Echocardiographic features and pathological ultrastructural characteristics of fetal interruption of aortic arch. / èƒŽå„¿ä¸»åŠ¨è„‰å¼“ç¦»æ–­çš„è¶ å£°å¿ƒåŠ¨å›¾å’Œç— ç†å­¦è¶ å¾®ç»“æž„ç‰¹å¾.

OBJECTIVES: Interruption of aortic arch (IAA) is a rare congenital heart disease. This study aims to investigate echocardiographic features and pathological ultrastructural characteristics of fetal IAA and to further analyze its pathological evolution. METHODS: A retrospective analysis was conducted on prenatal echocardiographic, post-surgical, or autopsy findings of fetuses prenatally diagnosed with IAA. Prenatal echocardiographic tracking was used to observe the internal diameters and Z-scores of different segments of the aortic arch and the changes in the narrowed section. These observations were combined with autopsy and pathological findings to explore the potential intrauterine evolution of IAA and its cytological basis. RESULTS: The study included 34 fetuses with IAA, with 3, 3, and 28 fetuses prenatally diagnosed with aortic arch dysplasia (AAD), coarctation of aorta (CoA), and IAA, respectively. The 3 AAD and 3 CoA fetuses chose termination of pregnancy 1 to 2 weeks after prenatal ultrasound diagnosis, and autopsy confirmed IAA. Among the 28 fetuses prenatally diagnosed with IAA, 6 cases of CoA progressively worsened, eventually evolving into type A IAA as observed through echocardiographic follow-up. The remaining 22 cases were diagnosed as IAA on the first prenatal ultrasound. Postnatal surgery corrected 3 cases, while 27 cases opted for pregnancy termination, and 4 cases resulted in intrauterine death. Echocardiographic features of the fetal IAA included a significantly smaller left ventricle compared with the right or negligible difference on the four-chamber view, a significantly smaller aorta than the pulmonary artery on the three-vessel view, and a lack of connection between the aorta and the descending aorta on the three-vessel-trachea and aortic arch views. The aortic arch appears less curved and more rigid, losing the normal "V" shape between the aorta, ductus arteriosus, and descending aorta. Color Doppler ultrasound showed no continuous blood flow signal at the interruption site, with reversed blood flow visible in the ductus arteriosus. Transmission electron microscopy of 7 IAA fetuses revealed numerous disorganized smooth muscle cells between the elastic membranes near the aortic arch interruption site, significantly increased in number compared with the proximal ascending aorta. The elastic membranes were thicker and more twisted near the interruption site. The interruption area lacked normal endothelial cells and lumen, with only remnants of necrotic endothelial cells, disorganized short and thick elastic membranes, and randomly arranged smooth muscle cells. CONCLUSIONS: Prenatal echocardiography is the primary diagnostic tool for fetal IAA. Post-surgical follow-up and autopsy help identify complications and disease characteristics, enhancing diagnostic accuracy. Some fetal IAA may evolve from AAD or CoA, with potential pathogenesis related to ischemia, hypoxia, and migration of ductal constrictive components.

Anatomical variations and embryological basis of arch of aorta and aortic valve.

Variations in the arch of the aorta and aortic valves among fetal, cadaveric, and post-mortem specimens present a spectrum of anatomical configurations, posing challenges in establishing a standard norm. While some variations hold surgical significance, many bear little functional consequence but provide insights into embryological origins. The aortic arch exhibits diverse branching patterns, including common trunks and different orders, relevant for endovascular surgeries. Meanwhile, malformations in the aortic valve, affecting the aorta, may lead to ischemia and cerebral infarction, warranting understanding of coexisting arch and valve anomalies to predict complications like aortic dissection. Studies in the Indian population mirror global variations, underscoring the need to explore embryological, clinical, and surgical implications for safer vascular surgeries involving the aortic arch and valves. The study's objectives included examining branching patterns, diameters, and distances between arch branches and exploring aortic valve variations. Employing a cross-sectional design, the study was conducted across Anatomy, Forensic Medicine, and Obstetrics and Gynecology departments. A sample of 100, comprising cadavers, fetuses, and postmortem specimens, were gathered. Specimens ranged from 14 weeks of intrauterine life to 85 years, with intact thoracic cages as inclusion criteria. Methodology involved dissection, specimen fixation, and macroscopic examination for variations and morphological parameters. Results showed aortic diameter increase with age, with significant gender differences. A statistically significant association between arch variations and anomalous valves was observed, suggesting mutual predictability. Individuals with valve anomalies should undergo comprehensive cardiology evaluation to avert complications like aortic dissection during endovascular surgeries. While atheromatous plaques were prevalent in younger groups, their frequency rose with age, necessitating vigilant vascular monitoring. Careful handling during surgeries is paramount, given potential adverse outcomes resulting from variations. Overall, the study underscores the importance of comprehensive anatomical understanding in clinical contexts, guiding effective management strategies and ensuring patient safety in vascular surgeries.

