The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Torvid Kiserud - One of the best experts on this subject based on the ideXlab platform.
-
maternal diabetes alters the development of Ductus Venosus shunting in the fetus
Acta Obstetricia et Gynecologica Scandinavica, 2018Co-Authors: Torvid Kiserud, Agnethe Lund, Cathrine Ebbing, Svein Rasmussen, Jorg KesslerAbstract:INTRODUCTION: Despite adequate glycemic control, the risks of fetal macrosomia and perinatal complications are increased in diabetic pregnancies. Adjustments of the umbilical venous distribution, including increased Ductus Venosus shunting, can be important fetal compensatory mechanisms, but the impact of pregestational diabetes on umbilical venous and Ductus Venosus flow is not known. MATERIAL AND METHODS: In this prospective study, 49 women with pregestational diabetes mellitus underwent monthly ultrasound examinations from gestational week 20 to 36. The blood velocity and the mean diameters of the umbilical vein and Ductus Venosus were used for calculating blood flow volumes. The development of the umbilical venous flow, Ductus Venosus flow and Ductus Venosus shunt fraction (% of umbilical venous blood shunted through the Ductus Venosus) was compared with a reference population, and the effect of HbA1c on the Ductus Venosus flow was assessed. RESULTS: The umbilical venous flow was larger in pregnancies with pregestational diabetes mellitus than in low-risk pregnancies (p < 0.001) but smaller when normalized for fetal weight (p = 0.036). The distributional pattern of the Ductus Venosus flow developed differently in diabetic pregnancies, particularly during the third trimester, being smaller (p = 0.007), also when normalized for fetal weight (p < 0.001). Correspondingly, the Ductus Venosus shunt fraction was reduced (p < 0.0001), most prominently at 36 weeks. There were negative relations between the maternal HbA1c and the Ductus Venosus flow velocity, flow volume and shunt fraction. CONCLUSIONS: In pregnancies with pregestational diabetes mellitus, prioritized umbilical venous distribution to the fetal liver and lower Ductus Venosus shunt capacity reduce the compensatory capability of the fetus and may represent an augmented risk during hypoxic challenges during late pregnancy and birth.
-
Maternal diabetes alters the development of Ductus Venosus shunting in the fetus
Acta obstetricia et gynecologica Scandinavica, 2018Co-Authors: Agnethe Lund, Torvid Kiserud, Cathrine Ebbing, Svein Rasmussen, Jorg KesslerAbstract:INTRODUCTION Despite adequate glycemic control, the risks of fetal macrosomia and perinatal complications are increased in diabetic pregnancies. Adjustments of the umbilical venous distribution, including increased Ductus Venosus shunting, can be important fetal compensatory mechanisms, but the impact of pregestational diabetes on umbilical venous and Ductus Venosus flow is not known. MATERIAL AND METHODS In this prospective study, 49 women with pregestational diabetes mellitus underwent monthly ultrasound examinations from gestational week 20 to 36. The blood velocity and the mean diameters of the umbilical vein and Ductus Venosus were used for calculating blood flow volumes. The development of the umbilical venous flow, Ductus Venosus flow and Ductus Venosus shunt fraction (% of umbilical venous blood shunted through the Ductus Venosus) was compared with a reference population, and the effect of HbA1c on the Ductus Venosus flow was assessed. RESULTS The umbilical venous flow was larger in pregnancies with pregestational diabetes mellitus than in low-risk pregnancies (p
-
Velocity profiles in the human Ductus Venosus: a numerical fluid structure interaction study
Biomechanics and Modeling in Mechanobiology, 2013Co-Authors: Paul R. Leinan, Torvid Kiserud, Joris Degroote, Bjørn Skallerud, Jan Vierendeels, Leif R. HellevikAbstract:The veins distributing oxygenated blood from the placenta to the fetal body have been given much attention in clinical Doppler velocimetry studies, in particular the Ductus Venosus. The Ductus Venosus is embedded in the left liver lobe and connects the intra-abdominal portion of the umbilical vein (IUV) directly to the inferior vena cava, such that oxygenated blood can bypass the liver and flow directly to the fetal heart. In the current work, we have developed a mathematical model to assist the clinical assessment of volumetric flow rate at the