Artery Blood Flow Volume Research Articles

Doppler Ultrasonography for the Noninvasive Measurement of Uterine Artery Volume Blood Flow Through Gestation in the Pregnant Sheep

Accurate noninvasive quantification of volume blood flow in the uterine arteries (UtAs) would have clinical and research benefits. We evaluated the correlation and agreement between uterine artery volume blood flow (UtABF) as calculated (cUtABF) from color/pulsed-wave Doppler acquisitions and that measured (mUtABF) by bilateral perivascular transit-time flow probes in 6 pregnant sheep at 2 gestational ages. Out of 22 Doppler acquisitions, 19 were successful. The overall correlation between cUtABF and mUtABF was 0.55 (n = 19, P = .01). Calculated UtABF and mUtABF were significantly correlated in late gestation (n = 11, r = 0.71, P = .01) but not at mid-gestation (n = 8, r = .02, P = .96). By Bland-Altman analysis, the mean cUtABF/mUtABF was 1.15 with 95% limit of agreement (-0.26 to 2.56), similar to results previously achieved using power/pulsed-wave Doppler. Despite the acceptable correlation, the limits of agreement between Doppler and transit-time flow probe measurements remain wide. This makes Doppler ultrasonography less than a desirable method to quantify UtABF in studies where accurate quantification is required.

Blood flow volume of uterine arteries in human pregnancies determined using 3D and bi-dimensional imaging, angio-Doppler, and fluid-dynamic modeling

The primary aim of this pilot study was to study uterine artery (UtA) blood flow volume in uneventful human pregnancies delivered at term, at mid and late gestation by means of 3D and bi-dimensional ultrasound imaging with angio-Doppler combined with fluid-dynamic modeling. Secondary aims were to correlate flow volume to placental site and to UtA Pulsatility Index (PI).Women with singleton, low-risk pregnancies were examined at mid and late gestation. The structure and course of the uterine artery (UtA) was studied in each patient by means of 3D-angio-Doppler and included vessel diameter D, blood flow velocity and PI (measured along the UtA). Fetal weight estimation and placental insertion site were assessed by ultrasound. A robust fluid-dynamic modeling was applied to calculate absolute flow and flow per unit fetal weight.Mean UtA diameter and blood flow velocity increased significantly (p < 0.0001) from mid-gestation to late gestation from 2.6 mm and 67.5 cm/s, to 3.0 mm and 85.3 cm/s, respectively, yielding an increasing absolute flow troughout gestation. h coefficient, derived by fluid-dynamic modeling to calculate mean velocity, increased significantly from 0.52 at mid-gestation to 0.57 at late gestation. UtA blood flow volume ml/min/kg-fetal weight was significantly higher at mid-gestation than at late gestation (535 ml/min/kg vs 193 ml/min/kg; p < 0.0001). In cases with strictly lateral placentas the ipsilateral UtA accommodates at mid and late gestation 63% and 67% of the total UtA flow. In central placentas UtA flow was evenly distributed between the two vessels. An inverse correlation was observed between PI and blood flow volume ml/min/kg (Pearson's coefficient r = −0.54).Our work confirms the technological and methodological limitations in the measurement of uterine artery blood flow. However, Doppler measurements supported by three-dimensional angio imaging of the uterine vessel, high resolution imaging and diameter measurement, and a robust mathematical model of local circulation adds a genuine new area of investigation into human uterine circulation during pregnancy.