Prenatal diagnosis of interrupted aortic arch using high-definition flow render mode and spatiotemporal image correlation.

OBJECTIVES: To evaluate the clinical utility of two dimensional (2D) ultrasound combined with spatiotemporal image correlation (STIC) in diagnosing interrupted aortic arch (IAA) in fetal life. METHODS: A total of 53 cases of fetal IAA were diagnosed using 2D ultrasound combined with STIC, and 53 normal fetuses of the same gestational week were selected. These cases were retrospectively analyzed to assess the utility of employing 2D ultrasound combined with STIC in the diagnosis of IAA. RESULTS: 2D ultrasound combined with STIC detected 22 cases of type A IAA, 24 cases of type B IAA, and seven cases of type C IAA. Furthermore, combining 2D ultrasound with STIC enabled dynamic visualization of the IAA, aiding in prenatal diagnosis. The diagnostic coincidence rate of IAA was found to be higher in the HD-flow combined with STIC than that in the 2D combined with HD-flow. CONCLUSION: HD-flow combined with STIC can assist in diagnosing fetal IAA, and this technique has important clinical value.

Prenatal cardiac findings and 22q11.2 deletion syndrome: Fetal detection and evaluation.

Clinical features of 22q11.2 microdeletion syndrome (22q11.2DS) are highly variable between affected individuals and frequently include a subset of conotruncal and aortic arch anomalies. Many are diagnosed with 22q11.2DS when they present as a fetus, newborn or infant with characteristic cardiac findings and subsequently undergo genetic testing. The presence of an aortic arch anomaly with characteristic intracardiac anomalies increases the likelihood that the patient has 22q11.2 DS, but those with an aortic arch anomaly and normal intracardiac anatomy are also at risk. It is particularly important to identify the fetus at risk for 22q11.2DS in order to prepare the expectant parents and plan postnatal care for optimal outcomes. Fetal anatomy scans now readily identify aortic arch anomalies (aberrant right subclavian artery, right sided aortic arch or double aortic arch) in the three-vessel tracheal view. Given the association of 22q11.2DS with aortic arch anomalies with and without intracardiac defects, this review highlights the importance of recognizing the fetus at risk for 22q11.2 deletion syndrome with an aortic arch anomaly and details current methods for genetic testing. To assist in the prenatal diagnosis of 22q11.2DS, this review summarizes the seminal features of 22q11.2DS, its prenatal presentation and current methods for genetic testing.

Buffering Mechanism in Aortic Arch Artery Formation and Congenital Heart Disease.

BACKGROUND: The resiliency of embryonic development to genetic and environmental perturbations has been long appreciated; however, little is known about the mechanisms underlying the robustness of developmental processes. Aberrations resulting in neonatal lethality are exemplified by congenital heart disease arising from defective morphogenesis of pharyngeal arch arteries (PAAs) and their derivatives. METHODS: Mouse genetics, lineage tracing, confocal microscopy, and quantitative image analyses were used to investigate mechanisms of PAA formation and repair. RESULTS: The second heart field (SHF) gives rise to the PAA endothelium. Here, we show that the number of SHF-derived endothelial cells (ECs) is regulated by VEGFR2 (vascular endothelial growth factor receptor 2) and Tbx1. Remarkably, when the SHF-derived EC number is decreased, PAA development can be rescued by the compensatory endothelium. Blocking such compensatory response leads to embryonic demise. To determine the source of compensating ECs and mechanisms regulating their recruitment, we investigated 3-dimensional EC connectivity, EC fate, and gene expression. Our studies demonstrate that the expression of VEGFR2 by the SHF is required for the differentiation of SHF-derived cells into PAA ECs. The deletion of 1 VEGFR2 allele (VEGFR2SHF-HET) reduces SHF contribution to the PAA endothelium, while the deletion of both alleles (VEGFR2SHF-KO) abolishes it. The decrease in SHF-derived ECs in VEGFR2SHF-HET and VEGFR2SHF-KO embryos is complemented by the recruitment of ECs from the nearby veins. Compensatory ECs contribute to PAA derivatives, giving rise to the endothelium of the aortic arch and the ductus in VEGFR2SHF-KO mutants. Blocking the compensatory response in VEGFR2SHF-KO mutants results in embryonic lethality shortly after mid-gestation. The compensatory ECs are absent in Tbx1+/- embryos, a model for 22q11 deletion syndrome, leading to unpredictable arch artery morphogenesis and congenital heart disease. Tbx1 regulates the recruitment of the compensatory endothelium in an SHF-non-cell-autonomous manner. CONCLUSIONS: Our studies uncover a novel buffering mechanism underlying the resiliency of PAA development and remodeling.

