Peripheral right pulmonary artery blood flow velocimetry: Doppler sonographic study of normal and abnormal fetuses.

The knowledge of fetal lung circulation in normal and abnormal human fetuses is limited. Our objectives were to assess normal values for flow velocity waveforms in the fetal pulmonic circulation and to test the hypothesis that Doppler velocimetry can predict lung hypoplasia. In a cross-sectional study, peripheral right pulmonary artery flow velocimetry was investigated prospectively in 96 healthy fetuses between 14 and 37 weeks' gestation and four fetuses with abnormalities known to induce lung hypoplasia. The pulsatility index was used to quantify the velocity waveforms. In normal fetuses the mean pulsatility index in the peripheral right pulmonary artery was low, being equivalent to that corresponding to 14 to 17 weeks' gestation (2.89; confidence interval = 2.35 to 3.42), increasing at midgestation to 3.44, with a confidence interval of 3.04 to 3.83; P < 0.01. Thereafter, during the late second and third trimesters the mean pulsatility index did not change significantly with GA, being 3.66 (confidence interval = 3.04 to 4.04) at term. In fetuses with proven lung hypoplasia, the pulsatility index measurements were within the 95% confidence limits of those for normal fetuses. In a normal pregnancy, except for the early stages, a relatively stable high vascular resistance of the fetal pulmonary circulation was found. Our preliminary data suggest that the pulsatility index of the lung circulation cannot be used as an indicator of lung hypoplasia.     

Segmentary fetal branch pulmonary artery blood flow velocimetry: in utero Doppler study.

OBJECTIVE: To evaluate changes in human, fetal segmentary, pulmonary artery blood flow velocimetry throughout pregnancy. DESIGN: Ninety-nine women with a singleton, low-risk gestation between 14 and 37 weeks of pregnancy were selected to participate in a prospective, cross-sectional study. All fetuses were evaluated using power and color Doppler ultrasound. Flow velocity waveforms at three sites of the right pulmonary artery were obtained. The pulsatility index (PI) was calculated in the proximal, mid and distal segment of the pulmonary artery. Mean values and 95% confidence interval (CI) for each segment were determined in correlation with gestational age. RESULTS: A full study that included Doppler measurements of all three segments of the pulmonary artery was completed on 99 fetuses. The highest mean PI of 2.36 was obtained in the proximal segment of the right pulmonary artery (CI = 2.29-2.42), whereas in the mid and distal segments the mean PI decreased significantly to 1.57 (CI = 1.53-1.61) and 1.02 (CI = 1.0-1.0) (P < 0.001), respectively. Throughout gestation, the mean PI measurements in the proximal, middle and distal segments of the branch pulmonary artery increased slightly, but without statistical significance (r = 0.274, 0.248, 0.047), respectively; (P > 0.5). CONCLUSIONS: The data obtained suggests that pulmonary circulation maintains stable vascular resistance during gestation in the human fetus. However, the PI obtained from the separate segments of the branch pulmonary artery is unique and each differs from the other, reflecting the proximity to the heart and the peripheral impedance at each location.     

Middle cerebral artery blood flow velocimetry among healthy fetuses with a single umbilical artery.

OBJECTIVE: A single umbilical artery (SUA) is an independent risk factor for perinatal morbidity and mortality in healthy fetuses. The aims of the study were (1) to determine middle cerebral artery (MCA) blood flow velocimetric values among fetuses without structural or chromosomal anomalies with an SUA and to compare them with nomograms of patients with a 3-vessel cord and (2) to measure the pulsatility index (PI) of the umbilical artery among these patients. METHODS: The PI values of the MCA and umbilical arteries were determined prospectively among 98 healthy fetuses with an SUA. The PI values were compared with nomograms of patients with a 3-vessel umbilical cord. For the MCA, peak systolic velocity (PSV) was also measured. Patients carrying fetuses with intrauterine growth restriction or congenital anomalies were excluded from the study. Middle cerebral artery PI values below the fifth percentile and PSV values above the 95th percentile adjusted for gestational age were considered abnormal. RESULTS: Gestational age ranged between 22 and 37.9 weeks (median, 30.3 weeks). After adjusting for gestational age, no alterations in the MCA PI and umbilical PI were found in comparison with the normal range for a 3-vessel cord known in the literature. Middle cerebral artery PSV values were also within the normal range for gestational age in all patients. CONCLUSIONS: The MCA PI and PSV values among healthy fetuses with an isolated SUA were similar to nomograms for fetuses with a 3-vessel umbilical cord. Therefore, abnormal MCA PI and PSV values among fetuses with an SUA should be treated the same as in patients with a 3-vessel umbilical cord.     

