Wavefront Propagation Research Articles

Lower contact force predicts right pulmonary vein carina breakthrough after ablation index-guided pulmonary vein isolation using high-power short-duration.

Carina breakthrough (CB) at the right pulmonary vein (RPV) can occur after circumferential pulmonary vein isolation (PVI) due to epicardial bridging or transient tissue edema. High-power short-duration (HPSD) ablation may increase the incidence of RPV CB. Currently, the surrogate of ablation parameters to predict RPV CB is not well established. This study investigated predictors of RPV CB in patients undergoing ablation index (AI)-guided PVI with HPSD. The study included 62 patients with symptomatic atrial fibrillation (AF) who underwent AI-guided PVI using HPSD. Patients were categorized into two groups based on the presence or absence of RPV CB. Lesions adjacent to the RPV carina were assessed, and CB was confirmed through residual voltage, low voltage along the ablation lesions, and activation wavefront propagation. Out of the 62 patients, 21 (33.87%) experienced RPV CB (Group 1), while 41 (66.13%) achieved first-pass RPV isolation (Group 2). Despite similar AI and HPSD, patients with RPV CB had lower contact force (CF) at lesions adjacent to the RPV carina. Receiver operating characteristic (ROC) curve analysis identified CF < 10.5 g as a predictor of RPV CB, with 75.7% sensitivity and 56.2% specificity (area under the curve: 0.714). In patients undergoing AI-guided PVI with HPSD, lower CF adjacent to the carina was associated with a higher risk of RPV CB. These findings suggest that maintaining higher CF during ablation in this region may reduce the occurrence of RPV CB.

Electrographic flow mapping of persistent atrial fibrillation: intra- and inter-procedure reproducibility in the absence of 'ground truth'.

Validating mapping systems that identify atrial fibrillation (AF) sources (focal/rotational activity) is confounded by the absence of ground truth. A key concern of prior mapping technologies is spatiotemporal instability, manifesting as poor map reproducibility. Electrographic flow (EGF) employs a novel algorithm that visualizes atrial electrical wavefront propagation to identify putative AF sources. We analysed both intra- (3 min) and inter- (>3 months) procedure EGF map reproducibility. In 23 persistent AF patients, after pulmonary vein isolation (PVI), EGF maps were generated from 3 serial 1 min recordings using a 64-electrode basket mapping catheter (triplets) at right and left atrial locations. Source prevalence from map triplets was compared between recordings. Per protocol, 12 patients returned for 3-month remapping (1 non-inducible): index procedure post-PVI EGF maps were compared with initial EGF remapping at 3-month redo. Intra-procedure reproducibility: analysing 224 map triplets (111 right atrium, 113 left atrium) revealed a high degree of map consistency with minimal min-to-min shifts: 97 triplets (43%), exact match of leading sources on all 3 maps; 95 triplets (42%), leading source within 1 electrode space on 2 of 3 maps; and 32 triplets (14%), chaotic leading source pattern. Average deviation in source prevalence over 60 s was low (6.4%). Inter-procedure reproducibility: spatiotemporal stability of EGF mapping >3 months was seen in 16 of 18 (89%) sources mapped in 12 patients with (re)inducible AF. Electrographic flow mapping generates reproducible intra- and inter-procedural maps, providing rationale for randomized clinical trials targeting these putative AF sources.

Structure and phase composition of SHS composites based on Al–Ti–B system with different Al content

The paper deals with the influence of the Al content in the initial Al–Ti–B system on self-propagating high-temperature synthesis (SHS) processes, structure, and phase composition of synthesized products. It is found that the higher Al content leads to a temperature decrease of exothermic reaction and changes its wavefront propagation from layerwise to spinwise multiple locations. SHS products obtained from the Al–Ti–B system contain titanium diboride (TiB2) and aluminum (Al) phases. The weight content of phases in SHS products depends on the Al content in the initial powder mix and approximately matches the weight content of its components. The higher Al content provides a decrease in the size of the coherent scattering region for detected phases. SHS products obtained from the Al–Ti–B system with 10 wt% Al, consist of separate TiB2 particles coated with aluminum film. The Al content increased up to 30 and 60 wt%, provides the formation of the metal matrix structure. In this case, synthesis products consist of the aluminum matrix with TiB2 particles distributed inside. It is found that the growth in the Al content from 10 to 60 wt% in the initial Al–Ti–B system, results in the size reduction of TiB2 particles in SHS products from 3.37 to 0.41 μm, respectively.

