Multi-scale modelling of vascular disease: abdominal aortic aneurysm evolution

We present a fluid-solid-growth (FSG) computational framework to simulate the mechanobiology of the arterial wall. The model utilises a realistic constitutive model that accounts for the structural arrangement of collagen fibres in the medial and adventitial layers, the natural reference configurations in which the collagen fibres are recruited to load bearing and the (normalised) mass-density of the elastinous and collagenous constituents. Growth and remodelling (G&R) of constituents is explicitly linked to mechanical stimuli: computational fluid dynamic analysis produces snapshots of the frictional forces acting on the endothelial cells; a quasi-static structural analysis is employed to quantify the cyclic deformation of the vascular cells. We apply the computational framework to simulate the evolution of a specific vascular pathology: abdominal aortic aneurysm (AAA). Two illustrative models of AAA evolution are presented. Firstly, the degradation of elastin (that is observed to accompany AAA evolution) is prescribed, and secondly, it is linked to low levels of wall shear stress (WSS). In the first example, we predict the development of tortuosity that accompanies AAA enlargement, whilst in the latter, we illustrate that linking elastin degradation to low WSS leads to enlarging fusiform AAAs. We conclude that this computational framework provides the basis for further investigating and elucidating the aetiology of AAA and other vascular diseases. Moreover, it has immediate application to tissue engineering, e.g., aiding the design and optimisation of tissue engineered vascular constructs.