Dissertations / Theses on the topic 'Heart valve prosthesis'
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Dellgren, Göran. "Aortic valve replacement with stentless bioprostheses : prospective long-term studies of the Biocor and the Toronto SPV /." Stockholm : Karolinska institutet, 2002. http://diss.kib.ki.se/2002/91-7349-152-7.
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Damen, Bas Stefaan, and bsdamen@hotmail com. "Design, Development, and Optimisation of a Culture Vessel System for Tissue Engineering Applications." Swinburne University of Technology. n/a, 2003. http://adt.lib.swin.edu.au./public/adt-VSWT20040512.125051.
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A Tissue Engineering (TE) approach to heart valve replacement has the aim of producing an implant that is identical to healthy tissue in morphology, function and immune recognition. The aim is to harvest tissue from a patient, establish cells in culture from this tissue and then use these cells to grow a new tissue in a desired shape for the implant. The scaffold material that supports the growth of cells into a desired shape may be composed of a biodegradable polymer that degrades over time, so that the final engineered implant is composed entirely of living tissue. The approach used at Swinburne University was to induce the desired mechanical and functional properties of tissue and is to be developed in an environment subjected to flow stresses that mimicked the haemodynamic forces that natural tissue experiences. The full attainment of natural biomechanical and morphological properties of a TE structure has not as yet been demonstrated.
In this thesis a review of Tissue Engineering of Heart Valves (TEHVs) is presented followed by an assessment of biocompatible materials currently used for TEHVs. The thrust of the work was the design and development of a Bioreactor (BR) system, capable of simulating the corresponding haemodynamic forces in vitro so that long-term cultivation of TEHVs and/or other structures can be mimicked. A full description of the developed BR and the verification of its functionality under various physiological conditions using Laser Doppler Anemometry (LDA) are given. An analysis of the fluid flow and shear stress forces in and around a heart valve scaffold is also provided.
Finally, preliminary results related to a fabricated aortic TEHV-scaffold and the developed cell culture systems are presented and discussed. Attempts to establish viable cell lines from ovine cardiac tissue are also reported.
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Bishop, Winona F. "Hydrodynamic performance of mechanical and biological prosthetic heart valves." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29461.
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One of the major achievements in cardiac surgery over the past 30 years has been the ability to replace severely diseased heart valves with prosthetic ones. The option of using prosthetic heart valves for the treatment of valvular diseases has improved and prolonged many lives. This is reflected in around 120,000 heart valve replacement operations carried out every year in North America alone to correct the cardiovascular problems of stenosis, insufficiency, regurgitation, etc.
The development of artificial heart valves depends on reliable knowledge of the hemodynamic performance and physiology of the cardiovascular system in addition to a sound understanding, at the fundamental level, of the associated fluid mechanics.
It is evident from the literature review that noninvasive measurements in a confined area of complex transient geometry, providing critical information relating to valve performance, are indeed scarce.
This thesis presents results of an extensive test program aimed at measuring turbulence
stresses, steady and transient velocity profiles and their decay downstream of the mitral valve. Three mechanical tilting disc-type heart valves (Björk-Shiley convexo- concave, Björk-Shiley monostrut, and Bicer-Val) and two biological tissue valves (Hancock II and Carpentier-Edwards supraannular) are studied. The investigation
was carried out using a sophisticated and versatile cardiac simulator in conjunction with a highly sensitive, noninvasive, two-component three-beam laser doppler anemometer system. The study covers both the steady (valve fully open) and pulsatile (resting heart rate) flow conditions. The continuous monitoring of the parametric time histories revealed useful details of the complex flow as well as helped establish location and timing of the peak parameter values. In addition,
orientation experiments are conducted on the mechanical valves in an attempt to reduce
stresses by altering the position of the major orifice. The experiments suggest correlation between high stresses and orientation.
Based on the the data, the following general conclusions can be made:
(i) Hemodynamic test results should be presented in nondimensional form to render them independent of test facilities, flow velocities, size of models, etc. This would facilitate comparison of results by different investigators, using different facilities and test conditions.
(ii) The valves tested showed very disturbed flow fields which generated high turbulent stresses presenting a possibility of thromboembolism and, perhaps,
haemolysis.
(iii) Implantation orientation of the valve significantly affect the mechanical prostheses
flow field. The single vortex formation in the posterior orientation results in a reduction in stresses compared to the anterior configuration.
(iv) The present results together with the earlier information on pressure drop and regurgitation provide a comprehensive and organized picture of the valve performance.
(v) The information is fundamental to the improvement in valve design, and development of guidelines for test methodology and acceptable performance criteria for marketing of the valves.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Jones, Mark I. "Haemocompatibility and charactersation of candidate coatings for heart valve prosthesis." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301695.
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Prosthetic cardiac valve surgery is a well-established technique, but the search continues for engineering materials with sup..e rior mechanical characteristics in order to extend the service life of the implant. The introduction of pyrolytic carbon was seen as a breakthrough in the development of wear resistant, non-thrombogenic materials for such applications. However, thrombo-embolic phenomena and the need for anticoagulation treatment following valve insertion remain the main problems associated with artificial materials in this application. The work carried out in this research has studied the haemocompatibility of a commercially available, wear resistant TiffiN/TiCfDLC multilayer structure, and a second TiN coating deposited by RF reactive sputtering of a titanium target in a ArIN2 environment, as candidate materials for a heart valve prosthesis. The structure of the RF deposited tiN coating was assessed as a function of deposition conditions, and was seen to develop a particular preferred crystallographic orientation. The nature of this texture was influenced by the condition of the underlying substrate. The effect of substrate condition on the biocompatibility of the tiN coating was studied by assessment of fibroblast attachment and spreading, and by haemolytic analysis of released haemoglobin. The results showed that the initial attachment and orientation of fibroblast cells was influenced by the substrate condition, but no influence on the degree of spreading and haemolytic nature was observed. Characterisation of the TiN coating and the components of the multilayer structure was carried out by Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), stylus profilometry and contact angle measurement. Haemocompatibility was studied by the interaction of the surfaces with plasma proteins, blood platelets and red blood ceUs. Cytotoxicity was studied using the MTT test. The degree of platelet activation on the surfaces correlated with their surface energy. The greatest degree of platelet spreading was observed on the more hydrophilic coatings. The lack of platelet activation seen on the DLC coating is attributed to its smooth surface and hydrophobic nature, resulting in higher levels of adsorption of anticoagulation proteins. The RF sputtered TiN coating caused significant levels of haemolysis and fibroblast cell death. None of the components of the multilayer structure caused such effects, although thrombus formation was observed to a degree on the Ti, TiN and TiC components of this structure. The toxic nature of the RF deposited TiN coating was not attributed to surface chemistry or roughness, but rather to a combination of the hydrophilic nature and the defect state of the surface.
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Simon, Hélène A. "Influence of the implant location on the hinge and leakage flow fields through bileaflet mechanical heart valves." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04012004-192539/unrestricted/helene%5Fsimon%5Fa%5F200405%5Fmast.pdf.
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Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2003.Sambanis Athanassios, Committee Member ; Sotiropoulos Fotis, Committee Member ; Yoganathan Ajit, Committee Chair. Includes bibliographical references (leaves 239-243).
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Kidani, Derrick D. A. "Surface modifications to improve the biocompatibility of polymeric vascular prostheses." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/11263.
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Yap, Cheng-Hon. "Factors influencing cryopreserved allograft heart valve degeneration." Connect to thesis, 2006. http://repository.unimelb.edu.au/10187/2120.
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Heart valve replacement is becoming more commonplace in developed nations. Despite this the ideal valve prosthesis has not been found. The allograft valve has been used for over 40 years and remains an important prosthesis with many advantages. However, like other biological valve prosthesis, they have a finite durability. The causes of allograft valve degeneration are still unknown. The study aims to identify factors associated with cryopreserved allograft valve degeneration. Knowledge of such factors will improve our understanding of the potential causes and mechanisms of allograft heart valve degeneration. (For complete abstract open document)
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Murphy, David Wayne. "The application of passive flow control to bileaflet mechanical heart valve leakage jets." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31700.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Co-Chair: Ajit Yoganathan; Committee Co-Chair: Ari Glezer; Committee Member: Rudy Gleason. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Bachlah, Dana Mohamad. "Modeling of the inner structural band of the aortic valve bio prosthesis." Bachelor's thesis, Igor Sikorsky Kyiv Polytechnic Institute, 2021. https://ela.kpi.ua/handle/123456789/43660.
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Обсяг дипломної роботи становить 73 сторінок, містить 28 ілюстрацій, 20 таблиць. Загалом опрацьовано 59 джерел.
