Bilateral type 1 proatlantal arteries with absence of vertebral arteries

The persistent proatlantal artery is a well-described communication between the carotid and vertebrobasilar system. However, persistence of bilateral proatlantal arteries is exceptionally rare. Although usually noted as an incidental finding, the presence of a proatlantal artery, particularly when bilateral, may result in unusual symptoms or may have implications for therapy. We report a case of bilateral proatlantal arteries, describe their embryology, and consider potential clinical implications of this finding.

Middle cerebral artery to umbilical artery resistance index ratio in the prediction of neonatal outcome

OBJECTIVE

The objectives of this study were to evaluate the usefulness of the middle cerebral artery to umbilical artery resistance index ratio (C/U ratio) as a predictor of adverse perinatal outcome, and to show that the absence of fetal umbilical artery end-diastolic velocity (AEDV) in SGA fetuses is associated with high morbidity and mortality.

METHOD

In this prospective study, color Doppler flow imaging was used for the estimation of the C/U ratio in fetuses that were small for their gestational age, in 70 singleton pregnancies between 29 and 42 weeks of gestation. The subjects were categorized into two groups, with Group A consisting of 35 small for gestational age (SGA) fetuses with a normal C/U ratio (1.05 or higher), and Group B comprising 35 SGA fetuses with an abnormal C/U ratio (below 1.05).

RESULT

The mean C/U ratio values for birth weight and gestational age were higher in group A than in group B. Fetuses born to mothers in group B stayed longer in the neonatal special care unit (NSCU), whereas the period from ultrasound examination to delivery was higher in the cases in group A. A higher percentage of mothers with an abnormal C/U ratio underwent cesarean section. Fetuses with an absent end-diastolic velocity of the umbilical artery had a higher morbidity. Three stillbirths occurred in fetuses with an absent end-diastolic velocity of the umbilical artery.

CONCLUSION

Our results suggest that the C/U ratio is a good predictor of neonatal outcome, and could be used to identify fetuses at risk of morbidity and mortality. Fetal umbilical artery AEDV with intrauterine growth restriction is associated with high perinatal morbidity and mortality.

Dual role of PKC in modulating pharmacomechanical coupling in fetal and adult cerebral arteries

This study tested the hypothesis that protein kinase C (PKC) has dual regulation on norepinephrine (NE)-mediated inositol 1,4, 5-trisphosphate [Ins (1,4,5)P(3)] pathway and vasoconstriction in cerebral arteries from near-term fetal ( approximately 140 gestational days) and adult sheep. Basal PKC activity values (%membrane bound) in fetal and adult cerebral arteries were 38 +/- 4% and 32 +/- 4%, respectively. In vessels of both age groups, the PKC isoforms alpha, beta(I), beta(II), and delta were relatively abundant. In contrast, compared with the adult, cerebral arteries of the fetus had low levels of PKC-epsilon. In response to 10(-4) M phorbol 12,13-dibutyrate (PDBu; PKC agonist), PKC activity in both fetal and adult cerebral arteries increased 40-50%. After NE stimulation, PKC activation with PDBu exerted negative feedback on Ins(1,4,5)P(3) and intracellular Ca(2+) concentration ([Ca(2+)](i)) in arteries of both age groups. In turn, PKC inhibition with staurosporine resulted in augmented NE-induced Ins(1,4,5)P(3) and [Ca(2+)](i) responses in adult, but not fetal, cerebral arteries. In adult tissues, PKC stimulation by PDBu increased vascular tone, but not [Ca(2+)](i). In contrast, in the fetal artery, PKC stimulation was associated with an increase in both tone and [Ca(2+)](i). In the presence of zero extracellular [Ca(2+)], these PDBu-induced responses were absent in the fetal vessel, whereas they remained unchanged in the adult. We conclude that, although basal PKC activity was similar in fetal and adult cerebral arteries, PKC's role in NE-mediated pharmacomechanical coupling differed significantly in the two age groups. In both fetal and adult cerebral arteries, PKC modulation of NE-induced signal transduction responses would appear to play a significant role in the regulation of vascular tone. The mechanisms differ in the two age groups, however, and this probably relates, in part, to the relative lack of PKC-epsilon in fetal vessels.

Longitudinal changes in the ductus venosus, cerebral transverse sinus and cardiotocogram in fetal growth restriction

OBJECTIVE

To evaluate the changes in flow velocity waveforms in the transverse cerebral sinus in growth-restricted fetuses and to correlate these changes with (1) flow velocity waveforms in the ductus venosus and (2) changes in computerized analysis of the fetal cardiotocogram.

