Caractérisation de la fonction hémodynamique suite au remplacement valvulaire mitral. Etude in-vitro

Ce travail de doctorat se décompose en quatre parties distinctes. La première partie concerne la caractérisation hémodynamique sur simulateur cardiovasculaire de prothèses valvulaires mitrales de différents constructeurs en vue de leur évaluation clinique et du diagnostique de leur dysfonction. La seconde partie se focalise sur les prothèses valvulaires mécaniques bi-clapet au travers desquels le phénomène de recouvrement de pression dû au passage de l'écoulement à travers les trois orifices formés par les clapets peut engendrer une surestimation du gradient transvalvulaire. Ce phénomène peut entrainer une ambiguïté lors de l'évaluation de la prothèse en cas de gradient transvalvulaire important. Cette partie s'attache à quantifier ce phénomène et à évaluer l'influence d'une dysfonction (disproportion patient-prothèse ou obstruction d'un clapet) sur celui-ci. La troisième partie concerne la procédure valve-in-valve dans laquelle une prothèse percutanée est implantée dans une bioprothèse défaillante. Elle fournit une caractérisation in vitro, première au niveau mondial, d'assemblages de la prothèse SAPIEN Edwards dans des bioprothèses issues de différents constructeurs. Enfin et suite à la mise en évidence dans les parties précédentes de profils de vitesse en amont de la prothèse ne pouvant être assimilés à des profils plats, l'étude des patrons de flux auriculaires a été réalisée grâce à des acquisitions in-vitro.This PhD work is divided into four different parts. the first part concerns the hemodynamic characterization by in-vitro cardiovascular testing of mitral valvular prosthesis from different manufacturers in order to provide reference values for clinical diagnosis. The second part focus on bi leaflet mechanical heart valve in each pressure recovery resulting of flow through the three orifices could lead to an overestimation of transvalvular pressure gradient. This could create ambigious assessment in case of high value of transvalvular pressure gradient. This part aims to quantify this pressure recovery and identify the influence of dysfunction (leaflet obstruction or patient prosthesis mismatch) on this value. Third part consists in valve-in-valve procedure in which a transcatheter valve is impllanted in a failled bioprosthesis. It provides in vitro testing, first globally, of assemblies composed of SAPIEN Edwards prostheses in different manufacturers' bioprosthesis.As highlighted in the previous parts inflows of the mitral prostheses can not be considered as plane and results of left atrium flow patterns. The last part studies the left atrium flow following mitral valve replacement

Stress effects of the cerebrospinal pulsatile flow on the spinal cord by a 3D fluid-structure modeling

44th Congress of the Société de Biomécanique, Poitiers, FRANCE, 28-/10/2019 - 30/10/2019The mechanical phenomena which occur in the subarachnoid space have been studied either from a structural point of view particularly focusing on the spinal cord (SC) or from a fluid point of view focusing on the cerebrospinal fluid (CSF) flow. Fluid-structure interaction (FSI) approaches provide new perspectives to numerically describe the physiological phenomenon. It has been showed that the CSF acts in a passively way on the central nervous system as shock absorber in compressive spinal cord injuries (Fradet et al. 2016). However, we are not aware of any study that provide stress values induced by the active physiological role of the pulsatile CSF flow profile on the spinal cord in 3D. The purpose of this study is to quantify the maximum Von Mises stress generated in the spinal cord induced by an healthy pulsatile flow profile of the CSF

Cervical Canal Morphology: Effects of Neck Flexion in Normal Condition - New Elements for Biomechanical Simulations and Surgical Management

