Modelagem computacional de uma bioprótese de válvula cardíaca: análise dinâmica e fenômeno de flutter

• Ano de defesa: 2019
• Autor(a) principal: Gabriel Fontes Iásbeck
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ENG - DEPARTAMENTO DE ENGENHARIA MECÂNICA; Programa de Pós-Graduação em Engenharia Mecanica; UFMG
• Palavras-chave em Português: Bioprótese de válvula cardíaca; Flutter; Estenose; Elementos finitos; Bioengenharia; Engenharia mecânica; Método dos elementos finitos; Prótese; Estenose da válvula aórtica
• Link de acesso: http://hdl.handle.net/1843/30068

Cardiovascular diseases are the leading causes of death, accounting for more than 17.6 million cases worldwide. Among the main diseases, it can be highlighted the problems related to malfunctioning of heart valves such as stenosis, where there is a reduction of the opening area of the valve due to the stiffening of the tissue. An effective solution to this disease is the replacement of the valve for a prosthesis. The two most common types of prostheses are the mechanical and biological. Mechanical valves provide good durability, between 20-30 years, but are thrombus-forming forcing the patient to take anti coagulants throughout their entire life. Biological valves have excellent organism acceptance; however, their durability is reduced by effects such as tissue calcification and fatigue which cause them to operate between 10-15 years. A phenomenon that occurs in biological prostheses and is considered more destructive than any other mechanism is flutter. Although known and widely mentioned in scientific studies, few were concerned with quantifying and evaluating the influence of variables in this phenomenon. Among those who did, none of them have used computational modeling techniques. The objective of this work is to computationally model a bioprosthetic heart valve, focusing on the calculation of the maximum opening area and the flutter phenomenon. A transient analysis of a cardiac cycle with physiological boundary conditions was performed initially and the results were qualitatively validated with experiments from the literature. Then the effectiveness of quasi-static analyzes with different types of elements was tested in the calculation of the maximum opening area. Finally, the influence of the stiffness of the valve tissue on the dynamics and flutter phenomenon was tested. The results showed that the transient analysis was able to represent the physical problem through experimental validation. As for the quasi-static analyzes, those using first and second order triangular, 1st order quadrilateral and 2nd order tetrahedral elements were effective in calculating the maximum opening area and had a maximum variation of 8.2%, however, the model that used first order tetrahedral elements obtained completely non-physical results, which make their use extremely inappropriate in problems of this nature. Regarding tissue stiffness analysis, it was observed that the increase in modulus of elasticity reduced the displacements and the maximum opening area of the valve, with the greatest variation reaching 6.3%. There was no change in valve opening time. In the study of the flutter phenomenon, three frequency bands were present in all cases. The modulus of elasticity had influence in which of these bands dominated the response and in their displacement amplitude. The methodology developed in this work provides tools for a quick and effective analysis of the flutter phenomenon and the dynamics of heart valves.