Abstract
Focusing on a representative abdominal aortic aneurysm (AAA) with
a bifurcating stent-graft (SG), a fluid-structure interaction (FSI)
solver with user-supplied programs has been employed to solve for
blood flow, AAA/SG deformation, sac pressure and wall stresses, as
well as the downward forces acting on the SG. Simulation results
indicate that implanting a SG can significantly reduce sac pressure,
mechanical stress, pulsatile wall motion, and maximum diameter change
in AAAs; hence, it may restore normal blood flow and prevent AAA
rupture effectively. The transient SG drag force is similar in trend
as the cardiac pressure. Its magnitude depends on multi-factors including
blood flow conditions, as well as SG and aneurysm geometries. Specifically,
AAA neck angle, iliac bifurcation angle, neck aorta-to-iliac diameter
ratio, SG size, and blood waveform play important roles in generating
a fluid flow force potentially leading to SG migration. It was found
that the drag force can exceed 5 N for an AAA with a large neck or
iliac angle, wide aortic neck and narrow iliac arteries, large SG
size, and/or abnormal blood waveform. Thus, the fixation of self-expandable
or balloon-expandable SG contact may be inadequate to withstand the
forces of blood flowing through the implant and hence means of extra
fixation should be considered. A comprehensive FSI analysis of the
coupled SG-AAA dynamics provides physical insight for evaluating
the luminal hemodynamics, and maximum AAA-stresses as well as biomechanical
factors leading potentially to SG migration. (c) 2005 Elsevier Ltd.
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