Hemodynamic Alterations Associated with Coronary and Cerebral Arterial Remodeling Following a Surgically-Induced Aortic Coarctation - Computer Models in Biomechanics - page 194

back to normal values) and spatially (from proximal to distal sites), see Hayenga
( 2010 ).
Although additional experimental data will be needed to understand better
these spatio-temporal adaptations, computational fluid-solid-growth (FSG) models
(Figueroa et al., 2009 ) offer considerable promise both in the design and interpreta-
tion of such experiments and in implicating possible biomechanical mechanisms.
Building on recent advances in computational modeling (Figueroa et al., 2006 ;
Vignon-Clementel et al., 2006 ; Kim et al., 2009a , b ; Moireau et al., 2012 ), the goal
of this work was to simulate possible effects of a surgically created coarctation in
the descending thoracic aorta on the hemodynamics within the proximal aorta and
the coronary, carotid, and cerebral arteries following both an acute cardiac compen-
sation (i.e., maintenance of cardiac output) and early arterial wall remodeling (i.e.,
spatially varying wall thickening and stiffening).
15.2 Methods
15.2.1 Model Geometry
15.2.1.1 Baseline Model
Computed tomographic (CT) images were collected from two adult male human
subjects free of cardiovascular disease to collectively encompass all major arteries
from the brain to the diaphragm. Separate 3D geometric models were constructed
from the CT datasets using custom software based on a 2D vessel segmentation
procedure, see Fig. 15.1 . A finite element mesh was created by discretizing the 3D
model coarsely, running a steady-state flow simulation, and then performing field-
based adaptive mesh refinement (Sahni et al., 2006 ). The final finite element mesh
consisted of 2,462,487 linear tetrahedral elements and 477,872 nodes.
15.2.1.2 Coarctation Model
A thoracic aortic coarctation was modeled by introducing a 75 % diameter narrow-
ing in the aorta just above the diaphragm, consistent with both the location and the
degree of a surgically induced coarctation in mini-pigs in studies that provide in-
formation on temporal and spatial changes in arterial wall composition (Hu et al.,
2008 ; Hayenga, 2010 ).
15.2.2 Numerical Methods
Equations enforcing balance of mass and linear momentum (Navier-Stokes) were
solved for the flow of an incompressible Newtonian fluid within a deformable do-
main using a stabilized finite element formulation implemented in the open-source