Artery Blood Flow Velocity Waveforms Research Articles

Effects of Right Lateral Position on Changes of Fetal Hemodynamics in Late Pregnancy.

We aim to evaluate the effect of right lateral position on fetal hemodynamics (including umbilical artery [UA] and middle cerebral artery (MCA) blood flow-velocity waveform). In total, 150 low-risk singleton full-term pregnant women were included in the study from November 2021 to January 2022. Doppler flow velocity waveforms of the fetal UA and MCA tested by ultrasound were collected in gestation of 37-40 weeks. Computational analysis was performed using the one-way ANOVA test. Compared with the maternal left lateral position, there was a significant increase in Doppler indices of UA-RI (P = .033), UA-S/D (P = .019) and MCA-PSV (P = .021) and a significant decrease in MCA-RI (P = .030) in the supine position group. There was no statistical significance in all Doppler indices between the left and right lateral position (P > .05). Among the Doppler indices of three different maternal positions, there was no significance in both UA-PI and MCA-PI (P > .05). There were no significant differences on changes of the fetal hemodynamics between left and right lateral positions. Pregnant women could adopt to lie in the left or right lateral position alternately to relieve the discomfort in late pregnancy.

Respiratory Variations in Peak Peripheral Artery Velocities and Waveforms for Rapid Assessment of Fluid Responsiveness in Traumatic Shock Patients.

BackgroundThis study aimed to assess the correlation between the variability of the end-inspiratory and end-expiratory blood flow waveform and fluid responsiveness (FR) in traumatic shock patients who underwent mechanical ventilation by evaluating peripheral arterial blood flow parameters.Material/MethodsA cohort of 60 patients with traumatic shock requiring mechanical ventilation-controlled breathing received ultrasound examinations to assess the velocity of carotid artery (CA), femoral artery (FA) and brachial artery (BA). A rehydration test was performed in which of 250 mL of 0.9% saline was administered within 30 min between the first and second measurement of cardiac output by echocardiography. Then, all patients were divided into 2 groups, a responsive group (FR+) and a non-responsive group (FR−). The velocity of end-inspiratory and end-expiratory peripheral arterial blood flow of all patients was ultrasonically measured, and the variability were measured between end-inspiratory and end-expiratory.ResultsThe changes in the end-inspiratory and end-expiratory carotid artery blood flow velocity waveforms of the FR+ groups were significantly different from those of the FR− group (P<0.001). A statistically significant difference in ΔVmax (CA), ΔVmax (BA), and ΔVmax (FA) between these 2 groups was found (all P<0.001). The ROC curve showed that ΔVmax (CA) and ΔVmax (BA) were more sensitive values to predict FR compared to ΔVmax (FA). The sensitivity of ΔVmax (CA), ΔVmax (FA), and ΔVmax (BA) was 70.0%, 86.7%, and 93.3%, respectively.ConclusionsThe study showed that periodic velocity waveform changes in the end-inspiratory and end-expiratory peripheral arterial blood flow can be used for quick assessment of fluid responsiveness.

Comparison of the resistive indices obtained in the uterine artery and the ophthalmic artery in preeclamptic and normotensive patients in Doppler US.

IntroductionPreeclampsia is a medical condition characterized by hypertension and proteinuria during pregnancy, with the symptoms generally manifesting in the 3rd trimester. Hypertension brings hemodynamic changes; it is therefore expected that arterial blood flow velocity waveforms will be different in the uterine and ophthalmic arteries in preeclampsia. Vascular changes do occur in preeclampsia, which in turn induces hemodynamic changes.AimTo compare mean values of the resistive index of the ophthalmic and uterine arteries in patients with preeclampsia and normotensive individuals in Doppler US.MethodsIn this cross-sectional observational study, ultrasound of the uterine and ophthalmic arteries was performed in 60 pregnant women in the 2nd and 3rd trimester of pregnancy to compare the resistive index of these arteries in preeclamptic and normotensive individuals. All the patients, i.e. 30 preeclamptic and 30 normotensive pregnant women, took part in this study voluntarily. The study was approved by the institutional review board (IRB) of the University of Lahore.ResultsThe mean resistive index of the uterine artery was 0.50 ± 0.08 in normotensive participants and 0.64 ± 0.09 in preeclamptic women, with the p-value <0.001. The mean resistive index of the ophthalmic artery was 0.70 ± 0.05 in normotensive participants and 0.63 ± 0.04 in preeclamptic women, with the p-value <0.001.ConclusionsThere was a significant negative correlation between the resistive index of the uterine and ophthalmic arteries among the patients with preeclampsia and a significant positive correlation among normotensive individuals. Preeclampsia could be easily diagnosed with Doppler ultrasound based on hemodynamic changes in response to vascular changes in the ophthalmic and uterine arteries.

