Relationship between Intraventricular Flow Patterns and the Shapes of the Aliasing Area in Color M-mode Doppler Echocardiograms : A CFD Study with an Axisymmetric Model of the LV

Spatiotemporal maps of the velocity of intraventricular blood flows obtained with color M-mode Doppler (CMD) echocardiography are used to assess the diastolic function of the left ventricle (LV). However, theoretical basis for that is unclear. Hence, we studied the relationship between flow patterns in the LV and the shapes of aliasing areas that appear in CMD echocardiograms by means of computational fluid dynamics using an axisymmetric model of the LV. The results showed that a ring vortex formed in the early stage of expansion and grew larger while shifting its center towards the apex of the LV, occupying a large annular space between the mainflow along the long axis and the lateral wall of the LV and constricting the mainflow. Due to that, fluid elements in the mainflow increased their velocities and proceeded further deeper into the LV with high velocities, which appeared to be an elongated shape of the aliasing area in the CMD echocardiogram. From these results it was concluded that the shape of the aliasing area in a CMD echocardiogram shows the change in the velocity of the mainflow affected by the growth and migration of a ring vortex formed in the LV.