DESIGN

Fetuses between 22 and 37 weeks' gestation with an estimated fetal weight below the fifth centile were included in this prospective longitudinal study. Doppler measurements of the umbilical artery, descending aorta, middle cerebral artery, transverse cerebral sinus and ductus venosus were recorded. Fetal heart rate was analyzed by a computer system according to the Dawes-Redman criteria.

RESULTS

We measured a significant correlation between pulsatility index in the cerebral transverse sinus and in the ductus venosus over the study period and at delivery. There was a negative correlation between these indices and short- and long-term variability of the fetal heart rate. There was a parallel increase in pulsatility in the ductus venosus and the transverse cerebral sinus. These changes were inversely correlated with fetal heart rate variability and preceded fetal distress.

CONCLUSION

Cerebral venous blood flow in IUGR fetuses may be a useful additional investigation to discriminate between fetal adaptation and fetal decompensation in chronic hypoxemia.

Effect of external cephalic version at term on fetal circulation

OBJECTIVE

We sought to investigate the subclinical effect of external cephalic version on fetal circulation.

STUDY DESIGN

A prospective observational study was conducted on 136 subjects who had external cephalic version at or beyond 36 weeks of gestation without clinical complication. Doppler ultrasonographic studies of the umbilical and middle cerebral circulations were performed before and after the external cephalic version. The following Doppler indexes were measured: (1) the pulsatility index of the umbilical artery, which represents disturbance of placental circulation, and (2) the pulsatility index of the fetal middle cerebral artery, which represents fetal response. The Wilcoxon signed rank test was used for all statistical analyses.

RESULTS

There was no significant difference in pulsatility index of the umbilical artery before and after external cephalic version (P =.674). There was a statistically significant reduction in the pulsatility index of the middle cerebral artery after external cephalic version (P =.043), and this difference existed only among multiparous women (P =.029), among those in whom the external cephalic version was considered to be difficult (P =.038), and when the placenta was posteriorly located (P =.028). The reduction in pulsatility index was not related to whether the external cephalic version was successful. In all cases the Doppler indexes remained within the normal ranges, and there were no associated fetal complications.

CONCLUSION

External cephalic version was not associated with any significant disturbance of placental resistance to blood flow. Conversely, external cephalic version was associated with a significant reduction in the pulsatility index of the middle cerebral circulation, especially among the multiparous women, after a difficult procedure or in those with a posterior placenta. This probably represents a normal fetal physiologic response to manipulation of the fetal head.

The application of color power angiography to the longitudinal quantification of blood flow volume in the fetal middle cerebral arteries, ascending aorta, descending aorta, and renal arteries during gestation

OBJECTIVE

This study was undertaken to determine by means of color power angiography the longitudinal changes in the diameters and the flow volumes of 4 major fetal arteries during gestation.

STUDY DESIGN

The middle cerebral artery, the ascending aorta, the descending aorta, and the renal arteries in 81 appropriate-for-gestational-age fetuses were examined longitudinally between 24 and 38 weeks' gestation by means of color power angiography. In addition to measurement of the diameters of these arteries, Doppler velocimetry was performed. Flow volume was calculated from the cross-sectional areas of the arteries and the velocity integral of the Doppler waveforms.

RESULTS

The mean (+/-SD) gestational age at delivery and birth weight were 39.8 +/- 1. 6 weeks and 3326 +/- 345 g, respectively. The diameters and flow volumes of all the arteries increased significantly as gestational age advanced. Flow volume increased from 39 +/- 19.0 mL/min to 140 +/- 63.9 mL/min in the middle cerebral artery, from 216.2 +/- 77.6 to 937.4 mL/min in the ascending aorta, from 124.4 +/- 76.6 to 390.0 mL/min in the descending aorta, and from 27.5 +/- 16.8 to 80.3 +/- 57.3 mL/min in the renal arteries. When blood flow volume was adjusted to milliliters per kilogram body weight, an initial significant fall in blood flow was seen in all the vessels to a minimal level at 30 weeks' gestation; blood flow rose thereafter, although not significantly, until term. The ratios of flow volume in the ascending aorta to those in the other vessels increased with gestation, with the highest ratio being that between the ascending aorta and the renal arteries.

CONCLUSION

Identification of fetal arteries with color power angiography is easy and highly sensitive. The distributions of blood flow in various fetal arteries exhibited regional differences, with significantly more blood flow to the brain. These normative baseline values may be useful in the diagnosis of congenital cardiac anomalies and also in the diagnosis and monitoring of fetuses with intrauterine growth restriction.

