New Methods for Atrial Activity Extraction in Atrial Tachyarrhythmias

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A Spatio-Temporal Study of Ischemia and the Time-Frequency Coupling Variations between the ST Amplitude, Heart Rate and Dominant Angle

Abstract An analysis of the Long Term ST Database (LTSTDB) was conducted to quantify the spatio-temporal dynamics of ischemic and non-ischemic episodes. For all 86 recordings the ischemic episode length is decribed by a lognormal distribution and the non-ischemic episode length by a generalized extreme value distribution. For the 15 recordings that possess orthogonal (EASI) leads sets we derived the 12 standard leads and analyzed the spatial time course (from the j-point to j+120 ms) of each episode over time to identify dominant trends. Although the magnitude of the ischemic episodes did not reveal any inter-subject trend (except for generally exhibiting Brownian-like motion), there appeared to be strong correlations with the heart rate (HR). Wavelet cross-spectral coupling with significance testing was then applied to the ST-amplitude and HR evolution over the course of each episode. In all subjects significant cross-spectral correlations were found at very low frequencies (<0.04 Hz), as well as at respiration and baroreflex frequencies. This may indicate that the ischemic episodes are modulated by blood pressure and activity or HR-related phenomena and that all episodes in the LTSTDB may be of a 'mixed' type at some point in their duration. The dominant angle also showed significant correlation (p<0.01) with the ST amplitude and HR changes at similar frequencies to those described above. All three protocols used to define ischemia in the LTSTDB gave similar results. Introduction Modelling the short-and long-term spatial and temporal changes in the ECG during ischemia provides a mechanism for baseline testing of relevant signal processing algorithms. Our aim in this work was to provide a description of such changes in order to provide information to build an accurate simulation of the ECG during ischemia. Methods Data The data used in this study were taken from the LongTerm ST Database (LTSTDB) [1] available from PhysioNet which contains 21-24 hour multi-channel ECG recordings and annotated ischemic and non-ishemic ST changes. An ischemic episode was defined to start when the ST deviation exceeded a lower threshold, V lower = 50µV . Next, the deviation was required to reach or exceed an upper threshold, V upper , for at least a continuous interval of T min seconds. Finally, the episode ended when the deviation dropped to less than V lower = 50µV in the following T sep = 30 s. The values of (V upper , T min ) were (75 µV , 30 s), (100 µV , 30 s) and (100 µV , 60 s) defined as protocol STA, STB and STC respectively. All analysis was performed in the vectorcardiogram (VCG) space. The LTSTDB contains 15 recordings (s30691 through s30801) which used the EASI lead system Similarly they give the transformation from the EASI configuration to the vectorcardiogram (X, Y, Z) configuration, V , the matrix Temporal analysis of the episodes The lengths of each ischemic and non-ischemic episode for all 86 patients in the LTSTDB were calculated using all available leads. An episode was taken to start if any lead satisfied the criteria for the relevant protocol and was taken to end when all leads ceased to satisfy the same pro

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe

Salmon louse infestation levels on sea trout can be predicted from a hydrodynamic lice dispersal model

1. The abundance of the parasitic salmon louse has increased with the growth in aquaculture of salmonids in open net pens. This represents a threat to wild salmonid populations as well as a key limiting factor for salmon farming. The Norwegian ‘traffic light’ management system for salmon farming aims to increase aquaculture production while securing sustainable wild salmonid populations. However, this system is at present solely focusing on mortality in wild Atlantic salmon, while the responses of sea trout with different ecological characteristics are not included. 2. We analyse lice counts on sea trout from surveillance data and use Bayesian statistical models to relate observed lice infestations to the environmental lice infestation pressure, salinity and current speed. These models can be used in risk assessment to predict when and where lice numbers surpass threshold levels for expected serious health effects in wild sea trout. 3. We find that in production areas with the highest density of salmon farms (West coast), more than 50% of the sea trout experienced lice infestations above the levels of expected serious health effects. 4. We also observed high lice infestations on sea trout in areas with salinities below louse tolerance levels, indicating that fish had been infested elsewhere but were returning to low-saline waters to delouse. This behavioural response may over time disrupt anadromy in sea trout. 5. The observed infestations on sea trout can be explained by the hydrodynamic lice dispersal model, which provides continuous estimates of lice exposure along the whole Norwegian coast. These estimates, which are used in Atlantic salmon research and management, can also be used for sea trout. 6. Synthesis and applications. Wild sea trout, spending its entire feeding migration in fjords and coastal areas, is at higher risk than wild Atlantic salmon to lice infestations from industrial salmon farming. The high levels of lice infestation we observed on sea trout question the environmental sustainability of the current aquaculture industry in areas with intensive farming. We discuss the complex responses of sea trout to salmon lice and how the Norwegian ‘traffic light’ management system may include data on sea trout

