Journal of Ultrasound in Medicine, Vol 17, Issue 6 357-368, Copyright © 1998 by American Institute of Ultrasound in Medicine
Hemodynamic factors affecting uterine artery Doppler waveform pulsatility in sheep
H. M. Saunders, P. N. Burns, L. Needleman, J. B. Liu, R. Boston, J. A. Wortman and L. Chan
Department of Clinical Studies-Philadelphia, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, 19104-6010, USA.
Quantitative analysis of vascular resistance from the Doppler time-velocity
waveform relies on measuring arterial pulsatility. However, input pressure
waveform pulsatility, impedance, and resistance have all been found to
effect artery flow waveform pulsatility in circulatory mathematic models
and in umbilical sheep preparations in vivo. The present study used an in
vivo sheep preparation to determine that embolization of the uteroplacental
circulation and maternal angiotensin II administration caused changes in
the uterine Doppler time-velocity waveform pulsatility that were dependent
on input pressure waveform pulsatility, fundamental impedance, and
resistance changes. Uteroplacental vascular embolization increased vascular
resistance and the uterine artery Doppler waveform resistive index; the
mean component of flow (mean pressure/resistance) decreased. Decreased
uterine artery Doppler resistive index occurred despite angiotensin
II-induced vasoconstriction and increased vascular resistance because the
pulse component of flow (pulse pressure/impedance) decreased.