Doppler sonographic findings for hypertension in pregnancy and HELLP syndrome

Doppler examinations of the umbilical artery, both uterine arteries, and the fetal middle cerebral artery were performed in the third trimester in 18 patients with pregnancy induced hypertension, 52 patients with preeclampsia, and 32 patients with HELLP syndrome and the results were correlated with the parameters fetal outcome. For 74% of the patients this was the first pregnancy, in 93% of the cases a cesarean section was necessary; 66% of the newborn babies were dystrophic and 90% of them were born prematurely. The blood flow in one uterine artery was restricted in 95% of all 102 pregnant women, only 5% did not show any pathological findings. A pathological blood flow was observed on Doppler sonography in the umbilical artery in 70% of the group and 39% showed a pathologically increased perfusion of the fetal middle cerebral artery. The average birth weights and gestational ages in the study group were markedly reduced in comparison with healthy pregnant women (pregnancy induced hypertension: 1620 g/35 weeks; preeclampsia: 1660 g/34 weeks; HELLP syndrome: 1160 g/31 weeks, respectively). The lowest values for average birth weight and gestational age occurred when all four investigated blood vessels showed pathological Doppler findings: 1180 g/31 weeks (0 to 1 pathological vascular findings: 2780 g/38 weeks; 2 pathological vascular findings: 1845 g/34.5 weeks; 3 pathological vascular findings: 1330 g/31 weeks). This Doppler study underlines the importance of examining four blood vessels: the uterine, the umbilical, and the fetal middle cerebral arteries for a complete analysis of the fetoplacental hemodynamics. On account of the severely impaired hemodynamics observed in the placentas of our patients with hypertensive diseases in pregnancy or HELLP syndrome, we believe the early diagnosis of these disorders by Doppler sonography and an early start of therapy to be essential.

Clinical applications of the Doppler technique in monitoring the fetus

The application of Doppler velocimetry in the evaluation of the normal human fetal circulation targeting organs such as the placenta, the liver, the brain, and the lungs is presented. Conditions wherein evaluation of the fetal circulation becomes important are many. These conditions include, but are not limited to, intrauterine growth retardation, fetal hydrops, and multiple gestation. The importance of combining Doppler velocimetry with M-mode echocardiography and B-mode scanning is also addressed.

Effects of maturation on adrenergic neurotransmission in ovine cerebral arteries

The present studies examine the hypothesis that multiple adrenergic neuroeffector mechanisms are not fully developed in fetal, compared with adult, ovine middle cerebral arteries. In arteries denuded of endothelium and pretreated with 1 microM atropine to block involvement of muscarinic receptors, 10 microM capsaicin to deplete sensory peptidergic neurons, and 10 microM nitro-L-arginine methyl ester (L-NAME) to block possible influences from nitric oxidergic innervation, transmural stimulation at 16 Hz increased contractile tensions to 9.5 +/- 3.7% (n = 6) of the potassium maximum in adult arteries. Corresponding values in fetal arteries, however, were significantly less and averaged only 1.1 +/- 0.6% (n =10). However, postsynaptic sensitivity to norepinephrine (NE) was similar in the two age groups; NE pD(2) values (-log EC(50)) averaged 6.11 +/- 0.12 (n = 6) and 6.33 +/- 0.09 M (n = 9) in fetal and adult arteries, respectively. Similarly, NE content measured via HPLC was also similar in the two age groups and averaged 32.4 +/- 5.0 (n = 17) and 32.5 +/- 3.9 ng/ng wet wt (n = 13) in fetal and adult middle cerebral arteries, respectively. In contrast, stimulation-induced NE release was greater in fetal than in adult arteries, whether calculated as total mass released [883 +/- 184 (n = 17) vs. 416 +/- 106 pg NE/mg wet wt (n = 13)] or as fractional release [51.1 +/- 5.3 (n = 17) vs. 22.8 +/- 3.8 pg/pg NE content per pulse x 10(-6)]. Measured as an index of synaptic density, neuronal cocaine-sensitive NE uptake was similar in fetal and adult arteries [1.55 +/- 0.40 (n = 10) and 1.84 +/- 0.51 pmol/mg wet wt (n = 7), respectively]. Overall, age-related differences in postsynaptic sensitivity to NE, NE release, and NE uptake capacity cannot explain the corresponding age-related differences in response to stimulation. The data thus suggest that total synaptic volume and cleft width, in particular, are probably greater and/or that adrenergic corelease of vasoactive substances other than NE is altered in fetal compared with adult middle cerebral arteries.

