Doppler Ultrasound Evaluation of the Fetus and Placenta

Fundamentals of Doppler Imaging Arterial Doppler A simple way of thinking about the arterial flow waveform (in all vascular beds except the coronary) is that it depends on the forward ejection of blood from the fetal heart, the elastic properties of the vessel, and the viscosity of ejected blood. The most relevant measures are the peak systolic velocity (PSV) and the end diastolic velocity (EDV). During systole, the velocity of the blood ejected after the semilunar valve opens increases to a maximum (the PSV), evidenced as the highest point in the waveform. During diastole, when the cardiac contraction can no longer maintain forward flow against the elastic properties of the downstream vascular bed and the viscosity of the blood, flow decelerates to its nadir (the EDV), the lowest point on the arterial waveform. The EDV is primarily dependent on downstream vascular impedance, the combined result of resistance and vascular response, and to a lesser degree input pressure. Fig. 171.1 illu...