Influence of Abdominal Aortic Curvature and Resting Versus Exercise Conditions on Velocity Fields in the Normal Abdominal Aortic Bifurcation

Local hemodynamics are considered an important atherogenetic factor in the abdominal aortic bifurcation. This study addresses the quantitative flow fields in a pulsatile flow model of a normal abdominal aortic bifurcation when encountering realistic upstream anatomy, realistic inlet flow conditions and different physiologic flow conditions (rest vs. exercise). Two-dimensional laser Doppler anemometry measurements gave axial as well as radial velocities. The localization and magnitude of peak velocities, retrograde flow and secondary velocity patterns were found to be determined to a great extent by the curvature of the abdominal aorta, the triphasic flow wave form and the inlet velocity profile. Significant changes were also seen when simulating different physiologic flow conditions. Thus retrograde velocities were present at both the flow divider and the lateral vessel wall for the rest condition but not for the exercise flow conditions, and the location of low and retrograde velocities during diastole were as much determined by abdominal aortic curvature as by the bifurcation for nearly all flow conditions and locations. In conclusion, the anatomy and hemodynamics in the abdominal aorta cannot be neglected when studying the hemodynamics in the abdominal aortic bifurcation.