Impact of transmural heterogeneities on arterial adaptation

Abstract

Recent experimental and computational studies have shown that transmurally heterogeneous material properties through the arterial wall are critical to understanding the heterogeneous expressions of constituent degrading molecules. Given that expression of such molecules is thought to be intimately linked to local magnitudes of stress, modelling the transmural stress distribution is critical to understanding arterial adaption during disease. The aim of this study was to develop an arterial growth and remodelling framework that can incorporate both transmurally heterogeneous constituent distributions and residual stresses, into a 3-D finite element model. As an illustrative example, we model the development of a fusiform aneurysm and investigate the effects of elastinous and collagenous heterogeneities on the stress distribution during evolution. It is observed that the adaptive processes of growth and remodelling exhibit transmural variations. For physiological heterogeneous constituent distributions, a stress peak appears in the media towards the intima, and a stress plateau occurs towards the adventitia. These features can be primarily attributed to the underlying heterogeneity of elastinous constituents. During arterial adaption, the collagen strain is regulated to remain in its homoeostatic level; consequently, the partial stress of collagen has less influence on the total stress than the elastin. However, following significant elastin degradation, collagen plays the dominant role for the transmural stress profile and a marked stress peak occurs towards the adventitia. We conclude that to improve our understanding of the arterial adaption and the aetiology of arterial disease, there is a need to: quantify transmural constituent distributions during histopathological examinations, understand and model the role of the evolving transmural stress distribution.

Modelling evolution and the evolving mechanical environment of saccular cerebral aneurysms

“…enlarging (and stabilising) cylindrical and spherical membranes (Watton et al 2009b), the evolution of saccular cerebral aneurysms of the internal carotid artery (Watton and Ventikos 2009) and integrated into a computational framework to couple the G&R of aneurysmal tissue to local haemodynamic stimuli (Watton et al 2009a). Schmid et al 2009 have implemented the G&R framework into a thick-walled FEM model of the arterial wall to explore the effect of transmural heterogeneties on the effects of G&R.…”

Anisotropic AAA: Computational comparison between four and two fiber family material models

“…In analogy to some previous works (Schmid et al, 2007(Schmid et al, , 2009, to measure the mesh convergence we considered the integral of the relative error made when computing maximum principal stresses with two sequential mesh refinements A and B:…”

Influence of Medial and Adventitial Layer on Arterial Adaptation

“…A previous study from our group [8] introduced a fully 3D FE model of arterial adaptation. This study considers substantially different properties of the media and adventitia and investigates the effects of varying adaptation rates in these layers on the overall geometry and the transmural stress distribution.…”

“…The values f g , f e and f i c are the amount of ground matrix, elastin and collagen, respectively, and a i represents the direction of the collagen fibres. The adaptation parameters are T, α, β and c min which are degradation time, remodelling rate constant, growth rate constant and amount of elastin after time T, respectively (see [8] for further details). The equations for remodeling and growth of collagen attempting to reach the collagen attachment strain E i a in addition to the elastin degradation equation are given as:…”