Study of blood flow in large aneurysms at modeling different levels of physiological activity

Rupture of cerebral aneurysm can lead to intracranial hemorrhage and cause disability or death. One of the key factors affecting the dynamics of blood flow in vessels is changing in heart rate that occurs during physical activity. Such changes will significantly affect the flow velocity and flow pattern, which affects the condition of aneurysm. This article presents the results of numerical modeling of blood flow dynamics in large aneurysms during physical activity and relax. This study was made on four different geometries of cerebral vessels with aneurysms, obtained from angiography results of real patients, and four synthetic models during the same cardiac cycles. The changes of streamlines in aneurysms were analyzed, because this area is completely dependent on hemodynamic forces. The results show that maximum vortex area inside the aneurism increases with physical activity, which may indicate a high stress on the walls in this condition. Distributions of velocity, pressure fields, WSS (Wall Shear Stress) and OSI (Oscillatory Shear Index) were obtained for selected cases. During physical activity, vessel wall pressures in some cases increase by a factor of 4 with small changes in WSS. At the same time, the increase in WSS in the other model was not accompanied by a significant change in pressure. Analysis of the results allows to conclude that the aneurysm’s geometry plays a significant role in determining the flow pattern. It confirms the necessity to consider individual anatomical features of vessels. The results of the study indicate that not only hemodynamic parameters, but also the specificity of geometry contribute to the character of blood flow.