American journal of physiology. Heart and circulatory physiology
-
Am. J. Physiol. Heart Circ. Physiol. · Apr 2004
Relationships among Doppler-derived umbilical artery absolute velocities, cardiac function, and placental volume blood flow and resistance in fetal sheep.
We hypothesized that umbilical artery (UA) absolute blood flow velocities measured by Doppler ultrasonography reflect placental volume blood flow (Q(UA)) and placental vascular resistance (R(UA)) in a late gestation fetal sheep model. In addition, we examined the relationships between umbilical artery absolute blood flow velocities and parameters of fetal cardiac function. Twenty-six sheep fetuses were instrumented at 112-132 days of gestation. ⋯ A significant positive correlation was present between UA PI and R(UA). Doppler-derived UA parameters did not correlate with fetal arterial blood pressures, cardiac output, ventricular ejection forces or IRT%. In fetal sheep, Doppler-derived UA PI and absolute velocities, except PSV, are closely related to directly measured Q(UA) and R(UA), validating the use of noninvasive Doppler velocimetry in the assessment of placental circulation.
-
Am. J. Physiol. Heart Circ. Physiol. · Apr 2004
Effects of left ventricular contractility and coronary vascular resistance on coronary dynamics.
Wave-intensity analysis, which separates upstream from downstream events and defines their interaction, has been used to study the effects of changes in left ventricular (LV) contractility (E(max)) and left circumflex coronary artery resistance (R(LCx)) on the coronary systolic flow impediment (CSFI). In 10 anesthetized, open-chest dogs, we measured coronary, aortic, and LV pressures, coronary velocity (Flowire), and flow. ⋯ I(W-) was proportional to the CSFI. We conclude that contractility and coronary resistance change CSFI by modulating the backward-going compression wave.