P18.03: Human uterine artery blood flow velocity waveforms following maternal glucose loading related to fetal size: a cross‐sectional observational study

P18.03: Human uterine artery blood flow velocity waveforms following maternal glucose loading related to fetal size: a cross‐sectional observational study

Doppler Audio Signal Analysis as an Additional Tool in Evaluation of Umbilical Artery Circulation

Purpose To investigate the predictive capacity of a new method for sound spectrum analysis of Doppler signals recorded from the umbilical artery in high-risk pregnancies. Material and Methods The retrospective study comprised 127 pregnant women with various pregnancy complications between 23 and 39 gestational weeks. Umbilical artery blood flow velocity waveforms were recorded with Doppler ultrasound and characterized by pulsatility index (PI) and blood flow class (BFC). Doppler audio signals were stored on a digital video recorder and the sound frequency at the energy level 15 dB below its peak (MAXpeak-15 dB) was estimated off-line. The prediction of probability for composite adverse pregnancy outcome (operative delivery for fetal distress, admission to neonatal intensive care unit, perinatal death) was evaluated using the area under the curve (AUC) of the receiver operating characteristics (ROC) curve. Results With increasing umbilical artery BFC, the MAXpeak-15 dB frequencies decreased (p < 0.0001) and the PI increased (p < 0.0001). The ROC AUCs for adverse outcome for MAXpeak-15 dB and for PI were 0.842 and 0.836 (p = 0.88), respectively. For the combination of MAXpeak-15 dB and PI, the corresponding AUC was 0.894, significantly higher than that of PI (p < 0.03) and of MAXpeak-15 dB (p < 0.05). Conclusion Umbilical artery Doppler sound spectrum analysis might be a useful supplement to PI in the clinical evaluation of fetoplacental circulation.

Hemodynamic Correlates of Late Systolic Flow Velocity Augmentation in the Carotid Artery

Background. The contour of the common carotid artery (CCA) blood flow velocity waveform changes with age; CCA flow velocity increases during late systole, and this may contribute to cerebrovascular disease. Late systolic flow velocity augmentation can be quantified using the flow augmentation index (FAIx). We examined hemodynamic correlates of FAIx to gain insight into determinants of CCA flow patterns. Methods. CCA Doppler ultrasound and wave intensity analysis (WIA) were used to assess regional hemodynamics in 18 young healthy men (age 22 ± 1 years). Forward waves (W 1) and backward waves (negative area, NA) were measured and used to calculate the reflection index (NA/W 1 = RIx). Additional parameters included W 2 which is a forward travelling expansion/decompression wave of myocardial origin that produces suction, CCA single-point pulse wave velocity (PWV) as a measure of arterial stiffness, and CCA pressure augmentation index (AIx). Results. Primary correlates of FAIx included W 2 (r = − 0.52, P < 0.05), logRIx (r = 0.56, P < 0.05), and AIx (r = 0.60, P < 0.05). FAIx was not associated with CCA stiffness (P > 0.05). Conclusions. FAIx is a complex ventricular-vascular coupling parameter that is associated with both increased expansion wave magnitude (increased suction from the left ventricle) and increased pressure from wave reflections.

Ultrasonography and Doppler studies in twin-to-twin transfusion syndrome.