inlet of the Ductus Venosus. With a robust estimate of the velocity profile shape coefficient (VC), the volumetric flow rate may be estimated as the product of the time-averaged cross-sectional area, the time-averaged cross-sectional maximum velocity and the VC. The time average quantities may be obtained from Doppler ultrasound measurements, whereas the VC may be estimated from numerical simulations. The mathematical model employs a 3D fluid structure interaction model of the bifurcation formed by the IUV, the Ductus Venosus and the left portal vein. Furthermore, the amniotic portion of the umbilical vein, the right liver lobe and the inferior vena cava were incorporated as lumped model boundary conditions for the fluid structure interaction model. A hyperelastic material is used to model the structural response of the vessel walls, based on recently available experimental data for the human IUV and Ductus venous. A parametric study was constructed to investigate the VC at the Ductus Venosus inlet, based on a reference case for a human fetus at 36 weeks of gestation. The VC was found to be $$0.687\,\pm \,0.023$$ (Mean $$\pm $$ SD of parametric case study), which confirms previous studies in the literature on the VC at the Ductus Venosus inlet. Additionally, CFD simulations with rigid walls were performed on a subsection of the parametric case study, and only minor changes in the predicted VCs were observed compared to the FSI cases. In conclusion, the presented mathematical model is a promising tool for the assessment of Ductus Venosus Doppler velocimetry.
-
Human Ductus Venosus Velocity Profiles in the First Trimester
Cardiovascular Engineering and Technology, 2013Co-Authors: Paul R. Leinan, Torvid Kiserud, Leif R. HellevikAbstract:The fluid dynamics in the human fetal Ductus Venosus in the early stage of pregnancy is not well explored. Consequently, there is an uncertainty in the interpretation of the temporal and spatial velocity variation in the Ductus Venosus. A robust estimation procedure for non-invasive measurement of the blood flow, based on conventional Doppler ultrasound measurements, is therefore missing. The aim of the present study was to describe the spatial and temporal velocity distribution at the Ductus Venosus bifurcation for boundary condition typical for fetuses at 11–13 weeks of gestation by means of a mathematical model. In particular we wanted to investigate velocity profiles at the Ductus Venosus inlet region in early pregnancy under normal conditions, to assess whether robust estimates of velocity profile shape coefficients may be given in order to provide noninvasive volumetric flow rate assessment in the Ductus Venosus. Such information will be useful in a clinical assessment of the fetus. Our model predicted a close to parabolic velocity profile in the inlet section of the Ductus Venosus during the cardiac cycle, with a shape factor of 0.53. Our simulations also showed that during atrial contraction (the A-wave), transient simultaneous positive and negative velocities may be observed in the same cross-section, in Womersley-like velocity profiles. Thus, as previous clinical investigators have reported these velocities as either positive or negative, our findings challenge clinical interpretation.
-
The Ductus Venosus.
Seminars in perinatology, 2001Co-Authors: Torvid KiserudAbstract:Until recently, our information on the Ductus Venosus was based on postmortem and experimental studies. The present review relates to the modern concept of this vein predominantly founded on clinical studies. Recent publications show that the blood distribution through the Ductus Venosus is particularly sensitive to changes in umbilical venous pressure, blood viscosity, and an active regulation of diameter of the entire Ductus Venosus. The mean fraction of umbilical blood shunted through the Ductus is reduced from 30% to 20% during the second half of the human pregnancy, indicating that, during this period, the fetal liver has a higher priority than the shunting through the Ductus Venosus, apart from the compensatory redistribution needed during extreme challanges of placental compromize and hypoxemia. Additionally, the Ductus Venosus acts as a transmission line to the umbilical vein for pulse waves generated in the heart. These waves, reflecting cardiac function, are substantially influenced by the local variation of impedance and compliance.
