pace mapping (77.8%). Median [IQR] maximum PASO correlation was 98.2% [97.1–98.6] for successful ablations and 96.5% [92.9–97.5] for unsuccessful ablations (p=0.030). The optimal cut-off value for successful ablation of the PASO correlation was 97.6% (AUC 0.754, sensitivity 68%, specificity 88%). There were no significant differences in other ablation parameters between both groups. Conclusion This study indicates that pace mapping using PASO is a good alternative for activation mapping for localisation of the PVC. A minimum PASO correlation coefficient of 97.6% is the optimal cut-off value for successful PVC ablation. ROC of maximum PASO coefficient Funding Acknowledgement Type of funding source: None

Slow conduction zone as an early electrical remodeling change in patients with atrial fibrillation

Abstract Background The slow conduction zone (SCZ) in the left atrium (LA) detected using 3-D mapping and high-resolution imaging system has attracted attention as an arrhythmia substrate of atrial fibrillation (AF). However, the occurrence mechanism of SCZ remains unclear. Purpose This aim of this study is to clarify whether SCZ is related to the low voltage zone (LVZ) or the LA anatomical contact areas with other organs such as aorta or thoracic spine in patients with AF. Methods We studied 36 patients (21 males, 68±10 years, 14 paroxysmal AF; PAF, 17 persistent AF; PeAF, 5 long-standing persistent AF; LS-PeAF) who received catheter ablation for AF. High-density LA mapping during sinus rhythm or right atrial pacing after pulmonary vein isolation were constructed by acquiring more than 2000 endocardial points in each patient. Isochronal activation maps were created at 5-ms interval setting, and the SCZ was identified on the activation map by finding a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s (figure). The LVZ was defined as the following; mild (<1.5 mV), moderate (<1.0 mV), and severe LA-LVZ (<0.5 mV). The LA contact areas (CoAs; ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using computed tomography. Results The SCZ was distributed linearly (figure), and observed in 35 of 36 patients (97.2%). The SCZ was often found in the anterior (89%), roof (64%), and septal wall (47%) of LA, and longest in patients with LS-PeAF (PAF: 56±34 mm, PeAF; 79±41 mm, LS-PeAF; 107±34mm, P=0.0351). The prevalence rate of SCZ (97.2%) was higher than LVZ (figure, mild LA-LVZ; 91.7%, moderate LA-LVZ: 66.7%, severe LA-LVZ; 25%). The 55.8% of SCZ overlapped with mild LA-LVZ, 37.6% of SCZ with moderate LA-LVZ, and 19.1% of SCZ with severe LA-LVZ. The LA CoAs were found in all patients. A total of 72 CoAs (average surface area, 7.0±4.0 cm2) were identified. A CoA was found in each of the three representative regions, ascending aorta-anterior LA (4.1±2.0 cm2, 36 of 36 patients, 100%), descending aorta-posterior LA (2.3±1.2 cm2, 12 of 36 patients, 33%), and vertebrae-posterior LA (3.4±2.1 cm2, 24 of 36 patients, 67%). However, only 22% of SCZ matched with the LA anatomical contact areas. Conclusion The slow conduction zone reflects LA electrical remodeling and may be a precursor finding of the low voltage zone, not LA contact areas in patients with atrial fibrillation. Funding Acknowledgement Type of funding source: None

Variations in P-wave Travel Times Based on a Digital Seismogram Dataset

The paper presents the parameters of digital seismograms of artificial seismic events observed in from 1967 to 1990. The data were provided to the authors from the archive of the Sadovsky Institute of Geosphere Dynamics (IDG RAS). Seismograms were obtained after reformatting digital records. The archived data were analyzed to obtain a posteriori information on P-wave travel times, determined from the moment of the first arrival on the record of the vertical component (Z) of the short-period channel. The practice has shown that combining these data is sufficient to compile a map of signal arrival times from seismic sources. We present the regional travel-time curve for three test sites and linear trends of P-wave travel times by calendar date, as well as an isochron map for one of the sites.