Alterations in segmentary branch pulmonary artery blood flow velocimetry in fetuses of diabetic mothers.

OBJECTIVE: To evaluate pulmonary blood flow in fetuses of diabetic mothers by measuring changes in fetal segmentary pulmonary artery blood flow velocimetry throughout pregnancy. METHODS: Thirty-eight women with pregestational diabetes between weeks 18 and 38 were compared with 99 women with singleton low-risk gestations as controls. Flow velocity waveforms at the proximal middle and distal segments of the right pulmonary artery were obtained with power and color Doppler sonography in all fetuses. The pulsatility index of each segment was compared between the 2 groups. The mean value and 95% confidence interval for each segment were determined in correlation with gestational age for both groups. RESULTS: The highest mean pulsatility indices were obtained in the proximal segment of the pulmonary artery and were 2.25 in the diabetes group and 2.36 in controls. The mean pulsatility indices were significantly decreased in the middle and distal segments to 1.59 and 1.10 in the diabetes group and to 1.57 and 1.02 in controls (P < .05). There were no significant differences in pulsatility indices measured at the proximal and middle segments between the study and control groups. However, the mean pulsatility index +/- SD measured at the distal segment in the diabetic group was 9% higher than in controls (1.10 +/- 0.13 versus 1.02 +/- 0.12; P = .01). The mean pulsatility index (in the study and control groups) in each arterial segment did not change significantly throughout gestation (P > .1). CONCLUSIONS:. In human fetuses throughout gestation, the pulmonary circulation maintains stable vascular resistance in both diabetic and normal pregnancies. However, in all gestations, the pulsatility index in each segment of the pulmonary artery is unique and reflects the proximity to the heart and the impedance at each location. The significantly higher pulsatility index in the diabetes group might be related to alterations in the microcirculation of diabetic patients.     

Doppler sonographic study of fetal brachial and umbilical artery blood flow during pregnancy

PURPOSE: The purpose of this study was to evaluate the fetal brachial artery resistance index (RI), its changes throughout gestation, and its relationship to the umbilical artery RI. METHODS: One hundred fifty-four sonographic examinations of the brachial and umbilical arteries in 71 fetuses were performed between 12 and 40 weeks' gestational age in 71 women with normal pregnancies. For each week of gestational age, the mean, standard deviation, range, and t-distribution 95% confidence interval of the fetal brachial artery RI were calculated. RESULTS: The fetal brachial artery RI, although relatively lower at the beginning of gestation, showed a pattern of high resistance, with a slight increase until term, whereas the fetal umbilical artery RI decreased progressively. CONCLUSIONS: The brachial artery RI is high in normal fetuses with good oxygenation. Umbilical artery RIs showed a progressive decrease until the end of term.     

Fetal cerebral blood flow redistribution in late gestation: identification of compromise in small fetuses with normal umbilical artery Doppler.

OBJECTIVE: To evaluate the role of middle cerebral artery Doppler in small fetuses during the late third trimester. DESIGN: Prospective observational study of structurally normal fetuses with an estimated fetal weight < 5th percentile for gestation. Perinatal outcome was determined using a structured datasheet sent to each referring obstetrician. SUBJECTS: Structurally normal fetuses at 35 or more weeks of gestation referred during a 2-year period to the fetal growth clinic of a regional fetal medicine unit in North London. Fetuses with aneuploidy and/or major structural abnormalities were excluded. METHODS: Umbilical artery and middle cerebral artery (MCA) Doppler waveforms were recorded and considered abnormal if above 95th or below 5th percentiles, respectively. Amniotic fluid was considered reduced if the maximum vertical cord-free pool was < 2 cm. The placenta was considered mature if the Grannum grade was II or III. The head circumference (HC)/abdominal circumference (AC) ratio was considered abnormal if > 95th percentile for gestation. Fetal growth, amniotic fluid, biophysical profile score and umbilical artery Doppler were used to advise the referring obstetrician about fetal well-being and he/she independently decided both the timing and mode of delivery. RESULTS: Forty-seven fetuses fulfilled the entry criteria. Thirty-four (72%) demonstrated normal umbilical artery Doppler waveforms. Sixteen (34%) demonstrated middle cerebral artery redistribution, of which nine (56%) had normal umbilical artery Doppler waveforms. MCA blood flow redistribution was associated with an increased incidence of cesarean delivery and need for neonatal admission. Of all gray-scale parameters, an elevated HC/AC ratio has the strongest association with MCA blood flow redistribution (15/16 vs. 1/31; P < 0.01). CONCLUSIONS: MCA Doppler may be a useful tool to assess the health of small fetuses in the late third trimester. Redistribution may occur in the presence of normal umbilical artery Doppler and should be suspected when the HC/AC ratio is elevated.     