B Simensen - One of the best experts on this subject based on the ideXlab platform.
-
Ductus Venosus blood velocity and the umbilical circulation in the seriously growth retarded fetus
Ultrasound in Obstetrics & Gynecology, 1994Co-Authors: Torvid Kiserud, Leif Rune Hellevik, S H Eiknes, H G Blaas, B SimensenAbstract:Based on the assumption that the Ductus Venosus is regulator of oxygenated blood in the fetus, the present study investigated the blood flow velocity of the Ductus Venosus in relation to the umbilical circulation in the that seriously growth-retarded fetus. The study group of 38 fetuses (gestational week 17-39) had no chromosomal aberrations or structural malformations and had an ultrasonographic biometry of < 2.5th centile and birth weight of
-
Ductus Venosus blood velocity and the umbilical circulation in the seriously growth retarded fetus
Ultrasound in Obstetrics & Gynecology, 1994Co-Authors: T Kiserud, Leif Rune Hellevik, S H Eiknes, H G Blaas, B SimensenAbstract:Based on the assumption that the Ductus Venosus is regulator of oxygenated blood in the fetus, the present study investigated the blood flow velocity of the Ductus Venosus in relation to the umbilical circulation in the that seriously growth-retarded fetus. The study group of 38 fetuses (gestational week 17–39) had no chromosomal aberrations or structural malformations and had an ultrasonographic biometry of < 2.5th centile and birth weight of ≤ 2.5th centile. Of the 38 fetuses seven died in utero and four died postnatally. The ultrasonographic examination included pulsed Doppler measurement of the umbilical artery pulsatility index (PI), the umbilical vein dimension and blood flow velocity, and the peak and maximum blood flow velocities of the Ductus Venosus. The majority of fetuses had a raised PI in the umbilical artery (26/38) and reduced blood flow in the umbilical vein (25/33). Despite such changes in the umbilical circulation, a normal peak velocity in the Ductus Venosus was maintained in all fetuses. During the atrial contraction, however, 13 fetuses had reduced or reversed blood velocity in the Ductus Venosus. Reduced Ductus Venosus velocity during atrial contraction seemed to be a serious finding linked to raised PI and absent or reversed end-diastolic flow in the umbilical artery, and umbilical vein pulsation. The results support the assumption that the blood flow of the Ductus Venosus is a preferential bloodstream in the human fetus that is maintained within normal ranges as long as possible during placental hemodynamic compromise. Copyright © 1994 International Society of Ultrasound in Obstetrics and Gynecology
Leif Rune Hellevik - One of the best experts on this subject based on the ideXlab platform.
