Numerical study of hemodynamic and diagnostic parameters affected by stenosis in bifurcated artery

Numerical assessment of using various outlet boundary conditions on the hemodynamics of an idealized left coronary artery model

Vascular diseases are greatly influenced by the hemodynamic parameters and the accuracy of determining these parameters depends on the use of correct boundary conditions. The present work carries out a two-way fluid-structure interaction (FSI) simulation to investigate the effects of outlet pressure boundary conditions on the hemodynamics through the left coronary artery bifurcation with moderate stenosis (50%) in the left anterior descending (LAD) branch. The Carreau viscosity model is employed to characterise the shear-thinning behaviour of blood. The results of the study reveal that the employment of zero pressure at the outlet boundaries significantly overestimates the values of hemodynamic variables like wall shear stress (WSS), and time-averaged wall shear stress (TAWSS) compared with human healthy and pulsatile pressure outlet conditions. However, the difference between these variables is marginally low for human healthy and pulsatile pressure outlets. The oscillatory shear index (OSI) remains the same across all scenarios, indicating independence from the outlet boundary condition. Furthermore, the magnitude of negative axial velocity and pressure drop across the plaque are found to be higher at the zero pressure outlet boundary condition.

Numerical computation of pulsatile hemodynamics and diagnostic concern of coronary bifurcated artery flow for Newtonian and non-Newtonian fluid

Atherosclerotic with the high occurrence of plaque formation due to stenosis has attracted wide attention among researchers. The left coronary artery has been studied in two-dimensional and in three-dimensional (3D) bifurcation as the models of blood flow through Newtonian and non-Newtonian fluids to better understand the physical mechanism. The computational Fluid Dynamics (CFD) technique is incorporated in COMSOL Multiphysics and then it is justified by satisfactory validation. It is found that the Newtonian model shows larger recirculation zones than non-Newtonian does. The present study also focuses on the evaluations of the lesion of diagnostic and the coefficient of pressure drop assessments on the basis of the diagnostic parameter's critical values affected by the rheological model. Nevertheless, the leading concentration of the subsisting investigation works is confined to the change of importance factor (IFc) affected by arterial blockage. But the IFc of non-Newtonian fluid for 3D left coronary artery bifurcation model decreases with increasing bifurcation angle and the time-averaged inlet pressure is the least for smaller bifurcation angles. The current research further concentrates that the flow separation length reduces with developing bifurcation angle in bifurcated geometry. It is significant to mention that non-Newtonian blood flow model incorporating hemodynamic and diagnostic parameters has great impacts on instantaneous flow systems.

Role of the left coronary artery geometry configuration in atherosusceptibility: CFD simulations considering sPTT model for blood

The achievement of clinically viable methodologies to simulate the hemodynamics in patient-specific coronary arteries is still a major challenge. Therefore, the novelty of this work is attained by the introduction of the viscoelastic property of blood in the numerical simulations, to study the role of the left coronary artery (LCA) geometry configuration in the atherosusceptibility. Apparently healthy patients were used and four different methodologies were tested. The methodology giving the most accurate results at the same time of having the lowest computational time is the one considering the viscoelastic property of blood and computational fluid dynamics. A Pearson correlation analysis was used to highlight relationships between geometric configuration and hemodynamic descriptors based on the simulated wall shear stress (WSS). The left main stem (LMS) has the greatest atherosusceptibility followed by the left anterior descending artery (LAD) since the relative residence time (RRT) average values are 3.81 and 3.70 Pa^-1, respectively. The geometric parameters with relevant contribution to directional flow change are the cross-sectional areas, especially the one of LMS segment (A_LMS), and the curvature of LMS segment. For LMS and LAD segments, when A_LMS increases, blood flow disturbance (r = 0.81 in LMS and r = 0.74 in LAD) and atherosusceptibility (r = 0.84 in LMS and r = 0.85 in LAD) increases. When the LMS curvature decreases, the WSS magnitude (r = 0.80 in LMS and r = 0.83 in LAD) decreases, and disturbance (r=-0.80 in LMS and r=-0.91 in LAD) and atherosusceptibility (r=-0.74 in LMS and r=-0.74 in LAD) increases.