Flow velocity distributions in the left ventricular outflow tract and in the aortic annulus in patients.with localized basal septal hypertrophy

BACKGROUND: The velocity distributions in the left ventricular outflow tract and in the aortic annulus in normal subjects and certain cardiac patients are skewed, with the highest velocity along the anterior wall and septum. An abnormal anatomical structure of the interventricular 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 outflow tract and in the aortic annulus were constructed by using Doppler colour flow mapping in nine patients with localized basal septal hypertrophy, and in 10 normal subjects. The apical long axis view was used. RESULTS: In the studied patients, the velocity distributions in the left 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 channel changed from one level to another. At the point of maximal basal septal hypertrophy, the velocity distribution was most skewed with the highest velocity along the anterior wall (e.g. basal septum). Distal to this level, the highest velocities of the skewed velocity profiles were gradually located closer to the central part of the flow channel. According to the time-velocity integral profile at the level of the aortic annulus, the pattern of skewness (in terms of the difference of the average time-velocity integrals between the anterior and posterior halves of the diameter) was significantly different between the normal and patient groups (5.51 +/- 3.55 cm 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). CONCLUSION: Localized basal septal hypertrophy significantly affects velocity distributions in the left ventricular outflow tract and in the aortic annulus.