Computational and mathematical models to assess early stages Abdominal Aortic Aneurysm (AAA) growth

Cardiovascular diseases such as Abdominal Aortic Aneurysm (AAA) can be effectively modelled for biomechanical studies using computational and mathematical tools enabling development of non-invasive algorithms for disease diagnoses. AAA is usually infrarenal and occurs when the abdominal aorta balloons abnormally, wherein a major expansion (at least one and half times the diameter of healthy aorta) to the lumen diameter leads to a decrease in blood supply to key organs and limbs, as well as the possibility of artery rupture. A realistic abdominal aorta for a patient showing the potential for AAA growth is investigated using ANSYS®2021 R1 Fluent after converting 2D MRI images (segments) to a 3D model considering the abdominal aorta and the iliac bifurcation. The 3D model is analysed using clinical boundary conditions presented as the blood waveform at the inlet of the aorta and the pressure waveforms at the outlet of the iliac bifurcation using Two-Way Fluid-Structure Interaction (FSI) methods. In this study, the wall shear stress (WSS) and circumferential strain (CS) are investigated at four different times: 0.15s when the aortic valve opens; 0.35s at the systolic pressure; 0.45s when the aortic valve closes; and 0.85s at diastolic pressure based on the propagated waveforms. The abdominal aorta is examined using Non-Newtonian Carreau-Yasuda blood flow properties for specific patient data. The phase angle (PA) between WSS and CS shows the effect of early-stage abdominal aorta geometry growth rate due to the risk of aneurysm growth, on wave propagations with a range 200° to −180°.