Coronary Flow in Patients with Three-Vessel Disease: Simulated Hemodynamic Variables in relation to Angiographically Assessed Collaterality and History of Myocardial Infarction.

International audienceWe study patients with stenoses of the left main coronary artery (LMCA), left anterior descending artery (LAD), and left circumflex branch (LCx) and with chronic occlusion of the right coronary artery (RCA), undergoing off-pump coronary surgery. An analog electrical model is used to provide quantitative estimations of the distribution of flows and pressures across the coronary network (in the stenosed native arteries, the collateral branches, the capillary areas, and so forth). The present paper demonstrates that the clinical information collected for the 10 patients included in the study (Rentrop score, history of myocardial infarction, left ventricular ejection fraction (LVEF)) are well correlated with the predicted hydrodynamic data. Patients with a good collaterality (Rentrop score = 3) or patients without anterior myocardial infarction have (i) less severe stenoses on the LMCA, (ii) lower microvascular resistances, (iii) higher grafts flow rates when the revascularization is performed, (iv) higher collateral flow rates towards the territory of the occluded artery, (v) better perfusion of this area, and (vi) better total perfusion of the heart

MagnetoHemoDynamics in Aorta and Electrocardiograms

Preprint of Vincent Martin et al 2012 Phys. Med. Biol. 57 3177 doi:10.1088/0031-9155/57/10/3177International audienceThis paper addresses a complex multi-physical phenomemon involving cardiac electrophysiology and hemodynamics. The purpose is to model and simulate a phenomenon that has been observed in MRI machines: in the presence of a strong magnetic field, the T-wave of the electrocardiogram (ECG) gets bigger, which may perturb ECG-gated imaging. This is due a magnetohydrodynamic (MHD) eff ect occurring in the aorta. We reproduce this experimental observation through computer simulations on a realistic anatomy, and with a three-compartment model: inductionless magnetohydrodynamic equations in the aorta, bidomain equations in the heart and electrical di ffusion in the rest of the body. These compartments are strongly coupled and solved using fi nite elements. Several benchmark tests are proposed to assess the numerical solutions and the validity of some modeling assumptions. Then, ECGs are simulated for a wide range of magnetic field intensities (from 0 to 20 Tesla).Cet article traite d'un phénomène multi-physique complexe incluant l'électrophysiologie cardiaque et l'hémodynamique. Le but est de modéliser et simuler un phénomène qui a été observé dans les machines IRM : en présence d'un champ magnétique intense, l'onde T de l'électrocardiogramme (ECG) s'accroît, ce qui peut perturber l'imagerie médicale synchronisée par les ECG. Nous reproduisons cette observation expérimentale grâce à des simulations sur ordinateur utilisant une anatomie réaliste et un modèle à trois compartiments : les équations de la magnétohydrodynamique "sans induction" dans l'aorte, les équations bidomaine dans le coeur et la diffusion électrique dans le reste du corps. Ces compartiments sont couplés fortement entre eux et résolus par la méthode des éléments finis. Plusieurs cas-tests sont proposés pour tester les solutions numériques et vérifier la validité de certaines hypothèses de modélisation. Enfin, des ECGs sont simulés pour une large gamme de champs magnétiques (de 0 à 20T). En présence d'un champ magnétique intense, l'écoulement du sang dans l'aorte induit un potentiel électrique qui est la cause d'une augmentation de l'onde T d'un électrocardiogramme (ECG). Ce phénomène peut perturber l'imagerie médicale synchronisée par ECG. Le but de cette étude est de reproduire cette observation expérimentale par le biais de simulations numériques sur une anatomie réaliste. Le modèle informatique est constitué de trois compartiments : la magnetohydrodynamique (MHD) dans l'aorte, les équations bidomaine dans le coeur et les équations de l'électrostatique dans le reste du corps. Ces modèles sont fortement couplés ensemble et résolus par la méthode des éléments finis. Les tests numériques montrent que ce modèle est bien capable de reproduire le comportement attendu sur l'ECG

Blood flow simulation and magnetohydrodynamics effects in MRI

International audienceIn order to improve the quality of the images provided by Magnetic Resonance Imaging (MRI), the magnetic field used in MRI is getting larger and larger: from 3T nowadays, it might increase in the future up to 10T in clinical scanners. The impact of such a large magnetic field on health is still in debate. We focus in this study on the perturbations induced by the magnetic field on the electrocardiogram (ECG). Indeed, the blood flow (containing charged particles) immersed in the magnetic field induces an electric field that may alter the electric potential measured during ECG. In particular, the induced electric field may increase the T-wave in the ECG. We investigate this phenomenon and try to simulate such an effect

