Echocardiographic Assessment of Pulmonary Arterial Hypertension Following Inhaled Nitric Oxide in Infants with Severe Bronchopulmonary Dysplasia.

OBJECTIVES: Inhaled nitric oxide (iNO) is an effective pulmonary vasodilator. However, the efficacy of iNO in former premature infants with established bronchopulmonary dysplasia (BPD) has not been studied. This study aimed to determine the efficacy of iNO in reducing pulmonary artery pressure in infants with severe BPD as measured by echocardiography. STUDY DESIGN: Prospective, observational study enrolling infants born at less than 32 weeks gestation and in whom (1) iNO therapy was initiated after admission to our institution, or (2) at the outside institution less than 48 h before transfer and received an echocardiogram prior to iNO initiation, and (3) had severe BPD. Data were collected at three time-points: (1) before iNO; (2) 12-48 h after initiation of iNO; and (3) 48-168 h after initiation of iNO. The primary outcome was the effect of iNO on pulmonary artery pressure measured by echocardiography in patients with severe BPD between 48 and 168 h after initiating iNO therapy. RESULTS: Of 37 enrolled, 81% had echocardiographic evidence of pulmonary arterial hypertension (PAH) before iNO and 56% after 48 h of iNO (p = 0.04). FiO2 requirements were significantly different between time-points (1) and (3) (p = 0.05). There were no significant differences between Tricuspid Annular Plane Systolic Excursion (TAPSE) Z-Scores, time to peak velocity: right ventricular ejection time (TPV:RVET), and ventilator changes. CONCLUSIONS: Although we found a statistically significant reduction of PAH between time-point (1) and (3), future trials are needed to further guide clinical care.

A retrospective observational study of real-time ultrasound-guided peripheral arterial cannulation in infants.

OBJECTIVE: To examine first attempt success and overall success of real-time ultrasound guided peripheral arterial cannulation in infants. STUDY DESIGN: Retrospective review of 477 ultrasound guided peripheral arterial cannulations in infants less than 1 year of age. Procedural and patient characteristics were evaluated to better understand factors related to procedural success. RESULTS: Ultrasound guided peripheral arterial cannulation had a first attempt success rate of 65% and an overall success rate of 86%. Success rates significantly differed by arterial location (p < 0.001). First attempt success and overall success were highest in the radial artery (72%, 91%) and lowest in the posterior tibial artery (44%, 71%). Success was more likely with greater age and greater weight (p = 0.006, p = 0.002). CONCLUSION: Success rates are high when using a real-time ultrasound-guided technique for peripheral arterial cannulation in infants. An infant's weight and selected artery are strong predictors of success when performing peripheral arterial cannulation. The use of procedural ultrasound may reduce unnecessary attempts and minimize procedure-related harm.

Real-Time Ultrasound Guidance for Umbilical Venous Cannulation in Neonates With Congenital Heart Disease.

OBJECTIVES: Umbilical venous cannulation is the favored approach to perinatal central access worldwide but has a failure rate of 25-50% and the insertion technique has not evolved in decades. Improving the success of this procedure would have broad implications, particularly where peripherally inserted central catheters are not easily obtained and in neonates with congenital heart disease, in whom umbilical access facilitates administration of inotropes and blood products while sparing vessels essential for later cardiac interventions. We sought to use real-time, point-of-care ultrasound to achieve central umbilical venous access in patients for whom conventional, blind placement techniques had failed. DESIGN: Multicenter case series, March 2019-May 2021. SETTING: Cardiac and neonatal ICUs at three tertiary care children's hospitals. PATIENTS: We identified 32 neonates with congenital heart disease, who had failed umbilical venous cannulation using traditional, blind techniques. INTERVENTIONS: Real-time ultrasound guidance and liver pressure were used to replace malpositioned catheters and achieve successful placement at the inferior cavoatrial junction. MEASUREMENTS AND MAIN RESULTS: In 32 patients with failed prior umbilical venous catheter placement, real-time ultrasound guidance was used to successfully "rescue" the line and achieve central position in 23 (72%). Twenty of 25 attempts (80%) performed in the first 48 hours of life were successful, and three of seven attempts (43%) performed later. Twenty-four patients (75%) were on prostaglandin infusion at the time of the procedure. We did not identify an association between patient weight or gestational age and successful placement. CONCLUSIONS: Ultrasound guidance has become standard of care for percutaneous central venous access but is a new and emerging technique for umbilical vessel catheterization. In this early experience, we report that point-of-care ultrasound, together with liver pressure, can be used to markedly improve success of placement. This represents a significant advance in this core neonatal procedure.