Injectable conductive hydrogel restores conduction through ablated myocardium.

Therapies for substrate-related arrhythmias include ablation or drugs targeted at altering conductive properties or disruption of slow zones in heterogeneous myocardium. Conductive compounds such as carbon nanotubes may provide a novel personalizable therapy for arrhythmia treatment by allowing tissue homogenization. A nanocellulose carbon nanotube-conductive hydrogel was developed to have conduction properties similar to normal myocardium. Ex vivo perfused canine hearts were studied. Electroanatomic activation mapping of the epicardial surface was performed at baseline, after radiofrequency ablation, and after uniform needle injections of the conductive hydrogel through the injured tissue. Gross histology was used to assess distribution of conductive hydrogel in the tissue. The conductive hydrogel viscosity was optimized to decrease with increasing shear rate to allow expression through a syringe. The direct current conductivity under aqueous conduction was 4.3 × 10-1 S/cm. In four canine hearts, when compared with the homogeneous baseline conduction, isochronal maps demonstrated sequential myocardial activation with a shift in direction of activation to surround the edges of the ablated region. After injection of the conductive hydrogel, isochrones demonstrated conduction through the ablated tissue with activation restored through the ablated tissue. Gross specimen examination demonstrated retention of the hydrogel within the tissue. This proof-of-concept study demonstrates that conductive hydrogel can be injected into acutely disrupted myocardium to restore conduction. Future experiments should focus on evaluating long-term retention and biocompatibility of the hydrogel through in vivo experimentation.

Is the abnormal conduction zone of the left atrium a precursor to a low voltage area in patients with atrial fibrillation?

The abnormal conduction zone (ACZ) in the left atrium (LA) has attracted attention as an arrhythmia source in atrial fibrillation (AF). We investigated the hypothesis that the ACZ is related to the low voltage area (LVA) or the LA anatomical contact areas (CoAs) with other organs. We studied 100 patients (49 non-paroxysmal AF, 66 males, and 67.9 ± 9.9 years) who received catheter ablation for AF. High-density LA mapping during high right atrial pacing was constructed. Isochronal activation maps were created at 5-ms interval setting, and the ACZ was identified on the activation map by locating a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s. The LVA was defined as the following; mild ( < 1.3 mV), moderate (<1.0 mV), and severe LVA (<0.5 mV). The CoAs (ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using computed tomography. The ACZ was linearly distributed, and observed in 95 patients (95%). The ACZ was most frequently observed in the anterior wall region (77%). A longer ACZ was significantly associated with a larger LA size and a prevalence of non-PAF. The 51.2 ± 36.2% of ACZ overlapped with mild LVA, 32.9 ± 32.8% of ACZ with moderate LVA, and 14.6 ± 22.0% of ACZ with severe LVA. In contrast, only 25.6 ± 28.0% of ACZ matched with the CoAs. The ACZ reflects LA electrical remodeling and may be a precursor finding of the low voltage zone and not the LA CoAs in patients with atrial fibrillation.

Trace Mapping: A New Visualization Technique for Analyzing Gastrointestinal High-Resolution Electrical Mapping Data.

Visualization techniques are an important tool for understanding high-resolution mapping data in gastric electrophysiology. Isochronal maps and animations provide excellent depictions of spatial propagation patterns, but fail to capture temporal features of electrical activity. In this work, 'trace mapping' was developed and validated as a method for visualizing high-resolution mapping data. A combination of dots and lines represent events and temporal groups, respectively, creating patterns that can be quickly and efficiently interpreted. This work outlines trace mapping methods and introduces a shape-based pattern recognition method for efficient interpretation of trace maps. These methods provide a new perspective for understanding and evaluating gastric electrophysiology.Clinical Relevance-This work provides new visualization methods that can help clinicians interpret and diagnose gastric electrical abnormalities in patients with functional gastrointestinal disorders.

