Aortic dissection is the most common acute catastrophic event affecting the aorta. The
majority of patients presenting with an uncomplicated type B dissection are treated
medically, but 25% of these patients develop subsequent dilatation and aortic aneurysm
formation. The reasons behind the long‐term outcomes of type B aortic dissection are
poorly understood. As haemodynamic factors have been involved in the development
and progression of a variety of cardiovascular diseases, the flow phenomena and
environment in patient‐specific models of type B aortic dissection have been studied in
this thesis by applying computational fluid dynamics (CFD) to in vivo data. The present
study aims to gain more detailed knowledge of the links between morphology, flow
characteristics and clinical outcomes in type B dissection patients.
The thesis includes two parts of patient‐specific study: a multiple case cross‐sectional
study and a single case longitudinal study. The multiple cases study involved a group of
ten patients with classic type B aortic dissection with a focus on examining the flow
characteristics as well as the role of morphological factors in determining the flow
patterns and haemodynamic parameters. The single case study was based on a series of
follow‐up scans of a patient who has a stable dissection, with an aim to identify the
specified haemodynamic factors that are associated with the progression of aortic
dissection. Both studies were carried out based on computed tomography images
acquired from the patients. 4D Phase‐contrast magnetic resonance imaging was
performed on a typical type B aortic dissection patient to provide detailed flow data for
validation purpose. This was achieved by qualitative and quantitative comparisons of
velocity‐encoded images with simulation results of the CFD model.
The analysis of simulation results, including velocity, wall shear stress and turbulence
intensity profiles, demonstrates certain correlations between the morphological
features and haemodynamic factors, and also their effects on long‐term outcomes of
type B aortic dissections. The simulation results were in good agreement with in vivo
MR flow data in the patient‐specific validation case, giving credence to the application of
the computational model to the study of flow conditions in aortic dissection. This study
made an important contribution by identifying the role of certain morphological and
haemodynamic factors in the development of type B aortic dissection, which may help
provide a better guideline to assist surgeons in choosing optimal treatment protocol for
individual patient.