A Computational Study of Blood Flow and Vascular Nitric Oxide Transport
Author(s)
Plata Garcia, Ana M.
Type
Thesis
Abstract
Atherosclerosis occurs in a spatially heterogeneous fashion within the arterial system.
The patchy nature of the disease is thought to reflect spatial variation in
haemodynamic factors such as wall shear stress (WSS) and in the concentration of
vascular species. This thesis numerically investigates blood flow and vascular transport
of the atheroprotective agent nitric oxide (NO) using a spectral/hp element
method.
Firstly, NO distribution is analysed within a parallel-plate flow chamber coated
with endothelial cells. Contrary to the accepted hypothesis that NO concentration
increases with WSS (as does NO production), it is observed that NO concentration
depends on WSS in a non-monotonic fashion. Furthermore, these results emphasise
the effect of convection on in vitro NO transport, which has been overlooked or
misinterpreted in most previous computational studies.
Secondly, blood flow and NO transport are investigated within a detailed representation
of the rabbit thoracic aorta and its branches, which was reconstructed using high
resolution computed tomography (CT) scan data of a vascular corrosion cast. The
computed WSS distribution exhibits significant spatial heterogeneity, reflecting the
complexity of the blood flow. In particular it is observed that two Dean-type vortices
(associated with a skewed velocity profile) form in the aortic arch and propagate
along the descending aorta. This results in streaks of WSS similar in nature to the
fatty streaks of early stage atherosclerosis observed in mature rabbits. This finding
provides further support for the hypothesis that blood flow mediates atherogenesis. The vascular distribution of NO is found to depend significantly on the relationship
between NO production and WSS. Furthermore, it is concluded that mechanisms
preventing NO consumption by haemoglobin (such as diffusional barriers) must exist
in order for NO to exert its atheroprotective action. This study represents the first effort to model NO transport in a realistic representation of the major arteries.
The patchy nature of the disease is thought to reflect spatial variation in
haemodynamic factors such as wall shear stress (WSS) and in the concentration of
vascular species. This thesis numerically investigates blood flow and vascular transport
of the atheroprotective agent nitric oxide (NO) using a spectral/hp element
method.
Firstly, NO distribution is analysed within a parallel-plate flow chamber coated
with endothelial cells. Contrary to the accepted hypothesis that NO concentration
increases with WSS (as does NO production), it is observed that NO concentration
depends on WSS in a non-monotonic fashion. Furthermore, these results emphasise
the effect of convection on in vitro NO transport, which has been overlooked or
misinterpreted in most previous computational studies.
Secondly, blood flow and NO transport are investigated within a detailed representation
of the rabbit thoracic aorta and its branches, which was reconstructed using high
resolution computed tomography (CT) scan data of a vascular corrosion cast. The
computed WSS distribution exhibits significant spatial heterogeneity, reflecting the
complexity of the blood flow. In particular it is observed that two Dean-type vortices
(associated with a skewed velocity profile) form in the aortic arch and propagate
along the descending aorta. This results in streaks of WSS similar in nature to the
fatty streaks of early stage atherosclerosis observed in mature rabbits. This finding
provides further support for the hypothesis that blood flow mediates atherogenesis. The vascular distribution of NO is found to depend significantly on the relationship
between NO production and WSS. Furthermore, it is concluded that mechanisms
preventing NO consumption by haemoglobin (such as diffusional barriers) must exist
in order for NO to exert its atheroprotective action. This study represents the first effort to model NO transport in a realistic representation of the major arteries.
Date Issued
2010
Date Awarded
2011-03
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Sherwin, Spencer
Krams, Rob
Sponsor
Fundacion Caja Madrid, Imperial College London and the British Heart Foundation
Creator
Plata Garcia, Ana M.
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)