Continuous measurements and computation of absolute metrics of cervical subarachnoid space (CSS) and spinal cord (SC) geometries proposed are based on in vivo magnetic resonance imaging and 3D reconstruction. OBJECTIVE: The aim of the study is to offer a new methodology to continuously characterize and to quantify the detailed morphology of the CSS and the cervical SC in 3D for healthy subjects in both neutral supine and flexion. SUMMARY OF BACKGROUND DATA: To the best of our knowledge, no study provide a morphological quantification by absolute indices based on the 3D reconstruction of SC and CSS thanks to in vivo magnetic resonance imaging. Moreover, no study provide a continuous description of the geometries. METHODS: Absolute indices of SC (cross-sectional area, compression ratio, position in the canal, length) and of CSS (cross-sectional area, occupational ratio, lengths) were computed by measures from 3D semi-automatic reconstructions of high resolution in vivo magnetic resonance images (3D T2-SPACE sequence) on healthy subjects (N=11) for two postures: supine neutral and flexion neck positions. The variability induced by the semi-automatic reconstruction and by the landmarks positioning were investigated by preliminary sensitivity analyses. Inter and intra-variability were also quantified on a randomly chosen part of our population (N = 5). RESULTS: The length and cross-sectional area of SC are significantly different (p \textless 0.05) in flexion compared to neutral neck position. Spinal cord stays centered in the canal for both postures. However, the cross-sectional area of CSS is submitted to low variation after C3 vertebra for both postures. OR and CR after C3 are significantly lower in flexion. CONCLUSIONS: This study presented interpretations of morphological measures: 1) left-right stability (described by the Left-Right eccentricity index) ensured by the denticulate ligaments and the nerve roots attached to the dural sheaths, 2) a Poisson effect of the SC was partially notified through its axial (AP diameter, OR, CR) and its longitudinal geometrical descriptions (LSC). Such morphological data can be useful for geometrical finite element modeling and could now be used to compare with injured or symptomatic subjects

Biomechanical evaluation of Back injuries during typical snowboarding backward falls

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Left ventricle vortex detection by 3D + t phase contrast MRI: a feasibility study

44th Congress of the Société de Biomécanique, Poitiers, FRANCE, 28-/10/2019 - 30/10/2019The motivation to focus on coherent structure detection in cardiovascular systems is two-fold: 1) the ability to reliably detect abnormal inefficient flow patterns from a normal optimal state; and 2) the detection of flow conditions conducive to secondary pathological processes such as thrombosis - as the coherent structures are thought to perform an important role in avoiding stasis by ?washing out' the cardiac cavities (e.g. the atrial appendage or LV apex; Birdwell et al. 1978). Detection of the coherent structures could be performed using a number of different vorticity criteria, such as: threshold of vorticity magnitude, Q-criterion and ?2-criterion. However, prior application and evaluation of these different criteria in the cardiovascular system by 3D?+?t phase contrast (PC) flow MRI is limited as most approaches have used ?2- or Q-criteria (Elbaz et al. 2014) without comparison with other approaches. There is therefore a need to more broadly assess the capacity of these criteria to detect and describe coherent structures. Initial work by Garcia et al. (2013), reported the influence of noise and the spatial resolution of helicity. An alternative approach using data clustering has been reported by Wong et al. (2010). The primary aim of this work is to compare criteria for the assessment of coherent structures in the left ventricle by 3D?+?t PC flow MRI in healthy volunteers. To investigate the influence of diastolic function on the coherent structures in healthy volunteers detected by different criteria (vorticity, Q- or ?2-criteria) is the second aim of this work

Isometric osteopathic manipulation influences on cervical ranges of motion and correlation with osteopathic palpatory diagnosis: A randomized trial

Introduction Isometric manipulation is a current practice in osteopathy and treatment benefits have been reported in the literature. Such benefits could be assessed using experimental non-invasive cervical mobility measurements. The main objective was to quantitatively measure the effects of isometric manipulation on principal and compensatory cervical motions. Methods 101 healthy volunteers were included in this study. 51 healthy volunteers selected randomly underwent the experimental protocol before and after isometric treatment and were compared to 50 healthy volunteers who underwent a placebo treatment. Osteopathic diagnosis was performed on each healthy volunteer before and after the treatment. The experimental protocol included measurements by a motion capture system focusing on principal range of motion and compensatory motions. Results In both the isometric and the placebo sample, respectively including 51 (age: 29.2 ± 8.1, BMI: 22.2 ± 3.5) and 50 healthy volunteers (age: 27.4 ± 6.8, BMI: 22.9 ± 2.8), a pre-treatment diagnosis revealed a light cervical dysfunction in all subjects, mainly in levels C3 and C4. Altered ranges of motion thresholds (C3/C4 alterations) were identified: 113.2° for flexion, 130.0° for rotation and 90.2° for lateral flexion. After manipulations, the volunteers who underwent the isometric treatment presented a slight increase in amplitude for lateral flexion (p \textless 0.04), which was not found in the volunteers who underwent the placebo treatment. Compensatory motions showed differences pre and post isometric treatment without reaching significant values. Conclusion Principal ranges of motion were found significantly higher after osteopathic treatment when compared to the placebo treatment. Osteopathic palpatory diagnosis showed significant correlation with range of motions before treatment

Characterization of Effective Orifice Areas of Mitral Prosthetic Heart Valves: An In-Vitro Study.