Role of Ca(2+) channels in NE-induced increase in [Ca(2+)](i) and tension in fetal and adult cerebral arteries

In vascular smooth muscle, elevation of agonist-induced intracellular Ca(2+) concentration ([Ca(2+)](i)) occurs via both Ca(2+) release from intracellular stores and Ca(2+) influx across the plasma membrane. In the cerebral vasculature of the fetus and adult the relative roles of these mechanisms have not been defined. To test the hypothesis that plasma membrane L-type and receptor-operated Ca(2+) channels play a key role in NE-induced vasoconstriction via alterations in plasma membrane Ca(2+) flux and that this may change with developmental age, we performed the following study. In main branch middle cerebral arteries (MCA) from near-term fetal ( approximately 140 days) and nonpregnant adult sheep, we quantified NE-induced responses of vascular tension and [Ca(2+)](i) (by use of fura 2) under standard conditions in response to several Ca(2+) channel blockers and in response to zero extracellular Ca(2+). In fetal and adult MCA, maximal NE-induced tensions (g) were 0.91 +/- 0.12 (n = 10) and 1.61 +/- 0.13 (n = 12), respectively. The pD(2) values for NE-induced tension were both 6.0 +/- 0.1, whereas the fetal and adult maximum responses (%K(max)) were 107 +/- 16 and 119 +/- 7, respectively. The fetal and adult pD(2) values for NE-induced increase of [Ca(2+)](i) were 6.2 +/- 0.1 and 6.4 +/- 0.1, respectively, whereas maximum [Ca(2+)](i) responses were 81 +/- 9 and 103 +/- 15% of K(max), respectively. After 10(-5) M NE-induced contraction, nifedipine resulted in dose-dependent decrease in vessel tone and [Ca(2+)](i) with pIC(50) values for fetal and adult tensions of 7.3 +/- 0.1 and 6.6 +/- 0.1, respectively (P < 0.01; n = 4 each), whereas pIC(50) for [Ca(2+)](i) responses were 7.2 +/- 0.1 and 6.9 +/- 0.1, respectively. The pIC(50) values for tension for diltiazem and verapamil were somewhat lower but showed a similar relationship. The receptor-operated Ca(2+) channel blocker 2-nitro-4 carboxyphenyl-N,N-diphenyl carbamate showed little effect on NE-induced vessel contractility or [Ca(2+)](i). In the absence of extracellular Ca(2+) for 2 min, 10(-5) M NE resulted in markedly attenuated responses of adult MCA tension and [Ca(2+)](i) to 39 +/- 7 and 73 +/- 8% of control values (n = 4). For fetal MCA, exposure to extracellular Ca(2+) concentration resulted in essentially no contractile or [Ca(2+)](i) response (n = 4). Similar blunting of NE-induced tension and [Ca(2+)](i) was seen in response to 10(-3) M lanthanum ion. These findings provide evidence to suggest that especially in fetal, but also in adult, ovine MCA, Ca(2+) flux via L-type calcium channels plays a key role in NE-induced contraction. In contrast, Ca(2+) flux via receptor-operated Ca(2+) channels is of less importance. This developmental difference in the role of cerebrovascular plasma membrane Ca(2+) channels may be an important association with increased Ca(2+) sensitivity of the fetal vessels.

Intracranial arteries of human fetuses are more resistant to hypercholesterolemia-induced fatty streak formation than extracranial arteries

BACKGROUND

Atherosclerotic lesions in intracranial arteries occur later and are less extensive than in extracranial arteries. To investigate potential mechanisms responsible for this difference, in particular the atherogenic response to hypercholesterolemia and LDL oxidation, we compared the extent of fatty streak formation and the composition of these very early lesions in intracranial arteries of human fetuses from normocholesterolemic and hypercholesterolemic mothers with those in extracranial arteries.

METHODS AND RESULTS

Lesions were quantified by computer-assisted image analysis of 30 oil red O-stained sections, each from the middle cerebral, basilar, and common carotid arteries and the abdominal aorta of human fetuses (spontaneous abortions and premature newborns who died within 12 hours of birth; both of fetal age 6.2+/-1.3 months) from 43 hypercholesterolemic mothers and 34 normocholesterolemic mothers. Macrophages, apolipoprotein B, and 2 epitopes of oxidized LDL in lesions were determined immunocytochemically. Activities of superoxide dismutase, catalase, and glutathione peroxidase in the arterial wall were also determined. Lesion numbers and sizes were dramatically greater in the abdominal aorta (area of the largest lesion per section: 66.5+/-10.9 x10(3) microm2) and the carotid (11. 6+/-5.3 x10(3) microm2) than in the basilar and middle cerebral artery (0.4+/-0.1 and 0.8+/-0.2 x10(3) microm2, respectively; P<0. 0001). Hypercholesterolemia resulted in a significant increase of lesion size in extracranial arteries but only a marginal increase in intracranial arteries. In analogy, hypercholesterolemia induced a much greater increase in the intimal presence of macrophages, apolipoprotein B, and oxidized LDL (oxidation-specific epitopes) in extracranial than in intracranial arteries. Immunocytochemistry did not indicate that lesions of intracranial arteries contain relatively less oxidized LDL than similar-size lesions of extracranial arteries. Activities of Mn-superoxide dismutase but not of Zn-superoxide dismutase, catalase, or glutathione peroxidase were significantly higher in both intracranial arteries.