Increased Pulmonary-Aortic Interspace in Fetal Right Aortic Arch: A Matched Case-Control Study.

INTRODUCTION: The prenatal detection rate of a right aortic arch (RAA) has increased with the implementation of the three-vessel view (3VV) to the second-trimester anomaly scan formed by the pulmonary artery (PA), aorta (Ao), and superior vena cava (SVC). We examined the value of measuring the distance between PA and Ao in the 3VV in cases with an RAA. METHODS: We conducted a case-control study in which fetuses with an isolated RAA were matched to 3 healthy controls. Using 3VV images, the distances between PA, Ao, and SVC were measured and the ratio between PA to Ao (PAAo) distance and Ao to SVC (AoSVC) distance was calculated. RESULTS: Fifty-four RAA cases and 162 matched controls were included. The mean absolute distance PAAo was 3.1 mm in cases and 1.8 mm in controls (p < 0.001), and the mean PAAo/AoSVC ratio was 2.9 and 1.4, respectively (p < 0.001). The ROC curve of PAAo/AoSVC ratio showed a cut-off point of 1.9 with sensitivity and specificity over 87% for the diagnosis of RAA. CONCLUSIONS: The pulmonary-aortic interspace and the PAAo/AoSVC ratio were significantly larger for RAA cases as compared to controls. If an increased pulmonary-aortic interspace is observed, a PAAo/AoSVC of ≥1.9 can be helpful in the diagnosis of an RAA.

Prenatal Detection and Postnatal Outcome of Persistent Left Superior Vena Cava and Agenesis of Ductus Venosus Associated with Postnatal Bovine Aortic Arch.

BACKGROUND: Isolated agenesis of ductus venosus (ADV) is usually a benign condition, but it may be associated with cardiovascular defects, hydrops, growth restriction, and chromosomal abnormalities. Additionally, persistent left superior vena cava (PLSVC) and bovine aortic arch are relatively common fetal anomalies. To the author's knowledge, this is the first report of prenatal detection of DV agenesis and PLSVC associated with the postnatal bovine aortic arch with a hypoplastic transverse aortic arch. CASE: A 25-year-old, G2P1 woman was referred to our department at 31 weeks due to fetal growth restriction and short femur. On fetal echocardiography, DV could not be viewed via two-dimensional (2D) and Doppler ultrasound (US) imaging; there was also evidence of the co-occurrence of PLSVC and an aortic arch anomaly. We revealed the intrahepatic continuation of the umbilical vein. A weekly follow-up program was scheduled for the patient and the rest of the pregnancy was uneventful. Postnatal, thorax computer tomography and transthoracic echocardiography (TTE) demonstrated PLSVC and bovine aortic arch associated with hypoplastic transverse aortic arch. Routine echocardiographic examinations revealed that the blood flow of the aortic arch had increased gradually, and the male infant's aortic arch had significantly widened and reached the normal range until the baby was discharged from the hospital. CONCLUSION: DV agenesis and PLSVC are usually benign conditions but underlying serious heart diseases may accompany them. Therefore, in situations like ours, a prenatal aortic arch evaluation is of capital importance. Postnatal hemodynamic changes should be taken into consideration in the management of these cases. This is the first example in the literature that these abnormalities co-existed in one case.