Real-time ultrasound-guided lumbar puncture in the neonatal intensive care unit.

OBJECTIVE: To determine the rates of traumatic lumbar puncture (LP) and overall success rates using the real-time ultrasound-guided technique when performed by a neonatal point-of-care ultrasound provider. STUDY DESIGN: Retrospective observational study of 17 infants in the neonatal intensive care unit who underwent a real-time ultrasound-guided LP between March 2015 and November 2016. Spearman's correlation was calculated. RESULTS: The first attempt and overall success rates were 65% and 100%, respectively. The rate of nontraumatic LP was 69%. CSF RBC count was inversely correlated with both PMA (Spearman's correlation coefficient (rs) = -0.74, p = 0.0017) and weight (rs = -0.74, p = 0.0015) at the time of LP. CONCLUSIONS: This study is the first to provide evidence of high success rates with real-time ultrasound-guided LP when performed by a neonatologist. Our data demonstrate feasibility in neonates over a broad range of weights, including premature infants as small as 750 g.

Point-of-care ultrasound for the evaluation of venous cannula position in neonatal extracorporeal membrane oxygenation.

OBJECTIVE: To assess the ability of point-of-care ultrasound (POCUS) to identify venous cannula position in neonates on extracorporeal membrane oxygenation (ECMO) and compare with conventional imaging. STUDY DESIGN: Retrospective review of 37 infants on ECMO with 51 POCUS studies between January 2017 and October 2019. Studies were reviewed for identification of venous cannula location and compared with plain radiography and echocardiography. Kappa statistic and predictive values were calculated. RESULTS: Venous cannula tip position was identified in 90% of POCUS studies. Fifty percent of the cannula tips were malpositioned. Plain radiography, the most commonly used method for evaluating tip position, showed poor agreement (57%) with POCUS (kappa 0.13). There was substantial agreement (89%) between echocardiography and POCUS (kappa 0.78). CONCLUSION: This study provides preliminary evidence that POCUS is more accurate than plain radiography for the evaluation of ECMO venous cannula position. Adoption of this practice may prevent potentially catastrophic ECMO complications.

The Clinical Evaluation of Severe Bronchopulmonary Dysplasia.

Bronchopulmonary dysplasia is a common disease of prematurity that presents along a wide spectrum of disease severity. Infants with high severity require prolonged hospitalizations and benefit from multidisciplinary care. We describe our approach to the evaluation of infants with severe bronchopulmonary dysplasia. Important considerations include the phenotypic heterogeneity in clinical presentation that necessitates individualized care, the common presence of comorbidities and importance of a comprehensive multisystem evaluation, and the value of applying a chronic care model that prioritizes long-term respiratory and neurodevelopmental goals. Key features of the history, physical examination, and diagnostic studies are discussed with these considerations in mind.

Point-of-care ultrasound in the neonatal ICU.

PURPOSE OF REVIEW: Point-of-care ultrasound (POCUS) is an emerging clinical tool in the neonatal intensive care unit (NICU). Recent literature describing the use of POCUS for various applications in the NICU has garnered increased interest among neonatologists. RECENT FINDINGS: Diagnostic applications for POCUS in the NICU include the evaluation and serial monitoring of common pulmonary diseases, hemodynamic instability, patent ductus arteriosus (PDA), persistent pulmonary hypertension of the newborn (PPHN), necrotizing enterocolitis (NEC), and intraventricular hemorrhage (IVH), among others. Procedural applications include vascular access, endotracheal intubation, lumbar puncture, and fluid drainage. SUMMARY: Experience with POCUS in the NICU is growing. Current evidence supports the use of POCUS for a number of diagnostic and procedural applications. As use of this tool increases, there is an urgent need to develop formal training requirements specific to neonatology, as well as evidence-based guidelines to standardize use across centers.

