Velocity distributions in the left ventricular outflow tract and the aortic anulus measured with Doppler colour flow...

This study was designed to investigate the velocity distributions in the left ventricular outflow tract and aortic anulus. In 18 out of 22 healthy male individuals, instantaneous cross-sectional flow velocity profiles were constructed at different levels of the left ventricular outflow tract and aortic anulus by time interpolation of digital velocity data from sequentially delayed Doppler colour flow maps. The results showed that: (1) the velocity distributions in the left ventricular outflow tract and the aortic anulus were skewed with the highest velocities along the anterior and septal parts of the flow channel; (2) based on the time-velocity integral profiles in the aortic anulus, which were also skewed with the highest integrals along the anterior and septal parts, the maximal time-velocity integrals were higher than the mean cross-sectional time-velocity integrals by approximately 30% in the four chamber view and 40% in the long axis view. However, the time-velocity integrals at the middle point of the diameter correlated significantly with the mean cross-sectional time-velocity integrals in the four chamber view (10.3 +/- 0.8 vs 9.9 +/- 0.9 cm; r = 0.95) and in the long axis view (12.5 +/- 0.9 vs 11.8 +/- 0.8 cm; r = 0.95). Therefore, it can be concluded that: (1) the velocity distributions in the left ventricular outflow tract and the aortic anulus are skewed; (2) if the aortic anulus is used for cardiac output measurement by pulsed Doppler echocardiography in normal subjects, the middle point of its diameter is the best sampling site.