FLOW VELOCITY DISTRIBUTIONS IN THE LEFT-VENTRICULAR OUTFLOW TRACT ANDIN THE AORTIC ANNULUS IN PATIENTS WITH LOCALIZED BASAL SEPTAL HYPERTROPHY

Background The velocity distributions in I-he left ventricuIar outflow tract and in the aortic annulus in normal subjects and certain cardia c patients are skewed, with the highest velocity along the anterior wa ll and septum. An abnormal anatomical structure of the interventricula r septum changes the shape of the left ventricular outflow tract, and may consequently change the pattern of velocity distribution. Methods The cross-sectional velocity distributions in the left ventricular out flow tract and in the aortic annulus were constructed by using Doppler colour flow mapping in nine patients with localized basal septal hype rtrophy, and in 10 normal subjects. The apical lone axis view was used . Results In the studied patients, the velocity distributions in the l eft ventricular outflow tract and in the aortic annulus were skewed in a different way from those in normal subjects. The relative location of the maximal velocity on the cross-sectional diameter of the flow ch annel changed from one level to another. At the point of maximal basal septal hypertrophy, the velocity distribution was most (e.g. basal se ptum). Distal to this level, the highest velocities of the skewed velo city profiles were gradually located closer to the central part of the Bow channel. According to the time-velocity integral profile at the l evel of the aortic annulus, the pattern of skewness (in terms of the d ifference of the average time-velocity integrals between the anterior and posterior halves of the diameter) was significantly different betw een the normal and patient groups (5.51 +/- 3.55cm vs 0.03 +/- 2.07 cm ; P<0.01), while the extent of skewness (in terms of the ratio of the maximal to the cross-sectional mean time-velocity integrals) was close between two groups (1.36 +/- 0.28 vs 1.27 +/- 0.13; P>0.05). Conclusi on Localized basal septal hypertrophy significantly affects velocity d istributions in the left ventricular outflow tract and in the aortic a nnulus.