Pulsatile flow visualization in a model of the human abdominal aorta and aortic bifurcation.

The infrarenal abdominal aorta and aortic bifurcation are frequent sites of atherosclerosis. The local hemodynamics are considered to be atherogenetic factors; a detailed description of these flow fields is, therefore, essential to understand their relationship to atherosclerosis. The aim of this study was, therefore, to provide such detailed information using a flow visualization technique in an anatomically realistic flow model of the abdominal aorta and its main branches in which the complex pulsatile flow waveforms and flow rates were simulated for two physiologic flow conditions (rest and exercise). At rest, the particle path lines in the suprarenal abdominal aorta were straight with no visible signs of flow reversal. Vortices were initiated opposite to the main branches. In the infrarenal aorta, large flow separation zones formed at the posterior aortic wall and at the lateral walls in the aortic bifurcation during systolic deceleration, and flow reversal was present during diastole. Under exercise conditions, the particle path lines were straight, and only slight flow reversal was seen. This study emphasizes, that rather than being a straight tube with forward-moving fluid, the abdominal aorta has to be considered as a complex part of the arterial tree. Distinct local hemodynamic qualities of importance for explaining atherogenesis were pointed out. At rest, the suprarenal abdominal aorta had much less complicated flow characteristics than the infrarenal abdominal aorta where the distal, posterior vessel wall and the lateral walls of the bifurcation were sites of flow patterns thought to be associated with atherosclerosis. During exercise, the infrarenal flow patterns changed dramatically away from the flow patterns associated with the induction of atherosclerosis.