PULSATILE VELOCITY-MEASUREMENTS IN A MODEL OF THE HUMAN ABDOMINAL-AORTA UNDER RESTING CONDITIONS

Oscillations in near-wall velocity direction have been found to correlate with atherosclerotic plaque localization in the carotid sinus bifurcation. However, it remains unproven whether these conditions could account for the localization of the disease at other sites where atherosclerosis forms. The abdominal aorta is an important site of clinical disease in a relatively straight segment of artery. This study was initiated to quantify the velocity field in the abdominal aorta in order to determine if local differences in hemodynamic velocity directions could account for the localization of disease in this segment. Magnetic Resonance Imaging velocimetry was used to measure the pulsatile velocity profiles in an anatomically accurate in vitro model of the abdominal aorta. Velocities measured in the suprarenal aorta were laminar and reversed minimally, comparing well with theoretical solutions of Womersley flow (r=0.96). The time-averaged velocity was +3.0 cm/s near-wall at a distance of 1 mm away from the wall. In the infrarenal aorta, the maximal velocities were skewed toward the anterior wall. At the posterior wall, velocity oscillated in direction and was retrograde for 82 percent of the cardiac cycle. The time-averaged velocity near the posterior wall was - 12.5 cm/s as compared to +3.00 cm/s near the anterior wall. At the aortic bifurcation, the locations of maximal and minimal velocities in this slice were concentrated near the lateral posterior walls. This study quantifies the magnitude of low and oscillatory velocity that may exist in the abdominal aorta and suggests that there is a strong relationship between the velocities in the retrograde direction under resting conditions and the distribution of atherosclerotic plaque.