Blood Flow Dynamics with Special Reference to Atherogenesis

Owing to the difficulties in analyzing the in vivo blood flow characteristics, a number of experimental studies on blood flow has been conducted using simplified models of arteries and arterial molds. Visualization of flow through transparent arterial models may be useful for understanding of disturbance in flow field expected in in vivo.Each aorta was made transparent under a transmural pressure of 100mmHg to ensure its in vivo configuration. Methyl salicyclate with kinematic viscosity of 2.6 centi Stokes was substituted for blood and polystyrene microspheres with diameters of 0.08-0.3mm were used to trace the streamlines of the flow.Flow disturbances observed in the aortic arch have characteristics similar to those of secondary flow, called the horseshoe vortex, produced at Y- and T-junctions. The particles captured by the swirling secondary flow near the flow divider, for instance, moved in a direction opposite or perpendicular to the main flow. A typical stagnant region, resulted from the generation of the vortex, appeared over the wall of the aorta just proximal to the branching site of the brachiocephalic and the left subclavian arteries. When the flow rate into the branching artery decreased, a separation of flow took place over the proximal outer wall of the artery.Comparison between the present results and topographical pattern of atherosclerosis reported in the literature suggests that it is in such low shear regions that lipid deposition tends to occur most.