Congenital vascular rings: a clinical challenge for the pediatrician.

Vascular rings are congenital anomalies that lead to variable degrees of respiratory problems or feeding difficulties by forming a complete or partial ring compressing the trachea, the bronchi, and the esophagus. The clinical diagnosis of vascular rings is often challenging for the pediatrician because the clinical manifestations are heterogeneous and nonspecific. Symptoms can vary from wheezing, stridor, dyspnea, and/or dysphagia to life-threatening conditions; however, they may not be present. The aim of this study is to review the recent literature on this subject and describe new developments in diagnostics and imaging.

Mophometric study of the aortic arch and its major branches in rat fetuses on the 21st day of gestation.

The anatomy and embryology of the aortic arch and its branching tributaries (brachiocephalic trunk, left common carotid artery and left subclavian artery) in man and animals are well substantiated. However, the anatomical variations and morphometry of the aortic arch and its branching tributaries in rat fetus at the 21st gestation day have not been studied. Pregnant rats were hysterectomized and the arterial systems of 114 fetuses were injected with a polymerisable resin through the umbilical artery. After maceration, the vascular casts were dissected out and prepared for observations under a scanning electron microscope (SEM). The resulting SEM pictures were studied with a picture analyser and different vessel parameters (diameters, lengths and angles) were measured. The success rate of the microvascular cast injection was 46.5%. Out of the 53 observed aortic arch casts, 98.1% showed the classical branching pattern and one (1.9%) had no brachiocephalic trunk. Morphological analysis showed many differences, which were not linked to the litter. The statistical processing of the measurements enabled us to determine that the aorta diameter after the branching of the left subclavian artery was the most replicable parameter. Moreover, the results revealed some strong correlations between different parameters. There are probably no discrete categories among the various observed parameters as diameters and angles. Some parameters show very little variability and can thus be used as reference points for further studies such as the comparison of a control population with a population treated with a relevant xenobiotic.

The variability and morphometry of the brachiocephalic trunk in human foetuses.

In prenatal and pediatric cardiovascular surgery knowledge of the various arrangements of the aortic arch and its branches as well as the normative data are essential. The variability and morphometric features of the brachiocephalic trunk in 131 human foetuses (65 male, 66 female) ranging from 15 to 34 weeks of gestation were studied by means of anatomical, digital and statistical methods. In all the foetuses examined the left aortic arches were found to have three different arrangements. In 74.05% of cases the usual pattern of the aortic arch with its three main branches were observed. A common origin of the brachiocephalic trunk and left common carotid artery occurred in 20.61% of individuals. In 5.34% of cases the left vertebral artery was an additional vessel and arose from the aortic arch between the left common carotid and subclavian arteries. No significant gender differences were found with respect to the brachiocephalic trunk (p > or = 0.05). The developmental increase in length (r1 = 0.78) and diameter (r2 = 0.83) correlated with a linear function but the increase in volume in relation to age corresponded to a quadratic function (r3 = 0.73). Our results show the largest increases in the brachiocephalic trunk according to the following parameters: the length - between the 4(th) and 5(th), and 7(th) and 8(th) months, diameter - between the 8(th) and 9(th) months and volume - between the 4(th) and 5(th), and 7(th) and 9(th) months of gestation (p < or = 0.01). The present study constructs a normal range for the morphometric features of the foetal brachiocephalic trunk.

Morphological aspect of the thyroid ima artery in human fetuses.

Some morphological characteristics of the variable thyroid ima artery were investigated on the injected fetal arteries and explained on their 106 static images. Thyroid ima artery of different origin was proven in 18 (16.9%) cases. With respect to the vascular sources of the investigated artery, the branching of the brachiocephalic trunk and right common carotid artery was found in 72.1% of the cases. At the same time, the thyroid ima and superior or inferior thyroid arteries were obvious in all cases, as well as the presence of single or multiple variations and abnormalities of neighbouring arteries in 38.8% of the cases. No major anatomical difference was noted between the fetal form of the variable thyroid artery reported in this paper and the postnatal form reviewed from the literature. Thyroid ima artery probably represents an example of the arterial self-differentiation and induced differentiation of the unilateral vascular trunk.

Ventrally emigrating neural tube cells contribute to the normal development of heart and great vessels.

