Faculty of Engineering of the University of Porto

120 Pages·2017·5.5 MB·English

by  Boris Sowah

Faculty of Engineering of the University of Porto

June 19, 2017
Faculty of Engineering of the University of Porto

Mechanical Characterization of the Human Atria
Based on Patient-Specific FEM Models

Boris Nii Ako Sowah

Dissertation carried out under
Masters in Biomedical Engineering

Supervisor: Prof. João Manuel R. S. Tavares

Co-supervisor: Dr Marco Lages Parente

June 19, 2017

© Boris Nii Ako Sowah, 2017
Summary

The left atrium (LA) of the heart serves vital roles that exerts profound effect on the left
ventricle (LV) filling and subsequently the overall performance of the cardiovascular process.
There are common diseases such as atrial fibrillation (AF) and atrial stunning (AS) that alters the
effective functioning of the atria. In view of this, access to the LA is very vital to perform sever-
al minimally invasive cardiac interventions of the left heart to rectify these abnormalities.
Transseptal puncture technique (TSP) is the commonest minimally invasive technique that in-
volves the puncturing of the atrial septum by the use of a catheter inserted in the right atrium
(RA) through the venous system under a bi-dimensional fluoroscopic guidance. There are associ-
ated complications; possibility of multiple puncturing and procedural failures using this tech-
nique even though it has been in existence for several years and the success rate basically de-
pends on the experience of the physician.
To resolve these complications, the exact location at which the septum requires to be trav-
ersed needs to be simulated. The objective of this project is to develop technologies to help the
physicians when performing TSP technique using the finite element method (FEM) software
(Abaqus) based on FEM models. There will be a complete study of the mechanical properties of
the human atrium, specifically the interatrial septal wall as well as the simulation of the needle
insertion into soft tissues to aid in the effective optimization of the TSP technique.

i
ii
Abstract

Atrial fibrillation (AF) is the most common cardiac arrhythmia in the world affecting more
than 9 million of person per year in Europe. AF is described by a dysfunction of the electric con-
duction system of the cardiac atria. The traditional treatment requires an ablation of the dys-
functional tissues at the atria using a minimally invasive cardiac intervention, called radio-
frequency ablation therapy. The success of this procedure is dependent of the experience of
the operator, which could be sub-optimal in abnormal anatomy situations.
During this project, I intend to develop FEM models of the atrium to simulate the needle in-
sertion procedure. Secondly, a strategy will be developed and used to generate the meshes for
the FEM models and needle designed for this dissertation. The Coupled Eulerian-Lagrangian
(CEL) FEM analysis technique will be used during the simulation of the needle insertion into the
developed FEM models. The mechanical properties of the tissue will be obtained from litera-
ture review and related works. Three sets of simulation results will be studied and discussed
after the simulation process and the simulation results include: the needle insertion forces, the
effect of varying the dimensions of the FEM model and finally the Mises stress distribution.

Keywords: Biomedical Engineering, Cardiovascular diseases, Coupled Eulerian-Lagrangian,
Finite Element Method, Biomechanics.

iii
iv
Appreciations

All praise and honour be to the Almighty God for the gift of life, good health and also the op-
portunity to pursue my master’s program in this noble institution. Indeed, to everything there is
a season and a time to every purpose under the heaven (Ecclesiastes 3:1).
A special appreciation goes to my parents and siblings for their continues support, guidance,
understanding and prayers that has brought me this far. I say a very big thank you and I pray for
God’s blessings in all you do in order to achieve your heart desires and aspirations.
Also, I am indebted to DREAM partnership within the Erasmus Mundus Action 2 represented
by University of Porto as the coordinating institution for giving me this great priviledge and op-
portunity to pursue my full master degree program in Portugal for a period of 22 months and also
providing me with the needed financial support to successfully achieve my dreams and aspira-
tions.
Furthermore, I am most grateful to my supervisors Prof. João Manuel R. S. Tavares and Dr.
Marco Lages Parente for their guidance, patience, directions, contributions and support through-
out this dissertation. I have acquired enormous wealth of knowledge whiles working with you
and it was certainly a pleasure working with and learning from you. I say “obrigado” and I prom-
ise to make you proud by effectively implementing the acquired knowledge in all my endeavors.
I am grateful to all the lecturers and technicians I encountered during my brief but lovely pe-
riod here. I acknowledge the efforts you made to teach in English as well as getting me the
course documents in English.
Finally, a very big thank you to all my colleagues of the Biomedical Engineering Master pro-
gram. The journey has been relatively long, interesting and bumpy but I could not ask for any-
thing else because of your understanding, assistance, support and friendship I have been able to
make it this far. To all my friends I say thank you for being there for me and helping me through
this journey.

v
vi