Non-axisymmetric dilatation of a thick-walled aortic aneurysmal tissue

The objective of this paper is to use the constrained mixture theory of growth and remodeling to simulate the non-axisymmetric dilatation of a thick-walled aortic aneurysmal tissue. The primary load carrying constituents of the vascular tissue are elastin and collagen and the contribution of smooth muscle cells is secondary and therefore not included. In the homeostatic state a blood vessel is in a mechanobiologically stable regime. Hence, a loss of wall material is compensated by production of new material without a significant dilatation of the artery. Using the theory we find that a local degradation of the matrix material produces a mechanobiologically unstable regime that causes aneurysm formation. It induces an increase of mass locally achieved via production of new material that exceeds the removal of old material. The combined effects of loss of elastin, degradation of existing and deposition of new collagen as well as remodeling results in a continuous enlargement of the aneurysm bulge. Numerical results are included to verify and validate the theory.