In 40 twin pregnancies, the evaluation of hemodynamics by ultrasound was performed during the period January 1986 through September 1991. The blood flow velocities' waveforms in the umbilical artery, umbilical vein and tricuspid valve, and the total cardiac dimension, were obtained by ultrasonography in conjunction with 3.5 MHz pulsed Doppler ultrasound. Six patients with twin pregnancies were identified as having twin-to-twin transfusion syndrome (TTS), on the basis of like-sex twins with monochorionic diamniotic placentation, vascular anastomosis in the placenta, and umbilical cord venous blood hemoglobin difference exceeding 5 g/dl at delivery. No distinctive findings for TTS were revealed by the measurement of umbilical artery blood flow velocity waveforms. However, cardiomegaly in 5 recipient fetuses and tricuspid regurgitation and biphasic umbilical vein waveforms in 3 recipient fetuses constituted characteristic features of TTS. Ultrasonography and a Doppler study might be beneficial in diagnosing TTS and evaluating the hemodynamics in a recipient fetus.

Root-MUSIC analysis of nitric oxide-mediated changes in ophthalmic artery blood flow velocity waveforms

Clinical and experimental studies indicate that structural and functional changes in the microvasculature can predate or accompany risk factors for cardiovascular disease at the earliest stages in the disease process. In the current work, both simulated and actual Doppler ultrasound maximum blood velocity waveform envelopes recorded from the ophthalmic artery were analysed using a root-MUSIC and least squares fitting approach to determine amplitude frequency spectra. Both amplitude and frequency components of noise contaminated simulated waveforms were reliably determined indicating the robustness of the technique. The technique was then used to compare the spectral content of the ophthalmic artery blood velocity waveforms of normal controls in three test states: at baseline, following administration of GTN, a nitric oxide donor, and following administration of L-Name, a nitric oxide inhibitor. Principal components derived from root-MUSIC analysis discriminated between waveforms in baseline and non-baseline test states ( p < 0.00001) and between GTN and non-GTN test states ( p = 0.0002).

A Modification of the Uterine Artery Restriction Technique in the Guinea Pig Fetus Produces Asymmetrical Ultrasound Growth

Aims To evaluate the use of diathermy ablation of branches of the uterine artery to produce growth restriction in the fetal guinea pig, and to compare this new approach with the more conventional use of uterine artery ligation. The development of growth restriction was documented by measuring fetal biparietal diameter (BPD) and the resistance index (RI) of the umbilical artery blood flow velocity waveform. Methods At 30–35 days of gestation (term = 70 days), one uterine artery was ligated in 29 sows. In another 16 sows, branches of one uterine artery were ablated using diathermy. Fetuses in contralateral horns were used as controls. Ultrasound measurements were made weekly, and at 59–69 days of gestation animals were euthanased to determine fetal position in utero as well as fetal and placental weights. In some fetuses, brain and liver weights were also recorded. Results Both surgical techniques resulted in similar reductions in fetal body and placental weights. The number of fetuses surviving to term was greater in the diathermy group (53%) compared to the ligation group (22%) ( P < 0.05). Results from these two groups were combined and referred to as “treated” fetuses. The brain/liver weight ratio was increased by 245% in the treated fetuses compared to control fetuses. Ultrasound measures of BPD in the treated fetuses were within the normal range. The mean RI of the treated group showed a slight but significant increase near term compared to the mean RI of the normal range. Conclusion We have shown that the diathermy technique produces asymmetrical fetal growth restriction (with normal head size) in the guinea pig to the same extent as the conventional ligation technique. It is associated with a lower fetal mortality rate and therefore should be the preferred method. The minimal increase in umbilical artery resistance index only at the end of gestation amongst the intrauterine growth restriction (IUGR) fetuses suggests that an obliterative vasculopathy in the umbilical circulation is not the cause of growth failure when there is maternal uteroplacental restriction.

829: Temporal changes in fetal heart rate patterns—a new dimension in fetal assessment

To compare temporal changes (trends) in computed FHR parameters obtained by numerical analysis of repeated non-stress tests between normal pregnancies and pregnancies with an abnormal biophysical profile or an increase in the resistance to flow in umbilical artery blood flow velocity waveforms (FVW's).