Assessing Early Cardiac Outflow Tract Adaptive Responses Through Combined Experimental-Computational Manipulations.

Mechanical forces are essential for proper growth and remodeling of the primitive pharyngeal arch arteries (PAAs) into the great vessels of the heart. Despite general acknowledgement of a hemodynamic-malformation link, the direct correlation between hemodynamics and PAA morphogenesis remains poorly understood. The elusiveness is largely due to difficulty in performing isolated hemodynamic perturbations and quantifying changes in-vivo. Previous in-vivo arch artery occlusion/ablation experiments either did not isolate the effects of hemodynamics, did not analyze the results in a 3D context or did not consider the effects of varying degrees of occlusion. Here, we overcome these limitations by combining minimally invasive occlusion experiments in the avian embryo with 3D anatomical models of development and in-silico testing of experimental phenomenon. We detail morphological and hemodynamic changes 24 hours post vessel occlusion. 3D anatomical models showed that occlusion geometries had more circular cross-sectional areas and more elongated arches than their control counterparts. Computational fluid dynamics revealed a marked change in wall shear stress-morphology trends. Instantaneous (in-silico) occlusion models provided mechanistic insights into the dynamic vessel adaptation process, predicting pressure-area trends for a number of experimental occlusion arches. We follow the propagation of small defects in a single embryo Hamburger Hamilton (HH) Stage 18 embryo to a more serious defect in an HH29 embryo. Results demonstrate that hemodynamic perturbation of the presumptive aortic arch, through varying degrees of vessel occlusion, overrides natural growth mechanisms and prevents it from becoming the dominant arch of the aorta.

Cell-Extracellular Matrix Interactions Play Multiple Essential Roles in Aortic Arch Development.

RATIONALE: Defects in the morphogenesis of the fourth pharyngeal arch arteries (PAAs) give rise to lethal birth defects. Understanding genes and mechanisms regulating PAA formation will provide important insights into the etiology and treatments for congenital heart disease. OBJECTIVE: Cell-ECM (extracellular matrix) interactions play essential roles in the morphogenesis of PAAs and their derivatives, the aortic arch artery and its major branches; however, their specific functions are not well-understood. Previously, we demonstrated that integrin α5ß1 and Fn1 (fibronectin) expressed in the Isl1 lineages regulate PAA formation. The objective of the current studies was to investigate cellular mechanisms by which integrin α5ß1 and Fn1 regulate aortic arch artery morphogenesis. METHODS AND RESULTS: Using temporal lineage tracing, whole-mount confocal imaging, and quantitative analysis of the second heart field (SHF) and endothelial cell (EC) dynamics, we show that the majority of PAA EC progenitors arise by E7.5 in the SHF and contribute to pharyngeal arch endothelium between E7.5 and E9.5. Consequently, SHF-derived ECs in the pharyngeal arches form a plexus of small blood vessels, which remodels into the PAAs by 35 somites. The remodeling of the vascular plexus is orchestrated by signals dependent on the pharyngeal ECM microenvironment, extrinsic to the endothelium. Conditional ablation of integrin α5ß1 or Fn1 in the Isl1 lineages showed that signaling by the ECM regulates aortic arch artery morphogenesis at multiple steps: (1) accumulation of SHF-derived ECs in the pharyngeal arches, (2) remodeling of the EC plexus in the fourth arches into the PAAs, and (3) differentiation of neural crest-derived cells adjacent to the PAA endothelium into vascular smooth muscle cells. CONCLUSIONS: PAA formation is a multistep process entailing dynamic contribution of SHF-derived ECs to pharyngeal arches, the remodeling of endothelial plexus into the PAAs, and the remodeling of the PAAs into the aortic arch artery and its major branches. Cell-ECM interactions regulated by integrin α5ß1 and Fn1 play essential roles at each of these developmental stages.

Prenatal diagnosis of aortic arch anomalies: Echocardiography, 3D-ultrasonography, and computed tomography angiogram findings. A case-report.

We report the case of a fetus presenting aortic arch anomalies associated with a ventricular septal defect (VSD). This fetus, which was referred at 25 weeks of gestation, was suspected to have coarctation of aorta (CoA) evidenced by enlarged right chambers at the four-chamber view during a routine obstetric ultrasonographic scan. The prenatal diagnosis of CoA remains a challenge. Here, we review the ultrasonographic findings that could contribute to this diagnosis.