Quantitative measurement of abdominal arterial blood flow using image-directed Doppler ultrasonography: Superior mesenteric,splenic, and common hepatic arterial blood flow in normal adults

To measure volume blood flow quantitatively in human abdominal arteries, we used an ultrasonic image-directed Doppler system and electromagnetic flow-meter to first measure volume flow in canine arteries. In dogs, there was a strong linear correlation (R = 0.98) between the product of the time average of the maximum blood flow velocity and the average cross-sectional area and the volume blood flow measured by an electromagnetic flow-meter. These results enabled measurement of volume blood flow in the human superior mesenteric (SMA), splenic (SPA), and common hepatic (CHA) arteries from the abdominal wall. Comparison of pulsatility index values indicated a larger vascular resistance in the SMA than in the SPA or CHA.     

In vivo validation of image-directed Doppler measurement of superior mesenteric artery blood flow.

Image-directed Doppler measurement of superior mesenteric artery blood flow in volunteers was validated in two artificial models with either a venous or an arterial flow profile. In the "venous" model, the Doppler device overestimated the real flow velocity by 86 +/- 7%, and in the "arterial" model by 24 +/- 9%. The areas under the time-frequency curves (AUCs) from the arterial model were measured by planimetry. A correction factor of 1.47 between flow velocities calculated after planimetry and real flow was established. Correction for this factor resulted in a flow velocity of 19.5 +/- 4.7 cm/s and a blood flow rate of 377 +/- 166 ml/min in the volunteers.     

Smoking prevents the expected postprandial increase in intestinal blood flow: a Doppler sonographic study.

OBJECTIVE: To assess whether cigarette smoking had an effect on superior mesenteric artery postprandial blood flow. METHODS: Forty-six subjects were studied in 3 groups with Doppler sonography. Group A consisted of nonsmokers; groups B and C consisted of smokers. In group B, subjects were allowed to smoke cigarettes postprandially, whereas in group C, postprandial smoking was prohibited. A baseline Doppler evaluation was performed in the fasting state, and consecutive Doppler evaluations were performed postprandially with 30-min intervals for 120 minutes. Doppler sonographic measurements of the superior mesenteric artery, including peak systolic and end-diastolic velocities, resistive index, and diameter, were calculated. Statistical analysis was performed by analysis of variance. RESULTS: All groups showed significant changes with time for all parameters (P < .001 for all). The changes in time were significantly different at 90 and 120 minutes for peak systolic velocity, at 90 minutes for end-diastolic velocity, and at 120 minutes for diameter between groups. Group B had the greatest differences. Compared with group A, changes in peak systolic velocity at 90 to 120 minutes were significantly lower in group B (P = .007 and .006, respectively), and compared with groups A and C, changes in end-diastolic velocity at 90 minutes (P = .006 and .004, respectively) and diameter at 120 minutes (P = .007 and .011, respectively) were significantly lower in group B. CONCLUSIONS: Smoking immediately after meals was associated with a superior mesenteric artery blood flow increase that was lower than expected, which may explain the belief that smoking reduces body weight. Postprandial smoking may have undesired results in patients with chronic intestinal ischemia.     

Transvaginal color Doppler study of middle cerebral artery blood flow in early normal and abnormal pregnancy.

Transvaginal color and pulsed Doppler sonography was performed on 106 singleton pregnant women; 75 had clinically normal pregnancies, and the remaining 31 patients had complicated pregnancies with vaginal bleeding. The gestational ages ranged from the 7th to 18th menstrual weeks. The aim of the study was to establish the earliest gestational age at which intracranial blood flow could be detected, in particular in the middle cerebral artery. The intracranial circulation becomes visible at the 8th week of gestation (7 weeks and 3 days). The end-diastolic component of blood flow is inconstantly present from the 11th to the 13th gestational week, and is always detected thereafter. A significant decrease in the pulsatility index (p < 0.05) and peripheral flow impedance index (p < 0.001) was observed during the early weeks of pregnancy in both the normal and complicated pregnancies. There was no significant difference between the groups (p > 0.05). Results suggest that Doppler studies of middle cerebral arteries in early pregnancy are unlikely to be of value in identifying fetal hemodynamic disorders in the early stages of spontaneous abortion.     

