3-DIMENSIONAL CROSS-SECTIONAL VELOCITY DISTRIBUTION IN THE ASCENDING AORTA IN CARDIAC PATIENTS

Knowledge of the distribution of velocities across the ascending aorta is important for measurements of cardiac output; for understanding th e function of normal and diseased valves and for the evaluation of pro sthetic valves. The aim of this study was to investigate, in detail, t he spatial distribution of axial velocities in the human ascending aor ta, covering a nearly complete cross-section of the lumen in a time co ntinuous modus. During open-heart surgery, blood velocities in the asc ending aorta were mapped in 10 patients. All patients had aortic valve s with no significant clinical evidence of disease. Pulsed Doppler ult rasound technique was used to measure blood velocity using an intralum inal probe with a 1 mm, 10 MHz crystal connected to a position-sensiti ve device. The distribution of blood velocity in the aorta 6-8 cm abov e the valve was characterized by a skewed and irregular peak systolic now, with maximum velocity posteriorly. There was a positive correlati on (r=0.854, P<0.002) between the maximum skewness slope and the strok e volume. Significant retrograde now was recorded in all patients in t he left posterior part of aorta in late systole and early diastole, Th e rotation of the point of maximal velocity was anticlockwise in six p atients, clockwise in three and alternating in one. The present study shows that there is a considerable individual variation in the velocit y distribution in the ascending aorta, with no plane symmetric feature s, and that large sampling volumes are required for reliable estimates of mean velocity.