Актуальність: Захворювання аортального клапана призводять до серйозних дисфункцій, спричинених зворотним потоком клапана або підвищенням його опору. Наслідком цієї патології є важка серцева недостатність, скорочення тривалості та якість життя. Єдине лікування - хірургічна заміна клапана на штучний протез або пластику аортального клапана. Заміна хворого аортального клапана на штучний протез є ефективним методом профілактики серцевої недостатності, збільшення тривалості та поліпшення якості життя.
Мета: Моделювання внутрішньої структурної смуги біопротезу аортального клапана.
Завдання: переглянути літературу з анатомії судин та клапанів серця; проаналізувати та виявити проблему; побудувати внутрішню структурну клапанну модель клапана у винахіднику AutoCAD; Аналіз варіантів матеріалів для виготовлення клапанного корпусу показав прийнятні механічні характеристики та біосумісність.
Основні результати: переглянуто літературу з суміжних тем; порівняльний аналіз існуючих прототипів штучних клапанів серця; вибір «біологічного нітинолу»; Розроблено 5 стандартних розмірів каркаса для біопротезування аортального клапана.The volume of the graduation work is 73 pages, contains 28 illustrations, 20 tables. In total 59 sources have been processed. Relevance: Aortic valve diseases lead to its severe dysfunction caused backflow on the valve or increased its resistance. The consequence of this pathology is severe heart failure, reduced duration and quality of life. The only treatment is surgical replacement of the valve with an artificial prosthesis or aortic valve plastic. Replacing of a sick aortic valve with an artificial prosthesis is an effective method of preventing heart failure, increasing duration and improving quality of life. Purpose: Modeling of the inner structural band of the aortic valve bio prosthesis. Tasks: to review literature on anatomy of blood vessels and heart valves; analyze and identify the problem; build inner structural band valve model in AutoCAD inventor; analyze the material options for the manufacture of the valve frame showed acceptable mechanical characteristics and biocompatibility. Main results: literature on related topics has been reviewed; comparative analysis of existing prototypes of artificial heart valves; selection of “biological nitinol”; 5 standard sizes of frame for aortic valve bio prosthesis was designed.
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Meneses, LÃdia Stella Teixeira de. "Self-care practice of evaluation of patients with mechanical heart valve prosthesis." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15151.
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nÃo hÃOs pacientes com prÃtese cardÃaca valvar mecÃnica exigem acompanhamento regular da equipe de saÃde durante a vida, com vistas a praticar o autocuidado para recuperaÃÃo e promoÃÃo da sua saÃde. Tem-se como objetivo avaliar a prÃtica do autocuidado de pacientes com prÃtese valvar mecÃnica, acompanhados na consulta de enfermagem. Como objetivos especÃficos tÃm-se: identificar os fatores condicionantes para a prÃtica do autocuidado, considerando indicadores sociodemogrÃficos e clÃnicos; verificar as prÃticas de autocuidado e os dÃficits de autocuidado de pacientes portadores de prÃtese valvar mecÃnica; e levantar os consequentes decorrentes do dÃficit de autocuidado. Estudo descritivo e transversal, desenvolvido em dois ambulatÃrios de valvopatias de hospitais escola de Fortaleza-Ce. CompÃs a amostra 127 pacientes com prÃtese valvar mecÃnica. Coletou-se os dados por meio de entrevista, avaliaÃÃo da pressÃo arterial e medidas antropomÃtricas. O projeto foi aprovado pelo Comità de Ãtica e Pesquisa (No 422.098). Como resultados dos fatores condicionantes predominaram: sexo feminino (56,7%), faixa etÃria 40 a 59 anos (50,4%), estudaram mais de 5 anos (69,2%), casados/uniÃo estÃvel (63,8%), procedentes de Fortaleza (54,3%), renda familiar de atà um salÃrio mÃnimo (53,5%), cor da pele nÃo-branca (55,1%) e nÃo exerce atividade laboral (80,3%). As prÃticas de autocuidado universal de maior incidÃncia foram: higiene corporal (cabelos lavados-97,6%, banho diÃrio-92,1%); higiene oral (escova os dentes ao dormir-87,4%); ingestÃo de lÃquidos (ingere Ãgua potÃvel-95,2%); ingestÃo de alimentos (ingestÃo de sal < 2g/dia-92,1%, consumo de vegetais e frutas diariamente- 79,5%); eliminaÃÃes intestinais (sem sangue, muco ou secreÃÃo purulenta-96%, ausÃncia de parasitas-94,4%); eliminaÃÃes urinÃrias (ausÃncia de sangue ou pus-96,8%, frequÃncia urinÃria de 4 a 6 vezes ao dia-96%). Como requisitos de autocuidado desenvolvimental predominaram: nunca usou drogas ilÃcitas, nem fumou, nem bebeu ou parou na descoberta da doenÃa (70%). Como requisitos de autocuidado desvio de saÃde tem-se: faz uso de medicaÃÃo certa na dose certa (95,2%); comparecimento Ãs consultas da equipe de saÃde (cardiologista-92,1%; enfermagem-84,2%); controle do INR (identifica sinais de sangramento-85,8%); e conhecimento (57,4%). Os dÃficits de autocuidado universal foram: higiene corporal (unhas grandes ou sujas-43,6%, faz depilaÃÃo com aparelho manual-77,2%), higiene oral (nÃo usa fio dental-70,9%, usa palito de dentes-71,7%, nÃo realiza visita ao dentista-65,4%), ingestÃo de alimentos (consumo desregular de alimentos que contem vitamina k - 33,1%, faz poucas refeiÃÃes por dia- 36,3%); prÃtica de exercÃcio fÃsico (nÃo usa roupas adequadas-62,3%, faz exercÃcio fÃsico menos de 30 min-65,4%, faz exercÃcio fÃsico menos de 5 vezes na semana-70,9%,); sono e repouso (demora a dormir-37,1%). Como dÃficit de autocuidado de desvio de saÃde destacou-se: nÃo realiza controle laboratorial do INR (55,2%). Os consequentes do dÃficit de AC predominaram: eventos hemorrÃgicos (55,1%) e tromboembÃlicos (13,4%). Conclui-se que nenhum paciente com valva cardÃaca mecÃnica segue todas as prÃticas de autocuidado nos requisitos universais, desenvolvimentais e desvio de saÃde recomendadas, assim como nenhuma prÃtica à seguida por todos os participantes do estudo. Portanto, à necessÃrio que os profissionais dos ambulatÃrios de valvopatias estabeleÃam estratÃgias para reduÃÃo do dÃficit de autocuidado, considerando os fatores condicionantes do autocuidado dos pacientes.
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Van, Aswegen Karl. "Dynamic modelling of a stented aortic valve." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/1747.
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Travis, Brandon. "The effects of bileaflet prosthesis pivot geometry on turbulence and blood damage potential." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/10024.
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Thalassoudis, Kym. "Numerical studies of flow through prosthetic heart valves /." Title page, contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09PH/09pht365.pdf.
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Jensen, Morten Ølgaard Jegstrup. "Stentless mitral valve fixation : impact on hemodynamic performance." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14966.
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Watson, Stuart Kent. "Carbon deposition for artificial heart valves using liquid reagent CVD." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16908.
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Grande, Kathryn Jane. "The aortic root-aortic valve relationship in the normal, diseased, and surgically repaired states /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/8114.
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Mumpower, Edward Lee. "Effect of disc angulation on the fluid dynamics of a tilting disc mitral valve prosthesis." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/32827.
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Mitchell, Stuart B. "Electrospinning controlled architecture scaffolds for tissue engineering & the effect of scaffold mechanical properties on collagen synthesis in tissue engineered mitral valves /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8045.
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Cezo, James. "Aortic valve performance with transaortic ventricular cannula /." Online version of thesis, 2009. http://hdl.handle.net/1850/10830.
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Lynch, Patricia G. "The effects of geometry on the flow fields in the pulmonary bifurcation : an in vitro study." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/11890.
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Ellis, Jeffrey Thomas. "An in vitro investigation of the leakage and hinge flow fields through bileaflet mechanical heart valves and their relevance to thrombogenesis." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17384.
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Claiborne, Thomas Edward III. "Development and evaluation of a catheter deliverable artificial aortic heart valve prosthesis and delivery system." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/2371.
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Currently, malfunctioning heart valves are replaced via highly invasive and costly open-heart procedures. A new alternative approach is a catheter deliverable or percutaneous heart valve. Current PHV prototypes utilize fixed animal tissue as valves. This research investigated the feasibility of an artificial PHV and the development of a delivery system. A left hea11 simulator and a tensile tester were used to characterize the hydrodynamics and mechanics of a novel artificial PHV. Test results showed equal or better in vitro hydrodynamic performance when compared to a St. Jude mechanical valve and an Edwards-Sapien PHV, with a mean pressure drop of <15 mmHg and a mean regurgitation of <5%. The PHV's exceeded requirements for fixation and radial force. The 24 F delivery system successfully delivered and deployed a PHV. The work described herein proves the feasibility of an artificial PHV and delivery system and justifies further investigation into its design and function.