Hemodynamics of the radial artery, the site of traditional pulse diagnosis

Background Pulse diagnosis is a method used in traditional medicine around the world, and is mainly performed at the radial artery. However, there are few reports on radial artery hemodynamics because it is difficult to measure the blood flow volume in a thin vessel like this artery. Methods Thirty-three healthy volunteers (mean age: 34.2±7.6 years; 26 men and 7 women) were enrolled. We measured the hemodynamics of the right radial artery for approximately 50 s after 10 min of rest in the supine position. Hemodynamics was assessed with a Prosound α10 ® ultrasound system (Aloka Co., Ltd., Tokyo, Japan). This system had a high-resolution linear array transducer (13 MHz) and computer-assisted analytical software (e-Tracking system ® , Aloka Co., Ltd.) that allowed automatic detection of the vessel edge, as well as continuous measurement of the vessel diameter and blood flow volume. Analysis The mean end-systolic radial artery diameter, mean end-diastolic diameter, mean blood velocity, and mean blood flow volume were calculated each second after smoothing the per-beat values of end-systolic diameter, end-diastolic diameter, mean blood velocity, and mean blood flow volume with MATLAB (Ver.2007b, MathWorks).Then, fast Fourier transformation (FFT) was performed with MATLAB to obtain the power spectra of these indices. Results In all subjects, FFT-end systolic diameter, FFT-end diastolic diameter, FFT-flow velocity, and FFT-flow volume showed peaks of the power spectrum at a low frequency (LF) and a high frequency (HF).The LF and HF peaks of FFT-flow volume were significantly different from the LF and HF peaks of FFT-flow velocity ( p =0.011, p =0.041, respectively).However, the LF and HF peaks of FFT-flow volume were not significantly different from the LF and HF peaks of FFT-end systolic diameter and FFT-end diastolic diameter. Conclusion Two peaks in the power spectrum of flow volume were observed, indicating the existence of fluctuation of radial artery blood flow volume. It is suggested that fluctuation of the blood flow volume is influenced by fluctuation of the end-systolic diameter and end-diastolic diameter.

Assessment of blood volume flow in slightly curved arteries from a single velocity profile

Non-invasive estimation of arterial blood volume flow (BVF) has become a central issue in assessment of cardiovascular risk. Poiseuille and Womersley approaches are commonly used to assess the BVF from centerline velocity, but both methods neglect the influence of curvature. Based on the assumption that the velocity in curved tubes as function of the circumferential position for a given radial position can be approximated by a cosine, the BVF can also be estimated by averaging velocities at opposite radial positions, referred to as the cosine θ model (CTM). This study investigates the accuracy of BVF estimation in slightly curved arteries for BVF waveforms obtained in the brachial artery of 6 volunteers. Computational fluid dynamics simulations were used to compute the influence of curvature on velocity profiles. The BVF was then estimated from the simulation results with the CTM and methods based on Poiseuille, Womersley and using the center stream velocity and the velocity waveform at the position where the maximum velocity is observed, and compared to the prescribed BVF. The simulations show that the influence of curvature is strongest when the flow decelerates. For Poiseuille and Womersley, the time average BVF was underestimated by maximally 10.4% and 7.8% for a radius of curvature of 50 and 100 mm, respectively. The estimation error is lower for the CTM and equals 4.2% and 1.2% for a radius of curvature of 50 and 100 mm, respectively. From this study, we can conclude that the velocity waveform at the position of the maximum rather than the center stream velocity waveform combined with the Womersley method should be chosen. The CTM improves current estimation techniques if in-vivo velocity distributions are available.

Model-based assessment of dynamic arterial blood volume flow from ultrasound measurements

Model-based assessment of dynamic arterial blood volume flow from ultrasound measurements

Model-based assessment of dynamic arterial blood volume flow from ultrasound measurements

To assess in clinical practice arterial blood volume flow (BVF) from ultrasound measurements, the assumption is commonly made that the velocity profile can be approximated by a quasi-static Poiseuille model. However, pulsatile flow behaviour is more accurately described by a Womersley model. No clinical studies have addressed the consequences on the estimated dynamics of the BVF when Poiseuille rather than Womersley models are used. The aim of this study is to determine the influence of assumed Poiseuille profile instead of Womersley profile on the estimation and intrasubject variability of dynamical parameters of the BVF. For this purpose, a low number of volunteers sufficed. Brachial artery centerline velocity waveform and vessel diameter were measured with ultrasound within a small group of six volunteers. Within subjects, the intra- and inter-registration variability of BVF parameters estimates did not significantly differ. Poiseuille profiles compared to Womersley underestimates the maximum BVF by 19%, the maximum retrograde volume flow by 32% and the rise time by 18%. It can be concluded that when estimating in a straight vessel the dynamic properties of the BVF, Womersley profiles should preferably be chosen.