CONCLUSIONS

Exposure to hypercholesterolemia during fetal development results in extensive formation of fatty streaks in extracranial but not intracranial arteries. The fact that such a difference in lesion formation occurs in the absence of many other atherogenic risk factors found later in life suggests that differences in the atherogenic response to hypercholesterolemia are an important contributor to the slower onset of the disease in intracranial vessels in adults. Fetal arteries may allow elucidation of the mechanisms responsible, for example, better protection of intracranial arteries against free radical-mediated atherogenic processes.

Abnormal ductus venosus blood flow: a clue to umbilical cord complication

We report a case of umbilical cord complication causing, fetal hypoxemia and acidemia. At 30 weeks of gestation, the patient was referred because of slightly increased amniotic fluid volume and a non-reactive cardiotocogram. Biometry was appropriate for gestational age. Umbilical artery and fetal aortic Doppler findings were normal, whereas diastolic blood flow velocities in the middle cerebral artery were increased and the ductus venosus showed severely abnormal flow velocity waveforms with reversal of flow during atrial contraction. Since other reasons for fetal hypoxemia could be excluded, careful examination of the umbilical cord was performed. Traction of the hypercoiled umbilical cord due to its course around the fetal neck and shoulders was suspected. Cesarean section confirmed the sonographic findings and fetal blood gases revealed fetal acidemia. This case indicates that investigation of fetal venous blood flow may also help to identify fetal jeopardy due to reasons other than increased placental vascular resistance.

Responsiveness of human infant cerebral arteries to sympathetic nerve stimulation and vasoactive agents

Responses of segments of basilar and middle cerebral arteries of eight human infants to activation of perivascular nerves and to vasoactive drugs were studied using a resistance artery myograph. The infants ages ranged from 23 wk of gestation to 34 postnatal days. Neurogenic vasoconstriction occurred in all segments and at 8 Hz was 12.7 +/- 3.5% (11%) of tissue maximum and was blocked by phentolamine (10(-6) M). There was no evidence of a neurogenic dilator response. Catecholamine histofluorescence was seen in nerves in the adventitia at all ages studied. Norepinephrine ED50 was 7.6 +/- 1.8 x 10(-7) M, and its maximum effect was 43.1 +/- 5.7% of tissue maximum. Both neural and norepinephrine responses were greater than those of the proximal parts of adult human middle cerebral arteries obtained postmortem and surgically removed adult human pial arteries. Electron microscopy demonstrated that neural density at the adventitiomedial junction in the infant vessels was greater than in the pial arteries. Constrictor responses to serotonin and prostaglandin F2 alpha were minimal in the two infants of 23 and 24 wk of gestation but were clearly present in the older infants. Histamine and acetylcholine were potent vasodilators. Indomethacin potentiated agonist-induced contraction. In a limited number of trials angiotensin II, neuropeptide Y, caused contraction and bradykinin, relaxation. It is concluded that there is a quantitative similarity between the studied responses of infant cerebral artery segments and human pial arteries of similar diameter. However, sympathetic nerves may potentially play a more important role in the regulation of cerebrovascular tone in the infant compared with the adult, and during the gestational period examined these vessels possess an indomethacin-sensitive system that buffers agonist tone.

Regulation of Ca2+ sensitization by PKC and rho proteins in ovine cerebral arteries: effects of artery size and age

