Blood velocity in the fetal vein of Galen and the outcome of high-risk pregnancy

A case of giant vein of Galen malformation resulting in severe IUGR

Vein of Galen aneurysmal malformation (VGAM) is a rare congenital vascular malformation. We describe a unique case of VGAM diagnosed antenatally due to severe intrauterine growth restriction (IUGR) and heart failure. The neonate underwent two transarterial interventional embolization procedures on days 1 and 4 due to developing ventricular dilation and worsening cardiac failure. We emphazise the importance of a prenatal brain color-Doppler study in all cases of IUGR and the importance of tertiary center referral for a multidisciplinary team approach. Early embolization should be considered in the presence of antenatal heart failure, aiming to limit the neurological sequelae and the multiorgan failure.

Brain-Sparing in Intrauterine Growth Restriction: Considerations for the Neonatologist

Intrauterine growth restriction (IUGR) is most commonly caused by placental insufficiency, in response to which the fetus adapts its circulation to preserve oxygen and nutrient supply to the brain ('brain-sparing'). Currently, little is known about the postnatal course and consequences of this antenatal adaptation of the cerebral circulation. The altered cerebral haemodynamics may persist after birth, which would imply a different approach with regard to cerebral monitoring and clinical management of IUGR preterm neonates than their appropriately grown peers. Few studies are available with regard to this topic, and the small body of evidence shows controversy. This review discusses the cerebral circulatory adaptations of IUGR fetuses and appraises the available literature on their postnatal cerebral circulation with potential clinical consequences.

Can anomalies of fetal brain circulation be useful in the management of growth restricted fetuses?

Assessment of the fetal cerebral circulation provides important information on the hemodynamic changes associated with chronic hypoxia and intrauterine growth restriction. Despite the incorporation of new US parameters, the landmark for the fetal brain hemodynamic evaluation is still the middle cerebral artery. However, new vascular territories, such as the anterior and posterior cerebral arteries, might provide additional information on the onset of the brain sparing effect. The fractional moving blood volume estimation and three-dimensional power Doppler ultrasound indices are new techniques that seem to be promising in identifying cases at earlier stages of vascular deterioration; still, they are not available for clinical application and more information is needed on the reproducibility and advantages of three-dimensional power Doppler ultrasound blood flow indices. In the past, the brain sparing effect was considered as a protective mechanism; however, recent information challenges this concept. There is growing evidence of an association between brain sparing effect and increased risk of abnormal neurodevelopment after birth. Even in mild late-onset intrauterine growth restriction affected fetuses with normal umbilical artery blood flow, increased cerebral blood perfusion can be associated with a substantial risk of abnormal neuroadaptation and neurodevelopment during childhood.

Restrained cerebral hyperperfusion in response to superimposed acute hypoxemia in growth-restricted human fetuses with established brain-sparing blood flow

OBJECTIVE

To investigate the cerebral circulatory response to superimposed acute hypoxemia in growth-restricted fetuses with established brain-sparing flow (BSF) during basal conditions.

MATERIAL AND METHODS

76 term fetuses suspected of growth restriction were exposed to Doppler velocimetry in the umbilical artery (UA) and middle cerebral artery (MCA), and in 38-39 cases also in Galen's vein (GV), straight sinus (SS), and transverse sinus (TS), before and during an oxytocin challenge test (OCT), and simultaneous to electronic fetal heart rate monitoring. Nonparametric statistical analyses compared presence/absence of established BSF (MCA-to-UA pulsatility index [PI] ratio <1.08) with a two-tailed P<0.05 considered significant.

RESULTS

The OCT (positive/negative) was not different in the BSF group (BSFG, N=16) and the normal flow group (NFG, N=60) (P=0.2). During uterine contractions, the MCA PI decreased in the NFG, but not in the BSFG. De novo GV pulsations and increase of GV maximum flow velocity occurred during contractions in the NFG, but not in the BSFG. Significant SS flow velocity waveform changes were found in neither group and TS flow changes in the BSFG only.

CONCLUSIONS

Fetuses without established brain-sparing flow during basal conditions responded with both arterial and venous brain-sparing flow during acute hypoxemia, whereas in fetuses with established brain-sparing flow the cerebral circulatory responses were absent or equivocal. Fetuses with established brain-sparing flow may have a limited capacity of further cerebral hyperperfusion during superimposed acute hypoxic stress.

Acute changes of cerebral venous blood flow in growth-restricted human fetuses in response to uterine contractions

OBJECTIVE

The fetal cerebral venous circulation during acute hypoxic stress provoked by uterine contractions has not been studied previously. The aim of this study was to explore the cerebral venous circulation during an oxytocin challenge test (OCT) in intrauterine growth-restricted (IUGR) fetuses.

