BIOMECHANICS AND BIOCHEMISTRY OF THE AORTA IN CHRONIC AORTIC DISSECTION



Panpho, Phakakorn
(2021) BIOMECHANICS AND BIOCHEMISTRY OF THE AORTA IN CHRONIC AORTIC DISSECTION. PhD thesis, University of Liverpool.

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Abstract

Chronic aortic dissection (AD) is defined as being one in which there is a tear which originates in aortic wall and has been present for more than 30 days. Chronic AD tends to be associated with a weakened aortic wall. Eventually the degenerated, weakened aortic wall may rupture. Although tensile or biaxial testing techniques have previously been used in vitro for biomechanical testing of AD tissues at the macro-scale, little is known about how localised changes in aortic structure and biomechanics contribute to progression of chronic AD. To find a way to address this challenge, the nanoindentation technique and ball indentation tests were used to investigate localised mechanical properties and time-dependent deformation behaviour respectively, of human aortic tissue samples from chronic AD patients. Using ovine aortic tissue as a model, the utility of the nanoindentation technique and ball indentation methods were validated and optimised. The data were correlated with conventional uniaxial indentation testing. Further, the mechanical properties and biochemical composition (collagen, elastin and GAG) were correlated across the entire aortic length. The human tissue work characterised the biomechanics, biochemistry, and histology of the dissection flap (FP), true lumen outer wall (TL) and false lumen outer wall (FL) in chronic dissection. These micromechanical properties and biochemical properties were compared with clinical data (interval of index event to operation (IIEO) and aortic growth rate). The main outcome of this thesis was the demonstration of how structural properties of dissection tissues within the aortic wall alter with time. FP and TL are stiffer with the arrangement of elastin fibres being highly compact, long, and aligned, whereas the FL was more compliant with localised loss of elastic fibres and increased elastin fragmentation that correlated with IIEO. Overall, the findings of this thesis suggest that indications for surgery in chronic AD, which are currently based on aortic size, may be independent of features such as aetiology, aortic dimensions, and anatomical segment.

Item Type: Thesis (PhD)
Divisions: Faculty of Science and Engineering > School of Engineering
Depositing User: Symplectic Admin
Date Deposited: 14 May 2021 11:21
Last Modified: 18 Jan 2023 22:49
DOI: 10.17638/03121872
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3121872