Interpretation of Paleozoic paleokarst features in the Arkoma Basin of Oklahoma using 3D seismic and well logs

Paleokarst regions worldwide are repositories for hydrocarbons, mineral deposits, and groundwater. Time structure maps were generated for the Ordovician Viola Limestone, Mississippian Caney Shale, and Pennsylvanian Jefferson Sandstone and Wapanucka Limestone. Isochron maps indicate pronounced visible sinkhole time thickening in the Viola-Caney and Caney-Jefferson intervals relative to the Jefferson-Wapanucka. Sinkhole features in the Viola exhibit mappable structural depression, characterized by lower positive amplitude, higher seismic variance, and most-negative curvature. Curiously, spatially coincident sinkhole features in the shallower Wapanucka display the opposite characteristics relative to adjacent areas that have not been modified, namely, higher positive amplitude and lower seismic variance with no mappable time structure relief. Seismic amplitude analysis based on well logs and Gassmann modeling indicate that the Viola has a reduction in limestone acoustic impedance inside sinkholes that allows estimation of increased porosity near 10%. Identical analysis for the Wapanucka suggests that no reasonable alteration of the limestone acoustic impedance alone can account for the observed amplitude behavior, implying that the limestone and overlying shale must be altered in sinkhole areas. Some of these interpreted sinkhole features coincide with vertical pipe structures with up to 490 m (1610 ft) vertical extent, diameter up to 520 m (1700 ft), and separation of at least 460 m (1510 ft). We interpret the Viola sinkhole features and associated vertical pipes to be part of a mature epigene karst system. Conversely, the shallower and more subtle Wapanucka sinkholes we interpret as related to an immature mixed karst system with epigene and hypogene elements. Our study indicates for the first time the seismic evidence of pipe features that extend both below and above the Viola and the presence of Wapanucka sinkhole features in the Arkoma Basin of Oklahoma, which provides a better understanding of paleokarst occurrence and its possible impact on resource exploration.

High-Density Grid Catheter forDetailedMappingofSinusRhythm and Scar-Related Ventricular Tachycardia: Comparison With a Linear Duodecapolar Catheter.

This study aimed to evaluate the feasibility and accuracy of using a novel grid mapping catheter during scar-related ventricular tachycardia (VT) ablation. Ultra-high-density (UHD) mapping improves identification of local abnormal ventricular activities (LAVAs) and characterization of scar substrates. Consecutive patients underwent endocardial and/or epicardial ablation guided by a HD grid mapping catheter. A linear duodecapolar catheter was used in the initial cases for systematic correlation. Isochronal late activation mapping was performed during sinus rhythm to identify deceleration zones, and activation mapping of VT was performed when tolerated. In 38 patients, 51 electroanatomic maps (left ventricle: 26, epicardium: 21, right ventricle: 4) were created using a grid catheter. LAVAs were identified in 98% of cases and deceleration zones were observed in 86%. High-frequency electrograms with diastolic activation were identified during 44 sustained monomorphic VTs, and the critical isthmus was colocalized to deceleration zones during sinus rhythm in 96% of cases. In 17 cases that underwent sequential mapping with both grid and linear catheters, the low voltage area detected using the grid (HD wave) was significantly smaller, with ratios of 0.61 (<0.5mV) and 0.81 (<1.5mV) relative to the duodecapolar catheter. VT ablation guided by a novel HD grid catheter is safe and feasible for clinical use in human scar-related VT via both endocardial and epicardial approaches. Automated selection of larger bipolar amplitudes among orthogonal pairs consistently displayed smaller low voltage areas than a previously validated linear catheter.

Conduction slowing area during sinus rhythm harbors ventricular tachycardia isthmus.