Microstructure of early embryonic aortic arch and its reversibility following mechanically altered hemodynamic load release.

In the embryonic heart, blood flow is distributed through a bilaterally paired artery system composed of the aortic arches (AAs). The purpose of this study is to establish an understanding of the governing mechanism of microstructural maturation of the AA matrix and its reversibility, toward the desired macroscopic vessel lumen diameter and thickness for healthy, abnormal, and in ovo repaired abnormal mechanical loading. While matrix-remodeling mechanisms were significantly different for normal versus conotruncal banding (CTB), both led to an increase in vessel lumen. Correlated with right-sided flow increase at Hamburger & Hamilton stages 21, intermittent load switching between collagen I and III with elastin and collagen-IV defines the normal process. However, decreases in collagen I, elastin, vascular endothelial growth factor-A, and fibrillin-1 in CTB were recovered almost fully following the CTB-release model, primarily because of the pressure load changes. The complex temporal changes in matrix proteins are illustrated through a predictive finite-element model based on elastin and collagen load-sharing mechanism to achieve lumen area increase and thickness increase resulting from wall shear stress and tissue strain, respectively. The effect of embryonic timing in cardiac interventions on AA microstructure was established where abnormal mechanical loading was selectively restored at the key stage of development. Recovery of the normal mechanical loading via early fetal intervention resulted in delayed microstructural maturation. Temporal elastin increase, correlated with wall shear stress, is required for continuous lumen area growth.NEW & NOTEWORTHY The present study undertakes comparative analyses of the mechanistic differences of the arterial matrix microstructure and dynamics in the three fundamental processes of control, conotruncal banded, and released conotruncal band in avian embryo. Among other findings, this study provides specific evidence on the restorative role of elastin during the early lumen growth process. During vascular development, a novel intermittent load-switching mechanism between elastin and collagen, triggered by a step increase in wall shear stress, governs the chronic vessel lumen cross-sectional area increase. Mimicking the fetal cardiovascular interventions currently performed in humans, the early release of the abnormal mechanical load rescues the arterial microstructure with time lag.

Spatiotemporal remodeling of embryonic aortic arch: stress distribution, microstructure, and vascular growth in silico.

The microstructure for mature vessels has been investigated in detail, while there is limited information about the embryonic stages, in spite of their importance in the prognosis of congenital heart defects. It is hypothesized that the embryonic vasculature represents a disorganized but dynamic soft tissue, which rapidly evolves toward a specialized multi-cellular vascular structure under mechanical loading. Here the microstructural evolution process of the embryonic pharyngeal aortic arch structure was simulated using an in ovo validated long-term growth and remodeling computational model, implemented as an in-house FEBio plug-in. Optical coherence tomography-guided servo-null pressure measurements are assigned as boundary conditions through the critical embryonic stages. The accumulation of key microstructural constituents was recorded through zoom confocal microscopy for all six embryonic arch arteries simultaneously. The total amount and the radial variation slope of the collagen along the arch wall thickness in different arch types and for different embryonic times, with different dimension scales, were normalized and compared statistically. The arch growth model shows that the stress levels around the lumen boundary increase from [Formula: see text] (Stage 18) to a level higher than [Formula: see text] (Stage 24), depending on matrix constituent production rates, while the homeostatic strain level is kept constant. The statistical tests show that although the total collagen levels differentiate among bilateral positions of the same arch, the shape coefficient of the matrix microstructural gradient changes with embryonic time, proving radial localization, in accordance with numerical model results. In vivo cell number (DAPI) and vascular endothelial growth factor distributions followed similar trends.

Pbx4 limits heart size and fosters arch artery formation by partitioning second heart field progenitors and restricting proliferation.

