Computational analysis of oxygen transport in a patient-specific model of abdominal aortic aneurysm with intraluminal thrombus

Abdominal aortic aneurysm (AAA) is a degenerative disease in which the afflicted person suffers from a localised dilatation of the abdominal aorta. Intraluminal thrombus (ILT), which is present in approximately 75% of all AAAs, plays an important role in the progression of the disease. It has been suggested that ILT may attenuate oxygen diffusion to the aortic wall, resulting in further degeneration and weakening of the wall. Previous numerical studies using idealised AAA models have shown the effect of ILT thickness on oxygen diffusion, but patient-specific studies of oxygen transport incorporating convection, diffusion and reaction from the lumen to AAA wall are lacking. In the present study, a coupled fluid-thrombus-wall model was developed to simulate oxygen transport in a patient-specific AAA containing ILT. Blood flow in the lumen was governed by the Navier-Stokes equations and oxygen transfer was described by the convection-diffusion equation in the lumen, diffusion equation in the thrombus, and diffusion-reaction equation in the wall. A parametric study was performed to evaluate the sensitivity of numerical predictions to oxygen diffusivity in ILT and adventitial oxygen concentration. The results not only provide further support to previous findings that the presence of ILT may significantly impair oxygen transfer from blood to the aortic wall, but also demonstrate that adventitial oxygen concentration has a profound effect on oxygen concentration in the wall, and that the oxygen supply from the lumen to the wall can be reduced by 80% if the ILT thickness is greater than 5 mm.