We investigated the contributions of a recently described population of neural tube cells, which participates in the development of a variety of tissues, to the development of the heart and great vessels. These cells, termed as the ventrally emigrating neural tube (VENT) cells, originate in the ventral part of the hindbrain neural tube, emigrate at the site of attachment of the cranial nerves, and populate their respective target tissues. VENT cells of the caudal hindbrain neural tube at the level of the vagus nerve, which were previously reported to migrate into the heart, were tagged with replication-deficient retroviruses containing the LacZ gene in chick embryos, after the emigration of neural crest from this region. In older embryos, VENT cells were detected in a variety of locations including the ventricles, atria, their septa, aorticopulmonary septum, and great vessels of the heart. Immunostaining with a specific marker revealed that VENT cells differentiated into smooth muscle cells of great vessels. Differentiation of VENT cells into cardiac muscle cells was reported previously. Extirpation of the VENT cells prior to their departure from the neural tube resulted in some common cardiovascular malformations: thin-walled ventricles and atria, ventricular and atrial septal defects, persistent truncus arteriosus, and stenosis of the great vessels. These results suggest that a novel population of neural tube cells also contributes to the normal development of the heart and great vessels. Thus, the heart and great vessels develop from three sources of cells: mesoderm, neural crest, and VENT cells.

Skeletopy of the brachiocephalic trunk and the common carotid arteries in human fetuses.

By means of anatomical and radiological methods and with help of the Computer Digital Image Analysis System the brachiocephalic trunk and the common carotid arteries in relation to the vertebral column were studied in 60 human fetuses. The vessels were found to be between the upper borders: of the third thoracic vertebra and the first cervical vertebra (Th3s-C1s). In the 6th month of the ontogenetic development the vessels descended by one vertebra and established their location in the next prenatal compartment (8-9) between the lower borders: of these same vertebra (Th3i-C1i). We have counted the skeletopie age correlation coefficients of these vessels and found the diminuation of their values. Sexual skeletopic dimorphism have not been observed. These investigations have clinical implications.

Trisomy (12p) with telocentric and pseudoisodicentric chromosome formation in a fetus.

We report an 18-week-old fetus with at 47, XY, -12, +12q, +psu idic(12p) karyotype, mild dysmorphic features and absence of the brachiocephalic truncus.

Cerebral circulatory responses of near-term ovine fetuses during sustained fetal placental embolization.

To test the hypothesis that, in response to an increase in placental vascular resistance and progressive fetal asphyxia, the changes in external carotid blood flow waveforms are directly related to changes in external carotid vascular resistance, we embolized the fetal side of the placenta in pregnant sheep and measured cerebral and external carotid artery circulatory changes in relation to changes in external carotid artery flow waveforms. Chronically catheterized fetal sheep at 0.85 of gestation were embolized (n = 11) in the descending aorta for 6 h, until fetal arterial pH fell to approximately 6.90. Fetuses became rapidly hypoxemic (P < 0.0001) and developed a mixed respiratory and metabolic acidosis (P < 0.0001 for PCO2, pH, and base excess). There was a transient 40% increase in external carotid blood flow at pH approximately 7.25 and a parallel 32% increase in fetal arterial blood pressure (both (P < 0.01), whereas the external vascular resistance remained unaltered. Cerebral blood flow increased by 130% (P < 0.0001), and cerebral vascular resistance decreased by 125% (P < 0.0001) throughout the study. The external carotid resistance index (RI) decreased by 32% (P < 0.0001) at the time external carotid vascular resistance remained unchanged. This fall in external carotid RI was due almost entirely to a 110% increase in external carotid fundamental impedance (P < 0.001). We conclude that the poor relationship between the changes in external carotid vascular resistance and RI indicated that other hemodynamic factors such as vascular impedance to pulsatile flow must be measured for correct interpretation of changes in flow waveform shape under hypoxic conditions. In addition, changes in external carotid blood flow were not proportional to changes in cerebral blood flow in this model.

The structure of the mouse heart in late fetal stages.

Because of the opportunities for genetic manipulation, the mouse has become the major species for models of human disease. Recently, targeted and insertional mutations have induced many novel models of developmental abnormality, including several of congenital heart defects. Interpretation and use of such models requires a precise understanding of the similarities and differences between mouse and human in terms of cardiac development and structure. To this end, we have characterised the late fetal mouse heart using scanning electron microscopy and serial histological sections. Right atrial anatomy is dominated by the venous valves, which separate the orifices of the caval veins from the musculature of the primary atrium. Their structure and location suggest that the pulmonary vein is unlikely to develop from the venous sinus. The pectinated wall of the appendage serves to distinguish the morphologically right atrium, in that it runs around the atrioventricular junction, from the left atrium in which this vestibular region is smooth-walled. The persistence of the left superior caval vein draining to the right atrium, along with a solitary opening for the pulmonary vein in the left atrium, distinguishes the atrial anatomy of the mouse from that of the human. The flap valve of the oval foramen is extensive and represents the embryonic primary atrial septum. The superior rim of the foramen is an infolding of the atrial roof, as has been described in the human, showing that, contrary to orthodox opinion, there is no extensive formation of a secondary atrial septum. The region of the membranous septum seen in the human heart is a relatively thick structure in the late fetal mouse, and is located exclusively in an atrioventricular position. Unlike the human, there is little distinction between the apical trabeculations of the left and right ventricles of the mouse heart.