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.

Metabolic acidosis decreases fetal myocardial isovolumic velocities in a chronic sheep model of increased placental vascular resistance

We hypothesized that acute fetal metabolic acidosis decreases fetal myocardial motion in a chronic sheep model of increased placental vascular resistance (R(ua)). Eleven ewes and fetuses were instrumented at 118-122 days of gestation. After 5 days of recovery and 24 h of placental embolization to increase R(ua), longitudinal myocardial velocities of the right and left ventricles and interventricular septum (IVS) were assessed at the level of the atrioventricular valve annuli via tissue Doppler imaging (TDI). Ventricular inflow (E and A waves) and outflow velocities were obtained, and cardiac outputs were calculated. All measurements were performed at baseline and during fetal acidosis caused by epidural anesthesia-induced maternal hypotension, which decreased uterine artery volume blood flow, fetal oxygenation, arterial pH, and base excess and increased lactate. Compared with baseline, the peak isovolumic myocardial contraction and relaxation velocities of the ventricles and IVS, early relaxation velocity (E') of the ventricles, and systolic velocity of the IVS decreased during metabolic acidosis. The proportion of isovolumic contraction time of the cardiac cycle increased but the isovolumic relaxation and ejection time proportions and the TDI Tei index did not change. The E-to-E' ratio for both ventricles was higher during metabolic acidosis than at baseline. During metabolic acidosis, right and left ventricular cardiac outputs remained unchanged compared with baseline. In sheep fetuses with increased R(ua) and acute metabolic acidosis, global cardiac function was preserved. However, acute metabolic acidosis impaired myocardial contractility during the isovolumic phase and relaxation during the isovolumic and early filling phases of the cardiac cycle.

114: Doppler Ultrasonography to Evaluate Uterine Artery Blood Flow and Endometrial Volume

To evaluate the relationship between uterine arteries blood flow and endometrial and subendometrial volume and vascularity using three-dimensional (3D) power Doppler untrasonography in patients with recurrent spontaneous abortion (RSA).

OP15.01: Absolute uterine artery blood flow volume is increased in twin human pregnancies compared to singletons

Objectives: To compare (1) absolute and (2) weight-specific blood flow volume of uterine arteries (UtA) in normal twin pregnancies to normal singleton pregnancies. Methods: Twelve twin pregnancies (10 dichorionic, two monochorionic) with normal UtA PI and normal weight at birth were included. UtA diameter and time-averaged maximum velocity were obtained to calculate flow (mL/min) and UtA flow/EFW (mL/min/kg) in each UtA. UtA flow was estimated by the formula Q = hV · πD2/4; a patient-specific coefficient, h, was obtained by an ad hoc mathematical model. Total UtA flow was calculated as a sum of right and left vessel flow volume. Twins’ UtA flow was expressed per unit EFW considering the sum of the two EFWs. Twins were compared to 48 normal age-matched singletons. Results: Gestational age at exam was similar in twins and in singletons (25.9 ± 6.4 vs. 25.2 ± 6.2 weeks, NS). UtA flow (mL/min) was significantly increased in twins (509.3 ± 240.7 mL/min) compared to singletons (337.2 ± 257.0 mL/min) (P = 0.04). UtA flow (mL/min) exponentially increased along gestation in twins and in singletons. The twins’ trend was above the third interquartile range of singletons’ reference values. UtA diameter was significantly increased in twins (0.33 ± 0.07 cm) than in singletons (0.28 ± 0.05 cm), while no differences in UtA mean velocity were observed (77.5 ± 29.9 vs. 76.7 ± 29.1 cm/sec, respectively, NS). UtA flow per EFW did not differ between twins and singletons (384.4 ± 198.6 vs. 460.9 ± 302.9 mL/min/kg, respectively, NS). Conclusions: (1) UtA flow volume (mL/min) in twin pregnancies was significantly increased. This was determined by larger vessel diameter, compared to singletons. (2) Each twin proved to share an amount of UtA flow per unit estimated fetal weight not significantly different from singletons.

