References of "Collet, Arnaud"
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See detailA multi-scale cardiovascular system model can account for the load-dependence of the end-systolic pressure-volume relationship.
Pironet, Antoine ULg; Desaive, Thomas ULg; Kosta, Sarah ULg et al

in BioMedical Engineering OnLine (2013), 12(1), 8

ABSTRACT: BACKGROUND: The end-systolic pressure-volume relationship is often considered as a load-independent property of the heart and, for this reason, is widely used as an index of ventricular ... [more ▼]

ABSTRACT: BACKGROUND: The end-systolic pressure-volume relationship is often considered as a load-independent property of the heart and, for this reason, is widely used as an index of ventricular contractility. However, many criticisms have been expressed against this index and the underlying time-varying elastance theory: first, it does not consider the phenomena underlying contraction and second, the end-systolic pressure volume relationship has been experimentally shown to be load-dependent. METHODS: In place of the time-varying elastance theory, a microscopic model of sarcomere contraction is used to infer the pressure generated by the contraction of the left ventricle, considered as a spherical assembling of sarcomere units. The left ventricle model is inserted into a closed-loop model of the cardiovascular system. Finally, parameters of the modified cardiovascular system model are identified to reproduce the hemodynamics of a normal dog. RESULTS: Experiments that have proven the limitations of the time-varying elastance theory are reproduced with our model: (1) preload reductions, (2) afterload increases, (3) the same experiments with increased ventricular contractility, (4) isovolumic contractions and (5) flow-clamps. All experiments simulated with the model generate different end-systolic pressure-volume relationships, showing that this relationship is actually load-dependent. Furthermore, we show that the results of our simulations are in good agreement with experiments. CONCLUSIONS: We implemented a multi-scale model of the cardiovascular system, in which ventricular contraction is described by a detailed sarcomere model. Using this model, we successfully reproduced a number of experiments that have shown the failing points of the time-varying elastance theory. In particular, the developed multi-scale model of the cardiovascular system can capture the load-dependence of the end-systolic pressure-volume relationship. [less ▲]

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See detailAutonomous electrical activity induced by cardiac tissue deformation in a thermo-electro-mechanical background
Collet, Arnaud ULg; Desaive, Thomas ULg; Dauby, Pierre ULg

in 8th IFAC Symposium on Biological and Medical Systems (2012, August)

In a healthy heart, the mechano-electric feedback (MEF) process acts as an intrinsic regulatory mechanism of the myocardium which allows the normal cardiac contraction by damping mechanical perturbations ... [more ▼]

In a healthy heart, the mechano-electric feedback (MEF) process acts as an intrinsic regulatory mechanism of the myocardium which allows the normal cardiac contraction by damping mechanical perturbations in order to generate a new healthy electromechanical situation. However, under certain conditions, the MEF can be a generator of dramatic arrhythmias by inducing local electrical depolarizations as a result of abnormal cardiac tissue deformations, via stretch-activated channels (SACs). Then, these perturbations can propagate in the whole heart and lead to global cardiac dysfunctions. In the present study, we examine the spatio-temporal behavior of the autonomous electrical activity induced by the MEF when the heart is subject to temperature variations. For instance, such a situation can occur during a therapeutic hypothermia. This technique is usually used to prevent neuronal injuries after a cardiac resuscitation. From this perspective, we introduce a one-dimensional time-dependent model containing all the key ingredients that allow accounting for excitation-contraction coupling, MEF and thermoelectric coupling. Our simulations show that an autonomous electrical activity can be induced by cardiac deformations, but only inside a certain temperature interval. In addition, in some cases, the autonomous electrical activity takes place in a periodic way like a pacemaker. We also highlight that some properties of the action potentials that are generated by the MEF, are significantly influenced by temperature. Moreover, in the situation where a pacemaker activity occurs, we also show that the period is heavily temperature-dependent. [less ▲]

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See detailModèle unidimensionnel instationnaire de l'activité pacemaker cardiaque induite par le feedback mécano-électrique dans un environnement thermo-électro-mécanique
Collet, Arnaud ULg; Desaive, Thomas ULg; Dauby, Pierre ULg

in Annales de Cardiologie et d'Angeiologie (2012)

Aim of the study: In a healthy heart, the mechano-electric feedback (MEF) process acts as an intrinsic regulatory mechanism of the myocardium which allows the normal cardiac contraction by damping ... [more ▼]

