In Vitro Arrhythmia Generation by Mild Hypothermia - a Pitchfork Bifurcation Type Process

International audienceThe neurological damage after cardiac arrest (CA) constitutes a big challenge of hospital discharge. The therapeutic hypothermia (34°C-32°C) has shown its benefit to reduce cerebral oxygen demand and improve neurological outcomes after the cardiac arrest. However, it can have many adverse effects, among them the cardiac arrhythmia generation represents an important part (up to 34%, according different clinical studies). Monolayer cardiac culture is prepared with cardiomyocytes from new-born rat directly on the multi-electrodes array, which allows acquiring the extracellular potential of the culture. The temperature range is 37°C - 30°C - 37°C, representing the cooling and rewarming process in the therapeutic hypothermia. Both experiments showed that at 35°C, the acquired signals are characterized by period-doubling phenomenon, compared to signals at any other temperatures. Spiral waves, commonly considered as a sign of cardiac arrhythmia, are observed in the reconstructed activation map. With an approach from nonlinear dynamics, phase space reconstruction, it is shown that at 35°C, the trajectories of these signals formed a bifurcation, even trifurcation. Another transit point is found between 30°C - 33°C, which agreed with other clinical studies that induced hypothermia after cardiac arrest should not be below 32°C. The therapeutic hypothermia after cardiac arrest can be represented by a Pitchfork bifurcation, which could explain the different ratio of arrhythmia among the adverse effects after this therapy. This nonlinear dynamics suggests that a variable speed of cooling / rewarming, especially when passing 35°C, would help to decrease the ratio of post-hypothermia arrhythmia and then improve the hospital output

Segmentation of Positron Emission Tomography Images Using Multi-atlas Anatomical Magnetic Resonance Imaging (MRI)

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Impact of bipolar electrodes contact on fractionation index measurement.

International audience: Signals such as Complex Fractionated Atrial Electrograms (CFAE) are tracked during ablation procedures to locate the arrhythmical substrate regions. Most of CFAE classification tools use fractionation indexes. However, recordings from intracardiac catheter depend on electrode contact quality. This paper investigates the impact of electrode contact area on fractionation indexes. It is assessed through three kinds of arrhythmical activations resulting from a numerical simulation of a small piece of the cardiac tissue. Bipolar electrograms are extracted corresponding to 25 different contact areas and fractionation indexes (Shannon entropy, non linear energy operator and maximum peak ratio) are computed. Results yield that the Shannon entropy offers a good potential discrimination between arrhythmic scenarios and is less sensitive to the electrode contact variation

A New Mathematical Force Model that Predicts the Force-pulse Amplitude Relationship of Human Skeletal Muscle

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Mesure de la fatigue musculaire par électromyostimulation

National audienceLe but de cette étude est de définir un nouvel indice de fatigue musculaire, grâce à un calcul par transformée en ondelettes continue et de comparer cet indice à ceux habituellement utilisés dans la littérature. Tous ces indices sont obtenus à partir de l’activité électrique desmuscles enregistrée par électromyogramme (EMG) pendant une contraction du muscle stimulé par excitation (EMS), grâce à des traitements en temps réel des signaux EMG. Sa robustesse vis-à-vis du bruit ou de la troncature des signaux montre l’intérêt d’utiliser ce nouvel indice de fatigue

Mesure de la fatigue musculaire par électromyostimulation

National audienceLe but de cette étude est de définir un nouvel indice de fatigue musculaire, grâce à un calcul par transformée en ondelettes continue et de comparer cet indice à ceux habituellement utilisés dans la littérature. Tous ces indices sont obtenus à partir de l’activité électrique desmuscles enregistrée par électromyogramme (EMG) pendant une contraction du muscle stimulé par excitation (EMS), grâce à des traitements en temps réel des signaux EMG. Sa robustesse vis-à-vis du bruit ou de la troncature des signaux montre l’intérêt d’utiliser ce nouvel indice de fatigue

Input-Output Feedback Linearization Control (IOFLC) for Muscle Force Control by Functional Electrical Stimulation

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Memristor − the fourth fundamental passive electronic component and its memory interpretation

This paper aims to present to master students in electronics the recently discovered fourth basic passive circuit element − called memristor − and to better understand how the history memory of the already passed charge through it is taken into account in its I-V characteristic. In this attempt, a simple coupling device between 2 RC cells is investigated. Our calculations are in very good agreement with experiments on SPICE and Matlab softwares

Anatomical multiatlas segmentation using local texture statistical properties for matching descriptor with machine learning

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