Seeing Is Believing: Ultrasound in Pediatric Procedural Performance.

Point-of-care ultrasound is currently widely used across the landscape of pediatric care. Ultrasound machines are now smaller, are easier to use, and have much improved image quality. They have become common in emergency departments, ICUs, inpatient wards, and outpatient clinics. Recent growth of supportive evidence makes a strong case for using point-of-care ultrasound for pediatric interventions such as vascular access (in particular, central-line placement), lumbar puncture, fluid drainage (paracentesis, thoracentesis, pericardiocentesis), suprapubic aspiration, and soft tissue incision and drainage. Our review of this evidence reveals that point-of-care ultrasound has become a powerful tool for improving procedural success and patient safety. Pediatric patients and clinicians performing procedures stand to benefit greatly from point-of-care ultrasound, because seeing is believing.

Relationship between pulmonary artery acceleration time and pulmonary artery pressures in infants.

BACKGROUND: Pulmonary artery acceleration time measured by echocardiography inversely correlates with pulmonary artery pressures in adults and children older than 1 year of age. There is a paucity of data investigating this relationship in young children, particularly among preterm infants. OBJECTIVE: To characterize the relationship between pulmonary artery acceleration time (PAAT) and pulmonary artery pressures in infants. DESIGN/METHODS: Patients ≤ 1 year of age at Children's Hospital of Philadelphia between 2011 and 2017 were reviewed. Infants with congenital heart disease were excluded, except those with a patent ductus arteriosus (PDA), atrial septal defect (ASD), or ventricular septal defect (VSD). Linear regression analysis was used to assess the correlation between PAAT measured by echocardiography and systolic pulmonary artery pressure, mean pulmonary artery pressure, and indexed pulmonary vascular resistance from cardiac catheterization. RESULTS: Fifty-seven infants were included, of which 61% were preterm and 49% had a diagnosis of bronchopulmonary dysplasia. The median postmenstrual age and weight at catheterization were 51.1 weeks (IQR 35.8-67.9 weeks) and 4400 g (IQR 3100-6500 g), respectively. Forty-four infants (77%) had a patent ductus arteriosus (PDA). There was a weak inverse correlation between PAAT with mPAP (r = -0.35, P = 0.01), sPAP (r = -0.29, P = 0.03), and PVRi (r = -0.29, P = 0.03). CONCLUSION: There is a weak inverse relationship between PAAT and pulmonary artery pressures. This relationship is less robust in our population of infants with a high incidence of PDAs compared to previous studies in older children. Thus, PAAT may be less clinically meaningful for diagnosing pulmonary arterial hypertension in infants, particularly those with PDAs.

Association of Neonatologist Continuity of Care and Short-Term Patient Outcomes.

OBJECTIVES: To describe neonatologist continuity of care and estimate the association between these transitions and selected patient outcomes. STUDY DESIGN: We linked Children's Hospitals Neonatal Database records with masked neonatologist daily schedules at 4 centers, which use 2- and 3-week and 1-month "on service" blocks to provide care. After describing the neonatologist transitions, we estimated associations between these transitions and selected short-term patient outcomes using multivariable Poisson, logistic, and linear regression analyses, independent of length of stay (LOS) and case-mix. We also completed analyses after stratifying the cohort by LOS, birthweight, age at admission categories, and selected diagnoses. RESULTS: Stratified by LOS, patient transitions varied between centers in both unadjusted (P < .001) and multivariable analyses (adjusted incidence rate ratio; 95% CI for center B = 3.98 (3.81-4.15), center C = 4.92 (4.71-5.13), center D = 4.2 (4.0-4.4), P < .001), independent of LOS, gestational age, birthweight, surgical intervention, ventilator duration, and mortality. Only central venous line duration (adjusted incidence rate ratio 1.015, 95% CI 1.01-1.02) was minimally and independently associated with the number of transitions. No differences were observed in ventilator duration, oxygen use at neonatal intensive care unit discharge, bloodstream infections, or urinary tract infections. Surviving infants with meconium aspiration, hypoxic ischemic encephalopathy, cerebral infarction, bronchopulmonary dysplasia, and diaphragmatic hernia demonstrated similar findings. CONCLUSIONS: Transitions in neonatologists are frequent in regional neonatal intensive care units but appear unrelated to short-term patient outcomes. Future work to define continuity of care and develop effective strategies that promote longitudinal inpatient management is needed.