Aim of the study: In a healthy heart, the mechano-electric feedback (MEF) process acts as an intrinsic regulatory mechanism of the myocardium which allows the normal cardiac contraction by damping mechanical perturbations in order to generate a new healthy electromechanical situation. However, under certain conditions, the MEF can be a generator of dramatic arrhythmias by inducing local electrical depolarizations as a result of abnormal cardiac tissue deformations, via stretch-activated channels (SACs). Then, these perturbations can propagate in the whole heart and lead to global cardiac dysfunctions. In the present study, we qualitatively investigate the influence of temperature on autonomous electrical activity generated by the MEF. Method: We introduce a one-dimensional time-dependent model containing all the key ingredients that allow accounting for the excitation-contraction coupling, the MEF and the thermoelectric coupling. Results: Our simulations show that an autonomous electrical activity can be induced by cardiac deformations, but only inside a certain temperature interval. In addition, in some cases, the autonomous electrical activity takes place in a periodic way like a pacemaker. We also highlight that some properties of action potentials, generated by the mechano-electric feedback, are significantly influenced by temperature. Moreover, in the situation where a pacemaker activity occurs, we also show that the period is heavily temperature-dependent. Conclusions: Our qualitative model shows that the temperature is a significant factor with regards to the electromechanical behavior of the heart and more specifically, with regards to the autonomous electrical activity induced by the cardiac tissue deformations. [less ▲]

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See detailEffects of temperature on pacemaker activity induced by mechano-electric feedback in a one-dimensional model of a ring-shaped cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Dauby, Pierre ULg

in NCBME (Ed.) 10th Belgian Day on Biomedical Engineering (2011, December 02)

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See detailOne-dimensional time-dependent model of cardiac pacemaker activity generated by mechano-electric feedback in a thermo-electro-mechanical context
Collet, Arnaud ULg; Dauby, Pierre ULg

in Archives des Maladies du Coeur et des Vaisseaux. Pratique (2011, December), (Hors-série 3), 20

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

in XXIIIrd congress of the International Society of Biomechanics, July 3-7, 2011 (2011, July 05)

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

Poster (2011, July 05)

Recently, the influence of thermal processes on electrophysiology has clearly been underlined, using a FitzHugh–Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration ... [more ▼]

Recently, the influence of thermal processes on electrophysiology has clearly been underlined, using a FitzHugh–Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration (APD) has been shown to shorten, while the action potential (AP) amplitude decreases, and the conduction velocity increases. In the present study, we investigate the effects of thermoelectric coupling on mechano-electric feedback (MEF), and more specifically, on pacemaker activity generated by MEF. To investigate these effects, thermoelectric coupling is introduced in a one-dimensional ring-shaped electromechanical model of cardiac fiber, which takes into account excitation-contraction coupling (ECC), as well as MEF. [less ▲]

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

Poster (2011, June 01)

The mechano-electric feedback (MEF) in the heart consists in the influence of the tissue deformations on the cardiac electrical activity. Under certain conditions, tissue deformations can generate ... [more ▼]

The mechano-electric feedback (MEF) in the heart consists in the influence of the tissue deformations on the cardiac electrical activity. Under certain conditions, tissue deformations can generate electrical perturbations via stretch-activated channels, such that the membrane potential can exceed the threshold value needed in order to trigger cardiac action potentials (APs). In the present study, we have developed a one-dimensional ring-shaped model of cardiac fiber taking into account three different couplings: the excitation-contraction coupling (ECC), the MEF and the thermoelectric coupling (TEC). The main goal of this work is to examine the effects of the TEC on the different properties of the pacemaker activity generated by the MEF. [less ▲]

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See detailDynamique et chimie dans l'atmosphère de la face nocturne de Vénus
Collet, Arnaud ULg

Book published by Éditions Universitaires Européennes (2011)

L'atmosphère de Vénus est le siège de phénomènes lumineux appelés "airglows" traduits en français par "émissions du ciel". Ces émissions ont lieu dans les domaines UV et IR du spectre électromagnétique et ... [more ▼]

