Hemodynamic Control of End-Diastolic Velocity: An in Vitro Study

Abstract

In recent years, analysis of Doppler Frequency Shift Waveform has been used extensively in assessing peripheral hemodynamics (Woodcock, 1972; Pourcelot, 1974; Gosling and King, 1975; Blackshear et al., 1980). In the perinatal area, the use of normalized End-Diastolic Velocity (EDV) has been proposed as an index of adequacy of placental circulation (Maulik, 1982). In pediatric practice, neonatal cerebral perfusion has been assessed using the various Doppler indices including the EDV, and the efficacy of the technique has been compared against the ¹³³Xenon clearance method for measuring perfusion (Greisen, 1984). More recently, the absence of EDV in the umbilical artery has been shown to be an important predictor of fetal compromise (Rochelson et al., in press). The assumption underlying the use of these analytic techniques proposes that they can unravel the hemodynamic factors in the target circulation that control the shape of the Doppler waveform. This assumption, which is supported by empiric data, has not been subjected to in depth hemodynamic validation. Obviously, providing evidence of a reasonable hypothesis cannot act as a substitute for experimental verification. This ongoing project has been undertaken in order to address the above issue and to clarify the fundamental hemodynamic concepts which form the basis for using the Doppler waveform analysis to assess circulatory adequacy. Specifically, this paper presents the results from a preliminary study in which the effects of up and downstream hemodynamic alterations on the Doppler derived EDV were investigated in an in vitro circulatory system.