Cells in confined flows: some biomedical applications

International audienceTwo past research works related to the workshop topic can be briefly recalled:i)Flow and deformation of red blood cells in narrow channels, analysed by means of the occupied pore change of electrical resistivity. A device named Cell Transit Analyser (CTA) was used. The height and length of electrical pulses were related to the cell deformed shape in the pore and to its velocity. The influence of the flow strength, suspending medium viscosity and cell membrane elasticity was studied. [1] ii)The design and experimental characterization of a Hele-Shaw cell with a porous bottom wall in order to study the influence of flow induced forces (shear stress and transmural pressure) on cells adhering on porous biomaterials. Theoretical predictions for the flow in the chamber were provided and allowed to quantify the flow forces. [2]A short bibliographic overview of more recent studies in the same research area and of their biomedical applications can be also presented:i) flow rate or velocity calibrations with microparticles in microchannels, cell mechanics studies (change of mechanical properties of cells, effect of drugs, cell sorting, …), white blood cells deformation and transport in capillaries, vascularization and microcirculation in reconstructed tissues and organoïds, … ii) improvement of biomaterials for dialysis and blood filtration process, in vitro studies of white blood cells and cancer cells diapedesis, mechanotransduction studies with endothelial cells or other cells, test of biomaterials for the functional vascular grafts production, …Artificial microfluidic circuits may also be used to improve cell culture, proliferation and attachment (for example, stem cells cultivation and differentiation for artificial tissue production), or, on the contrary, to improve hydrodynamic dissociation of cell aggregates and tissues. Other applications of microfluidic devices are found in the context of space research and astronauts health (study of blood flow under microgravity conditions), … In any cases, the control of cells’ microenvironment and of the applied forces remains a challenge. References [1] Drochon, A. (2005) “Use of Cell Transit Analyser pulse height to study the deformation of erythrocytes in microchannels” Medical Engineering and Physics, Vol 27(2), 157-165.[2] Chotard-Ghodsnia, R., Drochon, A., Grebe, R. (2002) “A new flow chamber for the study of shear stress and transmural pressure upon cells adhering to a porous biomaterial” Journal of Biomechanical Engineering, Vol 124 (2), 258-261

Use of Cell Transit Analyser pulse height to study the deformation of erythrocytes in microchannels

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Sinusoïdal flow of blood in a cylindrical deformable vessel exposed to an external magnetic field

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Cells in confined flows: some biomedical applications

International audienceTwo past research works related to the workshop topic can be briefly recalled:i)Flow and deformation of red blood cells in narrow channels, analysed by means of the occupied pore change of electrical resistivity. A device named Cell Transit Analyser (CTA) was used. The height and length of electrical pulses were related to the cell deformed shape in the pore and to its velocity. The influence of the flow strength, suspending medium viscosity and cell membrane elasticity was studied. [1] ii)The design and experimental characterization of a Hele-Shaw cell with a porous bottom wall in order to study the influence of flow induced forces (shear stress and transmural pressure) on cells adhering on porous biomaterials. Theoretical predictions for the flow in the chamber were provided and allowed to quantify the flow forces. [2]A short bibliographic overview of more recent studies in the same research area and of their biomedical applications can be also presented:i) flow rate or velocity calibrations with microparticles in microchannels, cell mechanics studies (change of mechanical properties of cells, effect of drugs, cell sorting, …), white blood cells deformation and transport in capillaries, vascularization and microcirculation in reconstructed tissues and organoïds, … ii) improvement of biomaterials for dialysis and blood filtration process, in vitro studies of white blood cells and cancer cells diapedesis, mechanotransduction studies with endothelial cells or other cells, test of biomaterials for the functional vascular grafts production, …Artificial microfluidic circuits may also be used to improve cell culture, proliferation and attachment (for example, stem cells cultivation and differentiation for artificial tissue production), or, on the contrary, to improve hydrodynamic dissociation of cell aggregates and tissues. Other applications of microfluidic devices are found in the context of space research and astronauts health (study of blood flow under microgravity conditions), … In any cases, the control of cells’ microenvironment and of the applied forces remains a challenge. References [1] Drochon, A. (2005) “Use of Cell Transit Analyser pulse height to study the deformation of erythrocytes in microchannels” Medical Engineering and Physics, Vol 27(2), 157-165.[2] Chotard-Ghodsnia, R., Drochon, A., Grebe, R. (2002) “A new flow chamber for the study of shear stress and transmural pressure upon cells adhering to a porous biomaterial” Journal of Biomechanical Engineering, Vol 124 (2), 258-261

Necessity of an homogeneous environment for cell culture in bioreactors: a mini-review of the proposed solutions in the literature

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Blood rheology and mechanical properties of blood cells

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Bioreactor design for optimal cell culture conditions?

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