Discontinuous Galerkin methods for Fisher–Kolmogorov equation with application to [formula omitted]-synuclein spreading in Parkinson’s disease

This spreading of prion proteins is at the basis of brain neurodegeneration. This paper deals with the numerical modelling of the misfolding process of α-synuclein in Parkinson’s disease. We introduce and analyse a discontinuous Galerkin method for the semi-discrete approximation of the Fisher–Kolmogorov (FK) equation that can be employed to model the process. We employ a discontinuous Galerkin method on polygonal and polyhedral grids (PolyDG) for space discretization, to accurately simulate the wavefronts typically observed in the prionic spreading and we prove stability and a priori error estimates. Next, we use a Crank–Nicolson scheme to advance in time. For the numerical verification of our numerical model, we first consider a manufactured solution, and then we consider a case with wavefront propagation in two-dimensional polygonal grids. Next, we carry out a simulation of α-synuclein spreading in a two-dimensional brain slice in the sagittal plane with a polygonal agglomerated grid that takes full advantage of the flexibility of PolyDG approximation. Finally, we present a simulation in a three-dimensional geometry reconstructed from magnetic resonance images of a patient’s brain.

Terahertz Twistoptics-Engineering Canalized Phonon Polaritons.

The terahertz (THz) frequency range is key to studying collective excitations in many crystals and organic molecules. However, due to the large wavelength of THz radiation, the local probing of these excitations in smaller crystalline structures or few-molecule arrangements requires sophisticated methods to confine THz light down to the nanometer length scale, as well as to manipulate such a confined radiation. For this purpose, in recent years, taking advantage of hyperbolic phonon polaritons (HPhPs) in highly anisotropic van der Waals (vdW) materials has emerged as a promising approach, offering a multitude of manipulation options, such as control over the wavefront shape and propagation direction. Here, we demonstrate the THz application of twist-angle-induced HPhP manipulation, designing the propagation of confined THz radiation between 8.39 and 8.98 THz in the vdW material α-molybdenum trioxide (α-MoO3), hence extending twistoptics to this intriguing frequency range. Our images, recorded by near-field optical microscopy, show the frequency- and twist-angle-dependent changes between hyperbolic and elliptic polariton propagation, revealing a polaritonic transition at THz frequencies. As a result, we are able to allocate canalization (highly collimated propagation) of confined THz radiation by carefully adjusting these two parameters, i.e. frequency and twist angle. Specifically, we report polariton canalization in α-MoO3 at 8.67 THz for a twist angle of 50°. Our results demonstrate the precise control and manipulation of confined collective excitations at THz frequencies, particularly offering possibilities for nanophotonic applications.

Oscillating Nonlinear Acoustic Waves in a Mooney–Rivlin Rod

Harmonic wave excitation in a semi-infinite incompressible hyperelastic 1D rod with the Mooney–Rivlin equation of state reveals the formation and propagation of the shock wave fronts arising between faster and slower moving parts of the initially harmonic wave. The observed shock wave fronts result in the collapse of the slower moving parts being absorbed by the faster parts; hence, to the attenuation of the kinetic and the elastic strain energy with the corresponding heat generation. Both geometrically and physically nonlinear equations of motion are solved by the explicit Lax–Wendroff numerical tine-integration scheme combined with the finite element approach for spatial discretization.

Visualization of electrographic flow fields of increasing complexity and detection of simulated sources during spontaneously persistent AF in an animal model.

Mapping algorithms have thus far been unable to localize triggers that serve as drivers of AF, but electrographic flow (EGF) mapping provides an innovative method of estimating and visualizing in vivo, near real-time cardiac wavefront propagation. One-minute unipolar EGMs were recorded in the right atrium (RA) from a 64-electrode basket catheter to generate EGF maps during atrial rhythms of increasing complexity. They were obtained from 3 normal, animals in sinus rhythm (SR) and from 6 animals in which persistent AF which was induced by rapid atrial pacing. Concurrent EGF maps and high-resolution bipolar EGMs at the location of all EGF-identified sources were acquired. Pacing was subsequently conducted to create focal drivers of AF, and the accuracy of source detection at the pacing site was assessed during subthreshold, threshold and high-output pacing in the ipsilateral or contralateral atria (n = 78). EGF recordings showed strong coherent flow emanating from the sinus node in SR that changed direction during pacing and were blocked by ablation lesions. Additional passive rotational phenomena and lower activity sources were visualized in atrial flutter (AFL) and AF. During the AF recordings, source activity was not found to be correlated to dominant frequency or f wave amplitude observed in concurrently recorded EGMs. While pacing in AF, subthreshold pacing did not affect map properties but pacing at or above threshold created active sources that could be accurately localized without any spurious detection in 95% of cases of ipsilateral mapping when the basket covered the pacing source. EGF mapping can be used to visualize flow patterns and accurately identify sources of AF in an animal model. Source activity was not correlated to spectral properties of f-waves in concurrently obtained EGMs. The locations of sources could be pinpointed with high precision, suggesting that they may serve as prime targets for focal ablations.

