Investigation of hemodynamic response of the aneurysmal wall in an abdominal aortic aneurysms to di̇fferent hematocrit level by using computati̇onal fluid dynamics

The focal enlargement of the abdominal aorta is called abdominal aortic aneurysm (AAA), which is permanent, and abnormal dilatation. As its prevalence increases with age, approximately 150,000 new cases appear per year. The rupture of an AAA is the most feared and life-threatening complication, and also, inceases the risk of mortality up to 60-90%. Identification of hemodynamic insults eventually resulting in an AAA formation which are also associated with risk of rupture, are crucially important to manage the treatment method. Therefore, the computational fluid dynamics (CFD) to determine hemodynamic changes inside the aneurysm have been the focus of scientific researches recently. The aim of this study was to determine changes in fluid hemodynamics within the aneurysm of abdominal aorta caused by 3 different hematocrit levels (20%, 40% and 60%). We analyzed 2 healthy abdominal aorta and 6 patients with AAA derived from Gaziantep University Faculty of Medicine database. The 2D- Computed tomographic angiography images (CTA) were converted to 3D-model by using HOROS v3.3.5 (https://horosproject.org/) software and Meshlab (http://www.meshlab.org/). The 3D-models were entered to ANSYS® FLUENT program for evaluation of CFD parameters. We accepted the aneurysmal wall as a rigid structure while considering the blood as pulsatile and non-Newtonian fluid. The results of this study revealed that turbulence in a aneurysm inevitably occurs and its severity increases with an increase in hematocrit level. Moreover, areas representing low wall shear stress were always seen in the aneurysmal lumen and they widened with increasing hematocrit level. On the other hand, the width of the areas representing high-pressure points was inversely related to increasing hematocrit level. We suggest that non- invasive assessment of the hemodynamic risks related to rupture would help the physician to have accurate patient-specific precautions in every AAA case.