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Weston, Matthew W. "Characterization of the shear stress on the aortic valve leaflet surface and its effects on cellular biosynthetic activity." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/9369.
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Jouret, Chantal. "Effects of matrix and phenotype on human dermal fibroblast attachment under laminar shear stress : implications for the development of tissue-engineered heart valves." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/11251.
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Kim, Hee Sun. "Nonlinear multi-scale anisotropic material and structural models for prosthetic and native aortic heart valves." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29671.
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Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.Committee Chair: Haj-Ali, Rami; Committee Member: White, Donald; Committee Member: Will, Kenneth; Committee Member: Yavari, Arash; Committee Member: Yoganathan, Ajit. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ohri, Rachit. "Harnessing osteopontin and other natural inhibitors to mitigate ectopic calcification of bioprosthetic heart valve material /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/7994.
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Simon, Helene Anne. "Numerical simulations of the micro flow field in the hinge region of bileaflet mechanical heart valves." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/34861.
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Native heart valves with limited functionality are commonly replaced by a bileaflet mechanical heart valve (BMHV). However, despite their widespread use, BMHVs still cause major complications, including hemolysis, platelet activation, and thromboembolic events. These complications are believed to be due to the non-physiologic hemodynamic stresses imposed on blood elements by the hinge flows. Three-dimensional characterization of the hinge flows is therefore crucial to ultimately design BMHVs with lower complication rates. This study aims at simulating the pulsatile 3D hinge flows of various BMHVs placed and estimating the thromboembolic potential associated with each hinge.
The hinge and leaflet geometries of clinical BMHVs are reconstructed from micro-computed tomography scans. Simulations are conducted using a Cartesian sharp-interface immersed-boundary methodology combined with a second-order accurate fractional-step method. Physiologic flow boundary conditions and leaflet motion are extracted from the Fluid-Structure-Interaction simulations of the BMHV bulk flow. The accuracy of the solver is assessed by comparing the results with experimental data. The numerical results are analyzed using a particle tracking approach coupled with existing blood damage models to relate the flow structures to the risk for blood damage.
Calculations reveal complex, unsteady, and highly 3D flow fields. Zones of flow stagnation and recirculation, favorable to thrombosis and regions of elevated shear stresses, which may induce platelet activation, are identified throughout the hinge and cardiac cycle. The hinge gap width and, more importantly, the shape of the hinge recess and leaflet are found to impact the flow distribution. Avoiding sharp corners or sudden shape transitions appear as key geometrical design parameters to minimize flow disturbances and thromboembolic potential.
The computed flows underscore the need to perform full 3D pulsatile simulations throughout the cardiac cycle to fully capture the complexity and unsteadiness of the hinge flows. Though based only on three different designs, this study provides general guidelines to optimize the hinge design based on hemodynamic performance and thromboembolic potential. The developed framework enables rapid and cost-efficient pre-clinical evaluation of prototype BMHV designs prior to valve manufacturing. Application to a wide range of hinges with varying design parameters will eventually help in determining the optimal hinge design.
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Jiang, Mingxuan. "Fabrication and analysis of prosthetic heart valves using liquid reagent chemical vapor deposition." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/17702.
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Sung, Hsing-Wen. "In vitro velocity measurements in a pulmonary artery model." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/13388.
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Simon, Helene A. "Influence of the implant location on the hinge and leakage flow fields through bileaflet mechanical heart valves." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04012004-192539/.
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Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2004.Sambanis Athanassios, Committee Member ; Sotiropoulos Fotis, Committee Member ; Yoganathan Ajit, Committee Chair. Includes bibliographical references (leaves 239-243).
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Waller, Steven Christopher. "EVALUATION OF CHITOSAN AND COLLAGEN AS SCAFFOLDING FOR A TISSUE ENGINEERED HEART VALVE." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11072008-125401/.
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Children born with congenital heart valve defects require open-heart surgery to implant an artificial replacement valve. These valves are unable to grow with the developing child and need replacing every 5 years. Tissue engineered heart valves, capable of growing with the patient, would alleviate the need for repeat surgery. I hypothesize chitosan and collagen possess advantageous qualities as scaffolding for a tissue engineered heart valve. This study evaluated chitosan and collagen hydrogels as potential scaffold materials. Chitosan scaffolds had suitable pore size/distribution and scaffold strength; however, they were unable to sustain cell attachment or viability. Collagen gels were assessed for compaction, mechanical properties and expression of matrix metalloproteases in the presence or absence of biochemical and mechanical stimuli. Pressure increased the remodeling potential. This was augmented further in the presence of TGF-β. In conclusion, both materials have potential as scaffolding substrate in a tissue engineered heart valve.
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Tognon, Alexandre Pereira. "Efetividade e custo do tratamento invasivo da estenose valvar aórtica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/157648.
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O expressivo número de brasileiros que necessitam correção anatômica da estenose valvar aórtica acentuada e que não realizam cirurgia de substituição valvar devido ao risco proibitivo justifica a necessidade de investigação, tanto da efetividade no cenário clínico real quanto dos custos impostos ao Sistema Único de Saúde e aos planos de saúde suplementar brasileiros pela incorporação do implante transcateter de valva aórtica, que tem se demonstrado efetivo mas oneroso, internacionalmente. No primeiro artigo da tese, avaliaram-se os desfechos intra-hospitalares, a sobrevida e o reembolso pela internação hospitalar de 41 pacientes com idade média de 78,7 ± 6,3 anos, estenose valvar aórtica acentuada, com recusa cirúrgica e decisão multidisciplinar por tratamento transcateter entre outubro de 2010 e outubro de 2015. Os sujeitos foram seguidos prospectivamente por um período mediano de 15,2 (4,5 – 25,6) meses e a sobrevida estimada em 1 e 2 anos foi de 73,2% e 64,1%, respectivamente. Identificou-se que hipertensão pulmonar e revascularização miocárdica cirúrgica prévia estavam independentemente associadas à menor sobrevida. O valor mediano reembolsado pelos pacientes atendidos pelo Sistema Único de Saúde foi R$ 108.634,34 (101.051,05 – 127.255,27) e R$ 115.126,77 (94.603,21 – 132.603,01) para aqueles internados por planos de saúde suplementar ou particulares, sendo o respectivo valor mediano reembolsado pela prótese valvar de R$ 82.000,00 (82.000,00 – 95.450,00) e 84.050,00 (75.000,00 – 92.400,00) Em um grupo de 585 procedimentos de troca valvar aórtica cirúrgica em indivíduos com idade ≥ 60 anos, realizados entre janeiro de 2010 e dezembro de 2015 na mesma instituição, a mortalidade intra-hospitalar estava associada à idade e foi de 5,9% naqueles com idade entre 60 e 70 anos, 10,8% entre 70 e 80 anos e de 22,2% ≥ 80 anos. O reembolso mediano foi de R$ 14.035,96 (11.956,11 – 16.644,90) para os internados pelo Sistema único de Saúde e R$ 20.273,97 (15.358.03 – 32.815,49) pelos planos de saúde suplementar ou particulares. No segundo artigo da tese, identificou-se que do total de 819 pacientes consecutivamente incluídos no Registro Brasileiro de Implante de Bioprótese Aórtica por Cateter entre janeiro de 2008 e outubro de 2015, 15 (1,8%) sofreram perfuração do ventrículo esquerdo. Os pacientes que apresentaram perfuração eram mais idosos (85,4 ± 6,3 vs. 81,5 ± 7,3 anos, p=0,038), predominantemente mulheres (80,0% vs. 50,5%, p=0,024), apresentavam maior fração de ejeção (67,3 ± 7,8% vs. 58,6 ± 15,0%, p=0,001), menor massa ventricular esquerda (203,9 ± 47,1g vs. 247,6 ± 78,7g, p=0,039) e menor altura do tronco da coronária esquerda (11,2 ± 5,4mm vs. 14,0 ± 3,3mm, p=0,034). Os preditores independentes de perfuração do ventrículo esquerdo foram idade e fração de ejeção. No terceiro artigo, descreve-se um caso de ablação septal para tratamento de miocardiopatia hipertrófica obstrutiva assimétrica para posterior implante transcateter de valva aórtica, sugerindo que esta seja uma estratégia factível quando da concomitância dessas duas condições Em conclusão, os desfechos do tratamento transcateter da estenose valvar aórtica acentuada em pacientes inoperáveis são compatíveis com aqueles do cenário idealizado dos ensaios clínicos randomizados, apesar de estarem associados a custos maiores que os anteriormente estimados por painéis de especialistas. O tratamento cirúrgico, por sua vez, apresentou mortalidade maior que aquela idealizada ou relatada como usual. A hipercinesia do ventrículo esquerdo pode favorecer o trauma determinado pelo guia metálico, posicionado em seu interior para realização do procedimento, estando a fração de ejeção independentemente associada à chance de perfuração. Ainda, a ablação septal por álcool eletiva, anterior ao implante transcateter da valva aórtica, é uma abordagem factível para pacientes com hipertrofia ventricular esquerda assimétrica obstrutiva associada à estenose valvar aórtica.The expressive number of Brazilians who require an anatomic correction for severe aortic valve stenosis and who do not undergo valvar replacement surgery due to prohibitive risk justifies the need to investigate both the effectiveness in the real clinical scenario and the costs imposed to the Public Health System and the Supplementary Health System for the incorporation of the transcatheter aortic valve implantation, which has been shown to be effective but onerous, internationally. In the first article of the thesis, the in-hospital outcomes, long-term survival and reimbursement for 41 patients, with a mean age of 78.7 ± 6.3 years, sever aortic valve stenosis, with surgical refusal and multidisciplinary decision for transcatheter treatment, between October 2010 and October 2015 are described. Subjects were prospectively followed for a median period of 15.2 (4.5 - 25.6) months and the estimated survival at 1 and 2 years was 73.2% and 64.1%, respectively. It was identified that pulmonary hypertension and previous coronary artery bypass grafting were independently associated with lower survival. Median reimbursed values by the Public Health System was R$ 108,634.34 (101,051.05 - 127,255.27) and by supplementary health plans was R$ 115,126.77 (94,603.21 - 132,603.01). The respective median values reimbursed for the valve prosthesis was R$ 82,000.00 (82,000.00 - 95,450.00) and 84,050.00 (75,000.00 - 92,400.00) In a group of 585 surgical aortic valve replacement procedures in subjects aged ≥ 60 years, performed between January 2010 and December 2015 in the same institution, in-hospital mortality was associated with age and was 5.9% in those with age between 60 and 70 years, 10.8% between 70 and 80 years and 22.2% in ≥ 80 years. The median reimbursement was R$ 14,035.96 (11,956.11 - 16,644.90) for those hospitalized by the Public Health System and R$ 20,273.97 (15,358.03 - 32,815.49) by supplementary or private health plans. In the second article of the thesis, it was identified that of the total of 819 patients consecutively included in the Brazilian Registry of Aortic Bioprosthesis Implantation by Catheter (RIBAC) between January 2008 and October 2015, 15 (1.8%) suffered perforation of the left ventricle. Patients with perforation were older (85.4 ± 6.3 vs. 81.5 ± 7.3 years, p=0.038), predominantly women (80.0% vs. 50.5%, p=0.024), had a higher ejection fraction (67.3 ± 7.8% vs. 58.6 ± 15.0%, p=0.001), lower left ventricular mass (203.9 ± 47.1g vs. 247.6 ± 78, 7g, p=0.039) and shorter distance between the aortic annulus and the left main coronary artery ostium (11.2 ± 5.4mm vs. 14.0 ± 3.3mm, p=0.034). The independent predictors of left ventricular perforation were age and ejection fraction. In the third article, a case of septal ablation was described for the treatment of asymmetric obstructive hypertrophic cardiomyopathy for posterior transcatheter aortic valve implantation, suggesting that this is a feasible strategy when these two conditions are concomitant In conclusion, the outcomes of transcatheter treatment of severe aortic stenosis in inoperable patients are compatible with those in the ideal scenario of randomized clinical trials, although they are associated with higher costs than previously estimated by expert panels. Surgical treatment, on the other hand, presented higher mortality than that idealized or reported as usual. The left ventricle hyperkinesia may favor the trauma determined by the metallic guide, positioned inside it to perform the procedure, the ejection fraction being independently associated with the chance of perforation. Furthermore, elective alcohol septal ablation, prior to transcatheter aortic valve implantation, is a feasible approach for patients with obstructive asymmetric left ventricular hypertrophy associated with aortic valve stenosis.
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Marchand, Coralie. "Stent pour implantation percutanée d'une valve cardiaque." Phd thesis, Université de Haute Alsace - Mulhouse, 2009. http://tel.archives-ouvertes.fr/tel-00807225.
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Cette étude à pour but de développer un concept de stent atraumatique pour le remplacement percutanée de la valve aortique. Le stent est obtenu à partir de brins de Nitinol tressés, ce qui lui permet, de part sa géométrie et sa structure, d'être compressible, auto-expansible, et atraumatique. Le principe de fabrication des prototypes et les contraintes qui lui est associé sont présentées. Les performances de ces prototypes, en terme d'ancrage, de régurgitation statique et de régurgitation dynamique sont ensuite évaluées par des essais in vitro, pour lesquel le banc de test en flux pulsé a été optimisé afin de prendre en considération la compliance de la racine aortique. Les résultats obtenus permettent de mettre en évidence les différents paramètres de fabrication stent, tant au niveau dimensionnel (hauteur du cylindre, angle du cône...) qu'au niveau structurel (rigidité), qui ont une influence significative sur le comportement de l'endoprothèse.
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Vánky, Farkas. "Surgery for aortic stenosis : with special reference to myocardial metabolism, postoperative heart failure and long-term outcome /." Linköping : Linköpings universitet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7471.
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Smuts, Adriaan Nicolaas. "Design of tissue leaflets for a percutaneous aortic valve." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1625.
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MScEngThesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.
In this project the shape and attachment method of tissue leaflets for a percutaneous aortic valve is designed and tested as a first prototype. Bovine and kangaroo pericardium was tested and compared with natural human valve tissue by using the Fung elastic constitutive model for skin. Biaxial tests were conducted to determine the material parameters for each material. The constitutive model was implemented using finite element analysis (FEA) by applying a user-specified subroutine. The FEA implementation was validated by simulating the biaxial tests and comparing it with the experimental data. Concepts for different valve geometries were developed by incorporating valve design and performance parameters, along with stent constraints. Attachment techniques and tools were developed for valve manufacturing. FEA was used to evaluate two concepts. The influence of effects such as different leaflet material, material orientation and abnormal valve dilation on the valve function was investigated. The stress distribution across the valve leaflet was examined to determine the appropriate fibre direction for the leaflet. The simulated attachment forces were compared with suture tearing tests performed on the pericardium to evaluate suture density. In vitro tests were conducted to evaluate the valve function. Satisfactory testing results for the prototype valves were found which indicates the possibility for further development and refinement.
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Konduri, Suchitra. "The Influence of normal physiological forces on porcine aortic heart valves in a sterile ex-vivo pulsatile organ culture system." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-03042005-135623/unrestricted/konduri%5Fsuchitra%5F200505%5Fmast.pdf.
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Thesis (M. S.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005.Dr. Athanassios Sambanis, Committee Member ; Dr. Timothy M. Wick, Committee Member ; Dr. Ajit P.Yoganathan, Committee Chair. Includes bibliographical references.
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Costa, Jean Newton Lima. "Comparação entre o pericárdio bovino decelularizado e o pericárdio bovino convencional utilizado na confecção de biopróteses valvares cardíacas." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/5/5156/tde-08102014-114843/.
