Pulmonary hypertension in chronic neonatal lung disease

Sodium nitrite prevents impaired postnatal alveolar development

Deficient nitric oxide (NO) signaling plays a critical role in the pathogenesis of bronchopulmonary dysplasia (BPD); however, clinical trials of inhaled NO (iNO) as a preventive therapy for BPD have shown little to no benefit. A biochemical obstacle to effective NO-based therapy relates to the high reactivity of NO, potentially leading to harmful oxidation and nitration. Hypothesizing that nitrite-based therapy has less potential to produce adverse reactions, we compared the preventive effects of sodium nitrite (NaNO2) and iNO on lung morphology, NO content and signaling, S-nitrosothiols (SNOs), and tyrosine nitration in a novel rat model of experimental BPD. From postnatal days (PNDs) 1-21, rat pups were exposed to normoxia or to hyperoxia-intermittent hypoxia (H-IH; PND 1-7 85% O2, PND 7-14 60% O2, and PND 14-21 normoxia with intermittent exposure to 10% O2 for 10 min every 4 h) while receiving daily subcutaneous (sc) NaNO2 (20 mg/kg) or continuous iNO (10 ppm). Controls were treated with vehicle or were not exposed to iNO. Exposure to H-IH caused alveolar and pulmonary vascular hypoplasia, pulmonary hypertension (PH), decreased lung NO content and signaling, and increased tyrosine nitration. NaNO2 prevented abnormal lung morphology and PH, normalized NO content and signaling, and prevented nitration. iNO prevented PH, but had minimal effects on abnormal distal airspace morphology, and caused nitration and alveolar hypoplasia in control (normoxia-exposed) animals. Treatment with NaNO2 increased S-nitrosylation of nine lung proteins; none were increased by iNO. These observations provide a biological rationale for superior efficacy of NaNO2 in preventing experimental BPD.NEW & NOTEWORTHY Deficient nitric oxide (NO) signaling plays a critical role in bronchopulmonary dysplasia (BPD); however, human trials of inhaled NO (iNO) to prevent BPD have shown little to no benefit. We compared preventive effects of sodium nitrite (NaNO2) to iNO in a novel rat model of experimental BPD. NaNO2 prevented impaired postnatal alveolarization, whereas iNO had minimal effect. NaNO2 inhibited nitration and enhanced S-nitrosylation of several proteins in the lung, potentially explaining its superiority to iNO.

Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension: Basing Care on Physiology

Bronchopulmonary dysplasia (BPD) is the heterogeneous chronic lung developmental disease of prematurity, which is often accompanied by multisystem comorbidities. Pulmonary vascular disease and pulmonary hypertension (PH) contribute significantly to the pathogenesis and pathophysiology of BPD and dramatically influence the outcomes of preterm infants with BPD. When caring for those patients, clinicians should consider the multitude of phenotypic presentations that fall under the "BPD-PH umbrella," reflecting the need for matching therapies to specific physiologies to improve short- and long-term outcomes. Individualized management based on the patient's prenatal and postnatal risk factors, clinical course, and cardiopulmonary phenotype needs to be identified and prioritized to provide optimal care for infants with BPD-PH.

The infant with bronchopulmonary dysplasia on home oxygen: The oxygen weaning conundrum in the absence of good evidence

Bronchopulmonary dysplasia [BPD] is the most common complication of extremely preterm delivery and its optimal management remains challenging because of a lack of evidence to guide management. There has been improvement in the management of evolving BPD in the neonatal intensive care unit (NICU). The threshold for provision of home oxygen therapy, often occurring because of a preference for earlier discharge from the NICU, creates tensions for clincians and families. Once discharged in supplemental oxygen, the approaches for the weaning of this therapy vary considerably across the world. Regardless of guidelines and multidisciplinary team support, up to a third of families of an infant with BPD elect to withdraw home oxygen therapy independently of medical advice. There is a pressing need to derive evidence to better inform practice, generate international consensus and undertake large, appropriately funded, longitudinal studies of BPD with clinically meaningful outcomes (respiratory, cardiovascular and neurodevelopmental) from infancy to adulthood.