Venous Doppler velocimetry in the surveillance of severely compromised fetuses.

OBJECTIVE: To investigate whether venous Doppler velocimetric signs of cardiac decompensation might predict fetal demise in severely compromised fetuses. MATERIAL AND METHODS: This was a prospective study involving 154 growth-restricted fetuses, 37 of which were found to have reversed flow in the umbilical artery (BFC III). Doppler velocimetry of the right hepatic vein and ductus venosus were investigated serially and the presence of umbilical venous pulsations also registered. Only the final examination prior to birth or fetal demise was accepted for analysis and related to obstetric outcome defined as gestational age at birth, birth weight and perinatal mortality. In cases of BFC III the venous velocimetry of 15 nonsurviving fetuses was compared to that of the 22 survivors. RESULTS: There was a significant correlation between venous blood velocity and placental vascular resistance. In the right hepatic vein there was a significant decrease in peak systolic and end-systolic velocities and an increase of maximum velocity during atrial contraction and pulsatility (P < 0.05). A decrease of all velocities and increase of pulsatility were noted in the ductus venosus (P < 0.05). A reversed flow in the ductus venosus was found in 9/37 fetuses and double umbilical venous pulsations in 16/37 fetuses. However, the hepatic vein seemed to be a better predictor of impending mortality than the ductus venosus. Changes in diastolic venous blood velocity and a double pulsation in the umbilical vein were closely related to perinatal mortality, although these parameters did not provide a useful threshold to optimize the timing of delivery. CONCLUSION: Diastolic venous velocimetry changes significantly in severely compromised fetuses. These changes might be of great clinical value in deciding on the timing of delivery to minimize damage to the fetus and newborn.     

Doppler sonographic measurement of phasic renal artery blood flow velocity in patients with chronic glomerulonephritis

The phasic arterial blood flow velocity at the renal hilus was measured by Doppler sonography in 25 healthy subjects and 78 patients with chronic glomerulonephritis. Doppler velocity waveform was analyzed to give peak systolic velocity (S), end-diastolic velocity (D), resistive index (RI), and pulsatility index (PI). Creatinine clearance correlated with S (r = 0.76), D (r = 0.80), RI (r = -0.74), and PI (r = -0.85). Color Doppler sonography facilitated the detection of blood flow and permitted the measurement of absolute blood flow velocity, which previously had been difficult to determine. These results suggest that renal arterial blood flow as detected by Doppler ultrasonography may be useful for noninvasive, direct, rapid, and simple evaluation of renal function, although various modifying factors also need to be considered.     

Color Doppler sonographic diagnosis of dissecting aneurysm of the superior mesenteric artery

We report a case of dissecting aneurysm of the superior mesenteric artery (SMA) diagnosed on gray-scale and color Doppler sonography and confirmed on angiography. Spontaneous dissection of the SMA is rare, and there are few reported cases of the color Doppler sonographic findings. Gray-scale sonography revealed an aneurysmal dilatation of the SMA 3-4 cm from the SMA's origin, with an echogenic linear membrane (an intimal flap) within the aneurysm. Color Doppler sonography showed color flow within the aneurysm and showed that the intimal flap separated the aneurysm into 2 lumina. Spectral analysis revealed anterograde flow in the anterior (ie, true) lumen and retrograde flow in the posterior (ie, false) lumen.     

Color Doppler sonographic determination of renal blood flow in healthy children.

The volumetric measurement of the real renal perfusion is of interest in many clinical situations. It promises better understanding of renal function and development in healthy children and in children with acute or chronic renal failure, inflammation of any type, scarring, swelling, trauma, operations, and other conditions. Until now only scintigraphic techniques allowed measurement of the renal plasma flow in clinical practice. With color Doppler sonography all relevant data to calculate the volume of blood that passes through the kidney in a certain time can be measured. The aim of this paper is to investigate the utility of color Doppler sonography in describing renal perfusion in 63 healthy children in four separate age groups. It can be shown that the perfusion volume related to the body surface area is constant throughout childhood. Its mean value is 383 ml/min x m2. The results of the new technique of color Doppler sonographic volumetric determination of renal blood flow are then compared in 21 pediatric patients with the results of scintigraphic determination of the renal perfusion by 123I-hippurate clearance. This way a significant correlation of both methods can be demonstrated.     

