  Progressive aneurysmal dilatation is a well-recognized complication in
patients with chronic type B aortic dissection (cTBAD), which may lead to a
delayed rupture and create a life-threatening condition. However, our
understanding of such aortic expansion in cTBAD remains weak. In the present
paper, we propose to use numerical simulations to study the role of growth and
remodeling (G\&R) in aneurysmal dilatation after cTBAD. We set up a 3D
finite-element model of G\&R for aortic dissection within an open-source code.
Constitutive equations, momentum balance equations, and equations related to
the mechanobiology of the artery were formulated based on the homogenized
constrained mixture theory. The model was first applied to idealized aortic
geometries with cylindrical and toric shapes to demonstrate its feasibility and
efficiency. The model was then applied to a patient-specific aortic segment to
show its potential in more relevant and complex patient-specific clinical
applications. It was found that the G\&R tends to naturally trigger the
aneurysmal dilatation after dissection, in order to restore its tensional
equilibrium. Our results indicated that the value of the gain parameter,
related to collagen G\&R, plays an important role in the stability of aortic
expansion after cTBAD. A small gain parameter will induce an excessive
aneurysmal degeneration whilst a large gain parameter helps to recover a
stabilized state of the artery after dissection. Finally, it was found that
other mechanobiology-related parameters, such as the circumferential length of
the dissection, as well as the pressure in the false lumen, may also be
determinant for the stability of aneurysmal dilatation after cTBAD. Both a wide
tear and an elevated false lumen pressure favor an unstable development of
aortic expansion after cTBAD. As future work, the present model will be
validated through predictions of aneurysmal dilatation in patient-specific
clinical cases, in comparison with datasets followed over a significant period
of time.