-
Ductus Venosus blood velocity and the umbilical circulation in the seriously growth retarded fetus
Ultrasound in Obstetrics & Gynecology, 1994Co-Authors: Torvid Kiserud, Leif Rune Hellevik, S H Eiknes, H G Blaas, B SimensenAbstract:Based on the assumption that the Ductus Venosus is regulator of oxygenated blood in the fetus, the present study investigated the blood flow velocity of the Ductus Venosus in relation to the umbilical circulation in the that seriously growth-retarded fetus. The study group of 38 fetuses (gestational week 17-39) had no chromosomal aberrations or structural malformations and had an ultrasonographic biometry of < 2.5th centile and birth weight of
-
Ductus Venosus blood velocity and the umbilical circulation in the seriously growth retarded fetus
Ultrasound in Obstetrics & Gynecology, 1994Co-Authors: T Kiserud, Leif Rune Hellevik, S H Eiknes, H G Blaas, B SimensenAbstract:Based on the assumption that the Ductus Venosus is regulator of oxygenated blood in the fetus, the present study investigated the blood flow velocity of the Ductus Venosus in relation to the umbilical circulation in the that seriously growth-retarded fetus. The study group of 38 fetuses (gestational week 17–39) had no chromosomal aberrations or structural malformations and had an ultrasonographic biometry of < 2.5th centile and birth weight of ≤ 2.5th centile. Of the 38 fetuses seven died in utero and four died postnatally. The ultrasonographic examination included pulsed Doppler measurement of the umbilical artery pulsatility index (PI), the umbilical vein dimension and blood flow velocity, and the peak and maximum blood flow velocities of the Ductus Venosus. The majority of fetuses had a raised PI in the umbilical artery (26/38) and reduced blood flow in the umbilical vein (25/33). Despite such changes in the umbilical circulation, a normal peak velocity in the Ductus Venosus was maintained in all fetuses. During the atrial contraction, however, 13 fetuses had reduced or reversed blood velocity in the Ductus Venosus. Reduced Ductus Venosus velocity during atrial contraction seemed to be a serious finding linked to raised PI and absent or reversed end-diastolic flow in the umbilical artery, and umbilical vein pulsation. The results support the assumption that the blood flow of the Ductus Venosus is a preferential bloodstream in the human fetus that is maintained within normal ranges as long as possible during placental hemodynamic compromise. Copyright © 1994 International Society of Ultrasound in Obstetrics and Gynecology
-
Estimation of the pressure gradient across the fetal Ductus Venosus based on Doppler velocimetry.
Ultrasound in medicine & biology, 1994Co-Authors: Torvid Kiserud, Sturla H. Eik-nes, Leif Rune Hellevik, Bjorn A. J. Angelsen, H.‐g. BlaasAbstract:In the fetus, the umbilical vein is directly linked to the inferior vena cava by the narrow Ductus Venosus. Thus, the Ductus Venosus blood velocity probably reflects the pressure gradient between the umbilical vein and the central venous system. In a longitudinal study that included 29 normal fetuses, pulsed Doppler velocimetry was carried out in the umbilical vein and the Ductus Venosus during the last half of the pregnancy. By applying the Bernoulli equation, we estimated the pressure gradient across the Ductus Venosus to vary between 0-3 mm Hg during the heart cycle; it remained within those ranges during gestational weeks 18-40. During fetal inspiratory movement, pressure gradients up to 22 mm Hg were estimated. The estimated Ductus Venosus pressure gradient seems to be within ranges compatible with known umbilical venous pressures, and may provide a new opportunity to understand central venous hemodynamics and respiratory force in the fetus once methodological limitations are controlled.
-
Ultrasonographic velocimetry of the fetal Ductus Venosus.
Lancet (London England), 1991Co-Authors: Torvid Kiserud, Sturla H. Eik-nes, Harm-gerd K. Blaas, Leif Rune HellevikAbstract:In fetal lambs, the Ductus Venosus shunts well-oxygenated blood directly to the heart, a pattern expected to be found also in the human fetus. We aimed to describe the human Ductus Venosus in a longitudinal sonographic study of two-dimensional imaging, colour flow mapping, and pulsed doppler velocimetry every 3-4 weeks during the second half of pregnancy. The fetuses of 29 healthy women were studied. The Ductus Venosus and its blood flow were identified and recorded for later analysis that included maximum velocity tracing. In the 184 examinations analysed, the Ductus Venosus appeared as a narrow vessel projecting a high-velocity jet posteriorly to reach the foramen ovale. The mean peak velocity in the Ductus Venosus increased from 65 cm/s in week 18 to 75 cm/s at term. Low values of the time-averaged maximum velocity were found in 2 fetuses with cardiovascular abnormalities (1 supraventricular tachycardia, 1 congestive heart failure), as a result of reversed flow in the Ductus Venosus during atrial systole. The high peak velocity in the Ductus Venosus, which is comparable with arterial velocities, probably gives the blood sufficient momentum to reach the foramen ovale without extensive mixing with deoxygenated blood. Velocimetry of the Ductus Venosus carries new diagnostic possibilities.