Significance of retrograde diastolic uterine artery blood flow during regional anesthesia in instrumented pregnant sheep

We studied the interactions between uterine and placental hemodynamics during maternal hypotension in chronically instrumented fetal sheep. In addition, we investigated maternal hemodynamic characteristics, fetoplacental hemodynamics and fetal acid-base status when a retrograde diastolic uterine artery blood flow pattern is present during maternal hypotension. Invasive maternal and fetal hemodynamic parameters, uterine (Q(UtA)) and placental (Q(UA)) volume blood flows and acid-base values were examined in 24 chronically instrumented sheep at baseline and during epidural-induced maternal hypotension at 117-132 (term 145) days of gestation. Uterine artery blood flow velocity waveforms were obtained by Doppler ultrasonography. Maternal hypotension decreased Q(UtA) without affecting Q(UA). During hypotension, eight out of 24 sheep demonstrated a retrograde diastolic blood flow velocity waveform pattern in the uterine artery. Maternal systolic, diastolic and mean arterial blood pressures were significantly lower in the retrograde group than in the antegrade group. No statistically significant differences in Q(UtA), Q(UA) and fetal blood gas values were detected between the two groups during hypotension. An acute decrease in uterine artery volume blood flow during maternal hypotension is not compensated by increased placental volume blood flow. A retrograde diastolic blood flow pattern in the uterine artery is related to lower maternal arterial pressures, especially during diastole. A uterine artery retrograde diastolic blood flow pattern does not have any additional detrimental short-term effects on fetal acid-base status.

Variability of Middle Cerebral Artery Blood Flow with Hypercapnia in Women

We examined the effect of euoxic hypercapnia on middle cerebral artery (MCA) blood flow velocity waveform parameters in pre- and postmenopausal women by exposing 24 healthy women (12 pre-, 12 postmenopausal) to hypercapnia for 20 min. MCA blood flow velocity was measured continuously by transcranial Doppler ultrasound. The data were run through an algorithm that detected the feature points of the waveforms and then analyzed for statistically significant group differences. The changes in mean blood flow velocity with euoxic hypercapnia were not significant between the two groups. However, certain feature points, particularly the velocity of the reflected shoulder (V REFLEC), increased (89.4 ± 14.6 to 110.0 ± 20.5 cm/s and 102.3 ± 14.1 to 125.1 ± 14.9 cm/s from euoxic eucapnia to euoxic hypercapnia in pre- and postmenopausal women, respectively), as did the augmentation index (79.9 ± 10.4 to 85.9 ± 12.6% and 114.7 ± 12.8 to 119.0 ± 12.6%) and pulsatility index (0.86 ± 0.18 to 0.74 ± 0.15 and 0.71 ± 0.11 to 0.66 ± 0.11). Furthermore, while systolic peak velocity (V SYS) was the highest point of the waveform in premenopausal women, V REFLEC was the highest point for the postmenopausal cohort. The implications of this finding become obvious when calculating pulsatility index (PI), the values of which varied significantly for the postmenopausal women, depending on whether V SYS or the absolute maximum was used. These findings suggest that hypercapnia increases blood flow velocity waveform reflections, and that PI calculations, particularly for older age groups, may need to be considered more carefully, since these reflections often exceed the systolic peak velocity. (E-mail: poulin@ucalgary.ca)

P46.07: Perinatal outcome according to umbilical artery blood flow velocity waveform of term pregnancies with small for gestational age pregnancies

P46.07: Perinatal outcome according to umbilical artery blood flow velocity waveform of term pregnancies with small for gestational age pregnancies

Dynamic cerebral autoregulation: should intracranial pressure be taken into account?

