PULSATILE VELOCITY-MEASUREMENTS IN A MODEL OF THE HUMAN ABDOMINAL-AORTA UNDER SIMULATED EXERCISE AND POSTPRANDIAL CONDITIONS

This study examines the hemodynamics of the abdominal aorta during phy siological changes in flow rates and pulse rate that occur under exerc ise and postprandial conditions. Hemodynamic measurements were perform ed using an in vitro model which took into account seven major branche s, the curvature, and the pulsatile nature of brood flow of the abdomi nal aorta. Magnetic Resonance Imaging velocimetry employing phase-velo city encoding was used to measure the pulsatile axial velocity profile s for the entire cross-section at three axial locations. Under simulat ed exercise conditions, the forward velocities were approximately doub le those seen during rest, and the flow reversal seen for resting cond itions was greatly reduced. Near the posterior wall of the infrarenal aorta, the velocities were negative for only 21 percent of the cardiac cycle as compared with 82 percent for resting conditions. Postprandia l conditions produced a 25 percent reduction in peak velocity and a 33 percent reduction in mean velocity near the left anterior wall of the aorta just distal to the superior mesenteric artery (in comparison wi th resting conditions). The changes that can occur in abdominal aorta hemodynamics under different physiologic conditions may affect the rat e of progression of atherosclerosis at this site.