Vertebrate heart development requires the integration of temporally distinct differentiating progenitors. However, few signals are understood that restrict the size of the later-differentiating outflow tract (OFT). We show that improper specification and proliferation of second heart field (SHF) progenitors in zebrafish lazarus (lzr) mutants, which lack the transcription factor Pbx4, produces enlarged hearts owing to an increase in ventricular and smooth muscle cells. Specifically, Pbx4 initially promotes the partitioning of the SHF into anterior progenitors, which contribute to the OFT, and adjacent endothelial cell progenitors, which contribute to posterior pharyngeal arches. Subsequently, Pbx4 limits SHF progenitor (SHFP) proliferation. Single cell RNA sequencing of nkx2.5+ cells revealed previously unappreciated distinct differentiation states and progenitor subpopulations that normally reside within the SHF and arterial pole of the heart. Specifically, the transcriptional profiles of Pbx4-deficient nkx2.5+ SHFPs are less distinct and display characteristics of normally discrete proliferative progenitor and anterior, differentiated cardiomyocyte populations. Therefore, our data indicate that the generation of proper OFT size and arch arteries requires Pbx-dependent stratification of unique differentiation states to facilitate both homeotic-like transformations and limit progenitor production within the SHF.

Impact of prospective measurement of outflow tracts in prediction of coarctation of the aorta.

OBJECTIVES: Prenatal diagnosis of coarctation of the aorta (CoA) is associated with reduced mortality and morbidity, however, accurate prenatal prediction remains challenging. To date, studies have used retrospective measurements of the outflow tracts to evaluate their potential to predict CoA. Our primary objective was to evaluate prospectively acquired measurements of the outflow tracts in fetuses with prenatally suspected CoA. A secondary aim was to report the postnatal prevalence of bicuspid aortic valve in this cohort. METHODS: Pregnancies with suspicion of isolated CoA and with a minimum of 6 months' postnatal follow-up available were identified from the cardiac database of a tertiary fetal cardiology center in the UK, between January 2002 and December 2017. Measurement of the aortic valve, pulmonary valve, distal transverse aortic arch (DTAA) and arterial duct (AD) diameters were undertaken routinely in fetuses with suspected CoA during the study period. Z-scores were computed using published reference ranges based on > 7000 fetuses from our own unit. RESULTS: Of 149 pregnancies with prenatally suspected CoA included in the study, CoA was confirmed within 6 months after birth in 77/149 (51.7%) cases. DTAA diameter Z-score and the Z-score of second-trimester DTAA/AD diameter ratio were smaller in fetuses with postnatally confirmed CoA than those in false-positive cases (-2.8 vs -1.9; P = 0.039 and -3.13 vs -2.61; P = 0.005, respectively). Multiple regression analysis demonstrated that the Z-scores of DTAA and AD diameters were the only significant predictors of postnatal CoA (P = 0.001). Bicuspid aortic valve was identified in 30% of the false-positive cases. CONCLUSIONS: Measurement of DTAA and AD diameter Z-scores can be used to ascertain risk for postnatal CoA in a selected cohort. The high incidence of bicuspid aortic valve in false-positive cases merits further study with respect to both etiology and longer-term significance. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Ex vivo model for studying endothelial tip cells: Revisiting the classical aortic-ring assay.

A drug undergoes several in silico, in vitro, ex vivo and in vivo assays before entering into the clinical trials. In 2014, it was reported that only 32% of drugs are likely to make it to Phase-3 trials, and overall, only one in 10 drugs makes it to the market. Therefore, enhancing the precision of pre-clinical trial models could reduce the number of failed clinical trials and eventually time and financial burden in health sciences. In order to attempt the above, in the present study, we have shown that aortic ex-plants isolated from different stages of chick embryo and different regions of the aorta (pulmonary and systemic) have differential sprouting potential and response to angiogenesis modulatory drugs. Aorta isolated from HH37 staged chick embryo showed 16% (p < 0.001) and 11% (p < 0.001) increase in the number of tip cells at 72 h of culture compared to that of HH35 and HH29 respectively. The ascending order of the number of tip cells was found as central (Gen II), proximal (Gen I) and distal (Gen III) in a virtual zonal segmentation of endothelial sprouting. The HH37 staged aortas displayed differential responses to pro- and anti-angiogenic drugs like Vascular endothelial growth factor (VEGF), nitric oxide donor (spNO), and bevacizumab (avastin), thalidomide respectively. The human placenta tissue-culture however evinced endothelial sprouting only on day 12, with a gradual decrease in the number of tip cells until 21 days. In summary, this study provides an avant-garde angiogenic model emphasized on tip cells that would enhance the precision to test next-generation angiogenic drugs.

Congenital vascular ring.

