title: Hemodynamic factors affecting uterine artery Doppler waveform pulsatility in sheep.
abstract: 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.
authors.affiliation: Department of Clinical Studies-Philadelphia, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, 19104-6010, USA.
authors.forename: H M
authors.initials: HM
authors.lastname: Saunders
authors.forename: P N
authors.initials: PN
authors.lastname: Burns
authors.forename: L
authors.initials: L
authors.lastname: Needleman
authors.forename: J B
authors.initials: JB
authors.lastname: Liu
authors.forename: R
authors.initials: R
authors.lastname: Boston
authors.forename: J A
authors.initials: JA
authors.lastname: Wortman
authors.forename: L
authors.initials: L
authors.lastname: Chan
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000000981:diagnostic imaging / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D004617:Embolism / Q000503:physiopathology; D005260:Female; D008863:Microspheres; D021041:Placental Circulation / Q000502:physiology*; D011247:Pregnancy; D011673:Pulsatile Flow / Q000502:physiology*; D012756:Sheep; D018608:Ultrasonography, Doppler; D016216:Ultrasonography, Prenatal; D014599:Uterus / Q000098:blood supply*; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology
chemical_list: D000804:Angiotensin II