Severe hypertriglyceridemia associated with everolimus drug-eluting stent placement in an infant.

We report a case of severe hypertriglyceridemia associated with an everolimus drug-eluting stent in an infant with pulmonary vein stenosis. We review from current literature the mechanisms by which everolimus may cause dyslipidaemia, pharmacokinetics of everolimus in drug-eluting stents, and treatments of hypertriglyceridemia. This case demonstrates the need to closely monitor serum triglyceride levels after everolimus drug-eluting stent placement in infants.

Transcriptional profiling of the ductus arteriosus: Comparison of rodent microarrays and human RNA sequencing.

DA closure is crucial for the transition from fetal to neonatal life. This closure is supported by changes to the DA's signaling and structural properties that distinguish it from neighboring vessels. Examining transcriptional differences between these vessels is key to identifying genes or pathways responsible for DA closure. Several microarray studies have explored the DA transcriptome in animal models but varied experimental designs have led to conflicting results. Thorough transcriptomic analysis of the human DA has yet to be performed. A clear picture of the DA transcriptome is key to guiding future research endeavors, both to allow more targeted treatments in the clinical setting, and to understand the basic biology of DA function. In this review, we use a cross-species cross-platform analysis to consider all available published rodent microarray data and novel human RNAseq data in order to provide high priority candidate genes for consideration in future DA studies.

Effect of Prophylactic Indomethacin in Extremely Low Birth Weight Infants Based on the Predicted Risk of Severe Intraventricular Hemorrhage.

BACKGROUND: Prophylactic indomethacin reduces the risk of severe intraventricular hemorrhage (IVH) but does not reduce death or neurodevelopmental impairment (NDI) among extremely low birth weight (ELBW) infants. Some investigators have suggested that prophylactic indomethacin may have a greater treatment effect on severe IVH among infants at high risk for severe IVH. OBJECTIVE: To determine whether the relative treatment effects of prophylactic indomethacin on severe IVH and the composite outcome of death or NDI vary based on the risk of severe IVH. METHODS: Post hoc analysis of the Trial of Indomethacin Prophylaxis in Preterms (TIPP). We generated a model to predict the risk for severe IVH based on gestational age, birth weight, antenatal steroids, delivery mode, outborn status, sex, and 5-min Apgar score, and we divided the TIPP participants into risk quartiles. We used logistic regression to determine the adjusted odds ratios (aOR) of severe IVH and death or NDI based on indomethacin treatment for each quartile. RESULTS: The relative treatment effects of prophylactic indomethacin on severe IVH did not vary based on the predicted risk of severe IVH: quartile 1: aOR 0.68 (95% confidence interval [CI] 0.19-2.37); quartile 2: aOR 0.61 (95% CI 0.27-1.42); quartile 3: aOR 0.63 (95% CI 0.31-1.31); quartile 4: aOR 0.58 (95% CI 0.32-1.05). The relative treatment effect of prophylactic indomethacin on death or NDI did not vary significantly between quartiles. CONCLUSIONS: These findings do not support selective prophylactic indomethacin treatment to improve long-term outcomes of ELBW infants at high risk for severe IVH.

Transcriptional profiling reveals ductus arteriosus-specific genes that regulate vascular tone.

