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

Oscillations in near-wall velocity direction have been found to correl ate with atherosclerotic plaque localization in the carotid sinus bifu rcation. However, it remains unproven whether these conditions could a ccount for the localization of the disease at other sites where athero sclerosis forms. The abdominal aorta is an important site of clinical disease in a relatively straight segment of artery. This study was ini tiated to quantify the velocity field in the abdominal aorta in order to determine if local differences in hemodynamic velocity directions c ould account for the localization of disease in this segment. Magnetic Resonance Imaging velocimetry was used to measure the pulsatile veloc ity profiles in an anatomically accurate in vitro model of the abdomin al aorta. Velocities measured in the suprarenal aorta were laminar and reversed minimally, comparing well with theoretical solutions of Wome rsley flow (r=0.96). The time-averaged velocity was +3.0 cm/s near-wal l at a distance of 1 mm away from the wall. In the infrarenal aorta, t he maximal velocities were skewed toward the anterior wall. At the pos terior wall, velocity oscillated in direction and was retrograde for 8 2 percent of the cardiac cycle. The time-averaged velocity near the po sterior wall was - 12.5 cm/s as compared to +3.00 cm/s near the anteri or wall. At the aortic bifurcation, the locations of maximal and minim al velocities in this slice were concentrated near the lateral posteri or walls. This study quantifies the magnitude of low and oscillatory v elocity that may exist in the abdominal aorta and suggests that there is a strong relationship between the velocities in the retrograde dire ction under resting conditions and the distribution of atherosclerotic plaque.