The Role of the Interleukin-1 Family in Complications of Prematurity

Preterm birth is a major contributor to neonatal morbidity and mortality. Complications of prematurity such as bronchopulmonary dysplasia (BPD, affecting the lung), pulmonary hypertension associated with BPD (BPD-PH, heart), white matter injury (WMI, brain), retinopathy of prematurity (ROP, eyes), necrotizing enterocolitis (NEC, gut) and sepsis are among the major causes of long-term morbidity in infants born prematurely. Though the origins are multifactorial, inflammation and in particular the imbalance of pro- and anti-inflammatory mediators is now recognized as a key driver of the pathophysiology underlying these illnesses. Here, we review the involvement of the interleukin (IL)-1 family in perinatal inflammation and its clinical implications, with a focus on the potential of these cytokines as therapeutic targets for the development of safe and effective treatments for early life inflammatory diseases.

Hemosiderin-Laden Macrophages in Bronchoalveolar Lavage Samples of Children with Bronchopulmonary Dysplasia

OBJECTIVES

To evaluate the prevalence of hemosiderin-laden macrophages in children with bronchopulmonary dysplasia (BPD) and assess for an association between hemosiderin-laden macrophages and pulmonary arterial hypertension.

STUDY DESIGN

Retrospective case-control study of infants and children with and without BPD who underwent bronchoscopy with bronchoalveolar lavage (BAL) the at Children's Hospital of Philadelphia between 2012 and 2021.

RESULTS

BAL from 205 children with BPD and 106 controls without BPD matched for tracheostomy, infection, and age were reviewed for hemosiderin-laden macrophages. Seventy-one individuals (34.6%) with BPD had a BAL with 10% or more hemosiderin-laden macrophages compared with 3 (2.8%) controls (P < .0001; OR, 18.19; 95% CI, 5.57-59.41). Patients with pulmonary hypertension by echocardiogram (P = .04; OR, 3.69; 95% CI, 1.05-12.96) or an elevated mean pulmonary artery pressure during cardiac catheterization, r_s (14) = 0.56, P = .04, were more likely to have elevated hemosiderin-laden macrophages on BAL samples less than 60 days from bronchoscopy. After adjusting for birth weight, gestational age, BPD grade, and age at the time of bronchoscopy using logistic regression, pulmonary hypertension was associated with a higher odds of hemosiderin-laden macrophages of 10% or more (P = .02; OR, 6.37; 95% CI, 1.28-31.87). No association was observed between hemosiderin-laden macrophages and sex, race, gestational age, birth weight, tracheostomy, or infectious studies.

CONCLUSIONS

This retrospective study revealed increased hemosiderin-laden macrophages in BAL samples from patients with BPD and a significant association with pulmonary arterial hypertension. It is unclear whether elevated hemosiderin-laden macrophages within BPD contributes to the pathogenesis of lung and pulmonary vascular disease or is simply a biomarker of pulmonary arterial hypertension.

Cardiopulmonary Function Abnormalities in Cohort of Adults following Bronchopulmonary Dysplasia as Preterm Infants

OBJECTIVE

This study was aimed to describe the cardiopulmonary profiles of adult patients with bronchopulmonary dysplasia (BPD), comparing them to normative adult values.

STUDY DESIGN

This study presents a retrospective chart review of all BPD patients followed in the adult BPD clinic, identified from institutional and archive databases, born preterm at ≤33 weeks of estimated gestational age (EGA) between January 1980 and December 2000.

RESULTS

Forty-four patients with BPD (26.4 ± 2.7 weeks of EGA) were included. Average age at follow-up was 19 years. Majority (61.4%) of the patients had a diagnosis of asthma. Mean spirometry values were: first second of forced expiration (FEV1) 74.1%, forced vital capacity (FVC) 80.7%, and FEV1/FVC 82.5%. Echocardiography (ECHO) images were reviewed, left ventricular (LV) structure and performance did not differ between obstructive and nonobstructive pulmonary function test (PFT) groups, but values of LV longitudinal strain were 4.8% lower than expected normal for adults. Patients with obstructive PFT had additional decreased right ventricular (RV) function by ECHO.

CONCLUSION

BPD patients in this study were found to have a burden of cardiorespiratory alterations that persisted into adulthood, with RV performance abnormalities found among patients with obstructive PFT.

KEY POINTS

· BPD patients born at extremes of prematurity have cardiorespiratory alterations in adulthood.. · Among patients with obstructive lung function, subtle cardiac performance abnormalities were found.. · Future directions should include systematic follow-up of premature newborns with BPD..