彩色多普勒超声检查在正常成人肠系膜上动脉血流参数测定中的应用

目的测量正常人肠系膜上动脉（SMA）的血流参数。方法应用彩色多普勒血流显像测量160例健康人SMA的血流参数。结果SMA直径（D）、收缩期峰值流速（PSV）、平均流速（Vmean）、阻力指数（RI）、搏动指数（PI）男女性别之间、年龄组之间差异无显著性。结论确定了正常人SMA血流参数的正常值范围。     

Doppler sonography of the inferior mesenteric artery: a preliminary study.

The purposes of this study were to look for the inferior mesenteric artery in patients undergoing abdominal sonography, to determine in what percentage of patients it is visible, and to characterize Doppler flow patterns of the inferior mesenteric artery in fasting patients without intestinal vascular disease. The inferior mesenteric artery was sought in 100 consecutive fasting adults (mean age, 54 years; 63 women, 37 men), as follows: the infrarenal aorta was scanned in a transverse plane; the origin of the inferior mesenteric artery was identified on the left anterolateral surface of the aorta; the inferior mesenteric artery was then traced caudally along the left side of the aorta. The inferior mesenteric artery and the superior mesenteric artery were studied with Doppler sonography in 50 different subjects without clinical or Doppler sonographic evidence of abdominal vascular disease (mean age, 44.9 years; 17 men, 33 women). Pulsed Doppler samples were taken within the inferior mesenteric artery in sagittal planes. The resistive index was calculated from the superior mesenteric artery and the inferior mesenteric artery. The inferior mesenteric artery was detected in all but eight patients (92%). In seven patients obesity prevented visualization. The eighth patient had undergone abdominal surgery on the previous day, limiting the sonographic examination. The diastolic flow in the inferior mesenteric artery was less than that in the superior mesenteric artery in all patients. The resistive index was 0.959 +/- 0.045 in the inferior mesenteric artery and 0.856 +/- 0.046 in the superior mesenteric artery (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Coronary artery blood flow visualization signifies hemodynamic deterioration in growth-restricted fetuses.

OBJECTIVE: To determine the relationship between fetal coronary blood flow (CBF) visualization in intrauterine growth restriction (IUGR), longitudinal changes in arterial and venous flow velocity waveforms and perinatal outcome. METHODS: A total of 48 IUGR fetuses (abdominal circumference below the 5th percentile for gestational age) with absent or reversed umbilical artery (UA) end-diastolic velocity (AREDV) were examined longitudinally by echocardiography attempting CBF visualization at each examination. Doppler evaluation of the middle cerebral artery, inferior vena cava (IVC), ductus venosus (DV) and umbilical vein (UV) was performed at each examination. Doppler measurements were correct for gestational age by conversion into Z-scores (delta-indices). Doppler results and outcome from fetuses in which CBF was visualized (group 1, n = 20) and those in which CBF was never visualized (group 2, n = 28) were compared. Outcome parameters analyzed included Apgar scores, cord arterial blood gases, perinatal mortality, respiratory distress, bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis and postpartum circulatory failure requiring pressor support. RESULTS: There was no difference in Doppler indices between groups at study entry. CBF visualization coincides with a significant increase of UA-, IVC- and DV delta-indices. The greatest rate of change was observed for indices in the ductus venosus which occurred in the 24 h preceding CBF visualization. Group 1 fetuses required earlier delivery (median 27 + 4, vs. median 30 + 0), had lower birthweight (682 +/- 305 g vs. 936 +/- 416 g), lower cord pH (7.21 +/- 0.1 vs. 7.27 +/- 0.06) and cord pO2 (13 +/- 4.5 vs. 24.1 +/- 13.5 mmHg) compared to group 2 (all values P < 0.05). Mortality was similar (group 1 = 6/20, 30%; group 2 = 6/28, 21.4%). CONCLUSIONS: In IUGR, fetuses with AREDV and centralization are at high risk for hypoxemia, acidemia and adverse outcome. CBF visualization coincides with deteriorating venous flows. Operator dependence of CBF visualization and the strong association with abnormal venous flow stresses the importance of venous Doppler surveillance in these fetuses.