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O pericárdio bovino tratado com glutaraldeído (GTA) e armazenado em formaldeído tem sido utilizado para confecção de biopróteses cardíacas ao longo das últimas décadas, já se tendo acumulado grande experiência com seu manuseio. Sabemos, no entanto, que o uso do GTA associadamente à presença de restos celulares existentes em meio às fibras de colágeno e elastina do pericárdio, são fatores indutores de resposta inflamatória e de enucleação de cristais de cálcio, o que compromete a durabilidade da bioprótese in vivo a longo prazo. No presente trabalho, tivemos como objetivo comparar a resistência mecânica do pericárdio decelularizado com o pericárdio convencional, assim como avaliar sua capacidade de induzir resposta inflamatória em modelo experimental com ratos. Para estudar as duas técnicas, dividimos os pericárdios em dois grupos: Grupo I - pericárdio submetido a tratamento convencional com GTA e Grupo II - pericárdio submetido a tratamento de decelularização previamente ao tratamento convencional com GTA. Após o processamento químico dos pericárdios, as amostras do Grupo II foram histologicamente avaliadas para confirmar a eficácia da decelularização. A seguir, analisamos a resistência mecânica nos dois grupos de pericárdio através dos testes de tração e de desnaturação térmica. Em nossa casuística, os dois grupos tiveram desempenho semelhante. A capacidade de induzir resposta inflamatória foi avaliada em estudo experimental em 50 ratos Wistar, machos, com 3 meses de idade, os quais foram submetidos a implante subcutâneo no abdome de fragmentos de pericárdio dos dois grupos. Igualmente, não evidenciamos diferença significativa. Nossa terceira etapa de avaliação consistiu em confeccionar 3 biopróteses (mitral n. 29) com o pericárdio decelularizado e que foram submetidas a avaliação hidrodinâmica juntamente com uma bioprótese convencional de teste. As biopróteses decelularizadas mostraram ter desempenho hidrodinâmico semelhante à prótese de teste e ao padrão de avaliação de próteses já conhecido da Braile Biomédica (S.J.Rio Preto-SP), todas atingindo a marca de 150 milhões de ciclos. A avaliação histológica do pericárdio das próteses ao fim da ciclagem mostrou padrão microscópico habitual, não tendo havido ruptura ou fragmentação anormal induzida por estresse mecânico. Temos como conclusão que a técnica de decelularização mantém a resistência física do pericárdio em comparação àquele convencionalmente preparado, não levando à fragmentação da matriz de colágeno e elastina e nem à perda de sua resistência mecânica tanto estática quanto dinâmica, além de não ter induzido resposta inflamatória diferente daquela habitualmente encontrada no pericárdio convencionalThe bovine pericardium treated with glutaraldehyde (GTA) and stored in formaldehyde has been used in the manufacturing of cardiac bioprosthesis through the past decades, and a great knowledge has been acquired in this field. We know however that the use of the GTA and the presence of cell debris among the collagen and elastin fibers are triggers to induce inflammatory response and calcium deposition in the tissue, what compromises the long term durability of bioprosthesis in vivo. In this paper, our objective was to compare the decellularized and the conventional pericardium mechanical resistance and also its capability of inducing inflammatory response in an animal experimental model. In order to study these two techniques, we divided the pericardia into two groups: Group I- pericardia conventionally treated with GTA and Group II - pericardia previously decellularized and then conventionally treated with GTA. At first, after the pericardia chemical treatment, we performed histological analysis of Group II to certify the efficacy of the decellularization process. Afterwards, we analyzed the mechanical resistance in both groups using the stretching and shrinkage tests. In our samples, both groups had the same performance. The capacity of inducing inflammatory response was evaluated in an experimental study with 50 Wistar rats, male, 3 months old, which were operated to receive the pericardia patches of both groups underneath the dermal layer in the abdomen. We also did not find any difference between the groups. The third step of evaluation was to manufacture three decellularized bioprosthesis and one no decellularized one that were submitted to hydrodynamic tests. The decellularized and the test prosthesis showed the same performance and there was also no difference when compared with the known performance of the Braile Biomédica\'s (S.J.R. Preto-SP) bioprosthesis. They all reached 150 million cicles. The histological avaluation of the bioprosthesis showed the usual microscopic pattern, and there was no abnormal rupture or fragmentation caused by mechanical stress. We have therefore reached to the conclusion that the decellularization technique keeps the physical resistance of the pericardium when compared with the conventionally prepared. It does not cause damage or fragmentation of the collagen and elastin fibers and does not lead to loss of the mechanical resistance. And also, there was no difference in both groups regarding to inflammatory response studied in the animal model
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Junior, José de Lima Oliveira. "Influência da doença aterosclerótica arterial coronária crítica na mortalidade hospitalar de pacientes portadores de estenose aórtica submetidos à substituição valvar." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/5/5156/tde-05112008-110349/.
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Com o aumento da expectativa de vida nas últimas décadas, tem ocorrido aumento concomitante da prevalência da estenose aórtica degenerativa e da doença aterosclerótica arterial coronária. O presente estudo visa avaliar a influência da doença ateroslerótica arterial coronária crítica na mortalidade hospitalar de pacientes portadores de estenose aórtica submetidos à substituição valvar isolada ou combinada à revascularização do miocárdio. No período de janeiro de 2001 a março de 2006, no Instituto do Coração do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, foram analisados 448 pacientes submetidos à substituição valvar aórtica isolada (grupo GI) e 167 pacientes submetidos à substituição valvar aórtica combinada à revascularização do miocárdio (grupo GII). Os dados pré-operatórios eleitos para análise foram: sexo, idade, índice de massa corpórea, antecedentes de: acidente vascular cerebral, diabete melito, doença pulmonar obstrutiva crônica, febre reumática, hipertensão arterial sistêmica, endocardite, infarto agudo do miocárdio, tabagismo, fração de ejeção do ventrículo esquerdo, doença aterosclerótica arterial coronária crítica, fibrilação atrial crônica; operação valvar aórtica prévia (conservadora), classe funcional de insuficiência cardíaca congestiva, valor sérico de creatinina e de colesterol total, tamanho da prótese utilizada, extensão (completa ou incompleta) e número de anastomoses distais da revascularização do miocárdio, tempo de circulação extracorpórea e tempo de pinçamento aórtico. No estudo estatístico empregou-se análise univariada (teste Qui-Quadrado e teste t de Student) e multivariada (regressão logística) para avaliação da influência da doença aerosclerótica arterial coronária crítica na mortalidade hospitalar dos dois grupos estudados. No grupo GI (substituição valvar aórtica isolada), a mortalidade hospitalar foi 14,3% (64 óbitos), sendo 14,5% (58 óbitos) nos pacientes sem doença aterosclerótica arterial coronária crítica associada (grupo GIB) e 12,8% (6 óbitos) nos que apresentavam essa associação (grupo GIA). No grupo GII (substituição valvar aórtica combinada à revascularização do miocárdio), a mortalidade hospitalar foi 17,6% (29 óbitos), sendo 16,1% (20 óbitos) nos pacientes submetidos à substituição valvar aórtica combinada à revascularização completa do miocárdio (grupo GIIA) e 20,9% (9 óbitos) nos com revascularização incompleta do miocárdio (grupo GIIB). Nos pacientes submetidos à substituição valvar aórtica isolada, a presença de doença aterosclerótica arterial coronária crítica associada, em pelo menos duas artérias, influenciou a mortalidade hospitalar (p= 0,016). Nos pacientes submetidos à substituição valvar aórtica combinada à revascularização do miocárdio, o número de artérias coronárias com doença aterosclerótica crítica e a extensão da revascularização do miocárdio realizada não influenciaram a mortalidade hospitalar (p>0,05), mas a realização de mais de três anastomoses distais influenciou (p= 0,03).With the increase in life expectancy in recent decades has occurred concomitant increase in the prevalence of degenerative aortic stenosis and atherosclerotic coronary artery disease. This study aim to evaluate the influence of critical atherosclerotic coronary artery disease in hospital mortality of patients with aortic stenosis underwent isolated valve replacement or combined coronary artery bypass grafting. In the period of january 2001 to March 2006, at the Heart Institute University of Sao Paulo Medical Center were examined 448 patients underwent isolated aortic valve replacement (GI group) and 167 patients underwent combined aortic valve replacement and coronary artery bypass grafting (GII group). Preoperative data analised were: sex, age, body mass index, history of stroke, diabetes mellitus, chronic obstructive pulmonary disease, rheumatic fever, hypertension, endocarditis, myocardial infarction, smoking, chronic atrial fibrillation. Left ventricular ejection fraction, concomitant critical atherosclerotic coronary artery disease, previous surgical aortic valvuloplasty, congestive heart failure functional class, serum creatinine and cholesterol level, aortic valve prosthesis size, concomitant complete or incomplete coronary artery bypass grafting and number of bypass grafts, cardiopulmonary bypass and aortic cross clamping time. Univariate statistical analysis (Chi-square and Student\'s t test) and multivariate (logistic regression) were used to evaluate the influence of critical atherosclerotic coronary artery disease in hospital mortality of two groups. GI group (isolated aortic valve replacement) hospital mortality was 14.3% (64 deaths), and 14.5% (58 deaths) in patients without associated critical atherosclerotic coronary artery disease (GIB group) and 12.8% (6 deaths) in patients with that association (GIA group). GII group (combined aortic valve replacement and coronary artery bypass grafting) hospital mortality was 17.6% (29 deaths), and 16.1% (20 deaths) in patients underwent combined aortic valve replacement and complete coronary artery bypass grafting (GIIA group) and 20.9% (9 deaths) in patients with combined incomplete coronary artery bypass grafting (GIIB group). In patients underwent isolated aortic valve replacement, associated critical atherosclerotic coronary artery disease, of at least two arteries, influenced hospital mortality (p = 0016). In patients underwent combined aortic valve replacement and coronary artery bypass grafting, the number of coronary arteries with critical atherosclerotic disease and coronary artery bypass grafting extension didnt influenced hospital mortality (p> 0.05), but more than three coronary distal anastomoses influenced the hospital mortality (p = 0.03).
