Analysis of Aortic Arch Hemodynamics With Simulated Bird's Beak Effects.

OBJECTIVE: The objective of this study was to investigate the flow effects in different degrees of thoracic aortic stent graft protrusion extension by creating bird beak effect simulations using accurate 3D geometry and a realistic, nonlinear, elastic biomechanical model using computer-aided software SolidWorks. METHODS: Segmentation in 3D of an aortic arch from a computed tomography (CT) scan of a real-life patient was performed using SolidWorks. A parametric analysis of three models was performed: (A) Aortic arch with no stent, (B) 3 mm bird-beak configuration, and (C) 6.5 mm bird-beak configuration. Flow velocity, pressure, vorticity, wall shear stress (WSS), and time average WSS were assessed. RESULTS: The flow velocity in Model A remained relatively constant and low in the area of the ostium of the brachiocephalic artery and doubled in the left subclavian artery. On the contrary, Models B and C showed a decrease in velocity of 52.3 % in the left subclavian artery. Furthermore, Model B showed a drop in velocity of 82.7% below the bird-beak area, whereas Model C showed a decline of 80.9% in this area. The pressure inside the supra-aortic branches was higher in Model B and C compared with Model A. In Model A, vorticity only appeared at the level of the descending aorta, with low to non-vorticity in the aortic arch. In contrast, Models B and C had an average vorticity of 241.4 Hz within the bird beak area. Regarding WSS, Model A, and Model B shared similar WSS in the peak systolic phase, in the aortic arch, and the bird beak area, whereas Model C had an increased WSS by 5 Pa on average at these zones. CONCLUSION: In the present simulations' lower velocities, higher pressures, vortices, and WSS were observed around the bird beak zone, the aortic arch, and the supra-aortic vessels.

Biomechanical Profiling in Real-Life Abdominal Aortic Aneurysms in Different Clinical Scenarios.

BACKGROUND: The aim of this study was to demonstrate the biomechanical properties in different abdominal aortic aneurysm (AAA) presentations of real-life patients. We used the actual 3D geometry of the AAAs under analysis and a realistic, nonlinearly elastic biomechanical model. MATERIALS AND METHODS: Three patients with different clinical scenarios (R: rupture, S: symptomatic, and A: asymptomatic) with infrarenal aortic aneurysms were studied. Factors affecting aneurysm behavior such as morphology, wall shear stress (WSS), pressure, and velocities were studied and analyzed using steady state computer fluid dynamics using SolidWorks (Dassault Systems SolidWorksCorp., Waltham, Massachusetts). RESULTS: When analyzing the WSS, Patient R and Patient A had a decrease in the pressure in the bottom-back region compared with the body of the aneurysm. In contrast, WSS values appeared to be the most uniform across the entire aneurysm in Patient S. Furthermore, Patient A had focal small surface regions with high WSS values. The overall WSS in the unruptured aneurysms (Patient S and Patient A) were a lot higher than in the ruptured 1 (Patient R). All 3 patients showed a pressure gradient, being high at the top and low at the bottom. All patients had pressure values 20 times smaller in the iliac arteries compared with the neck of the aneurysm. The overall maximum pressure was similar between Patient R and Patient A, higher than the maximum pressure of Patient S. CONCLUSIONS: Computed fluid dynamics was implemented in anatomically accurate models of AAAs in different clinical scenarios for obtaining a broader understanding of the biomechanical properties that determine the behavior of AAA. Further analysis and the inclusion of new metrics and technological tools are needed to accurately determine the key factors that will compromise the integrity of the patient's aneurysms anatomy.