Date of Award

12-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Member

Ethan O Kung

Committee Member

Richard Figliola

Committee Member

Phanindra Tallapragada

Abstract

Univentricular heart defects represent one of the most complex forms of congenital heart defects, which left untreated, is fatal. Univentricular patients typically undergo three highly invasive surgeries that culminate in the Fontan procedure. The Fontan physiology is associated with several long-term complications, one of which is reduced exercise capacity. Previous studies have found an empirical correlation between the fluid power losses in the Fontan junction (indexed to body size and flow rate), and reduced exercise capacity. There is evidence suggesting that the narrowing of vessels in the Fontan junction results in increased indexed power loss and lowered exercise capacity. Several alternate configurations of the Fontan junction geometry have been proposed with the objective of mitigating the power loss. However, the significance of the power loss in the context of global haemodynamics remains unclear. The power loss characteristics of the alternate surgical configurations and their impact on global haemodynamics at various levels of exercise are also unknown.

In this thesis, we detail the development of competencies and techniques that allow us to characterize the power loss and its effects on the global haemodynamics using patient specific Fontan geometries and considering different levels of exercise physiologies. Starting from a dataset consisting of three surgical configurations for six patients developed under the guidance of a surgeon, we derive a pulmonary artery growth model from literature data to scale these geometries to an adult size. Next, we describe the process of realistically scaling these geometric models. Further, we describe an adaptive meshing protocol that we have developed leveraging an existing adaptive meshing algorithm for the automated optimal meshing of the scaled patient specific geometry. Multi-scale simulations provide closed-loop feedback between a finite element model and a lumped parameter model of the Fontan physiology, providing detailed local haemodynamic information and its impact on global haemodynamics. The succeeding portion of this document demonstrates the progress in performing multi-scale simulations and extracting results of local haemodynamic parameters such as power loss and global haemodynamic parameters such as the cardiac output, using an inferior vena cava stenosis in a Fontan patient as an example case scenario.

Available for download on Friday, December 31, 2021

Share

COinS