Visibility region and correlation in ELAA-MIMO LoS scenarios under planar and spherical wavefront propagation

Channel is one of the critical aspects of designing reliable wireless communication systems by accurately modeling the signal propagation along different physical scenarios where the wireless data transmission occurs. Although several channel models have already been developed for Massive MIMO (M-MIMO) systems, the novel extra-large array aperture multiple-input-multiple-output (ELAA-MIMO) systems impose a new challenge in the development of wireless channel models due to the proximity between users, scatterers, and the base station (BS) array, by establishing the spherical wavefront hypothesis. Spherical wavefront propagation and visibility regions (VR) are known as phenomenons that physically affects the ELAA-MIMO system performance and channel modeling, being essential for practical deployments of the next-generation wireless communications (B5G). In this work, we model and discuss the critical parameters of Line-of-Sight (LoS) M-MIMO and recent ELAA-MIMO channel models, such as physical aspects and generation of these wireless channels. We aim to provide insights on the parameters setting and VR determination based on a power threshold criterion to be considered in specific LoS ELAA-MIMO channel modeling.

Real-time programmable metasurface for terahertz multifunctional wave front engineering

Terahertz (THz) technologies have become a focus of research in recent years due to their prominent role in envisioned future communication and sensing systems. One of the key challenges facing the field is the need for tools to enable agile engineering of THz wave fronts. Here, we describe a reconfigurable metasurface based on GaN technology with an array-of-subarrays architecture. This subwavelength-spaced array, under the control of a 1-bit digital coding sequence, can switch between an enormous range of possible configurations, providing facile access to nearly arbitrary wave front control for signals near 0.34 THz. We demonstrate wide-angle beam scanning with 1° of angular precision over 70 GHz of bandwidth, as well as the generation of multi-beam and diffuse wave fronts, with a switching speed up to 100 MHz. This device, offering the ability to rapidly reconfigure a propagating wave front for beam-forming or diffusively scattered wide-angle coverage of a scene, will open new realms of possibilities in sensing, imaging, and networking.

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

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

Assessment of the Interelectrode Distance Effect over the Omnipole with High Multielectrode Arrays.

The development of high-density multielectrode catheters has significantly advanced cardiac electrophysiology mapping. High-density grid catheters have enabled the creation of a novel technique for reconstructing electrogram (EGM) signals known as "omnipole," which is believed to be more reliable than other methods, especially in terms of orientation independence. This study aims to evaluate how distance affects the omnipolar reconstruction of EGMs by comparing different configurations. Using an animal set up of perfused isolated rabbit hearts, recordings were taken using an ad hoc high-density epicardial multielectrode catheter. Inter-electrode distances ranging from 1 to 4 mm were analysed for their effect on the quality of resulting EGMs. Two biomarkers were computed to evaluate the robustness of the reconstructions: the areas contained within the bipolar loops and the amplitudes of the omnipoles. We hypothesised that both bipolar and omnipolar electrograms would be more robust at shorter inter-electrode distances. The results showed that an increase in distance triggers an increase in loop areas and amplitudes, which supports the hypothesis. This finding provides a more reliable estimate of wavefront propagation for the cross-omnipolar reconstruction method. These results emphasise the importance of distance in cardiac electrophysiology mapping and provide valuable insights into the use of high-density multielectrode catheters for EGM reconstruction.Clinical Relevance- The results of this study have direct clinical relevance in the application of the described techniques to recording systems in the cardiac electrophysiology laboratory, enabling clinicians to obtain more precise characterisation of signals in the myocardium.