Failure of the ductus arteriosus (DA) to close at birth can lead to serious complications. Conversely, certain profound congenital cardiac malformations require the DA to be patent until corrective surgery can be performed. In each instance, clinicians have a very limited repertoire of therapeutic options at their disposal - indomethacin or ibuprofen to close a patent DA (PDA) and prostaglandin E1 to maintain patency of the DA. Neither treatment is specific to the DA and both may have deleterious off-target effects. Therefore, more therapeutic options specifically targeted to the DA should be considered. We hypothesized the DA possesses a unique genetic signature that would set it apart from other vessels. A microarray was used to compare the genetic profiles of the murine DA and ascending aorta (AO). Over 4,000 genes were differentially expressed between these vessels including a subset of ion channel-related genes. Specifically, the alpha and beta subunits of large-conductance calcium-activated potassium (BKCa) channels are enriched in the DA. Gain- and loss-of-function studies showed inhibition of BKCa channels caused the DA to constrict, while activation caused DA relaxation even in the presence of O2. This study identifies subsets of genes that are enriched in the DA that may be used to develop DA-specific drugs. Ion channels that regulate DA tone, including BKCa channels, are promising targets. Specifically, BKCa channel agonists like NS1619 maintain DA patency even in the presence of O2 and may be clinically useful.

Jun is required in Isl1-expressing progenitor cells for cardiovascular development.

Jun is a highly conserved member of the multimeric activator protein 1 transcription factor complex and plays an important role in human cancer where it is known to be critical for proliferation, cell cycle regulation, differentiation, and cell death. All of these biological functions are also crucial for embryonic development. Although all Jun null mouse embryos die at mid-gestation with persistent truncus arteriosus, a severe cardiac outflow tract defect also seen in human congenital heart disease, the developmental mechanisms are poorly understood. Here we show that murine Jun is expressed in a restricted pattern in several cell populations important for cardiovascular development, including the second heart field, pharyngeal endoderm, outflow tract and atrioventricular endocardial cushions and post-migratory neural crest derivatives. Several genes, including Isl1, molecularly mark the second heart field. Isl1 lineages include myocardium, smooth muscle, neural crest, endocardium, and endothelium. We demonstrate that conditional knockout mouse embryos lacking Jun in Isl1-expressing progenitors display ventricular septal defects, double outlet right ventricle, semilunar valve hyperplasia and aortic arch artery patterning defects. In contrast, we show that conditional deletion of Jun in Tie2-expressing endothelial and endocardial precursors does not result in aortic arch artery patterning defects or embryonic death, but does result in ventricular septal defects and a low incidence of semilunar valve defects, atrioventricular valve defects and double outlet right ventricle. Our results demonstrate that Jun is required in Isl1-expressing progenitors and, to a lesser extent, in endothelial cells and endothelial-derived endocardium for cardiovascular development but is dispensable in both cell types for embryonic survival. These data provide a cellular framework for understanding the role of Jun in the pathogenesis of congenital heart disease.

Current Perspectives on Pathobiology of the Ductus Arteriosus.

The ductus arteriosus (DA) shunts blood away from the lungs during fetal life, but at birth this shunt is no longer needed and the vessel rapidly constricts. Postnatal persistence of the DA, patent ductus arteriosus (PDA), is predominantly a detrimental condition for preterm infants but is simultaneously a condition required to maintain systemic blood flow for infants born with certain severe congenital heart defects. Although PDA in preterm infants is associated with significant morbidities, there is controversy regarding whether PDA is truly causative. Despite advances in our understanding of the pathobiology of PDA, the optimal treatment strategy for PDA in preterm infants is unclear. Here we review recent studies that have continued to elucidate the fundamental mechanisms of DA development and pathogenesis.

Ash2l interacts with Tbx1 and is required during early embryogenesis.