Rare types of aortic arch anomalies.

Rare types of aortic arch malformations include isolation of the right or left subclavian arteries in conjunction with a left or right aortic arch respectively. Isolation of the innominate or carotid arteries and an aberrant left innominate artery may exist in association with a right aortic arch. Other anomalies are persistent fifth aortic arch, subclavian artery as the first branch of the aortic arch, pulmonary artery, and ductus arteriosus sling. The angiocardiographic features and embryology of each of these malformations are discussed.

A morphometric study of foetal and newborn cardiac growth in the horse.

A morphometric study of hearts in 81 equine foetuses, ranging in age from 190 to 330 days of foetal age, and in 26 newborn foals is reported. The mean weight, external dimensions, ventricular wall thickness and circumference of the atrio-ventricular orifice were measured. Features of the main associated vessels of the heart were also recorded. All cardiac measurements of foetuses increased linearly throughout the latter half of pregnancy and were highly correlated with foetal age. This linear growth pattern was also found in the parameters of the associated arterial trunks. The ratio of the right ventricular weight to the total ventricular weight in the equine foetuses increased gradually from 0.27 (Day 190) to 0.34 (full term), but in newborn foals, this ratio began to decrease soon after birth, declining from 0.32 to 0.28 by 11 days of age. The interventricular septum was thickest followed by the right ventricular wall, and the left ventricular wall was thinnest during the period of gestation studied. The right ventricle was 3.2 per cent to 31.5 per cent thicker than the left ventricle.

The carotid web: a developmental anomaly of the brachiocephalic system.

A case of a congenital carotid web is reported. This lesion is believed to be a very rare anomaly of carotid development. The embryologic development of the brachiocephalic arteries is discussed. Anomalies of the brachiocephalic arteries including anomalies of origin from the aortic arch, atresia, and persistent communications between the carotid and vertebral system are reviewed.

[Diverticulum of the brachiocephalic trunk--angiographic image and embryologic significance]. / Das Divertikel des Truncus brachiocephalicus--Angiographische Darstellung und embryologische Deutung.

A diverticulum of the brachiocephalic trunk is described in 5 children with unilateral absence of the pulmonary artery, in a child with tetralogy of Fallot, and in an other child with Bland-White-Garland syndrome. The diverticulum is a remnant of a contralateral ductus arteriosus, which cLosed after birth and represents the origin of the distal part of the sixth aortic arch.

Right aortic arch with isolation of left innominate artery.

A new entity of right aortic arch with isolation of the left innominate artery is described in a three-day-old boy with complete endocardial cushion defect. Embryologically, this type of anomaly will result if the interruption of the embryonic left aortic arch occurs at two sites, one between the left ductus arteriosus and the descending aorta and the other between the ascending aorta and the left common carotid artery. Absence of pulse in the left arm and on the left side of the neck strongly suggests this anomaly. The aortogram and pulmonary arteriogram may confirm the diagnosis of this anomaly during life.

Right aortic arch, right patent ductus arteriosus, and mirror-image branching of the brachiocephalic vessels.

Two patients with a right aortic arch, right patent ductus arteriosus, and mirror-image branching of the brachiocephalic vessels are described. The clinical, angiographic, and surgical findings in these two cases are detailed, and a description of the embryologic basis for these anomalies is given.

The embryology and management of vascular rings.

Among 34 patients with vascular rings, symptoms of tracheal and esophageal compression or both occurred during the first six months of life in 24 (71%). Diagnosis was made in all cases on either plain x-ray film or esophagogram, and was confirmed by operation or angiogram. Associated defects were numerous, with ventricular septal defect (5) and Down's syndrome (3) most common. Operative intervention was required in 18 cases (53%), including 12 of the 14 double arches. Only one of the ten patients with symptomatic recurrent subclavian artery underwent operation. Fourteen of the 18 patients operated upon had early total relief of symptoms, and 17 had excellent late results. A simple system for describing the embryology of vascular rings is presented, and the embryologic relationship between vascular rings and interrupted aortic arches is described. Because of frequent delay in recognition of vascular rings and other surgically correctable lesions, the work-up of every child with two or more episodes of pneumonia should include barium swallow.