Non-invasive diagnosis of diastolic dysfunction remains difficult in clinical practice. Non-invasive assessment of the flow field within the left ventricle (LV) using color M-mode Doppler (CMD) echocardiography provides a potential technique that can differentiate between the normal and diseased heart. A computer model is developed describing three-dimensional axi-symmetrical LV filling flow. The simulation results show that the hydrodynamical mechanism of LV flow wave propagation, as observed on 2D color and color M-mode Doppler echocardiograms, is the propagation of a vortex in the LV cavity.