HEMODYNAMIC FACTORS AFFECTING UTERINE ARTERY DOPPLER WAVE-FORM PULSATILITY IN SHEEP

Quantitative analysis of vascular resistance from the Doppler time-vel ocity waveform relies on measuring arterial pulsatility. However, inpu t pressure waveform pulsatility, impedance, and resistance have all be en found to effect artery flow waveform pulsatility in circulatory mat hematic models and in umbilical sheep preparations in vivo. The presen t study used an in vivo sheep preparation to determine that embolizati on of the uteroplacental circulation and maternal angiotensin II admin istration caused changes in the uterine Doppler time-velocity waveform pulsatility that were dependent on input pressure waveform pulsatilit y, fundamental impedance, and resistance changes. Uteroplacental vascu lar embolization increased vascular resistance and the uterine artery Doppler waveform resistive index; the mean component of flow (mean pre ssure/resistance) decreased. Decreased uterine artery Doppler resistiv e index occurred despite angiotensin II-induced vasoconstriction and i ncreased vascular resistance because the pulse component of flow (puls e pressure/impedance) decreased.