OP01.06: Reduction of uterine artery blood flow volume is correlated to reduced fetal mass in pregnancies with abnormal uterine resistance index

OP01.06: Reduction of uterine artery blood flow volume is correlated to reduced fetal mass in pregnancies with abnormal uterine resistance index

Experimental validation of uterine artery volume blood flow measurement by Doppler ultrasonography in pregnant sheep

To test the hypothesis that Doppler-derived (calculated) uterine artery volume blood flow (cQ(UtA)) reflects accurately volume blood flow measured directly (mQ(UtA)) in an experimental setting. Five pregnant sheep were instrumented at 122-130 days of gestation under general anesthesia. After a 4-day recovery period, maternal hemodynamics were varied by administering to the sheep under general anesthesia noradrenaline, beta-blocker, low oxygen gas mixture, epidural bupivacaine and ephedrine, consecutively. The central venous pressure was obtained with the help of a thermodilution catheter. The mean arterial pressure and acid-base status were monitored using a 16-gauge polyurethane catheter inserted into the descending aorta via a femoral artery. A 6-mm transit-time ultrasonic perivascular flow probe was used to measure the mQ(UtA). Doppler ultrasonography of the uterine artery was performed and volume blood flow was obtained simultaneously by the transit-time ultrasonic perivascular flow probe during each phase of the experiment. A total of 31 observations were made. The mQ(UtA) varied between 90 and 800 (mean +/- SD, 419 +/- 206) mL/min during the experiments. The corresponding values for the cQ(UtA) were 110 and 900 (mean +/- SD, 459 +/- 211) mL/min. There was a significant correlation (R = 0.76; P < 0.0001) between mQ(UtA) and cQ(UtA). The mQ(UtA) correlated positively with Doppler-derived uterine artery absolute velocities, i.e. peak systolic (R = 0.50; P = 0.004), end-diastolic (R = 0.53; P = 0.002) and time-averaged maximum (R = 0.69; P < 0.0001) and time-averaged intensity weighted mean (R = 0.75; P < 0.0001) velocities. cQ(UtA) correlates well with volume blood flow measured directly. Doppler-derived uterine artery absolute blood flow velocities reflect uteroplacental volume blood flow in pregnant sheep. Published by John Wiley & Sons, Ltd.

Total Cerebral Blood Flow Estimated by Color Velocity Imaging Quantification Ultrasound: A Predictor for Recurrent Stroke?

Although the Virchow's triad on thrombosis includes reduced blood flow as a factor, there has been relatively little data on the importance of total cerebral blood flow on the risk of subsequent stroke. In the current study, we investigate whether total cerebral blood flow helps predict stroke recurrence. Extracranial arterial blood flow volume estimated by color velocity imaging quantification ultrasound (CVIQ) is an index of cerebral blood flow measurement. We performed a cohort study of 210 consecutive acute stroke patients. Patients were studied with transcranial Doppler and duplex ultrasound for intra- and extracranial large artery disease within 3 days of symptom onset. The association between the risk of recurrent stroke and CVIQ was analyzed with Cox proportional hazards model. Thirty-nine patients (17.7%) developed an ischemic stroke during a mean follow-up of 47.5 months. The mean extracranial blood flow volume was significantly lower for patients who had a recurrent stroke than those without (594.4+/-130.3 versus 683.8+/-176.9 mL/min; P=0.003). In a Cox proportional hazards model adjusting for potential confounding variables, extracranial blood flow volume (hazard ratio (HR) for lowest tertile, 4.1; 95% confidence interval (CI), 1.5 to 11.0) along with male sex (HR, 2.5; 95% CI, 1.3 to 5.1), diabetes (HR, 2.5; 95% CI, 1.2 to 5.0) and large artery stenosis (HR, 2.2; 95% CI, 1.1 to 4.4) were independent predictors for stroke recurrence. Our data indicated that patient with low amount of blood flow to the brain is at risk of recurrent stroke.