G protein-regulated Ca2+ sensitivity of vascular contractile proteins plays an important role in cerebrovascular reactivity. The present study examines the intracellular mechanisms that govern G protein-regulated Ca2+ sensitivity in cerebral arteries of different size and age. We studied beta-escin-permeabilized segments of common carotid, basilar, and middle cerebral arteries from nonpregnant adult and near-term fetal sheep. Activation of protein kinase C (PKC) by (-)-indolactam V or a phorbol ester produced receptor-independent increases in Ca2+ sensitivity. Such increases were more marked in immature arteries and were inversely correlated with artery size in both mature and immature arteries. However, inhibitors of PKC did not significantly affect increases in Ca2+ sensitivity in responses to either serotonin (5-hydroxytryptamine, 5-HT) or guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS). Alternatively, deactivation of rho p21, a small G protein associated with Rho kinase, by exotoxin C3 fully prevented increases in Ca2+ sensitivity in responses to 5-HT or GTPgammaS in both adult and fetal arteries of all types. Neither inhibitors of PKC nor exotoxin C3 altered baseline Ca2+ sensitivity. We conclude that patterns of receptor- and/or G protein-mediated modulation of Ca2+ sensitivity are dependent on an intracellular pathway that involves activation of small G proteins and Rho kinase. In contrast, PKC has little, if any, role in agonist-induced Ca2+ sensitization under the present experimental conditions.

Effects of maturation, artery size, and chronic hypoxia on 5-HT receptor type in ovine cranial arteries

To test the hypothesis that variations in cerebrovascular reactivity to 5-HT among arteries of different size or type, during maturation, or during acclimatization to high altitude involve differences in serotonergic receptor subtype, we determined relative agonist potency orders and antagonist affinities in common carotid (Com), main branch middle cerebral (Main), and second branch middle cerebral (2BR) arteries from term fetal lambs and nonpregnant adult sheep acclimatized at sea level or at an altitude of 3,820 m for approximately 110 days. In normoxic adult Com segments, agonist potency order was 5-hydroxytryptamine (5-HT) > 5-carboxamidotryptamine (5-CT) >/= 8-hydroxy-2(di-n-propylamino)tetraline (8-OH-DPAT); sumatriptan (Suma) produced no contractile response; and antagonist dissociation constant (pKb) values were 9.4 and 9.5 for ketanserin against 5-HT and 5-CT, 7.5 for GR-127935 against 5-HT, and 7.2 for SB-206553 against 5-HT. In normoxic adult Main segments, agonist potency order was 5-HT > 5-CT >/= Suma >/= DPAT, and pKb values were 9.1 and 9.2 for ketanserin against 5-HT and 5-CT and 7.4 and 8.5 for GR-127935 against 5-HT and Suma, respectively. In the 2BR segments from normoxic adults, agonist potency order was 5-CT > 5-HT > Suma > DPAT and pKb values were 7.4 and 7.2 for ketanserin against 5-HT and 5-CT and 10.0 and 8.7 for GR-127935 against 5-HT and Suma, respectively. Compared with normoxic adults, none of these values were significantly different in hypoxic adults and in fetuses only the pKb values for ketanserin against 5-HT in the 2BR segments (8.8) were greater. From these results we propose that the ratio of 5-HT2 to 5-HT1 receptors is greatest in the Com and decreases progressively to its smallest values in 2BR or smaller segments. Because this gradient appears stable and relatively resistant to the effects of maturation and chronic hypoxia, changes in reactivity associated with these perturbations may involve alterations in receptor density and/or coupling efficiency for 5-HT in ovine cranial arteries.

Persistent trigeminal artery: an anatomic study

INTRODUCTION

The most frequent embryonic communication between the vertebrobasilar and carotid systems is a persistent trigeminal artery (PTA). It has been observed in 0.1 to 0.2% of cerebral angiograms. We found this variation in an anatomic specimen, and after microscopic dissection, we performed an analysis of the course of the PTA and its relationship with the abducens nerve and the meningohypophyseal trunk.

METHOD

A PTA was incidentally encountered in an injected cadaver specimen during a transpetrosal approach. This embryonic variation and its anatomic relationship are discussed.

RESULTS

The PTA can take either a lateral or medial course regarding its relationship with the abducens nerve. When the PTA originates from the posterolateral aspect of the posterior bend of the cavernous carotid artery (C4 segment), it crosses underneath and distorts the abducens nerve, continuing between the abducens and trigeminal nerves. When taking a medial course, the PTA arises from the posteromedial aspect of the posterior bend of the cavernous carotid at the same segment and pierces the clival dura at the dorsum sellae. Cranial nerve displacement or distortion is less likely in this variation. In an analysis of carefully described anatomic studies, the PTA and meningohypophyseal trunk were found arising from either common or separated origins.

CONCLUSION

The most frequent embryological anastomosis between the carotid and vertebrobasilar system is the PTA. Its course and relationship with the cranial nerves may determine its clinical presentation.

Effects of transdermal nitroglycerin on impedance to flow in the uterine, umbilical, and fetal middle cerebral arteries in pregnancies complicated by preeclampsia and intrauterine growth retardation

OBJECTIVE

We studied whether transdermal nitroglycerin, a donor of nitric oxide, affects uterine, umbilical, and fetal cerebral blood flow in pregnancies complicated by preeclampsia and impaired uteroplacental blood flow.

