Flow patterns and preferred sites of atherosclerotic lesions in the human aorta - II. Abdominal aorta.

OBJECTIVE As in Part I, to elucidate the role of fluid mechanical factors in the localized genesis and development of atherosclerotic lesions in man, here in the abdominal aorta. METHODS Flow patterns and preferred sites of atherosclerotic lesions in the aorta were studied in detail using the same isolated transparent aortic trees prepared from humans postmortem and the flow visualization and cinemicrographic techniques as in Part I. RESULTS Under steady flow simulating mid-systole, the flow was found to be disturbed at the aorto-celiac and aorto-superior mesenteric artery junctions by the formation of complex secondary and adverse flows along the lateral and posterior walls of the abdominal aorta. More complex secondary and adverse flows formed at the branching sites of the left and right renal arteries. Furthermore, considerable interactions occurred between the secondary and adverse flows formed at the branching sites of the above four arteries, resulting in the formation of a large and long recirculation zone along the lateral and posterior walls of the abdominal aorta corresponding to these branches. The velocity profile was almost flattened throughout the entire length of the descending aorta. CONCLUSIONS Atherosclerotic lesions were found mainly at the posterior and lateral walls of the abdominal aorta where slow adverse and recirculation flows formed and where wall shear stress was low.