Note that (111973004, SCT, "Systole") is used here to refer to the entire duration of ventricular systole, while (416430001, SCT, "End Systole") is used to refer to the point in time where the aortic valve closes (or in the case of the right ventricle, the pulmonary valve). Therefore, a Vmax measurement for systole would mean the maximum velocity over the period of systole, and a Vmax measurement for end systole would mean the maximum velocity at the time point of end systole.