Although the inclusion of cerebral perfusion pressure (CPP) is a standard feature in static testing of autoregulation after head injury, controversy surrounds the use of CPP versus arterial blood pressure (ABP) in dynamic tests. The aim of our project was to assess the discrepancies between methods of dynamic autoregulation testing based on CPP or ABP, and study possible differences in their prognostic value. Intermittent recordings of intracranial pressure (ICP), ABP and middle cerebral artery blood flow velocity (FV) waveforms were made in 151 anaesthetised and ventilated adult head injured patients as part of their required care. Indices of dynamic autoregulation were calculated as a moving correlation coefficient of 60 samples (total time 3 min) of 6 s mean values of FV and ABP (Mxa) or FV and CPP (Mx). Values of Mx and Mxa were averaged over multiple recordings in each patient and correlated with outcome at 6 months post injury. Association between Mx and Mxa was moderately strong (r(2) = 0.73). However, limit of 95% accordance between both indices was +/-0.32. Mxa was significantly greater than Mx (0.22 +/- 0.22 versus 0.062 +/- 0.28; p < 0.000001). The difference between Mx and Mxa decreased with impairment of autoregulation (r = -0.39; p < 0.000001). Mean value of Mx showed a significant difference between dichotomized outcome groups (better autoregulation in patients with favourable than unfavourable outcome), while Mxa did not. Although relatively similar in a large group of patients, the differences between these two methods of assessment of dynamic autoregulation may be considerable in individual cases. When ICP is monitored, CPP rather than ABP should be included in the calculation of the autoregulatory index.

Increased expression of N-myc downstream-regulated gene 1 (NDRG1) in placentas from pregnancies complicated by intrauterine growth restriction or preeclampsia

N-myc downstream-regulated gene 1 (NDRG1) modulates placental response to hypoxia. We therefore hypothesized that the expression of NDRG1 is altered in placentas from pregnancies complicated by intrauterine growth restriction (IUGR) or preeclampsia (PE), which are associated with fetoplacental underperfusion and cellular hypoxia. Thirty-five pregnant women in the third trimester of pregnancy were recruited according to the following 3 groups: (1) normal term pregnancy (n = 10), (2) pregnancy complicated by IUGR (n = 9), and (3) pregnancy with severe PE (n = 16). Placental samples were collected after cesarean delivery without labor. NDRG1 was measured with the use of immunostaining, Western blot, and real-time quantitative polymerase chain reaction (RT-qPCR). Umbilical artery blood flow velocity waveforms were recorded by Doppler ultrasound in women with IUGR and PE. By using immunostaining, we found a predominant expression of NDRG1 in the cytoplasm of villous trophoblasts. The expression of NDRG1 in samples from PE or IUGR was higher than control, with highest expression in PE. We confirmed these results by using immunoblotting and RT-qPCR. There was no correlation between the level of NDRG1 and umbilical artery blood flow. The expression of NDRG1 is upregulated in placentas from pregnancies complicated by severe PE or IUGR. This finding likely reflects trophoblast response to hypoxic injury.

Nitric oxide modulation of ophthalmic artery blood flow velocity waveform morphology in healthy volunteers

Quantitative analysis of the arterial pressure pulse waveform recorded by applanation tonometry of the radial artery can track NO (nitric oxide)-mediated modulation of arterial smooth muscle tone. The changes in pressure pulse waveform morphology result from pulse wave reflection arising predominantly from smaller arteries and arterioles. Employing Doppler ultrasound to record the spectral flow velocity waveform in the ophthalmic artery, we studied the effects of NO modulation on waveforms recorded in the proximity of the terminal ocular microcirculatory bed. In healthy young men (n=10; age 18-26 years), recordings were made at baseline, following 300 mug of sublingual GTN (glyceryl trinitrate) and during the intravenous infusion of 0.25 and 0.5 mg/kg of L-NAME (N(G)-nitro-L-arginine methyl ester). Peaks (P1, P2 and P3) and nodes (N1, N2 and N3) on the arterial flow velocity waveform were identified during the cardiac cycle and employed to quantify wave shape change in response to the haemodynamic actions of the pharmacological interventions. The administration of GTN resulted in a significant (P<0.05) increase in heart rate without significant alteration in blood pressure. At the doses employed, L-NAME did not significantly alter systemic haemodynamics. With the exception of peak Doppler systolic velocity, all other peaks and nodes decreased significantly in response to GTN (P<0.05 for all points compared with baseline). In response to the administration of L-NAME, all peaks and nodes decreased significantly (P<0.05 for all points compared with baseline). The resistive index, a ratio calculated from the peak and trough flow velocities employed to assess change in flow resistance, increased significantly in response to GTN (0.77 at baseline compared with 0.85; P<0.05). Quantification of changes in the flow velocity spectral waveform during the cardiac cycle sensitively identified NO modulation of smooth muscle tone prior to alteration in systemic haemodynamics. Focusing on the resistive index, which identifies isolated points on the waveform describing the excursions of flow, may provide misleading information in relation to the haemodynamic effects of drug interventions.

