Effects of hematocrit levels on flow structures and stress levels in the healthy and diseased carotid arteries

Flow structures and wall shear stress (WSS) distribution in human arteries depend strongly on blood rheology. Blood viscosity undergoes significant alterations due to varying hematocrit (Hct) levels. Hematocrit levels can change from the normal level (45%) due to numerous disorders such as leukemia, lymphoma, and congenital heart disease. However, the effects of Hct levels on the flow features and WSS levels in large stenotic arteries are not well reported in literature. The present study computationally assesses the variation in flow features in healthy and stenosed carotid arteries due to changes in blood Hct levels. We have reported variations in axial and secondary flow characteristics, vortex structures, and WSS-based parameters for different Hct levels. Specifically, we consider high (65%) and low (25%) Hct levels in addition to a normal Hct level. Our results reveal that both high and low Hct levels have adverse effects on the hemodynamic features inside a healthy carotid artery model. The low Hct level displays a much more widespread low time-averaged WSS (TAWSS) area, while the high Hct shows an increased oscillatory shear index (OSI) zone at the carotid sinus wall. In stenotic arteries, low Hct enhances the spread of the low TAWSS zone in the post-stenotic carotid sinus, whereas high Hct increases the risk of plaque rupture. The high Hct level also increases the spread of high OSI zone at the inner wall of internal carotid artery for the moderately stenosed artery.