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Etude expérimentale des propriétés mécaniques des artères : développement d'un banc électromécanique de tests in vitro, rhéologie pariétale d'artères normales, athéromateuses et cryoconservées, et applications cliniques

Abstract : The three-dimensional properties of the artery wall are a major element in ageing process and the development of vascular diseases (atherosclerosis, hypertension... ). Their degradation through processes like cryopreservation is subjected to , controversy. The more informative experimental data are those obtained from in vitro inflation tests of full segments in static or dynamic conditions. The mechanical model used hasto take into accounts the particular rheological characteristics of blood vessels (non linearity, finite strains and anisotropy among others). After recalling instrumentation (technology of measurement devices), physiological (normal and pathological) and biomechanical (theoretical and applied) data, this work presents the development, the realisation and the validation of a new electromechanical system of tests for blood vessels in vitro. This device includes a conditioning test chamber (temperature regulated bath) for full samples of arteries, an optoelectronics sensor allowing non-contacting measurement of extemal diameter, a differential pressure sensor for measurement of the transmural pressure and a force sensor measuring the longitudinal traction exerted during tension of the segment. After analog conditioning of the signais coming fram the various sensors, data are digitalized and stored. The hardware and software interfaces also allow to servo-control an hydrodynamic generator with the volume of perfused liquid.dilating the arterial segment. Thanks to the technological characteristics of the electronics instrumentation, the results obtained for 3 types of human arteries (normal, atherasclerotic and cryopreserved), associated with the consideration of various initial reference states (unloaded, zero stress) and with the expression of different models and parameters (thick-walled, strain energy density...) brought some complementary information on the compared rheology of these three types of vessels. For instance, the increased rigidity of atherosclerotic arteries is more significantly expressed by compliance than other elastic parameters and a low pressure study allows a better differentiation. Allografts show 3D strains highly increased (comparing to an identical initial state) which confirms the occurrence of a structural modification during the cryopreservation process. Thanks to the technical system developed, several straightforward clinical applications are in pragress or considered : integrity test and conditioning of allografts during surgical implantation, adequate relation between extension and distensibility, and cou pied protocol to echographic follow-up of implanted allografts.
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Walter Blondel. Etude expérimentale des propriétés mécaniques des artères : développement d'un banc électromécanique de tests in vitro, rhéologie pariétale d'artères normales, athéromateuses et cryoconservées, et applications cliniques. Médecine humaine et pathologie. Université Henri Poincaré - Nancy 1, 2000. Français. ⟨NNT : 2000NAN10291⟩. ⟨tel-01746878⟩

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