Key result
Fluid-structure interaction analysis of an endovascular implanted graft in an abdominal aortic aneurysm revealed that maximum sac wall deformation was approximately 2.1 mm and peak wall stress occurred at the graft neck.
Fluid-structure interaction modeling demonstrates that endovascular graft neck curvature and iliac bifurcation geometry significantly influence wall shear stress and sac deformation, contributing to endotension and potential graft migration.
No immediate clinical implications for EVAR; leaves open validation of FSI models for endotension risk.
Endovascular aneurysm repair is a new and minimally invasive repair for patients with abdominal aortic aneurysm (AAA). However, endotension is one of the post-operative compliances of endo-vascular aneurysm repair in abdominal aortic aneurysm. Typically, endotension is mainly a result of pressure transmitted to the aneurysm sac through endovascular implanted graft (EVG) by intermediary of the stagnant blood filled aneurysm cavity. Focusing on a representative AAA with an EVG, a fluid-structure interaction (FSI) solver has been employed to provide physical insight for evaluating the blood flow dynamics, maximum AAA-stresses and deformations. Although implanting an EVG can reduce the sac pressure, mechanical stress and wall deformation in AAAs significantly, they remain non-zero. These magnitudes depend on multi-factors including blood flow conditions such as velocity and pressure, as well as EVG and aneurysm geometries. In this study, it was found that blood flow velocity deceleration occurs on the graft due to the curvature of its neck, so greater curvature of the graft neck can contribute to vortex formation in this area and exert load on the graft wall. In the iliac bifurcation region, divaricating of the flow leads to a large net flow momentum change. It results in additional stress on the implant graft and may lead to graft migration. One of the peak wall stress points is in the neck region where the stent-graft is in contact with the aneurysm wall. This necessitates considering adequate graft fixation to withstand the stresses of blood flow through the implanted graft. Also, maximum deformation of sac wall occurs in around the large diameter of the sac, and deformation during the systole phase is higher than that during the diastole phase.
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Hooshyar et al. (2014) studied Abdominal Aortic Aneurysm (n=1). Endovascular implanted graft (EVG) simulation was evaluated on Wall shear stress and sac wall deformation. Fluid-structure interaction analysis of an endovascular implanted graft in an abdominal aortic aneurysm revealed that maximum sac wall deformation was approximately 2.1 mm and peak wall stress occurred at the graft neck.
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