1201: Fetal aortic blood flow velocity waveform: Effect of gestational age and its sampling points

Fetal arterial blood flow velocity waveforms of umbilical artery or middle cerebral artery have been widely used for estimation. Fetal descending aortic flow was used for fetal estimation and the end-diastolic reversed flow or absent end-diastolic flow of descending aorta was reported as those of umbilical arterial flow. But the umbilical arterial flow waveforms are more easily acquired than those of descending aorta, and recently the latter has not been used for fetal estimation. Otherwise, fetal descending aorta is able to be visualized linearly by 2D ultrasonography, and the blood flow velocity itself is able to be measured accurately when adequate insonation angle is acquired. Evaluation of fetal blood flow velocity might be useful tool for the fetal cardiac function. We cross-sectionally examined fetal descending aortic blood flow velocity waveforms from 551 normal singleton fetuses between 18 to 41 weeks of gestation in order to establish the reference values the Doppler indices (resistance index and maximum systolic velocity) and to clarify the characteristics of fetal aortic flow velocity waveform. Doppler flow velocity waveforms were acquired from three different sampling points: thoracic (behind fetal heart), upper abdominal (just below diaphragm) and lower abdominal (just below the origination of renal arteries) portions in each fetus. The resistance indices for the fetal descending aorta decreased from thoracic to lower abdominal portion, but no remarkable change was detected during fetal development (0.84 ± 0.05, 0.79 ± 0.04, 0.76 ± 0.05, thoracic, upper abdominal and lower abdominal, respectively, at 18 to 19 weeks of gestation, and 0.85 ± 0.03, 0.81 ± 0.02, 0.73 ± 0.05 at 40 to 41 weeks). Otherwise, maximum systolic velocity decreased from central to peripheral portion and increased during fetal development (69 ± 11, 58 ± 10, 49 ± 8 cm/s, thoracic, upper abdominal and lower abdominal, respectively, at 18 to 19 weeks of gestation, 134 ± 13, 112 ± 18, 92 ± 12 cm/s at 40 to 41 weeks). Moreover, fetal descending aortic flow velocity waveforms sometimes revealed systolic multiple peaks pattern and/or early-diastolic reversed flow patterns. These characteristic flows were more frequently observed in late third trimesters. Interestingly, they were more frequently observed at thoracic portion than at lower abdominal portion. There were no fetuses that revealed these characteristic flows at 18 to 19 weeks of gestation. But, multiple systolic peaks patterns were detected at thoracic, upper abdominal and lower abdominal portions in 64.3%, 42.8% and 35.7% of fetuses at 40 to 41 weeks of gestation. We also detected 9.1%, 3.6% and 1.8% of fetuses at 37 to 38 weeks of gestation at thoracic, upper abdominal and lower abdominal portions, respectively. In conclusion, we resulted that the Doppler flow velocity waveforms are affected by the sampling points on the fetal descending aorta. The resistance index and the maximum systolic velocity for the descending aorta gradually decrease from the thoracic to the lower abdominal portion. These changes are obviously detected throughout the course of pregnancy after 18 weeks of gestation.

