Flow Patterns in the Dog Descending Aorta under a Steady Flow Condition Simulating Mid-Systole

Hemodynamic factors are suspected to be involved in the localized pathogenesis and development of atherosclerotic lesions in the human thoracico-abdominal aorta. Hence, we studied the detailed flow patterns and the distributions of fluid velocity and wall shear stress there under the condition of a steady flow using five transparent aortic trees prepared from dogs as models of the human descending aorta and by means of flow visualization and high-speed cinemicrographic techniques. It was found that in all the cases the flow in the descending aorta was not fully developed to the extent to provide a parabolic velocity profile. Flow was disturbed at each junction, and most complex secondary and adverse flows formed at the branching site of the left renal artery adjacent to the lateral and posterior walls of the descending aorta. Furthermore, there was considerable interaction between the secondary and adverse flows formed at the branching sites of the four major arteries that stemmed off the descending aorta.