METHODS

Doppler recordings of blood flow in the vein of Galen (GV), straight sinus (SS) and transverse sinus (TS) before and during uterine contractions and relaxation were obtained at the same time as electronic fetal heart rate (FHR) monitoring in 44 term IUGR fetuses. The OCT was classified as negative (normal FHR) or positive (late FHR decelerations). Non-parametric statistics were used to test differences between OCT groups.

RESULTS

In OCT-negative cases (n = 39), de novo pulsations occurred in the GV, and SS flow velocities increased during contractions compared with basal measurements. There were no significant differences in TS flow. Flow recordings were less often obtained from OCT-positive cases (n = 5), making comparisons with OCT-negative cases uncertain.

CONCLUSIONS

In uncompromised IUGR fetuses an acute cerebral venous hyperperfusion develops in response to uterine contractions. Pulsations in the GV are detected but are unlikely to be an ominous sign in this situation. The more centrally located TS was less discriminating for acute cerebral venous blood flow changes.

Fetal cerebral venous Doppler velocimetry in normal and high-risk pregnancy

OBJECTIVE

In previous pilot studies, fetal vein of Galen (GV) blood velocity has been shown to be non-pulsatile in normal pregnancies. A pulsating pattern in high-risk pregnancies has been related to adverse outcome of pregnancy. The aim of this study was to establish reference ranges for fetal cerebral venous blood flow and compare them to the recordings in high-risk pregnancies in terms of predicting adverse perinatal outcome.

METHODS

The GV, straight sinus (SS) and transverse sinus (TS) were located by color Doppler ultrasound in 189 normal pregnancies between 23 and 43 weeks of gestation. Recordings were also made in 102 pregnancies complicated by pregnancy-induced hypertension and/or intrauterine growth restriction. The following parameters were measured: peak systolic velocity, minimum diastolic velocity, time-averaged maximum velocity, pulsatility index for veins (PIV) and preload index (PLI). GV pulsations were noted. In high-risk pregnancies, Doppler measurements were correlated to pregnancy outcome, including emergency operative intervention and/or neonatal distress. Umbilical vein and umbilical, uterine and middle cerebral artery blood velocities were also recorded at the same time.

RESULTS

In normal pregnancy, pulsating venous blood velocity was observed in GV in 8% of cases, in SS in 79% of cases and in TS in 100% of cases. GV and SS maximum velocity increased with gestational age and TS-PIV showed linear decreasing values and TS-PLI showed increasing values with gestational age. In high-risk pregnancies, pulsating blood velocity in the GV was found in 59 (58%) cases and was related to adverse outcome of pregnancy including mortality. Abnormal values for TS-PIV and PLI and SS maximum velocity were found in nine, six and five cases, respectively and were only related to perinatal mortality. GV pulsations were more frequent than umbilical venous pulsations.

CONCLUSIONS

Of the fetal cerebral veins studied, the presence of pulsations in the GV seems to be the best predictor of adverse outcome of high-risk pregnancy. Pulsations in the GV are more frequent than in the umbilical vein and might therefore appear earlier during worsening fetal condition, and thus be of potential value for fetal surveillance in high-risk pregnancies.

Evaluation of fetal circulation redistribution in pregnancies with absent or reversed diastolic flow in the umbilical artery

AIM

To record blood flow velocimetry in the superior mesenteric, hepatic and middle cerebral arteries for detection of circulation redistribution and prediction of perinatal outcome in fetuses with absent or reversed diastolic flow in the umbilical artery.

STUDY DESIGN

The fetal superior mesenteric, hepatic and middle cerebral artery blood velocimetry was recorded in 33 pregnancies complicated by pregnancy-induced hypertension and/or intra-uterine growth retardation between 27 and 41 weeks of gestation. Uterine artery and umbilical vein velocimetries were also recorded.

RESULTS

An abnormal mesenteric artery pulsatility index (PI) was found in four cases; two newborns died due to prematurity, growth retardation and necrotizing enterocolitis. An abnormal fetal hepatic artery PI was found in 17 cases. The brain-sparing effect in the middle cerebral artery was found in 16 cases; three newborns died after delivery. Signs of redistribution in mesenteric, hepatic and middle cerebral artery velocimetry were not related to most of the perinatal outcome variables. Umbilical vein velocimetry correlated with low arterial and venous pH. All perinatal mortalities had umbilical venous pulsations.

CONCLUSIONS

Signs of visceral circulation redistribution could not predict adverse outcome. Umbilical venous pulsations were, however, seen in nearly all fetuses; this was the only variable suggesting adverse outcome in the present study of severely compromised fetuses.