Degree Type

Dissertation

Date of Award

2018

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Major

Mechanical Engineering

First Advisor

Ming-Chen Hsu

Abstract

Bioprosthetic heart valves (BHVs) are prostheses fabricated from xenograft biomaterials for treating valvular disease. While these devices have mechanical and blood flow characteristics similar to the native valves, the durability remains limited to 10-15 years with device failure continues to result from leaflet structural deterioration mediated by fatigue and tissue mineralization. Improving BHV design remains an important clinical goal and represents a unique cardiovascular engineering challenge.

Transcatheter heart valves (THVs) have emerged as a minimally invasive alternative to surgical bioprosthetic heart valves therapy. THVs offer advantages such as less postoperative pain, faster rehabilitation, and better pressure gradients. However, issues such as paravalvular leakage, leaflet fatigue, and valve migration limit the widespread use of THV in the younger population, especially due to the lack of data concerning its long-term performance and durability. The friction force and the radial force between THV frames and the surrounding anatomy are important indicators for the safe anchoring. Thus, in-vitro measurement of these forces is vital for pre-operative planning of transcatheter aortic valve replacement (TAVR) procedures.

There is a profound need to develop a general understanding of heart valve mechanism through novel simulation technologies that take advantage of fluid–structure interactions (FSI). In this work, a framework for modeling BHVs using recently proposed isogeometric analysis based parametric design platform and immersogeometric FSI analysis is presented. Due to the complex motion of the heart valve leaflets, the blood flow domain undergoes large deformations, including changes of topology. The FSI simulations are carried out using our hybrid arbitrary Lagrangian--Eulerian/immersogeometric methodology, which allows us to efficiently perform a computation that combines a boundary-fitted, deforming-mesh treatment of the artery with a non-boundary-fitted treatment of the leaflets.

The development of modeling and simulation of full THV is integrated with the immersogeometric FSI analysis. With an effective material model considering the collagen fibers network of heart valve leaflets, and a novel method for the THV frame isogeometric design and simulation, a biomechanically rigorous and physiologically realistic computational FSI framework is carried out to study the interaction between THVs and aortic wall. From the computed friction force analysis, the anchoring ability of THVs is estimated, which is a valuable information for clinical planning and decision making of TAVR.

Copyright Owner

Cheng-Hao Wu

Language

en

File Format

application/pdf

File Size

120 pages

Share

COinS