The Influence of the Torsion Motion of Left Ventricle (Lv) on Features of Blood Flow

The torsional motion (or twisting) of the left ventricle (LV) plays a crucial role in the ejection and filling of the left ventricle. During the cardiac cycle,systolic twisting and early diastolic untwisting of the left ventricle occurs around its long axis due to oppositely directed apical and basal rotations.From the apex of the LV, the systolic apical rotation occurs counterclockwise, while the basal rotation occurs clockwise. The size and characteristicsof this torsional deformation have been described in various clinical and experimental studies, and it is well established that LV rotation is sensitive tochanges in both regional and global LV function. Therefore, the assessment of LV rotation represents an interesting approach for the quantitativeevaluation of LV function. Understanding blood flow patterns in the heart has numerous applications in hemodynamic analysis and clinical assessmentof heart function. This study presents numerical simulations of blood flow in an idealized model of the left ventricle (LV) and the aortic sinus. Themovement of the walls of the LV and aortic sinus was obtained from the analysis of kinematic images from MRI and used as constraints for the numericalcomputational fluid dynamics (CFD) model based on the moving boundary approach. The simulation results include detailed flow characteristicssuch as velocity, pressure, and wall shear stress for the entire volume. Additionally, to model the behavior of fluid flow within the human left ventricle,it is essential to consider the influence of non-Newtonian behavior of blood on numerical predictions throughout the entire cardiac cycle. Experimentalstudies indicate that blood significantly exhibits behavior associated with non-Newtonian properties in diseases such as myocardial infarction,cerebrovascular diseases, and hypertension; thus, the rheology of blood should be incorporated into numerical modeling of cardiovascular systems.Furthermore, due to recent advancements in CFD modeling, it has become easier to implement complex non-Newtonian assumptions into theNavier-Stokes equations. This article analyzes the impact of the torsional motion of the walls of the human left ventricle on the characteristics of bloodcirculation in the LV chamber and the initial section of the aorta. Non-Newtonian effects were considered using the Carreau-Yasuda model. Thismodel describes blood as a non-Newtonian fluid with finite Newtonian states corresponding to a constant viscosity value. It is important to note thatthis model representation aligns well with experimental data.