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MIRAOUI, MONGI. "Etude et realisation d'une valve a feuillets souples : application a la mecanique valvulaire cardiaque." Paris 6, 1986. http://www.theses.fr/1986PA066420.
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Roubertie, François. "Identification de substrats arythmogènes et des mécanismes de décompensation dans une population de tétralogie de Fallot à l’âge adulte et perspectives de prise en charge ultérieure." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0421/document.
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Le nombre d’adultes porteurs d’une tétralogie de Fallot opérée dans l’enfance est en constante augmentation. Initialement, ces patients étaient considérés comme guéris. A l’âge adulte, ils présentent en fait des complications d’ordre rythmique, responsables de morts subites, et des complications d’ordre mécanique : dilatation du ventricule droit (VD) liée à l’insuffisance pulmonaire chronique, séquellaire de la première chirurgie de réparation de la cardiopathie. Les mécanismes de l’arythmie ainsi qu’une éventuelle interaction entre la dysfonction VD et la survenue de ces arythmies ne restent que partiellement élucidés. Dans ce travail, en couplant les données d’études cliniques et les données expérimentales issues d’un modèle animal (MA) mimant une tétralogie de Fallot réparée, nous avons montré que 1) l’échocardiographie ne pouvait pas se substituer à l’IRM pour la surveillance des patients avec tétralogie de Fallot réparée 2) la valvulation pulmonaire restait une intervention à risque de mortalité 3) une bioprothèse non stentée était une bonne solution pour effectuer cette valvulation 4) en cas de fuite tricuspidienne sévère lors de cette valvulation, une plastie était indispensable 5) plusieurs gènes participaient au remodelage ventriculaire droit (analyse génétique effectuée sur le MA) 6) le remodelage électrophysiologique du VD (MA) s’accompagnait de propriétés pro-arythmogènes. Les mécanismes de décompensation sont intriqués : un lien entre dysfonction VD et arythmie paraît bien établi. D’autres analyses électrophysiologiques sont en cours au niveau du ventricule gauche (MA), pour rechercher d’autres mécanismes pro-arythmogènesThe number of adults with a repaired tetralogy of Fallot is increasing. In the past, those patients were considered healed. Nonetheless, they present arrhythmogenic issues, with frequent sudden death, and mechanical complications: right ventricular dilation due to long lasting pulmonary valve regurgitation, secondary to surgical repair. The origin of arrhythmia and its interaction with right ventricular dysfunction is only partially understood. In this study, combining clinical with experimental data, we pointed out: 1) concerning the follow-up of this population, echocardiography is not a substitute to MRI 2) operative mortality of pulmonary valve replacement (PVR) still exists 3) a stentless bioprosthesis represents a valid solution for PVR 4) a valve repair is mandatory for severe tricuspid valve regurgitation at PVR 5) the genetic analysis carried out in an animal model of repaired tetralogy of Fallot, demonstrated the involvement of numerous genes in right ventricular remodeling 6) remodeling of the right ventricle in this animal model generates pro-arrhythmic substrate. Heart failure mechanisms in repaired tetralogy of Fallot are complex: a link between right ventricular dysfunction and arrhythmias is demonstrated. Further studies are needed to investigate other pro-arrhythmic mechanisms involving the left ventricle
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Peruzzo, Angela Maria. "Avaliação mecânica e histológica de pericárdio bovino descelularizado submetido à pressão." Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/985.
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O pericárdio bovino é um tecido biológico utilizado na fabricação de vários produtos para a saúde e também em válvulas cardíacas desde o início da década de setenta, porém, ainda requer estudos mais aprofundados no que diz respeito às mudanças que os tratamentos químicos utilizados para confecção das válvulas ocasionam. Atualmente a engenharia de tecidos estuda a descelularização do pericárdio bovino como um processo para retirar os componentes celulares, mantendo intacta a matriz extracelular (MEC), preservando a integridade do colágeno e também pode atuar como anticalcificante. Porém, é necessário saber qual o impacto que o tratamento químico trará nas propriedades mecânicas do tecido, como tensão máxima, deformação específica e alongamento. Nos trabalhos observados, os testes mecânicos realizados nos pericárdios bovinos descelularizados foram feitos no tecido sem serem submetidos a uma pré-tensão, a qual é necessária na maioria das vezes, para formação das cúspides durante a confecção das válvulas cardíacas ou outro dispositivo médico. Por essa razão, foi realizado um estudo do efeito na propriedade mecânica que uma determinada pressão exerce sobre o pericárdio bovino, que passou pelo processo de descelularização. Em paralelo também foi feito uma avaliação histológica do tecido para verificar a ausência de células e a preservação das fibras de colágeno no tecido descelularizado. Foram preparados quatro grupos diferentes para a realização dos testes. O grupo I chamado de grupo controle. O grupo II, onde os pericárdios foram descelularizados com o método PUC I. O grupo III foi tratado como o grupo I, porém sob pressão de 240 mmHg. Já o grupo IV, os pericárdios foram descelularizados e em seguida submetidos à mesma pressão utilizando solução de glutaraldeído 0,2% e 0,5%. Após os tratamentos dos grupos, todas as amostras foram tingidas em solução de azul de metileno 0,03% para melhor visualização das fibras do tecido. Em seguida os tecidos foram cortados a laser para obtenção dos corpos de prova e submetidos ao ensaio de tração. Obteve-se a partir do ensaio, a tensão máxima das amostras, a deformação específica e o alongamento na ruptura. Foi observado que nos grupos onde foram submetidos à pressão tiveram uma tensão máxima menor do que os grupos sem pressão e um maior alongamento. Verificou-se que o efeito da pressão diminuiu a espessura dos tecidos. O processo de descelularização se mostrou eficaz uma vez que foi demonstrada a ausência de células e a preservação das fibras de colágeno após técnica utilizada.The pericardium is a biological tissue used in the manufacture of various products for medical advices and manufacture of heart valves since the early seventies, however, it still requires further study with regard to the changes that the chemical treatments used to manufacture the valves cause. Several studies show that the tissue often undergoes a process of calcification generated by mechanical stress of opening and closing of the leaflets, damaging the hydrodynamics making valvular replacement necessary. Currently tissue engineering study decellularization process of the bovine pericardium to remove cellular components while preserving the extracellular the matrix (ECM), preserving the integrity of collagen it and can also act as anti-calcification. However, one must know the impact that chemical treatment will bring on the mechanical properties of the tissue, such as tensile strength, strain and elongation percentage. In examined studies, the mechanical tests performed on bovine pericardium decellularized tissue was made without being subjected to a pre-tension which is necessary in most cases for formation of the leaflets during the manufacturing of heart valves. For this reason, a study of the effect on mechanical property that a certain pressure exerts on the pericardium, which passed the decellularization process was made. In parallel it was also made a histological evaluation of the tissue to verify the absence of cells and preservation of collagen fibers in decellularized tissue. Four different groups were prepared for test. The group I was called a control group. In group II, the pericardia were decellularized with the PUC method I. Group III was treated as group I, but under pressure of 240 mmHg. The group IV, the pericardia were decellularized and then subjected to pressure using glutaraldehyde 0.2% and 0.5%. After treatment of the groups, all samples were stained in a solution of blue methylene 0.03% for better visualization of the fibers of the tissue. Then the tissues were cut by laser to obtain the specimens and subjected to tensile test. It was obtained from the test, the tensile strength of the samples, the strain and elongation percentage at break. It is observed that the groups which underwent pressure had a lower tensile strength than those without pressure and on the other hand showed a greater elongation percentage. Thus, it can be verified that the effect of the pressure decreased the thickness of the tissues. The decellularization process has show efficient since it has demonstrated the absence of cells and preservation of collagen fibers after technique.
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Alleau, Thibaut. "Development of a numerical platform to model the mitral valve." Thesis, Compiègne, 2021. http://www.theses.fr/2021COMP2649.