L'atmosphère de Vénus est le siège de phénomènes lumineux appelés "airglows" traduits en français par "émissions du ciel". Ces émissions ont lieu dans les domaines UV et IR du spectre électromagnétique et permettent de déduire des informations à la fois sur la dynamique de l'atmosphère et sur sa composition en espèces minoritaires (oxygène et azote atomiques). L'émission IR à 1.27 µm est due à la désexcitation radiative de l'oxygène moléculaire excité dans l'état métastable singulet delta au sein de la haute mésosphère. Quant à l'émission UV, elle est produite par la recombinaison radiative d'atomes d'azote N(4S) et d'oxygène O(3P) dans la basse thermosphère. Les nombreuses observations de ces deux airglows ont montré qu'ils présentent de grandes variabilités spatiales et temporelles et ne semblent pas présenter de corrélation significative au niveau de leur intensité et de leur localisation spatiale. De plus, étant donné la multitude de processus physiques et chimiques impliqués dans la formation de ces airglows, il est indispensable, pour quantifier le rôle relatif des différents mécanismes, de traiter le problème numériquement. C'est précisément le sujet de cet ouvrage. [less ▲]

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See detailTwo-dimensional time-dependent model of the transport of minor species in the Venus night side upper atmosphere
Collet, Arnaud ULg; Cox, Cédric ULg; Gérard, Jean-Claude ULg

in Planetary and Space Science (2010), 58

We present a numerical tool developed to quantify the role of processes controlling the spatio-temporal distribution of the NO ultraviolet and O2 infrared nightglows in the Venus night side upper ... [more ▼]

We present a numerical tool developed to quantify the role of processes controlling the spatio-temporal distribution of the NO ultraviolet and O2 infrared nightglows in the Venus night side upper atmosphere, observed with the VIRTIS and SPICAV instruments on board Venus Express. This numerical tool consists in a two-dimensional chemical-transport time-dependent model which computes in a hypothetical rectangular solving domain the spatio-temporal distributions of the number densities of the four minor species at play in these two nightglow emissions. The coupled nonlinear system of the four partial differential equations, describing the spatio-temporal variations of the minorspecies, has been solved using a finite volume method with a forward Euler method for the time integration scheme. As an application, we have first simulated a time-constant supply of atoms through the upper boundary of the solving domain. The fluxes are inhomogeneous relative to its horizontal direction, in order to simulate regions of enhanced downward flow of oxygen and nitrogen giving rise to NO and O2 brightening. Given that these two emissions show large time variations, we have also simulated a time-dependent downward flux of O and N atoms. It results from these simulations that the lack of correlation between the NO and O2 nightglows largely result from to the coupling between horizontal and vertical transport processes and the very different chemical lifetimes of the two species. In particular,we have quantified the role of each process generating spatio-temporal de-correlations between the NO and O2 nightglows. [less ▲]

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See detailInfluence of thermoelectric coupling on ectopic beats generated by mechano-electric feedback (MEF) in a one-dimensional cardiac fiber model
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

in 9th Belgian Day on Biomedical Engineering, Friday November 26th 2010 in the Academy Palace, Hertogstraat 1, 1000 Brussels (2010, November 26)

The influence of thermal processes on electrophysiology has clearly been underlined by Bini et al., using a FitzHugh--Nagumo-type (FHN-type) model. When the temperature is raised, the action potential ... [more ▼]

The influence of thermal processes on electrophysiology has clearly been underlined by Bini et al., using a FitzHugh--Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration (APD) has been shown to shorten, while the action potential (AP) amplitude decreases, and the conduction velocity increases. In this research, we investigate the effects of thermoelectric coupling on mechano-electric feedback (MEF), and more specifically, on ectopic beats generated by MEF. To investigate these effects, thermoelectric coupling is introduced in a one-dimensional electromechanical model of a cardiac fiber, which considers excitation-contraction coupling (ECC), as well as MEF. [less ▲]

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See detailInfluence of thermoelectric coupling on ectopic beats generated by mechano-electric feedback (MEF) in a one-dimensional cardiac fiber model
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

Poster (2010, November 26)

The influence of thermal processes on electrophysiology has clearly been underlined by Bini et al., using a FitzHugh--Nagumo-type (FHN-type) model. When the temperature is raised, the action potential ... [more ▼]

The influence of thermal processes on electrophysiology has clearly been underlined by Bini et al., using a FitzHugh--Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration (APD) has been shown to shorten, while the action potential (AP) amplitude decreases, and the conduction velocity increases. In this research, we investigate the effects of thermoelectric coupling on mechano-electric feedback (MEF), and more specifically, on ectopic beats generated by MEF. To investigate these effects, thermoelectric coupling is introduced in a one-dimensional electromechanical model of a cardiac fiber, which considers excitation-contraction coupling (ECC), as well as MEF. [less ▲]

Detailed reference viewed: 44 (22 ULg)