RIS-Aided Near-Field Localization and Channel Estimation for the Terahertz System

The affordable hardware cost of ultra-large (XL) reconfigurable intelligent surfaces (RIS) renders them attractive solutions for the performance enhancement of localization and communication systems. However, XL-RIS results in near-field propagation channels, especially for the high-frequency terahertz (THz) communication system, which poses significant challenges for localization and channel estimation. In this paper, we focus on the spherical wavefront propagation in the near field of the THz system with the assistance of a RIS. A near-field channel estimation and localization (NF-JCEL) algorithm is proposed based on the derived second-order Fresnel approximation of the near-field channel model. To be specific, we carefully devise a down-sampled Toeplitz covariance matrix, which enables the decoupling and separate estimation of user equipment (UE) distances and angles of arrival (AoAs). Using the sub-space based method and one-dimensional search, we estimate the angles of arrival (AoAs) and user equipment (UE) distances. The channel attenuation coefficients are obtained through the least square (LS) method. To alleviate the impact of THz channel fading peaks caused by molecular absorption, estimates on multiple sub-bands are utilized for location estimation. Simulation results validate the superiority of the proposed NF-JCEL algorithm to the conventional far-field algorithm and show that higher resolution accuracy can be obtained by the proposed algorithm.

Структурні особливості детонаційного потоку

The subject of this research is the processes that occur during the formation and propagation of a detonation wave in a flat channel. The goal of this work is to study the features of the complex multiform structure of the detonation wave and its influence on the integral parameters of the detonation flow. The task of the research was to identify regularities during the formation process and propagation of the detonation wavefront, establish the nature of the influence of the detonation front structure on the processes that occur in the zone of stable flow parameters, and analyze the gas-dynamic parameters of the flow at the final stage of the process - at the stage of propagation of rarefaction waves. The main research method is mathematical simulation using CFD technologies (ANSYS Fluent package). The main results of the study: it was established that the values of gas-dynamic parameters at the triple points of shock waves are significantly greater than the corresponding values at the Neumann peak, and in the areas between the triple points are significantly smaller; the values of the parameters averaged over the cross-section of the detonation wave front almost do not differ from the values of the parameters at the Neumann peak; the propagation velocity of the detonation wave averaged over the cross-section of the flow also corresponds to the calculated velocity according to the Chapman-Jouguet model; outside the zone of chemical reaction, the formation of triple configurations is impossible, therefore the speed of the detonation wave front will be lower than the values of Chapman-Jouguet, which will affect the further processes of propagation of the detonation; the processes of formation and propagation of the detonation wave front in a certain way influence the distribution of steady flow parameters, while the wave processes spread to the Taylor zone, which leads to significant turbulence of the wall layer; due to the turbulence of the wall layer, the intensity of convective heat fluxes into the channel wall increases. Conclusion: the obtained results are in good agreement with the results of known experimental studies and can be used in the calculation of the integral impulse characteristics of the detonation engine chamber and in the design of its cooling system.

Evaluation and assessment of clique arrangements for the estimation of omnipolar electrograms in high density electrode arrays: an experimental animal model study

High-density catheters combined with Orientation Independent Sensing (OIS) methods have emerged as a groundbreaking technology for cardiac substrate characterisation. In this study, we aim to assess the arrangements and constraints to reliably estimate the so-called omnipolar electrogram (oEGM). Performance was evaluated using an experimental animal model. Thirty-eight recordings from nine retrospective experiments on isolated perfused rabbit hearts with an epicardial HD multielectrode were used. We estimated oEGMs according to the classic triangular clique (4 possible orientations) and a novel cross-orientation clique arrangement. Furthermore, we tested the effects of interelectrode spacing from 1 to 4 mm. Performance was evaluated by means of several parameters that measured amplitude rejection ratios, electric field loop area, activation pulse width and morphology distortion. Most reliable oEGM estimations were obtained with cross-configurations and interelectrode spacings le 2 mm. Estimations from triangular cliques resulted in wider electric field loops and unreliable detection of the direction of the propagation wavefront. Moreover, increasing interelectrode distance resulted in increased pulse width and morphology distortion. The results prove that current oEGM estimation techniques are insufficiently accurate. This study opens a new standpoint for the design of new-generation HD catheters and mapping software.

Towards a wavefront-preservation X-ray crystal monochromator for high-repetition-rate FELs.