STUDY DESIGN

Seventeen patients with preeclampsia were treated with a nitroglycerin patch, 10 mg per 24 hours, for three consecutive days between 28 and 36 weeks' gestation. The uterine, umbilical, and fetal middle cerebral artery pulsatility index and resistance index were assessed by color Doppler ultrasonography before the start of treatment, daily during treatment, and on the first 2 days after the removal of the last patch.

RESULTS

The nitroglycerin patch caused a significant fall in the mean uterine pulsatility index and resistance index that reached its maximum (18% +/- 4% and 17% +/- 3%, respectively, from baseline) on the last treatment day. After the removal of the last patch, uterine pulsatility index and resistance index rose to the pretreatment value within 12 hours. No significant changes in umbilical or middle cerebral artery pulsatility index and resistance index were observed during treatment. Maternal mean arterial pressure fell from 122 +/- 8 to 117 +/- 7 mm Hg (P = .05).

CONCLUSION

Transdermal administration of nitroglycerin may offer a potential for treatment for patients with preeclampsia who have increased uteroplacental impedance.

Doppler velocimetry in the umbilical and middle cerebral arteries in fetuses with intrauterine growth retardation or fetal distress

To clarify the usefulness of Doppler velocimetry in high-risk fetuses, i.e. with intrauterine growth retardation (IUGR) or with fetal distress, nomograms of the age-related changes in resistance and pulsatility indices in the fetal umbilical and middle cerebral arteries were made, and the best cut-off values for each parameter were determined. Included were 505 and 684 fetuses as the control and subject groups, respectively, between 22 and 41 weeks' gestation. Using the color-coded pulsed Doppler method, the resistance index in the umbilical and middle cerebral artery (RIUA, RIMCA), the pulsatility index in both these arteries (PIUA, PIMCA), and the RI and PI ratios between these arteries (RIUA/MCA, PIUA/MCA) were measured. In normal fetuses, RIUA and PIUA showed a gradual decrease with advance in gestational age. RIMCA and PIMCA showed a parabolic fashion with a peak around 30-31 weeks' gestation. RIUA/MCA and PIUA/MCA ratios decreased until 30-31 weeks' gestation and then increased to term. Analyses with receiver-operating-characteristic (ROC) curves revealed that PIUA is the most appropriate parameter in identifying IUGR under the cut-off point of 1.5 S.D., with a sensitivity, specificity, positive and negative predictive value, and accuracy of 60.6%, 93.3%, 75.2%, 87.6%, and 85.0%, respectively. As for fetal distress, the PIUA/MCA ratio was the most efficacious parameter under the cut-off point of 2.0 S.D., with a sensitivity, specificity, positive and negative predictive value, and accuracy of 67.3%, 97.4%, 72.9%, 96.7% and 94.6%, respectively. The findings obtained indicate that the measurement of PI value in the umbilical artery is enough to detect IUGR per se, probably due to the reflection of the decrease in the placental vascular bed, and that the ratio of indices between the umbilical artery and middle cerebral artery is more accurate than independent evaluations in identifying fetuses developing fetal distress, reflecting a brain sparing effect as well as fetoplacental insufficiency.

Intrinsic tone of cerebral artery segments of human infants between 23 weeks of gestation and term

Segments of basilar and middle cerebral arteries of eight human preterm and early postnatal infants have been examined using the resistance artery myograph technique for wire-mounted segments and the pressure perfusion arteriograph. Myograph-mounted segments spontaneously developed tone of varying duration and time course. Perfused segments showed maintained tone levels of approximately 40% of maximum possible constriction when the intraluminal pressure was 60 mm Hg. This level is not different from that found in adult human pial arteries of similar lumen diameter. Indomethacin (10[-5] M) either initiated tone increase or potentiated existing tone in the isometrically mounted segments. After washout of vasoconstrictors norepinephrine (10[-6] M) and angiotensin II (10[-8] M), indomethacin caused a pronounced, long lasting increase in basal tone. Spontaneous tone was reversed by acetylcholine (10[-6] M), isoproterenol (10[-8] to 10[-5] M), histamine (10[-8] to 10[-5] M), and papaverine (10[-5] M). Low levels of tone were increased and higher levels decreased by intraluminal flow. The pressure/diameter curves of these vessels were of similar shape as those of the equivalent size in the adult. It is concluded that intrinsic tone is a prominent feature of these large cerebral arteries, and it is modified by an endogenous indomethacin-sensitive process.