International audienceReference values of hemodynamic parameters for the assessment of prosthetic heart valves are necessary, and ideally need to be provided by entities independent of the valve manufacturers. Thus, the study aim was to provide, in vitro, normal reference values of the effective orifice area (EOA) for different models and sizes of mitral prosthetic valve, and to assess the determinants of EOA and mean transvalvular pressure gradient (mTPG)

Mitral bileaflet mechanical heart valves dysfunction and patient/prosthesis mismatch: in vitro investigation of differential diagnosis

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Les effets biphasiques de l'alcool dans le contexte de conduite

SEMOB 2021, 1er salon de la Sécurité Routière au service des Mobilités en entreprise, Toulouse, FRANCE, 23-/11/2021 - 24/11/2021Si les effets de la consommation de l'alcool sur la conduite sont étudiés depuis longtemps, les études se concentrent généralement sur une vision partielle du comportement de l'alcool dans l'organisme. En effet, si certaines conséquences de l'ingestion d'alcool peuvent être considérées comme dépendant de la dose ingérée, d'autres effets sont associés à la temporalité après ingestion. Ainsi, une fois ingérée, la course de l'alcool dans l'organisme produit une phase ascendante, un pic ou plateau puis une phase descendante (Ramaekers, 2020). Les effets de l'alcool pouvant varier en fonction de ces phases, ils sont décrits comme « effets biphasiques ». Ces effets biphasiques se manifestent, par exemple, par une prévalence d'effets stimulants lors de la phase ascendante et une prévalence d'effets sédatifs lors de la phase descendante (Hendler, Ramchandani, Gilman, & Hommer, 2011). Cependant elles se retrouvent également sur d'autres caractéristiques au niveau subjectif (p. ex., le sentiment d'intoxication disparaît durant la phase descendante?; Marczinski, Stamates & Maloney, 2018), au niveau comportemental (p. ex., la volonté de prendre le volant malgré l'état d'intoxication est plus grande durant la phase descendante, Marczinski, Stamates & Maloney, 2018), et au niveau cognitif (p. ex., la coordination motrice récupère lors de la phase descendante, Weafer, & Fillmore, 2012). Malgré cela, les différentes phases de l'alcoolémie ne sont que très peu étudiées dans le contexte de conduite

Are the Current Doppler Echocardiography Criteria Able to Discriminate Mitral Bileaflet Mechanical Heart Valve Malfunction? An In Vitro Study

International audienceMalfunction of bileaflet mechanical heart valves in the mitral position could either be due to patient-prosthesis mismatch (PPM) or leaflet obstruction. The aim of this article is to investigate the validity of current echocardiographic criteria used for diagnosis of mitral prosthesis malfunction, namely maximum velocity, mean transvalvular pressure gradient, effective orifice area, and Doppler velocity index. In vitro testing was performed on a double activation left heart duplicator. Both PPM and leaflet obstruction were investigated on a St. Jude Medical Master. PPM was studied by varying the St. Jude prosthesis size (21, 25, and 29 mm) and stroke volume (70 and 90 mL). Prosthesis leaflet obstruction was studied by partially or totally blocking the movement of one valve leaflet. Mitral flow conditions were altered in terms of E/A ratios (0.5, 1.0, and 1.5) to simulate physiologic panel of diastolic function. Maximum velocity, effective orifice area, and Doppler velocity index are shown to be insufficient to distinguish normal from malfunctioning St. Jude prostheses. Doppler velocity index and effective orifice area were 1.3 +/- 0.49 and 1.83 +/- 0.43 cm(2) for testing conditions with no malfunction below the 2.2 and 2 cm(2) thresholds (1.19 cm(2) for severe PPM and 1.23 cm(2) for fully blocked leaflet). The mean pressure gradient reached 5 mm Hg thresholds for several conditions of severe PPM only (6.9 mm Hg and mean maximum velocity value: 183.4 cm/s) whereas such value was never attained in the case of leaflet obstruction. In the case of leaflet obstruction, the maximum velocity averaged over the nine pulsed-wave Doppler locations increased by 38% for partial leaflet obstruction and 75% for a fully blocked leaflet when compared with normal conditions. Current echocardiographic criteria might be suboptimal for the detection of bileaflet mechanical heart valve malfunction. Further developments and investigations are required in order to further improve current guidelines