P07.05: Uterine artery blood flow volume growth rate in uncomplicated human pregnancies

Objective: 1) To study uterine artery (UtA) flow (ml/min) growth rate along gestation in normal human pregnancies; 2) to evaluate longitudinal changes of UtA flow expressed per unit estimated fetal weight (EFW) (ml/min/kg). Methods: A cohort of twelve singleton uneventful human pregnancies, with a normal mean UtA PI, was included in this longitudinal study. UtA was evidenced by power-Doppler mode and sampled 10–15 mm prior to bifurcation. UtA diameter was measured on a perpendicular view after removing power-Doppler. UtA PI and velocity were measured with a Doppler beam angle < 30◦. The average of three consecutive diameters and velocities was considered. UtA flow was estimated by the formula Q = hV · πD2/4; h coefficient (0.5) was obtained by an ad hoc mathematical model. UtA total flow (ml/min) (right plus left UtA flow) was then expressed per EFW (ml/min/kg). Using linear interpolation, including random effects for the intercept and the slope of gestational age for each fetus, a linear mixed effects model was fitted. Results: Forty-seven ultrasound examinations were performed. Ultrasound exams were performed at 14.3,b1.2 weeks and every 4 weeks until delivery. Each case was definitively included in the study after recording normal perinatal and neonatal outcomes. UtA total flow (ml/min) showed a significant correlation to gestational age (133.6 ml/min at 15 weeks; 415.9 ml/min at 35 weeks) (p < 0.001), with a linear increase of 14.1 ml/min per week (right UtA 5.4 vs. left UtA 8.7 ml/min per week, p NS). UtA flow per unit EFW (ml/min/kg) showed a significant reduction from 780.3 ml/min/kg at 15 weeks to 144.1 ml/min/kg at 35 weeks (reduction rate 40.3 ml/min/kg per week). Conclusions: UtA flow (ml/min) significantly increased along gestation in this longitudinal cohort of normal pregnancies. UtA flow per unit EFW (ml/min/kg) significantly decreased longitudinally, since UtA flow (ml/min) growth rate was lower than fetal weight gain rate along gestation.

OP13.11: Uterine artery blood flow volume: ranges in uncomplicated human pregnancies

OP13.11: Uterine artery blood flow volume: ranges in uncomplicated human pregnancies

P07.04: Uterine artery blood flow volume is reduced in human pregnancies with increase utero‐placental downstream impedance

P07.04: Uterine artery blood flow volume is reduced in human pregnancies with increase utero‐placental downstream impedance

OP10.08: Is uterine artery blood flow volume correlated to placental site in normal human pregnancies?

one case was lost to follow-up. Of the remaining 16 pregnancies, 15 women delivered at term and all the infants were healthy. The remaining case delivered a stillborn fetus at 28 week due to an E. coli intrauterine infection. The cause of death was considered unrelated to the PSC. Discussion: According to this series, PSCs are associated with a good perinatal outcome. In contrast with umbilical cord cysts, it is unlikely that PSCs can jeopardize fetal wellbeing, despite continuous growth during pregnancy in some of them. Owing to the close proximity to the umbilical cord in most cases, PSCs should be clearly differentiated from umbilical cord cysts, which carry a poorer prognosis.