Full textAbstract:
L’insuffisance mitrale est la valvulopathie mondiale la plus fréquente avec une prévalence de 2%. Lorsque le patient n’est pas en mesure d’être opéré à cœur ouvert, un implant percutané est utilisé pour aider la fermeture des feuillets. Le seul implant actuellement disponible est basé sur la réparation bord à bord de la valve mitrale. Il réduit le reflux vers l’oreillette lors de la systole, mais n’est pas adapté pour les patients souffrant d’insuffisance mitrale fonctionnelle, chez qui la pathologie provient du ventricule et non des éléments de la valve. L’objectif de la thèse est de fournir une plateforme numérique permettant d’aider au développement d’un implant adapté pour ces patients. Plusieurs géométries de valve ont été réalisées au moyen d’un modèle paramétrique, en utilisant des données anatomiques. La dynamique de la valve a été modélisée avec le logiciel ADINA par des simulations éléments finis en grandes déformations. Des modèles structurels de la valve ont permis de représenter la fermeture de la valve sous une pression uniforme. Les lois de comportement de matériaux ont été développé dans le but d’obtenir une fermeture réaliste de la valve. Cela a nécessité la prise en compte de l’hyperélasticité et de l’anisotropie des tissus. Des pathologies valvulaires, telles que la dilatation de l’anneau mitrale ou la rupture des cordages tendineux ont été modélisées, et plusieurs méthodes ont été testées pour y apposer des systèmes médicaux. En utilisant une description ALE et un couplage monolithique, les interactions fluide-structure ont été simulées pour une valve mitrale bi-dimensionnelle. La fermeture hermétique de la valve pendant la systole a pu être reproduite et l’ouverture de la valve étudiée pendant la diastole. La plateforme numérique développée permet de modéliser la fonction de la valve mitrale et peut être utilisée pour aider au développement d’un implant mitral grâce au modèle paramétrique reproduisant différentes géométries de valve et aux lois matériaux anisotropes. Une perspective reste la création d’un modèle 3D des interactions fluide-structure de la valve mitraleMitral insufficiency is the first valvular disease worldwide, with a 2% prevalence. When open-heartsurgery is impossible for the patient, surgeons use percutaneous devices to help the mitral leaflets coapt. However, the only device currently available is based on the edge-to-edge mitral valve repair technique. This type of implant is not adapted for patients suffering from functional mitral insufficiency, where the ventricle is responsible for the lack of coaptation of the leaflets. This thesis aims to provide a numerical platform to help the development of a mitral valve implant adapted for those patients. Several mitral valve geometries were created from a parametric model using anatomical measurements. Finite element simulations of the mitral valve were performed using ADINA to determine the valve closure under constant pressure. Several material models were developed in large strain and large deformation to model the valve closure accurately. Pathological behaviour such as annulus dilatation and chordae rupture were modelled, and several methods were tested to implement medical devices. Fluid-structure interaction of a 2D mitral valve was obtained using an ALE description and a monolithic coupling approach. Both the systole and the diastole were reproduced and studied, and the hermetic seal of the valve was detailed. The numerical platform developed is suited to model mitral valve function and can be used to help the development of mitral implants. In addition, the parametric geometry model and the anisotropic material model will be useful to depict with realism the valve function. A 3D fluid-structure interaction of the mitral valve could be developed
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Thornton, Miles. "Finite element analysis of pericardial heart valve prostheses." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265608.
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Akutsu, Toshinosuke. "Hydrodynamic performance of mechanical prosthetic heart valve." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/26638.
Full textAbstract:
Each year, more than 10,000 operations aimed at replacement of diseased heart valves by prosthetic devices are carried out in North America alone. Physiological compatibility, structural integrity and favorable hemodynamics represent three important criteria governing the design of a prosthetic heart valve. The thesis studies fundamental fluid characteristics of three widely used mechanical heart valve configurations, namely, the Starr-Edwards, Bjork-Shiley and St. Jude.
In the beginning, the pertinent available literature is reviewed which clearly points out limitations concerning the available information and their presentation.
This is followed by a detailed description of design, construction, calibration and Instrumentation of a steady flow glycerol-water solution tunnel and a pulsatile flow cardiac simulator. The former test facility is ideally suited for testing heart valves under fully open condition during which the maximum flow and pressure (energy) losses occur. The latter simulates the transient condition over a typical cardiac cycle rather precisely. Highly sensitive Barocel pressure transducing system, magnetic flowmeters, laser-doppler anemometer, and a microprocessor controlled waveform generator together with sophisticated data acquisition and processing system makes the facility ideal and unique for the purpose.
Finally, the results of three distinct series of experiments with prosthetic valves using:
(i) the steady flow glycerol-water solution tunnel;
(ii) the steady flow in the cardiac pulse duplicator; and
(iii) the pulsatile flow cardiac simulator; are presented and discussed.
The significant contribution of the project lies in the fundamental data on pressure drop and its partial recovery; velocity profile, turbulence intensity, shear stress and their decay downstream; both in steady and pulsatile flow conditions. The results provide a comprehensive picture, fundamental insight and physical appreciation as to the hydrodynamic performance of prosthetic heart valves which would serve as reference for future development.
Emphasis throughout is on the use of proper nondimensional parameters to make the information independent of test facilities, flow velocities, size of the models, etc., which should represent a welcome step forward. It would make comparison of results obtained by different investigators using different test-facilities possible.
Based on the results following general conclusions can be made:
(a) Nondimensional pressure drop and discharge coefficient results suggest the Starr-Edwards configuration to be fluid dynamically superior.
(b) There is a significant and rapid recovery of pressure in the wake which depends on the Reynolds number and size of the downstream section. In the present study it was found to be as large as 24%! Hence, considering pressure drop immediately across a heart valve as a measure of its performance, as widely reported in literature, can be misleading.
(c) The Starr-Edwards prosthesis has a relatively lower value for the maximum velocity and turbulence intensity and their rapid decay in the wake compared to the Bjork-Shiley and St. Jude valves.
(d) Adjustment of parameters characterizing the cardiac network affect details of the cardiac cycle.
(e) At the onset of systole all the valves show negative flow until the valve-closure is complete. The Starr-Edwards valve has the largest negative flow rate as well as the longest duration until its closure while the St. Jude valve shows the smallest amount of reversed flow over the shortest time. Negative flow is a significant parameter since the loss in volume must be compensated either by increasing the heart rate or the stroke volume.
(f) All the valves show a decrease in Cp with an Increase in the Reynolds number. Thus the valve performance improves at higher Reynolds numbers. The degree of improvement depends on the valve configuration and is relatively smaller for the ball and cage geometry.
(g) During the pulsatile flow study, the maximum velocity recorded for the Starr-Edwards valve, at a given downstream location, is essentially the same as that observed during steady flow case. On the other hand, the turbulence Intensity is distinctly lower. Similar trends were observed for the other two configurations. In general, the peak velocity and turbulence intensity for the St. Jude valve are smaller than those for the Bjork-Shiley case.
(h) For the Starr-Edwards prosthesis, the sticking character of the ball may substantially alter the pressure-flow rate relation. The thesis ends with several recommendations for future work which are likely to be rewarding.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Reynolds, Karen Jane. "Acoustic monitoring of prosthetic heart valves." Thesis, University of Leicester, 1994. http://hdl.handle.net/2381/34209.
Full textAbstract:
The aim of the work presented in this thesis was to examine the possibility of detecting structural changes to an implanted prosthetic heart valve by spectral analysis of the sounds produced by the valve. On closure, mechanical heart valves produce a distinct sound as the occluder strikes the metal frame of the valve. Any change in the mechanical state of the valve will produce changes in the modes of vibration of the entire structure, causing the spectrum of the closing sounds to change. Initial recordings were made in a large tank of water providing ideal valve actuation and recording conditions. Results showed that all valves produce a stable averaged spectrum, and that each valve has a unique averaged spectrum. A digital filtering technique was developed whereby a baseline spectrum recorded from each valve is used for comparison with all subsequently recorded spectra from that valve. Using this technique, averaged spectra from individual valves were found to be highly reproducible. However, a minor structural alteration to a valve (added mass, or strut fracture) caused significant spectral changes, readily detected by digital filtering. To investigate the effect of a finite recording volume, recordings were made in a tank with dimensions approximating those of a human thorax. Standing waves generated by reverberations were clearly visible in the results. Structural changes to a valve were still detectable. Recordings were also made from prosthetic valves implanted in patients. To reduce sound distortion at the thoracic surface, recordings were made with the patient submerged in water. Results showed that reproducible averaged spectra could be obtained from implanted valves provided recording conditions were kept constant. The technique has not yet been developed to the point where it can be applied clinically. Nevertheless the technique shows promise as a method of screening patients at risk.
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Barsanti, Stephen. "Observations on the mechanical behaviour of polyurethane heart valves." Thesis, University of the West of Scotland, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265928.
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Hernández, Enríquez Marco. "Transcatheter Aortic Valve Implantation: Moving Forward to Minimize Vascular and Bleeding Complications = Implante Transcatéter de Válvula Aórtica: Avanzando hacia la Reducción de Complicaciones Vasculares y Hemorrágicas." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/669896.
Full textAbstract:
INTRODUCTION:
TAVI has settled as the standard of care of AS for inoperable, high-risk, and selected intermediate-risk patients undergoing aortic valve replacement. Vascular and bleeding complications are related to worst outcomes.