A vascular ring is a rare congenital cardiovascular anomaly, which encircles and compresses the trachea or esophagus, or both. In this review we discuss the pathophysiology, theoretical embryopathogenesis, diagnostic modalities, and surgical treatment of the different types of vascular ring. Knowledge of the normal embryonic development of the aortic arch and related structures is important for understanding and classifying the various forms of vascular ring. The development of a vascular ring begins with the embryonic aortic arch system. The persistence, involution, or regression of the arches determines the multiple variations of vascular ring. With the development of new technologies, multi-detector computed tomography (MDCT) has become a good diagnostic modality for pre- and postoperative evaluation. MDCT provides an excellent image of aortic arch abnormalities and the related anatomy, as well as the tracheal pathology. For patients with symptoms, surgical division of the vascular ring usually achieves excellent outcomes with marked resolution of symptoms and a low risk of morbidity and mortality. Symptomatic vascular rings require early surgical intervention to prevent prolonged vascular compression of the airway and serious complications.

Maternal hyperoxygenation for the human fetus: should studies be curtailed?

Congenital hypoplasia of left heart structures in fetuses frequently progresses with gestational development. Interference with cerebral development is common in these fetuses. Chronic maternal hyperoxygenation (MHO) has been recommended to increase left ventricular size and to limit cerebral damage. The effects of MHO on cerebral blood flow and metabolism have been studied in normal fetuses and fetuses with left heart hypoplasia. Maternal hyperoxygenation increases fetal pulmonary blood flow. This is associated with reduction of foramen ovale flow, thus limiting the increase in left ventricular output. Modest increase in the size of left heart structures has been reported, but in another study, no significant improvement occurred. In sheep fetuses increased oxygenation results in marked reduction of cerebral blood flow, with no change in oxygen delivery or consumption by the brain, but significant reduction in cerebral glucose delivery and consumption. In one study of fetuses with left heart hypoplasia, chronic MHO was associated with decrease in head size. The effectiveness of MHO in improving left ventricular development is controversial. MHO is, however, associated with reduction of cerebral blood flow and possible interference with cerebral development. In view of this it is recommended that all studies of chronic maternal hyperoxygenation be curtailed.

The Diastolic and Systolic Velocity-Time Integral Ratio of the Aortic Isthmus Is a Sensitive Indicator of Aortic Coarctation in Fetuses.

BACKGROUND: Prenatal diagnosis of coarctation of the aorta (CoA) is challenging and is affected by high false-positive and false-negative rates. The aim of this study was to identify sonographic criteria to improve the identification of fetal CoA. METHODS: A retrospective review was conducted of subjects with prenatal suspicion for CoA who also had postnatal follow-up. Sixty-nine fetuses were identified with possible CoA, and 47 normal fetuses were selected as control subjects. Retrospective measurements of right ventricular/left ventricular ratio, pulmonary artery/aorta ratio, aortic isthmus (AOI) Z score, diastolic velocity-time integral (VTID), and systolic velocity-time integral (VTIS) at the AOI were recorded. Receiver operating characteristic curve analysis identified the parameter most predictive of postnatal CoA. RESULTS: When comparing subjects with (n = 31) and without (n = 38) CoA, significant differences were detected for the AOI Z score, VTID, VTID/VTIS ratio, and VTID/(VTID + VTIS) ratio (P < .001). The areas under the receiver operating characteristic curve were 0.92, 0.92, 0.78, 0.74, 0.71, and 0.68 for the VTID/VTIS ratio, VTID/(VTID + VTIS) ratio, VTID, AOI Z score (sagittal view), AOI Z score (three-vessel tracheal view), and pulmonary artery/aorta ratio, respectively. There was a 25% (95% CI, 14%-35%) improvement in the area under the curve after adding the VTID/VTIS ratio to the basic model (AOI Z score [sagittal view]), and this ratio (after transformation) showed significantly better discrimination and reclassification ability for determining CoA. The pulmonary artery/aorta ratio, VTID, VTID/VTIS ratio, and VTID/(VTID + VTIS) ratio were stable throughout the normal fetal developmental period in this study. CONCLUSIONS: In cases with suspected prenatal diagnosis of CoA, evaluation of spectral Doppler measurements, such as the VTID/VTIS ratio, may enhance the accuracy of diagnosis with fetal echocardiography.