Potential Value of Poststroke Extracranial Arterial Blood Flow Volume in the Prediction of Stroke Functional Outcome

Background and Purpose: Cerebral vasoreactivity and collateral circulation are important protective mechanisms against cerebral ischemia. Previous studies suggest that the efficiency of these mechanisms can be reflected by extracranial arterial blood flow volume. Brain damage leading to neurological impairments can influence patients’ functional recovery after stroke. This study attempted to explore the potential value of poststroke extracranial arterial blood flow volume in the prediction of stroke patients’ functional outcome. Methods: We prospectively studied 362 consecutive patients who were hospitalized for recent acute strokes. All patients underwent extracranial arterial blood flow volume measurement of the carotid and vertebral arteries by color velocity imaging quantification within 3 days after admission. Their functional recovery was assessed 6 months after stroke. The effect of poststroke extracranial arterial blood flow volume on patients’ functional outcome was tested by multivariate ordinal regression after controlling for other independent variables. Significance was at p < 0.05. Results: Poststroke extracranial arterial blood flow volume together with age, prestroke modified Rankin scale, the National Institutes of Health Stroke Scale and diabetes mellitus had significant effects on the patients’ 6-month functional outcome as measured by the modified Rankin scale after controlling for other independent variables (p < 0.05). Conclusions: Poststroke extracranial arterial blood flow volume is an independent outcome predictor. The graded predictive power of this parameter is potentially more superior than other outcome predictors by allowing classification of stroke outcome according to the degree of severity. A large prospective study is thus warranted to investigate its clinical value in the management of stroke patients.

OC27.05: Human uterine artery blood volume flow at mid‐gestation: relationship to uterine artery Doppler velocimetry and placental site

intraventricular hemorrhagia and elevated nucleated red blood cell counts at delivery. Results: 8 stillbirths (10.7%), 12 perinatal (16%) and 2 neonatal death (2%) occurred among 74 fetuses. Logistic regression analysis confirmed that abnormal Ductus venosus waveforms (R2 = 0.57, p < 0.001) together with gestational age (R2 = 0.57, p < 0.001) showed the strongest association with perinatal death, whereas gestational age only was significantly related with neonatal death (R2 = 0.67, p < 0.05). Abnormal ductus venosus Doppler waveforms (R2 = 0.86, p < 0.001) and gestation age (R2 = 0.49, p < 0.05) were strongly associated with adverse outcome. Abnormal venous Doppler flow patterns performed better in the prediction of fetal or perinatal demise than died ARED flow or brain sparing. Conclusion: Abnormal Ductus venosus waveforms in preterm growth-related fetuses with ARED flow are strongly relates to adverse fetal and perinatal outcomes below 32 weeks of gestational age. The possible benefit of these pregnancies to be prolonged can only be evaluated in a prospective randomized study.

Cerebral Vasoreactivity: A Comparison of Color Velocity Imaging Quantification and Stable Xenon-Enhanced CT

Compromised cerebral vasoreactivity increases the risk of stroke. In this study, we sought to determine whether extracranial arterial blood flow volume measured on color velocity imaging quantification could be predictive of cerebral vasoreactivity after the administration of acetazolamide. Cerebral blood flow and extracranial arterial blood flow volume of 35 patients with symptomatic carotid occlusive disease were measured before and after the administration of acetazolamide on stable xenon CT and color velocity imaging quantification, respectively. The changes in unilateral extracranial arterial blood flow volume and respective hemispheric cerebral blood flow were compared. The mean difference in the percentage of change in flow volume, the 95% limit of agreement, and Cohen's kappa coefficient were calculated. A total of 64 unilateral extracranial arterial blood flow volume changes were successfully compared with the changes in the ipsilateral hemispheric cerebral blood flow. The mean difference in percentage of change in flow volume between the two techniques was 4.7%, with the 95% limit of agreement ranging from -90.2% to 99.7%. Cohen's kappa coefficient was 0.41 (95% confidence interval, 0.13-0.68; p = 0.001). The performance of color velocity imaging quantification for evaluating cerebral vasoreactivity is comparable to that of transcranial Doppler sonography. Because color velocity imaging quantification is not as limited as transcranial Doppler sonography, it could be an ideal complementary tool to transcranial Doppler sonography. More studies are required to define its clinical value.