C. G. V. Murta - One of the best experts on this subject based on the ideXlab platform.
-
Ductus Venosus Doppler velocimetry in the prediction of acidemia at birth: which is the best parameter?
Prenatal diagnosis, 2005Co-Authors: Francisco Herlânio Costa Carvalho, C. G. V. Murta, Antonio Fernandes Moron, Rosiane Mattar, R. M. Santana, M. M. Barbosa, Maria Regina Torloni, Flávio Augusto Prado VasquesAbstract:Objectives To evaluate the prediction of acidemia at birth using Ductus Venosus Doppler velocimetry and to determine the best parameter and cut-off values for this prediction in pregnancies complicated with placental insufficiency. Methods Prospective cross-sectional study. Forty-seven patients with placental insufficiency managed in two Brazilian hospitals were submitted to Ductus Venosus Doppler velocimetry in the last 24 h before delivery. All pregnancies were singleton, at least 26 weeks of age and without structural or chromosomal anomalies. A ROC curve was calculated for each Ductus Venosus parameter (independent variable) and acidemia (dependent variable). A cut-off value was established. The McNemar test was used to compare the various parameters. Results The Ductus Venosus S, D and A peak velocities were not good predictors of acidemia at birth. Pulsatility Index for Veins (PIV) was a good predictor of acidemia (ROC curve area 0.79, p = 0.003), as well as S/A and (S − A)/S ratios (ROC curve area 0.818, p = 0.001). The cut-off values were PIV = 0.76, S/A = 2.67 and (S − A)/S = 0.63. Conclusions In this high-risk population, angle-independent Ductus Venosus Doppler indexes were good predictors of birth acidemia. The S/A and (S − A)/S ratios and the Ductus Venosus PIV were statistically equivalent in this prediction. Copyright © 2005 John Wiley & Sons, Ltd.
-
P236: The cylindrical shape of Ductus Venosus in the first trimester of gestation
Ultrasound in Obstetrics & Gynecology, 2003Co-Authors: C. G. V. Murta, F. A. P. Vasques, L. Nery, T. R. M. Gonçalves, Carlos Gilberto Almodin, Antonio Fernandes Moron, F. H. C. CarvalhoAbstract:Objective: To investigate the geometric shape of the Ductus Venosus between 10–13 weeks of gestation. Patients and methods: Ductus Venosus measurements were performed in 64 normal human fetus using ultrasound color Doppler imaging. The geometrical measurements obtained were: length (n = 64), isthmic width (n = 34) and outlet width (n = 20). For statistical analysis, the analysis of variance, linear regression, Kruskal-Wallis terst and the Spearman correlation were used. Results: At 10–13 weeks of gestation, the Ductus Venosus length indicates a continuous growth and the width did not change. The measurements (median) were: length = 2 mm, isthimic inlet = 1.4 mm, and outlet width +1.4 mm. Conclusion: The new geometric shape of the Ductus Venosus between 10–13 weeks of gestation has a cylindrical and not a slender trumpet-like shape as defined previously in the literature.
-
Application of Ductus Venosus Doppler velocimetry for the detection of fetal aneuploidy in the first trimester of pregnancy.
Fetal diagnosis and therapy, 2002Co-Authors: C. G. V. Murta, Antonio Fernandes Moron, M. A. P. Ávila, Carl P. WeinerAbstract:Objective: To test the hypothesis the application of Ductus Venosus Doppler velocimetry may serve as a screening tool between 10 and 14 weeks’ gestation for the detection of fetuses with chromosomal abnormalities. Methods: 372 consecutive fetuses were studied. Based on prior study, a chromosomal abnormality was suspected when either the nuchal translucency was above the 95th centile, or there was reversed or absent flow in the Ductus Venosus during atrial contraction. Sensitivity, specificity, and the negative and positive predictive values were calculated. Results: There were 29 chromosomally abnormal fetuses. Of these 29 fetuses, Ductus Venosus blood flow during atrial contraction was either absent (n = 2) or reversed (n = 25) in 93.1%. In the chromosomally normal fetuses (n = 343), only 6 (1.7%) had abnormal Doppler profiles in the Ductus Venosus (specificity = 98.3%, positive and negative predictive values = 81.8% and 99.4%, respectively). Conclusion: The Doppler waveform of the Ductus Venosus was at least equal to NT thickness measurement for the detection of chromosomal abnormalities.