Intraobserver variability of pulsatility index measurements in three fetal vessels in the first trimester

PURPOSE

The intraobserver repeatability of pulsatility index measurements in 3 fetal vessels in the early weeks of gestation was evaluated.

METHODS

The pulsatility index was calculated from the flow velocity waveforms from 3 fetal vessels in a series of 58 uneventful, low-risk, singleton first-trimester pregnancies using transvaginal color Doppler sonography. The intraobserver repeatability was expressed as the intraclass correlation coefficient. Mean menstrual age at the time of the examination was 10.3 weeks (range, 7.6-13).

RESULTS

Flow velocity waveforms from the umbilical artery, abdominal aorta, and middle cerebral artery were obtained in 100% (58/58), 98.3% (57/58), and 100% (34/34) of cases, respectively. The intraclass correlation coefficients for these vessels were 0.89, 0.79, and 0.93, respectively.

CONCLUSIONS

The intraobserver repeatability was acceptable for all the vessels studied.

Effect of antenatal administration of thyrotrophin releasing hormone on fetal flow velocity waveforms

AIM

To determine whether antenatal administration of thyrotrophin releasing hormone (TRH), to promote lung maturation, alters blood flow through the fetal middle cerebral, umbilical artery, or ductus arteriosus and through the maternal uterine arteries.

METHODS

The effect of transplacentally administered TRH on the fetal circulation was prospectively evaluated in 30 patients between 24 and 34 weeks' gestation. TRH (400 micrograms) was given to the mother intravenously either as a bolus or an infusion. Fetal effects were determined by measuring the maximum velocity and pulsatility index (PI) in middle cerebral artery, ductus arteriosus, uterine artery and umbilical artery Doppler waveforms. Measurements were made immediately before, and 10 and 60 minutes after maternal TRH administration.

RESULTS

Intravenous injection of TRH had no significant effect on PI in the uterine, umbilical, or middle cerebral artery and the ductus arteriosus within 60 minutes of administration in either group.

CONCLUSION

The antenatal use of TRH in conjunction with steroids for fetal lung maturity does not affect utero-placental or fetal haemodynamic variables, as measured by Doppler. These findings, therefore, do not support the suggestion that antenatal intravenous administration of TRH either as bolus or infusion may have immediate adverse vascular effects in the fetus.

[Fetal doppler flow velocimetry measurements as indications for cesarean section]

An effort was made to analyze fetal umbilical and cerebral arteries Doppler flow velocimetry patterns in pregnancies terminated with cesarean section emphasizing risk to the fetus. The flow velocimetry measurements were carried out at least 7 days prior to deliveries. The incidence of abnormal values of flow indices (SD, RI i PI) and ratio (CPR) were compared in pregnant women who delivered by cesarean section due to: I--threatening fetal distress (n = 28)--elective cesarean sections were performed on pregnant women with chronic placental insufficiency symptoms; II--fetal distress (n = 22)--emergency cesarean sections; III--obstetric indications for cesarean section (no symptoms of fetal distress were present). Increased resistance in placental circulation, and decreased resistance in cerebral vessels finally leading to reversed diastolic umbilical flow occur more often in pregnant women with chronic placental insufficiency. Umbilical factor seems to be responsible for the observed in every studied group higher incidence of abnormal flows in middle cerebral than in umbilical artery. Fetal Doppler flow velocimetry of umbilical and middle cerebral arteries allow for finding of the most proper time of high-risk pregnancy termination, hence should be considered in the elective cesarean sections.

Maternal anxiety in late pregnancy and fetal hemodynamics

The aim of this study was to investigate if fetal circulation is affected by maternal anxiety. 37 nulliparous women were studied prospectively in the third trimester of pregnancy, with self-rate tests of anxiety (STAI). Doppler ultrasound examination of the umbilical artery and fetal middle cerebral artery was performed at 37-40 gestational weeks. The pulsatility index (PI) was calculated and corrected for heart rate. The women were divided into groups of increasing levels of anxiety. The fetuses of women with high trait anxiety scores had significantly higher PI values in the umbilical artery (p = 0.0056), significantly lower PI values in the fetal middle cerebral artery (p = 0.0029) and significantly lower cerebro-umbilical PI ratios (p = 0.0002), suggesting a change in blood distribution in favor of brain circulation in the fetuses. Maternal weight, weight-increase, height, age, marital status, smoking habits, drinking habits and socio-economic factors known to affect fetal well-being did not interfere with these findings. No significant differences in birth-weight, length and head circumference were found between infants born to mothers with higher trait anxiety levels compared to mothers with lower trait anxiety levels. Our results suggest that maternal stress, in terms of trait anxiety, influences fetal cerebral circulation.