Abstract

Anatomically the aorta is divided in several parts, depending on the zone of the body that the vessel covers. The aorta is first called thoracic aorta as it leaves the heart, ascends, arches, and descends through the chest until it reaches the diaphragm when takes the name of abdominal aorta and continues down the abdomen. The abdominal aorta ends where it splits to form the two iliac arteries that go to the legs. Aorta is subject of aneurysm and it can develop anywhere along the length of the aorta.

The majority, however, are located along the abdominal zone. Most (about 90%) of abdominal aneurysms (AAA) are located below the level of the renal arteries, the vessels that leave the aorta to go to the kidneys. About two‐thirds of abdominal aneurysms are not limited to just the aorta but extend from the aorta into one or both of the iliac arteries. Normally aortic aneurysms take a fusiform shape. Nowadays, it is recognized that current clinical criteria for assessment of the abdominal aortic aneurysm rupture risk can be considered insufficient because they have not a physically theoretical basis [1], despite they are based on a wide empirical evidence. Hence, in last many years, researchers and physicians have had the challenge to identify a more reliable criterion associated with the actual rupture risk of the patient‐specific aneurysm. The literature begins to reflect the existence of a consensus that, rather than empirical criteria, the biomechanical approach, based on the material failure, could facilitate a better method to assess the AAA rupture risk. One of these AAA rupture criteria are based on the evaluation of the hemodynamic stresses inside the AAA.

To estimate the AAA rupture risk, from biomechanical point of view (material failure), an aneurysm ruptures when the stresses acting on the arterial wall exceed its failure strength.

According to the Laplace's law, the wall stress on an ideal cylinder is directly proportional to its radius and intraluminal pressure.  Even though, the AAA is not ideal cylinder, Laplace's law said that with a large diameter, the internal pressure increases, and therefore increases the risk of rupture. Due to the increasing of the internal pressure, against the aortic walls, the AAA diameter grows progressively, and eventually, it could be able to overcome the resistance of the aortic wall with its breakup. In turn, further increase of the AAA diameters produces internal flow recirculation producing ILT formation in the AAA sac. This phenomenon provokes AAA stabilization and starting a vicious circle inside the AAA. It is well documented [1], that the aneurysm shape has a strong influence on flow patterns and consequently on wall stress distribution (peak values and locations). It is reflected by the interaction between the arterial wall structural remodeling and the forces generated by blood flow within the AAA. Therefore, the AAA morphology has a significant influence in its potential rupture.

The study is focused on the behavior of the blood fluid, inside the aneurism and how this illness will change the normal path of the fluid. Vortices and abnormal fluid paths will affect the normal and physiological pressure field and also produce alterations in the Wall Shear Stress (WSS) on the vessel walls.

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