Aortic PWV was measured according to the well-validated method using MRI 19. From the velocity-encoded MRIs, aortic contours were automatically detected and manually adjusted in each slice area throughout the cardiac cycle. The transit time between the flow curves of each region of the aorta was determined from the midpoint of the systolic up-slope on the flow versus time curve 26-28. The up-slopes were identified by drawing a line between the points of 40% and 60% maximum velocity on the waveform. The distance between each aortic level was measured on black blood images using a curved line along the center of the aorta. Based on these data, the regional PWV was calculated as the ratio of the distance between levels and the time differences between the arrival of the pulse wave at each level. The PWV was measured at two regions: the proximal aorta (proximal PWV between level 1 and level 2) and the entire aorta (PWV-total between level 1 and level 4).