The wavefront preservation of coherent X-ray free-electron laser beams is pushing the requirement on the quality and performance of X-ray optics to an unprecedented level. The Strehl ratio can be used to quantify this requirement. In this paper, the criteria for thermal deformation of the X-ray optics are formulated, especially for crystal monochromators. To preserve the X-ray wavefront, the standard deviation of the height error should be sub-nm for mirrors and less than 25 pm for crystal monochromators. Cryocooled silicon crystals combined with two techniques can be used to achieve this level of performance for monochromator crystals: (1) using a focusing element to compensate the second-order component of the thermal deformation; (2)introducing a cooling pad between the cooling block and silicon crystal and optimizing the effective cooling temperature. Each of these techniques allows the thermal deformation in standard deviation of the height error to be reduced by an order of magnitude. As an example, for the LCLS-II-HE Dynamic X-ray Scattering instrument, the criteria on thermal deformation of a high-heat-load monochromator crystal can be achieved for a 100 W SASE FEL beam. Wavefront propagation simulations confirm that the reflected beam intensity profile is satisfactory on both the peak power density and focused beam size.

Multiplexing-based control of wavefront propagation: The interplay of inter-layer coupling, asymmetry and noise

We show how multiplexing influences propagating fronts in multilayer networks of coupled bistable oscillators. Using numerical simulation, we investigate both deterministic and noise-sustained propagation. In particular, we demonstrate that the multiplexing allows to reduce the intra-layer dynamics to a common regime where the front propagation speed in all the interacting layers attains the same fixed value. In the presence of noise the dynamics is more complicated and is characterized by the ability of the system to adjust to the common propagation speed for varying the multiplexing strength. In addition, we find that the noise-induced stabilization of wavefront propagation in multilayer networks allows to obtain less pronounced deviations of the wavefront compared to the stabilization achieved in the isolated layer. Finally, we demonstrate that the reduction of the wavefront deviations can be enhanced by increasing the number of interacting layers.

Antlion larvae localize long distant preys by a mechanism based on time difference.

Pit building antlions Euroleon nostras have been submitted to artificial cues in order to delineate their faculty to localize a prey. Series of propagating pulses in sand have been created from an extended source made of 10 piezoelectric transducers equally spaced on a line and located at a large distance from the pit. The envelope of each pulse encompasses six oscillations at a carrier frequency of 1250 Hz and up to eight oscillations at 1666 Hz. In one set of experiments, the first wave front is followed by similar wave fronts and the antlions respond to the cue by throwing sand in the opposite direction of the wave front propagation direction. In another set of experiments, the first wave front is randomly spatially structured while the propagation of the wave fronts inside the envelope of the pulse are not. In that case, the antlions respond less to the cue by throwing sand, and when they do, their sand throwing is more randomly distributed in direction. The finding shows that the localization of vibration signal by antlions are based on the equivalent for hearing animals of interaural time difference in which the onset has more significance than the interaural phase difference.

Electrographic flow mapping guided catheter ablation offers advantages for patients with persistent atrial fibrillation.

Catheter ablation (CA) remains challenging due to suboptimal success rates in persistent atrial fibrillation (AF). Existing mapping technologies cannot reliably distinguish sources in this patient population. Recently, the novel electrographic flow (EGF) mapping system was developed using a modified Horn-Schunk optical flow algorithm to detect and quantify patterns of electrical wavefront propagation in the atria. To test the hypothesis that targeted source ablation based on EGF mapping is superior to empiric AF ablation. We included all consecutive patients undergoing EGF guided ablation for persistent AF. All patients underwent pulmonary vein isolation (PVI) and were treated with the same EAM system (CARTO). The outcome of PVI+EGF guided CA was compared with data of PVI-only procedures (PVI-only group) and PVI plus additional empiric adjunctive linear and substrate ablations (PVI+LINES group). 12-months outcome as freedom from AF and atrial tachycardia/flutter (AT/AFL), procedural safety and efficiency characterized by procedure duration, fluoroscopy use, radiofrequency applications and duration, were analyzed. Both intention-to-treat and per protocol analysis were conducted. A total number of 70 patients (39 in PVI+EGF, 16 in PVI-only and 15 patients in PVI+LINES group) were enrolled. Intention-to-treat analysis showed fewer AF recurrences in PVI+EGF as compared with the PVI-only or PVI+LINES groups at 12 months (25.6%vs. 62.5%vs. 53.3%, p=.02). There were no differences in AT/AFL recurrence (17.9%vs. 37.5%vs. 20.0%, p=.37). Procedure times were longer in PVI+EGF group (p<.01), and there were no differences in fluoroscopy use (p=.67). Our data suggest that patients treated with EGF-guided CA developed fewer AF recurrences. Although the procedure times are longer, it seems to be safe and offers a more targeted, patient-specific ablation strategy beyond PVI than adjunctive empiric lines and substrate ablation in this complex group of patients.

