Measurement of regurgitation volume: The apical window is used to record the pulsed-wave velocities at the LV outflow tract and at the mitral annulus and to measure the diameter of the mitral annulus. The time-velocity integral is assessed. The stroke volumes of mitral annulus and LV outflow tract are obtained by multiplying the cross-sectional area by the respective time-velocity integral. The MR regurgitation volume is calculated as Regurgitation volume = (stroke volume of mitral annulus) - (stroke volume of LV outflow tract).