Jorg Kessler - One of the best experts on this subject based on the ideXlab platform.
-
maternal diabetes alters the development of Ductus Venosus shunting in the fetus
Acta Obstetricia et Gynecologica Scandinavica, 2018Co-Authors: Torvid Kiserud, Agnethe Lund, Cathrine Ebbing, Svein Rasmussen, Jorg KesslerAbstract:INTRODUCTION: Despite adequate glycemic control, the risks of fetal macrosomia and perinatal complications are increased in diabetic pregnancies. Adjustments of the umbilical venous distribution, including increased Ductus Venosus shunting, can be important fetal compensatory mechanisms, but the impact of pregestational diabetes on umbilical venous and Ductus Venosus flow is not known. MATERIAL AND METHODS: In this prospective study, 49 women with pregestational diabetes mellitus underwent monthly ultrasound examinations from gestational week 20 to 36. The blood velocity and the mean diameters of the umbilical vein and Ductus Venosus were used for calculating blood flow volumes. The development of the umbilical venous flow, Ductus Venosus flow and Ductus Venosus shunt fraction (% of umbilical venous blood shunted through the Ductus Venosus) was compared with a reference population, and the effect of HbA1c on the Ductus Venosus flow was assessed. RESULTS: The umbilical venous flow was larger in pregnancies with pregestational diabetes mellitus than in low-risk pregnancies (p < 0.001) but smaller when normalized for fetal weight (p = 0.036). The distributional pattern of the Ductus Venosus flow developed differently in diabetic pregnancies, particularly during the third trimester, being smaller (p = 0.007), also when normalized for fetal weight (p < 0.001). Correspondingly, the Ductus Venosus shunt fraction was reduced (p < 0.0001), most prominently at 36 weeks. There were negative relations between the maternal HbA1c and the Ductus Venosus flow velocity, flow volume and shunt fraction. CONCLUSIONS: In pregnancies with pregestational diabetes mellitus, prioritized umbilical venous distribution to the fetal liver and lower Ductus Venosus shunt capacity reduce the compensatory capability of the fetus and may represent an augmented risk during hypoxic challenges during late pregnancy and birth.
-
Maternal diabetes alters the development of Ductus Venosus shunting in the fetus
Acta obstetricia et gynecologica Scandinavica, 2018Co-Authors: Agnethe Lund, Torvid Kiserud, Cathrine Ebbing, Svein Rasmussen, Jorg KesslerAbstract:INTRODUCTION Despite adequate glycemic control, the risks of fetal macrosomia and perinatal complications are increased in diabetic pregnancies. Adjustments of the umbilical venous distribution, including increased Ductus Venosus shunting, can be important fetal compensatory mechanisms, but the impact of pregestational diabetes on umbilical venous and Ductus Venosus flow is not known. MATERIAL AND METHODS In this prospective study, 49 women with pregestational diabetes mellitus underwent monthly ultrasound examinations from gestational week 20 to 36. The blood velocity and the mean diameters of the umbilical vein and Ductus Venosus were used for calculating blood flow volumes. The development of the umbilical venous flow, Ductus Venosus flow and Ductus Venosus shunt fraction (% of umbilical venous blood shunted through the Ductus Venosus) was compared with a reference population, and the effect of HbA1c on the Ductus Venosus flow was assessed. RESULTS The umbilical venous flow was larger in pregnancies with pregestational diabetes mellitus than in low-risk pregnancies (p