Mapping function model representing the relationship between explosion shock wave pressure and wavefront temperature

The evaluation of ammunition damage power and guidance for ammunition design heavily relies on the shock wave pressure and wavefront temperature produced by an ammunition explosion. However, temperature test results are often inaccurate and unreliable. Therefore, this study utilized Autodyn explicit dynamics simulation software to conduct finite element numerical simulations of explosion shock wave pressure, wavefront temperature propagation, and distribution for trinitrotoluene explosives weighing 10, 20, 50, and 100 kg. The shock wave pressure and wavefront temperature were measured at different measuring points. The cloud maps of wavefront propagation evolution obtained at different explosion times were analyzed to determine the attenuation laws of pressure and temperature propagation in the near field and far field. Based on the similarity law of explosions and the dimensional analysis method, a mapping function model was established to represent the relationship between a shock wave’s peak pressure and peak temperature. The parameters of the model include explosive mass (w), measuring point radius (r), specific heat capacity in the air (c), and the peak pressure of an explosion shock wave (p). The model’s accuracy in calculating the explosion shock wavefront temperature exceeds 89.75%, effectively resolving the issue of low accuracy in the results of explosion field temperature tests and calculations. Therefore, this study provides data and theoretical support for testing and evaluating the damage power of ammunition explosives, and the proposed model has high applicability in the engineering field.

Study of the omnipolar EGM reconstruction for robustness against wavefront propagation in epicardial signals

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): National Research Program, Ministerio de Ciencia e Innovación, Spanish Government, Instituto de Salud Carlos III. Background Characterisation of electrophysiological substrate is commonly performed by examining cardiac tissue locally by using high-density (HD) arrays of equispaced electrodes – e.g. Advisor™ HD Grid Mapping Catheter, Sensor Enabled™ (SE). These allow creating activation maps of local tissue and substrate exploration. Recently, a novel operation mode arouse: the omnipole, which overcomes many limitations of bipolar and unipolar electrograms, as they are claimed to be orientation independent. Nevertheless, the current technique to reconstruct omnipolar EGMs has pitfalls as the estimation of some incidence angles of the propagation wavefront. We propose a novel reconstruction method to estimate omnipolar EGMs which overcomes the angle dependence weakness of the current one, providing a more robust EGM representation. We hypothesise that this technique will improve reconstruction of electrophysiological signals. Methods Prior electrophysiological experiments on isolated rabbit hearts were used [1], including recordings with a 128-electrode array 1mm apart over ventricular epicardium at 37ºC, with bipolar electrode stimulation. Four-electrodes cliques were designed from these experiments, with different inter-electrode distances as depicted in fig. 1A, reconstructing the current, and novel omnipolar configuration. Metrics to assess the quality of the EGM signals were designed, including the bipolar loop area, and the ratio of the bipolar components of the omnipole (ox and oy) – see fig. 1B. The bipoles were calculated from unipolar EGMs, the signal was corrected with the 45º offset in the cross, the propagation angle was then detected, and the local activation time (LAT) was estimated. Results In the bipole plots, it was observed that the morphology of the bipolar loop gets distorted with an increase in the interelectrode distance – thinner for distances &amp;lt;2mm. There is a direct relation between the areas in the bipolar loop and the inter-electrode distance (see fig. 2A). Furthermore, the values of the area in the cross are always comparable to the best performing triangular clique. For the ratio of bipoles, the relation is inversely to distance (see fig. 2B), similarly, the performance of the cross is comparable to the best performing triangular omnipole. Conclusion For reconstructing omnipolar EGMs, inter-electrode distances smaller than 2mm should be employed. Furthermore, if that condition is satisfied, the novel omnipolar reconstruction method proposed based on the cross configuration is more accurate and robust to wavefront propagation, given that the omnipolar EGM performs similarly or better than the best triangular configuration – and which triangle is fixed for the whole procedure, being the current reconstruction method less robust. Thus, a new standpoint to omnipolar reconstruction in high density electrode catheters is open, towards the design of new devices, and the practice in the clinic.