Salmon louse infestation levels on sea trout can be predicted from a hydrodynamic lice dispersal model

The abundance of the parasitic salmon louse has increased with the growth in aquaculture of salmonids in open net pens. This represents a threat to wild salmonid populations as well as a key limiting factor for salmon farming. The Norwegian ‘traffic light’ management system for salmon farming aims to increase aquaculture production while securing sustainable wild salmonid populations. However, this system is at present solely focusing on mortality in wild Atlantic salmon, while the responses of sea trout with different ecological characteristics are not included

Comparison of three artificial models of the magnetohydrodynamic effect on the electrocardiogram

Hay que agregar la siguiente descripción: "This is an Author's Accepted Manuscript of an article published in [include the complete citation information for the final version of the article as published in the [JOURNAL TITLE] [date of publication] [copyright Taylor & Francis], available online at: ."The electrocardiogram (ECG) is often acquired during magnetic resonance imaging (MRI), but its analysis is restricted by the presence of a strong artefact, called magnetohydrodynamic (MHD) effect. MHD effect is induced by the flow of electrically charged particles in the blood perpendicular to the static magnetic field, which creates a potential of the order of magnitude of the ECG and temporally coincident with the repolarisation period. In this study, a new MHD model is proposed by using MRI-based 4D blood flow measurements made across the aortic arch. The model is extended to several cardiac cycles to allow the simulation of a realistic ECG acquisition during MRI examination and the quality assessment of MHD suppression techniques. A comparison of two existing models, based, respectively, on an analytical solution and on a numerical method-based solution of the fluids dynamics problem, is made with the proposed model and with an estimate of the MHD voltage observed during a real MRI scan. Results indicate a moderate agreement between the proposed model and the estimated MHD model for most leads, with an average correlation factor of 0.47. However, the results demonstrate that the proposed model provides a closer approximation to the observed MHD effects and a better depiction of the complexity of the MHD effect compared with the previously published models, with an improved correlation (+5%), coefficient of determination (+1%) and fraction of energy (+22%) compared with the best previous model. The source code will be made freely available under an open source licence to facilitate collaboration and allow more rapid development of more accurate models of the MHD effect.Julien Oster is supported by the Royal Academy of Engineering under a Newton Fellowship [grant number 793/914/N/K/EST/DDPF/tkg/4004642].Oster, J.; Llinares Llopis, R.; Payne, S.; Tse, ZTH.; Schmidt, EJ.; Clifford, GD. (2014). Comparison of three artificial models of the magnetohydrodynamic effect on the electrocardiogram. Computer Methods in Biomechanics and Biomedical Engineering. 18(13):1400-1417. https://doi.org/10.1080/10255842.2014.909090S14001417181

Effect of anorthite on granite phase relations: Experimental data and models

International audienceNew experimental data on the effect of anorthite (An) on liquidus phase equilibria in the system Qz–Ab–Or are presented. The data were obtained for 5 wt% An added to variable Qz/Ab/Or compositions at 300 MPa and under H2O-saturated conditions. Crystal–liquid equilibria were determined for 13 synthetic glass compositions made from gels in experiments performed between 660 and 750 °C in cold-seal pressure vessels. Forward and reversal experiments were systematically conducted on each composition to demonstrate equilibrium. A total of 51 charges was examined. Three crystalline phases, quartz, alkali feldspar and plagioclase appear on the H2O-saturated liquidus surface. The determined minimum liquidus 5 wt% An “piercing” point (39% Qz, 33% Ab, 28% Or) is shifted away from the Ab apex toward the Qz–Or sideline when compared with the An-free 300 MPa H2O-saturated minimum. This shift is of the same type as that observed at 100 MPa in the same system and at 200 MPa in a rhyolitic system. The new experimental results are used to test both empirical and thermodynamic models for silicic magmas. Empirical models reproduce reasonably well the new experimental data, although more sophisticated calculations schemes appear to be required to improve their accuracy. The new experimental results in the haplogranodiorite system are not well reproduced with the model of Holland and Powell (2001), mainly because plagioclase stability appears greatly enhanced in the model. Rhyolite-MELTS satisfactorily reproduces the Qz-, Pl- and Af-liquid phase equilibria, but model H2O solubilities are significantly lower and crystallization temperatures higher than in experiments