Differences between middle cerebral artery blood velocity waveforms of young and postmenopausal women

We characterized middle cerebral artery (MCA) blood flow velocity waveforms measured by transcranial Doppler ultrasonography in premenopausal (26.6 +/- 6.1 years, mean +/- SD) and postmenopausal (54.0 +/- 3.6 years) women, of whom six were receiving hormone therapy (PM-HT) and seven were not (PM-non-HT). We hypothesized that feature points on MCA waveforms are altered in postmenopausal women compared with those in young women. A short protocol involved maintaining end-tidal PO2 at euoxia (88 mm Hg) and end-tidal PCO2 at 1.5 mm Hg above eucapnic values using a dynamic end-tidal forcing system. Doppler data for the velocity spectral outline (Vp) were collected every 10 ms, and velocity waveform analyses were done on a beat-by-beat basis. Waveform features were identified over each cardiac cycle, including the average Vp (VCYC), maximum acceleration (AMAX), and the ratio of the velocity at the reflected wave and the velocity at peak systole (VR:VMAX). VCYC was unchanged between premenopausal and postmenopausal women (69.4 +/- 9.6 and 67.5 +/- 11.1 cm/s, respectively). AMAX was significantly higher (P = 0.007) in premenopausal women (987.9 +/- 280.7 cm/s) compared with postmenopausal women (743.1 +/- 100.3). Conversely, VR:VMAX was significantly smaller (P < 0.001) in premenopausal women (0.90 +/- 0.09) compared with postmenopausal women (1.11 +/- 0.05). In postmenopausal women, the reflected wave is higher than the maximum velocity at peak systole, suggesting the presence of a shoulder in the MCA waveform. Further investigations are required to assess whether this waveform analysis can provide insight into pathophysiologic changes in cerebral hemodynamics with aging.

Clinical significance of uterine artery blood flow velocity waveforms during provoked uterine contractions in high-risk pregnancy.

To determine whether, in a group of high-risk pregnancies undergoing an oxytocin challenge test (OCT), uterine artery Doppler velocimetry will identify fetuses at risk of distress during the provoked contractions. Bilateral uterine artery Doppler velocimetry was performed simultaneously with electronic fetal heart rate (FHR) recordings in 67 high-risk pregnancies subjected to an OCT. Flow velocity waveforms (FVWs) were classified according to pulsatility index (PI), presence of diastolic notching and a novel classification of FVW shapes. The OCT was classified as negative (normal) or positive (late FHR decelerations). Only OCT-negative cases were allowed a trial of vaginal delivery. Non-parametric statistical methods were used to test for differences between the OCT groups. There was no difference in prevalence of high PI or diastolic notching in OCT-positive (n = 10) and OCT-negative (n = 57) cases at basal (resting) measurements or between uterine contractions in either uterine artery (P > or = 0.3). During contractions the PI could not be used for assessment due to the biphasic shape of the FVWs, but there was no difference in distribution of FVW classes between the groups in either the placental side (P > or = 0.3) or contraplacental side (P > or = 0.6) uterine artery. No significant associations between PI or FVW class distribution and birth asphyxia or operative delivery for fetal distress in labor were found (P > or = 0.1). During uterine contractions there is no difference in uterine artery FVW pattern between OCT-positive and OCT-negative cases. Recording of uterine artery FVWs during the OCT seems to be of limited clinical relevance.

Effect of antenatal glucocorticoid therapy on arterial and venous blood flow velocity waveforms in severely growth-restricted fetuses.

To study the effects of antenatal glucocorticoid (betamethasone) therapy on blood flow velocity waveform patterns in the umbilical artery (UA), middle cerebral artery (MCA) and ductus venosus (DV) in severely intrauterine growth-restricted (IUGR) fetuses. Fifty-five severely IUGR fetuses at 24-34 weeks of gestation were included in the study. The effect of antenatal glucocorticoid administration on Doppler findings in the UA, MCA and DV was studied using two statistical approaches, namely paired sample analysis and multilevel analysis. There were no effects of betamethasone on the pulsatility index (PI) of the vessels studied. The only changes noticed during the 14 days of observation were a gradual decrease of PI in the MCA, an increase in the UA-PI/MCA-PI ratio and an increase in the DV-PI. These changes with time may be explained by a progressive and gradual deterioration of the fetal condition. Antenatal glucocorticoids (betamethasone) do not affect fetal Doppler waveform patterns of the UA, MCA and DV in severely IUGR fetuses.