Type 2 immune polarization is associated with cardiopulmonary disease in preterm infants

Postnatal maturation of the immune system is poorly understood, as is its impact on illnesses afflicting term or preterm infants, such as bronchopulmonary dysplasia (BPD) and BPD-associated pulmonary hypertension. These are both cardiopulmonary inflammatory diseases that cause substantial mortality and morbidity with high treatment costs. Here, we characterized blood samples collected from 51 preterm infants longitudinally at five time points, 20 healthy term infants at birth and age 3 to 16 weeks, and 5 healthy adults. We observed strong associations between type 2 immune polarization in circulating CD3⁺CD4⁺ T cells and cardiopulmonary illness, with odds ratios up to 24. Maternal magnesium sulfate therapy, delayed hepatitis B vaccination, and increasing fetal, but not maternal, chorioamnionitis severity were associated with attenuated type 2 polarization. Blocking type 2 mediators such as interleukin-4 (IL-4), IL-5, IL-13, or signal transducer and activator of transcription 6 (STAT6) in murine neonatal cardiopulmonary disease in vivo prevented changes in cell type composition, increases in IL-1β and IL-13, and losses of pulmonary capillaries, but not gains in larger vessels. Thereby, type 2 blockade ameliorated lung inflammation, protected alveolar and vascular integrity, and confirmed the pathological impact of type 2 cytokines and STAT6. In-depth flow cytometry and single-cell transcriptomics of mouse lungs further revealed complex associations between immune polarization and cardiopulmonary disease. Thus, this work advances knowledge on developmental immunology and its impact on early life disease and identifies multiple therapeutic approaches that may relieve inflammation-driven suffering in the youngest patients.

Thrombospondin-1 Plays a Major Pathogenic Role in Experimental and Human Bronchopulmonary Dysplasia

RATIONALE

Extremely preterm infants develop bronchopulmonary dysplasia (BPD), a chronic lung injury that lacks effective treatment. Thrombospondin-1 is an anti-angiogenic protein that activates TGF-β1, a cytokine strongly linked to both experimental and human BPD.

OBJECTIVES

1) To examine effects of inhibiting thrombospondin-1-mediated TGF-β1 activation (LSKL) in neonatal rats with bleomycin-induced lung injury, 2) To examine effects of a thrombospondin-1-mimic (ABT-510) on lung morphology, and 3) To determine whether thrombospondin-1 and related signaling peptides are increased in lungs of human preterm infants at risk for BPD.

METHODS

From postnatal days 1-14, rat pups received daily i.p. bleomycin (1 mg/kg) or vehicle combined with daily s.c. LSKL (20 mg/kg) or vehicle. Separate animals were treated with vehicle or ABT-510 (30 mg/kg/d). Paraffin-embedded lung tissues from 47 autopsies (controls; death <28 days, n=30 and BPD at risk; death ≥28 days, n=17) performed on infants born <29 completed weeks' gestation were semi-quantified for injury markers (collagen, macrophages, 3-nitrotyrosine), thrombospondin-1 and TGF-β1.

MEASUREMENTS AND MAIN RESULTS

Bleomycin or ABT-510 increased lung TGF-β1 activity and macrophage influx, caused pulmonary hypertension and led to alveolar and microvascular hypoplasia. Treatment with LSKL partially prevented abnormal lung morphology secondary to bleomycin. Lungs from human infants at-risk for BPD had increased contents of thrombospondin-1 and TGF-β1 when compared to controls. TGF-β1 content correlated with markers of lung injury.

CONCLUSIONS

Thrombospondin-1 inhibits alveologenesis in neonatal rats, in part via up-regulated activity of TGF-β1. Observations in human lung suggest a similar pathogenic role for thrombospondin-1 in infants at-risk for BPD.

Weaning oxygen in infants with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a form of chronic lung disease commonly seen in preterm infants as the sequelae following respiratory distress syndrome. The management of evolving BPD aims to minimise lung injury and prevent the impact of hypoxia and hyperoxia. Proposed morbidities include respiratory instability, pulmonary hypertension, suboptimal growth, altered cerebral oxygenation and long-term neurodevelopmental impairment. The ongoing management and associated morbidity present a significant burden for carers and healthcare systems. Long-term oxygen therapy may be required for variable duration, though there is a lack of consensus and wide variation in practise when weaning supplemental oxygen. Furthermore, a shift in care towards earlier discharge and community care underlines the importance of a structured discharge and weaning process that eliminates the potential risks associated with hypoxia and hyperoxia. This review article describes recent evidence outlining oxygen saturation reference ranges in young infants, on which structured guidance can be based.

