In the human body, the aorta is the largest artery and is responsible for distributing oxygenated blood from the heart to the surrounding organs and tissues. However, the aorta is vulnerable to a number of disorders, many of which are life-threatening. The root cause of aortic disease is unknown, but we do know that some individuals are more prone than others. In some cases, individuals with a genetic abnormality are predisposed to an increased risk of aortic disease. This is true for females with Turner syndrome (TS), a rare genetic disorder, who have a higher prevalence of cardiovascular disease than the general population. While there are established clinical practice guidelines for cardiovascular risk assessment in TS, evaluation using the current guidelines have seen life-threatening aortic events occurring out with measurements classified within the normal threshold. This is largely due to a lack of clinical data and understanding of the developmental origins of the cardiovascular manifestations seen specifically in TS. Thoracic Endovascular Aortic Repair (TEVAR) is an established treatment for a range of aortic diseases, including aortic aneurysm and dissection, and is favored in acutely unstable patients or individuals with a high operative risk (inclusive of Turner syndrome). In this work, three-dimensional geometries of the diseased aorta from two patient groups were studied: the first being children with a genetic abnormality (Turner syndrome) and the second being adult patients without a genetic abnormality who underwent TEVAR for aortic aneurysm repair. Our aims were to: (1) characterise the aortic geometries and evaluate various morphological parameters, such as diameter, curvature, and torsion; (2) compute the flow field in these geometries using computational fluid dynamics (CFD); and (3) compare the morphological and haemodynamic results between TS children and their age-matched healthy counterparts, and Post- and Pre-TEVAR adults. CFD was chosen as it enables detailed, non-invasive characterisation of complex physiological pressure and flow fields, thus improving our understanding of haemodynamics in specific groups of patients. In recent years, CFD models have driven clinical decisionmaking, surgical planning, and the evaluation of innovative surgical techniques. In the child aorta, healthy-to-Turner syndrome differences were observed, with Turner syndrome children presenting a greater variance in aortic arch morphology than their healthy counterparts. The visualisation of multidirectional blood flow revealed an increase in vortical flow in the arch, supra-aortic vessels, and descending aorta, and a correlation between the presence of aortic abnormalities and disturbed flow. Additionally, markers of abnormal aortic morphology were significantly associated with markers of obesity, which is believed to accelerate the initiation and progression of endothelial dysfunction. Given the young age of our study group, these findings may be an indication of atherosclerotic disease manifesting earlier in life in these patients. Clinically, age, obesity and aortic morphology may, therefore, play a key role in assessing cardiovascular risk in TS children. In the adult aorta, pre- and post-TEVAR differences were observed, with significant remodeling of the aortic vessel wall post-TEVAR. The radius at the aneurysm site, aortic curvature, torsion, and the combined curvature-torsion score were all reduced in the postTEVAR geometries. A favourable return to more physiological flow structures and a decrease in overall aortic time-averaged wall shear stress was observed post-TEVAR. For these patients who underwent elective TEVAR for thoracic aortic aneurysm repair, the numerical simulations revealed a positive return to a more physiologically normal aorta within two years. Future work in this field would be to assess the aorta of Turner syndrome patients pre- and post-TEVAR and compare these results to those presented in this thesis.
| Date of Award | 9 Dec 2024 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | University of Strathclyde & EPSRC (Engineering and Physical Sciences Research Council) |
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| Supervisor | Asimina Kazakidi (Supervisor) & Terry Gourlay (Supervisor) |
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