The voltage map during sinus rhythm (SR) is a cornerstone of substrate mapping (SM) in scar-related ventricular tachycardia (VT) and frequently used with pace mapping (PM). Where to conduct PM is unclear in cases of an extensive or unidentified substrate. Conduction properties are another aspect incorporated by SM, and conduction slowing has gained interest as being related to successful ablation, although its mechanism has not been elucidated. We aimed to investigate the relationship between SR conduction properties and VT isthmuses. Nineteen patients (mean age, 62 years) who underwent VT ablation with voltage mapping and PM were reviewed. Isochronal late activation maps (ILAMs) with eight zones were reconstructed and sequentially named from one to eight according to the SR propagation. Good PM sites were superimposed on ILAMs, and the isthmus was defined using different pacing latencies. ILAM properties harboring isthmuses were investigated. Twenty-eight ILAMs (13 epicardium, 1 right ventricular [RV], and 14 left ventricular [LV] endocardium) were reviewed. Eighteen isthmuses of 24 target VTs were identified, in which the proximal ends were in a later zone than the distal ends (zone 6 vs 4; P < .001), suggesting a reverse isthmus vector to the SR. The conduction velocity of the zone involving the distal isthmus was significantly lower than that of the SR preceding zone (0.40 vs 1.30 m/s; P < .001). SR conduction velocity decelerated by 69.5% (range 59.7%-74.5%) before propagating into the isthmus area. Conduction slowing area during SR were related with the exit portion of the VT isthmuses.

Atypical Flutter with Atrial Isochronal Late-activation Map Correlating with the Critical Isthmus.

Atypical Flutter with Atrial Isochronal Late-activation Map Correlating with the Critical Isthmus.

Substrate Mapping in Ventricular Arrhythmias.

Ventricular tachycardia is typically hemodynamically unstable. Strategies to target the arrhythmogenic substrate during sinus rhythm are essential for therapeutic ablation. Electroanatomic mapping is the cornerstone of substrate-based strategies; ablation can be directed within a delineated scar region defined by low voltage. Bipolar voltage mapping has inherent limitations. Specific electrogram characteristics may improve the specificity of localizing the most arrhythmogenic regions within the substrate. Deceleration zones during sinus rhythm are niduses for reentry and can be identified by isochronal late activation mapping, which is a functional analysis of substrate propagation with local annotation to electrogram offset.

Deep gravity data interpretation using seismic reflection and well data: A case study of the West Gharib-Bakr area, Eastern Desert, Egypt

Abstract A rigorous processing and analysis of the gravity data with seismic reflection and borehole information enabled a general view of the deep-seated regional structures in the West Gharib-Bakr area, Eastern Desert, Egypt. In this context, several interpretational techniques were applied to learn more about the supra-basement structures and intra-basement sources. The interpretation started with a review of the seismic data to clarify the structural elements on top of the Miocene strata, where a number of isochronous reflection maps were constructed and had migrated into depth maps. The Bouguer anomaly map was processed using Fast Fourier Transform filtering based on spectral analysis to separate the gravity anomalies into its components. Gravity stripping was also performed under the seismic isopachs and density controls. The gravity effect of each rock unit was calculated and progressively removed from the original data to obtain a new gravity map on top of the Pre-Miocene. To ensure more reliable results, further filtering and analytical processes were applied to the stripped map. The results of seismic analysis show simple structural configurations at the Miocene level, with a significant increase of evaporite thickness along the Gulf of Suez coast. In contrast, analysis of the stripped gravity map reveals a more intricate structure at the Pre-Miocene level, with increasing numbers/lengths of faults on the basement surface. Lineament analysis shows two major peaks trending N0–20°W and N50–70°E, produced by two main forces in NNW–SSE (compression) and ENE–WSW (tension) directions. The models confirmed a rough and ruptured basement surface, with no evidence of any magmatic intrusions penetrating the sediments. The basement relief map delineates five basins/sub-basins in the area which are separated from each other by ridges/saddles.