The critical role of collagen VI in lung development and chronic lung disease

Type VI collagen (collagen VI) is an obligate extracellular matrix component found mainly in the basement membrane region of many mammalian tissues and organs, including skeletal muscle and throughout the respiratory system. Collagen VI is probably most recognized in medicine as the genetic cause of a spectrum of muscular dystrophies, including Ullrich Congenital Myopathy and Bethlem Myopathy. Collagen VI is thought to contribute to myopathy, at least in part, by mediating muscle fiber integrity by anchoring myoblasts to the muscle basement membrane. Interestingly, collagen VI myopathies present with restrictive respiratory insufficiency, thought to be due primarily to thoracic muscular weakening. Although it was recently recognized as one of the (if not the) most abundant collagens in the mammalian lung, there is a substantive knowledge gap concerning its role in respiratory system development and function. A few studies have suggested that collagen VI insufficiency is associated with airway epithelial cell survival and altered lung function. Our recent work suggested collagen VI may be a genomic risk factor for chronic lung disease in premature infants. Using this as motivation, we thoroughly assessed the role of collagen VI in lung development and in lung epithelial cell biology. Here, we describe the state-of-the-art for collagen VI cell and developmental biology within the respiratory system, and reveal its essential roles in normal developmental processes and airway epithelial cell phenotype and intracellular signaling.

Multicentre prospective observational study exploring the predictive value of functional echocardiographic indices for early identification of preterm neonates at risk of developing chronic pulmonary hypertension secondary to chronic neonatal lung disease

INTRODUCTION

Although chronic pulmonary hypertension (cPH) secondary to chronic neonatal lung disease is associated with increased mortality and respiratory and neurodevelopmental morbidities, late diagnosis (typically ≥36 weeks postmenstrual age, PMA) and the use of qualitative echocardiographic diagnostic criterion (flat interventricular septum in systole) remain significant limitations in clinical care. Our objective in this study is to evaluate the utility of relevant quantitative echocardiographic indices to identify cPH in preterm neonates, early in postnatal course and to develop a diagnostic test based on the best combination of markers.

METHODS AND ANALYSIS

In this ongoing international prospective multicentre observational diagnostic accuracy study, we aim to recruit 350 neonates born <27 weeks PMA and/or birth weight <1000 g and perform echocardiograms in the third week of age and at 32 weeks PMA (early diagnostic assessments, EDA) in addition to the standard diagnostic assessment (SDA) for cPH at 36 weeks PMA. Predefined echocardiographic markers under investigation will be measured at each EDA and examined to create a scoring system to identify neonates who subsequently meet the primary outcome of cPH/death at SDA. Diagnostic test characteristics will be defined for each EDA. Pulmonary artery acceleration time and tricuspid annular plane systolic excursion are the primary markers of interest.

ETHICS AND DISSEMINATION

Ethics approval has been received by the Mount Sinai Hospital Research Ethics Board (REB) (#16-0111-E), Sunnybrook Health Sciences Centre REB (#228-2016), NHS Health Research Authority (IRAS 266498), University of Iowa Human Subjects Office/Institutional Review Board (201903736), Rotunda Hospital Research and Ethics Committee (REC-2019-008), and UBC Children's and Women's REB (H19-02738), and is under review at Boston Children's Hospital Institutional Review Board. Study results will be disseminated to participating families in lay format, presented to the scientific community at paediatric and critical care conferences and published in relevant peer-reviewed journals.

TRAIL REGISTRATION NUMBER

NCT04402645.

A multidisciplinary chronic lung disease team in a neonatal intensive care unit is associated with increased survival to discharge of infants with tracheostomy

OBJECTIVE

To determine if multidisciplinary team-based care of severe BPD/CLD infants improve survival to discharge.

DESIGN/METHODS

Retrospective review of severe BPD/CLD infants cared for by dedicated multidisciplinary CLD team using consensus-driven protocols and guidelines.

