Toward a model for local drug delivery in abdominal aortic aneurysms

The formation of an abdominal aortic aneurysm (AAA) may eventually result in rupture, an event associated with a 50% mortality rate. This work represents a first step toward improving current stress estimation techniques and local transport simulations in AAA. Toward this aim, a computational parametric studywas performed on an axisymmetric cylindrical FEM of a 5 cm AAA with a 1.5 cm thick intraluminal thrombus (ILT). Both the AAA wall and ILT were modeled as porohyperelastic PHE materials using estimated values of AAA wall and ILT permeability. While no values for AAA wall permeability could be found in the literature, the value of ILT permeability was taken from a previous investigation by Adolph et al.⁷ Peak stresses, fluid velocities, and local pore pressure values within the ILT and wall were recorded and analyzed as a function of the cardiac cycle. While peak wall stress values for the PHE models did not largely differ from corresponding solid finite element simulations (186.2 N/cm² vs. 186.5 N/cm²), the stress in the abluminal region of the ILT increased by 17.4% (7.7 N/cm² vs. 6.5 N/cm²). Pore pressure values were relatively constant through the ILT while there were significant pore pressure gradients present in the AAA wall. The magnitude of fluid velocities varied in magnitude and direction throughout the cardiac cycle with large fluctuations occurring on the luminal surface. The combination of the patient-specific PHE AAA FEMs with mass transport simulations will result in spatially and time-varying concentration distributions within AAA, which may benefit future pharmaceutical treatments of AAA.