Disturbances of flow through transparent dog aortic arch.

The present study was carried out to determine the hydrodynamic structure of flow in an aortic arch and to correlate the findings with the possible involvement of fluid dynamics in atherogenesis and thrombogenesis. Each aorta was made transparent under a transmural pressure of 100 mmHg to maintain its in vivo configuration. Methyl salicylate with a kinematic viscosity of 2.6 cSt was substituted for blood and polystyrene microspheres, 0.08-0.30 mm in diameter, were used to trace the streamlines of the flow. Flow disturbances observed in the aortic arch have characteristics similar to those of secondary flow, which is called the horseshoe vortex, produced at Y- and T-junctions. The particles captured by the secondary flow near the flow divider, for instance, moved in a direction opposite or perpendicular to the mean flow. The vortex produced a typical stagnation region at the wall of the aorta just proximal to the branching site of the brachiocephalic and the left subclavian arteries. When the rate of flow to a daughter branch decreased, separation of the flow occurred at the proximal outer wall of the branch artery. Comparison between the present results and the topographical patterns of atherosclerosis reported in the literature suggests that it is in such low-shear regions that lipid deposition tends to occur most frequently.