TBX1 encodes a DNA binding transcription factor that is commonly deleted in human DiGeorge syndrome and plays an important role in heart development. Mechanisms of Tbx1 function, such as Tbx1 interacting regulatory proteins and transcriptional target specificity, are largely unknown. Ash2l is the mammalian homolog of Drosophila Ash2 (absent small homeotic 2) and is a core component of a multimeric histone methyltransferase complex that epigenetically regulates transcription via methylation of histone lysine residues. We undertook an unbiased yeast two-hybrid screen to look for functionally relevant Tbx1-interacting proteins and report a physical and functional interaction between Tbx1 and Ash2l. Tbx1 interacts with Ash2l in both yeast and mammalian cells and Ash2l acts as a transcriptional co-activator in luciferase reporter assays. Expression analysis shows that Tbx1 and Ash2l have overlapping mRNA and protein expression patterns during development. By generating an Ash2l knockout mouse utilizing gene-trap technology, we show that although Ash2l heterozygous mice are normal, Ash2l-null embryos die early during gestation. Thus, Ash2l is required for the earliest stages of embryogenesis. Furthermore, our finding of a physical interaction between Tbx1 and Ash2l suggest that at least some functions of Tbx1 may be mediated by direct interactions with a histone methyltransferase complex.

Murine Jagged1/Notch signaling in the second heart field orchestrates Fgf8 expression and tissue-tissue interactions during outflow tract development.

Notch signaling is vital for proper cardiovascular development and function in both humans and animal models. Indeed, mutations in either JAGGED or NOTCH cause congenital heart disease in humans and NOTCH mutations are associated with adult valvular disease. Notch typically functions to mediate developmental interactions between adjacent tissues. Here we show that either absence of the Notch ligand Jagged1 or inhibition of Notch signaling in second heart field tissues results in murine aortic arch artery and cardiac anomalies. In mid-gestation, these mutants displayed decreased Fgf8 and Bmp4 expression. Notch inhibition within the second heart field affected the development of neighboring tissues. For example, faulty migration of cardiac neural crest cells and defective endothelial-mesenchymal transition within the outflow tract endocardial cushions were observed. Furthermore, exogenous Fgf8 was sufficient to rescue the defect in endothelial-mesenchymal transition in explant assays of endocardial cushions following Notch inhibition within second heart field derivatives. These data support a model that relates second heart field, neural crest, and endocardial cushion development and suggests that perturbed Notch-Jagged signaling within second heart field progenitors accounts for some forms of congenital and adult cardiac disease.

Transcription factor Ap2delta associates with Ash2l and ALR, a trithorax family histone methyltransferase, to activate Hoxc8 transcription.

The family of Ap2 transcription factors comprises five members with highly conserved DNA-binding domains. Among the family members, Ap2delta is the most divergent, because it lacks highly conserved residues within the transactivation domain (TAD) and has weak affinity for known Ap2 binding sites. To identify specific Ap2delta coactivators/regulators during development, we performed a yeast two-hybrid screen, using Ap2delta's TAD. We identified the trithorax superfamily member, Ash2l, as a binding partner that interacts exclusively with Ap2delta. We showed that Ash2l positively mediates Ap2delta transactivation in a dose-dependent manner. Given the known role of Ash2l in histone modification, we determined whether Ap2delta was able to form a complex with that activity. Our results showed that Ap2delta associates with endogenous ASH2L and a member of the MLL family of histone lysine methyltransferases (HKMTs), MLL2 (ALR), forming a complex that methylates lysine 4 of histone H3 (H3K4). Additionally, we showed that Ap2delta is necessary for recruitment of Ash2l and Alr to the Hoxc8 locus and that recruitment of this complex leads to H3K4 trimethylation (H3K4me3) and subsequent gene activation. Altogether, we provide evidence of an association between a highly restricted gene-specific transcription factor and a Su(var), Enhancer of Zeste, Trithorax (SET)1/trithorax-like complex with H3K4 methyltransferase activity. Our studies also document a functional role for Ap2delta in recruiting histone methyltransferases (HMTs) to specific gene targets, such as Hoxc8. This role provides a mechanism through which these transcription factors can have diverse effects despite nearly identical DNA-binding motifs.