Numerical investigation of the hemodynamic effects of thrombus accumulation and effort conditions on abdominal aortic aneurysm

Abdominal aortic aneurysm is a significant health problem caused by the enlargement of the abdominal artery. If this disease is untreated, the aneurysm continues to grow and carries the risk of rupture. A potential aneurysm rupture can lead to severe blood loss and may result in death. Therefore, it is critically important to diagnose abdominal aneurysms at an early stage and to predict possible rupture risks. Generally, aneurysms with a diameter over 5 cm are considered risky. However, there are aneurysms with a diameter larger than 5 cm that do not rupture over a lifetime. On the other hand, there are abdominal aneurysms with a relatively small diameter of around 3 cm that do rupture. This indicates that using only the diameter value to identify risky cases is insufficient. Therefore, it is necessary to examine the hemodynamic variables inside the aneurysm and the structural parameters of the vessel wall in detail and in a patient-specific manner. In this study, hemodynamic and fluid-structure interaction analyses are performed using a real aneurysm geometry to determine the risk of aneurysm rupture. In the analyses, parameters such as thrombus volume, thrombus stiffness, and variability of effort conditions are considered. Regarding the thrombus volume, cases with no thrombus, low thrombus, medium thrombus, and high thrombus levels are considered. Regarding the thrombus stiffness, soft, normal, and stiff thrombus cases are considered. Regarding the effort conditions, low effort at rest, normal effort, and high effort during exercise are considered. To assess the risk of rupture, the maximum stress values occurring in the vessel wall are determined through fluid structure interaction analyses. As the stress values on the vessel increase, the risk of aneurysm rupture also increases. According to the results obtained, it is observed that increased thrombus accumulation and hardening of the thrombus reduced the stress levels in the vessel wall and thus decreased the risk of rupture. With the increase in effort conditions, the stresses on the vessel wall are partially increased. However, the effect of effort conditions is limited compared to the effect of thrombus accumulation. The regions where the risk of rupture is highest are identified as the region with the greatest enlargement in the aneurysm and the region where the aorta joins with the aneurysm. The results of the study revealed the hemodynamic changes occurring in the abdominal aortic aneurysm and highlighted the parameters that are critically important for the rupture risk.