HYPOTHESES:
a. The reduction and early recognition of vascular and bleeding complications might improve clinical outcomes in patients treated with TAVI.
b. A full percutaneous transfemoral approach for TAVI is related to a lower rate of major bleedings in comparison to the surgical cut-down approach.
c. The development of post-TAVI thrombocytopenia has a prognosis value in short-term clinical outcomes.
d. The kinetics of drop platelet count (DPC) after TAVI are different according to the type of valve implanted.
MATERIALS AND METHODS:
Sub-project 1: “Comparison of complications between percutaneous puncture or surgical cut-down for transfemoral access in TAVI”
Data from the Spanish TAVI Registry were analyzed. Patients undergoing transfemoral TAVI in 41 Spanish centers from January 2010 to July 2015 were included. Subjects were divided into percutaneous puncture (PG) and cut-down group (CG). A propensity-matched comparison was performed to avoid selection bias. Vascular and bleeding complications were evaluated at 30-days and mid-term follow-up.
Sub-project 2: “Study of Thrombocytopenia after TAVI”
a. Patients from 2 Spanish centers between 2012 to 2016 were included. Subjects with severe baseline thrombocytopenia (<100x109/L) and peri-procedural death were excluded. Laboratory analyses were performed. Two groups were created according the DPC: ≤30% or >30%. Clinical, procedural characteristics and outcomes were collected retrospectively.
b. Patients treated with transfemoral TAVI in a French high-volume center from 2008 to 2016 were included. Exclusion criteria were non-transfemoral approach, severe baseline thrombocytopenia and peri-procedural death. The study protocol was like the previous study.
RESULTS:
Sub-project 1
A total of 2,465 transfemoral TAVI patients were included. The PG had 1,833 patients (74,3%) and the CG had 632 patients (25,6%). Propensity matching score resulted in 615 pairs.
Vascular complications at 30-days were significantly higher in the PG (RR 2,66; IC95% [1,85-3,64], p = <0,001) mainly driven to minor vascular complications. In contrast, the bleeding complications were higher in the CG (RR 0,45; IC95% [0,26-0,78], p = 0,003).
At a mean follow-up of 323 days, the rates remained similar. Higher rates of vascular complications in the PG: 15% vs. 5,1% (HR 2,23; IC95% [1,6-3,11]; p = <0,001) and higher rates of major bleedings in the CG: 3,4% vs. 1,6% (HR 0,57; IC95% [0,35-0,95], p = 0,03).
Sub-project 2
a) The analyzed population included 195 patients: 100 (52,2%) treated with self-expanding valves (SEV) and 95 (48,8%) with balloon-expandable valves (BEV). The mean percentage of DPC was 31,9±15,3%. The DPC was significantly higher in the BEV population in comparison to SEV (36,3±15,1% vs 27,7±14,4, p<0,001). After multivariate analysis, the use of BEV was independently associated to a DPC>30% (67,4% vs. 36,0%; OR 3,4; 95% CI, 1,42-8,16). AT 30-days, the DPC>30% was associated to a higher rate of major and life-threatening bleedings, vascular complications, sepsis, and death. At 1-year there were no differences in mortality. (6,35% vs. 10,0%; HR 1,54; 95% CI, 0,56-4,25).
b) A total of 609 were included. The mean DPC was 32,5±13,9%. The DPC was higher in the BEV group (33.9±14.2 vs 30.7±13.4%, p=0.006), and the nadir was reached significantly later in comparison with the SEV group. (3,0±1,3 vs 2,5±1,1 days, p<0,001). After the multivariate analysis, the factors related to a DPC>30% were the use of BEV, known coronary disease and preserved left ventricle ejection fraction. At 30-days the DPC>30% was associated to a higher rate of major and life-threatening bleedings (6,8 vs 2,1%, p=0.009) and death (3,5 vs 0,8%, p=0.036). At 1-year there were no differences in mortality
CONCLUSIONS:
1. The reduction and early recognition of vascular and bleeding complications is associated to an improvement in clinical outcomes in patients treated with TAVI.
2. The completely percutaneous approach of transfemoral TAVI yielded lower rate of major bleedings and higher rate of minor vascular complications in comparison to the surgical cut-down and closure.
3. A post-procedural DPC>30% is related with worse clinical outcomes at 30-days after TAVI.
4. The use of balloon-expandable valves seems to be associated with a higher risk of drop on platelet counts after TAVI.El Implante Transcatéter de Válvula Aórtica (TAVI) se ha consolidado como el tratamiento de elección en pacientes inoperables, de alto y seleccionados con intermedio riesgo quirúrgico. Las complicaciones vasculares y hemorrágicas están asociadas a peores resultados clínicos y a mayor estancia intrahospitalaria. Subproyecto 1: “Comparación entre las complicaciones de la punción percutánea y disección quirúrgica en el Implante Transfemoral de Válvula Aórtica” Análisis retrospectivo del Registro Nacional TAVI. Se incluyeron pacientes tratados con TAVI transfemoral en 41 centros españoles desde enero 2010 hasta julio 2015. Se evaluaron la complicaciones vasculares y hemorrágicas a los 30 días y a medio término. Asimismo, se evaluó la frecuencia de ictus, daño renal agudo, infarto del miocardio y muerte. Para reducir el sesgo de selección se realizó un “score de propensión”. Subproyecto 2: “Estudio de la Trombocitopenia después del Implante Transcatéter de Válvula Aórtica” a) Se incluyeron pacientes tratados con TAVI en 2 centros españoles entre enero 2012 y diciembre 2016. Se excluyeron pacientes con plaquetopenia severa basal (<100x109/L) y con muerte peri-procedimiento. Se realizaron analíticas seriadas durante el ingreso. El seguimiento clínico se realizó a los 30 días, 3 meses y 1 año posterior al procedimiento. Se recogieron las características basales, del procedimiento y los eventos clínicos en una base de datos. Se crearon 2 grupos de acuerdo con el porcentaje de caída de plaquetas: ≤30% y >30%. b) Se incluyeron pacientes tratados con TAVI transfemoral en un centro francés de alto volumen de TAVI, entre enero 2008 y diciembre 2016. Se excluyeron los pacientes con acceso no transfemoral, con plaquetopenia severa pre-procedimiento y con muerte peri-procedimiento. El protocolo del estudio fue similar al del estudio previo. La disminución y el reconocimiento temprano de complicaciones vasculares y hemorrágicas permite mejores resultados clínicos en pacientes tratados con TAVI. El abordaje completamente percutáneo de la TAVI se asoció a una tasa menor de sangrados mayores y a una mayor tasa de complicaciones vasculares menores en comparación con el abordaje quirúrgico. La caída en el porcentaje de plaquetas >30% se relaciona con peores resultados clínicos a los 30 días post-TAVI. El uso de las prótesis balón-expandibles parece asociarse a un mayor riesgo de disminución de plaquetas.
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Sarathy, Srivats. "Development of cylindrical bacterial cellulose membranes for pulmonary heart valve prostheses." Thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/6496.
Full textAbstract:
Novel biomaterials provide a spectrum of possibilities. They can be engineered in different forms to understand how they would perform as different bioprosthetic conduits. Bacterial cellulose membranes may be suitable candidates as prosthetic valve leaflets in valve replacement surgeries due to their functional properties (hemodynamics, resistant to thrombosis). Biomaterials used for most bioprosthetic heart valves are cut, trimmed and sutured. A major challenge for the bi-leaflet configuration is that the cutting and suturing of biopolymers fabricated as sheets into a cylindrical form increases failure risk due to greater number of suture points and irregular coaptation. The objective was to culture the bacterial cellulose membrane as a continuous cylindrical construct and evaluate its mechanical properties. Various design features of the fabrication process such as culturing media and the hollow carrier-mandrel characteristics were evaluated. A comparative study of how bacterial cellulose grows on different hollow carrier membranes was conducted and thin smooth surface silicone tubes fabricated in the lab were found to be most suitable. A bioreactor for culturing cylindrical bacterial cellulose tubes on the outer surface of the hollow carrier was designed and fabricated. The mechanical properties of the fabricated tubes, specifically, their tensile strength, flexure, suture retention and tear resistance were characterized. Mechanical characterization studies showed the cylindrical bacterial cellulose tubes to be anisotropic, with preferential properties in the longitudinal (axial) direction of the tube. Preliminary results show that cylindrical bacterial cellulose tubes can be a promising candidate for use in prosthetic valve conduits.
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Palermo, Thierry. "Etude de l'effondrement d'un tube elastique encastre : modelisation d'une prothese valvulaire cardiaque." Paris 7, 1988. http://www.theses.fr/1988PA077132.
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Wilson, Paul. "Computational fluid dynamic investigation of blood flow through heart valve prostheses." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360773.
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