RESULTS

Total of 267 patients. Median gestational age was 26 weeks (IQR 24, 32); median birth-weight was 0.85 (IQR 0.64, 1.5). Twenty-four percent were preterm with severe BPD, 46% had other primary respiratory diseases (none BPD diseases). Total number of patients, proportion of patients with tracheostomy, prematurity, and genetic diagnoses increased over time. 88.8% survived to discharge. Unadjusted logistic regression showed that tracheostomy was not associated with odds of death; secondary pulmonary hypertension was associated with odds of tracheostomy (OR = 1.795 p value = 0.0264), or death (OR = 8.587 p value = <0.0001), or tracheostomy + death (OR = 13.58 p value = 0.0007).

CONCLUSIONS

Over time, mortality improved for infants with tracheostomy cared for by a multidisciplinary severe BPD/CLD team. Secondary pulmonary hypertension was associated with tracheostomy, or death, or tracheostomy + death.

Repair of isolated atrial septal defect in infants less than 12 months improves symptoms of chronic lung disease or shunt-related pulmonary hypertension

INTRODUCTION

Infants with isolated atrial septal defects are usually minimally symptomatic, and repair is typically performed after infancy. Early repair may be considered if there is high pulmonary blood flow and reduced respiratory reserve or early signs of pulmonary hypertension. Our aim was to review the characteristics and outcomes of a cohort of patients who underwent infant repair at our institute.

METHODS

The study included 56 infants (28 female, 19 trisomy 21) with isolated atrial septal defect (age: 8 months (1.5-12), weight: 6 kg (2.8-7.5), echo Qp/Qs: 1.9 ± 0.1) who underwent surgical closure (20 fenestrated). Three groups were identified: 1) chronic lung disease and pulmonary hypertension (group A: n = 28%); 2) acutely unwell infants with pulmonary hypertension but no chronic lung disease (group B: n = 20, 36%); and 3) infants with refractory congestive heart failure without either pulmonary hypertension or chronic lung disease (group C: n = 9, 16%).

RESULTS

Post-operatively, pulmonary hypertension infants (47/56) showed improvement in tricuspid annular plane systolic excursion z-score (p < 0.001) and right ventricular systolic/diastolic duration ratio (p < 0.05). All ventilator (14.3%) or oxygen-dependent (31.6%) infants could be weaned within 2 weeks after repair. One year later, weight z-score increased in all patients and by +1 in group A, +1.3 in group B and +2 in group C. Over a median follow-up of 1.4 years, three patients died, four patients continued to have pulmonary hypertension evidence and two remained on targeted pulmonary hypertension therapy.

CONCLUSION

Atrial septal defect repair within the first year may improve the clinical status and growth in infants with early signs of pulmonary hypertension or those requiring respiratory support and facilitate respiratory management.

Interleukin-1 Receptor Antagonist Protects Newborn Mice Against Pulmonary Hypertension

Pulmonary hypertension secondary to bronchopulmonary dysplasia (BPD-PH) represents a major complication of BPD in extremely preterm infants for which there are currently no safe and effective interventions. The abundance of interleukin-1 (IL-1) is strongly correlated with the severity and long-term outcome of BPD infants and we have previously shown that IL-1 receptor antagonist (IL-1Ra) protects against murine BPD; therefore, we hypothesized that IL-1Ra may also be effective against BPD-PH. We employed daily injections of IL-1Ra in a murine model in which BPD/BPD-PH was induced by antenatal LPS and postnatal hyperoxia of 65% O₂. Pups reared in hyperoxia for 28 days exhibited a BPD-PH-like disease accompanied by significant changes in pulmonary vascular morphology: micro-CT revealed an 84% reduction in small vessels (4-5 μm diameter) compared to room air controls; this change was prevented by IL-1Ra. Pulmonary vascular resistance, assessed at day 28 of life by echocardiography using the inversely-related surrogate marker time-to-peak-velocity/right ventricular ejection time (TPV/RVET), increased in hyperoxic mice (0.27 compared to 0.32 in air controls), and fell significantly with daily IL-1Ra treatment (0.31). Importantly, in vivo cine-angiography revealed that this protection afforded by IL-1Ra treatment for 28 days is maintained at day 60 of life. Despite an increased abundance of mediators of pulmonary angiogenesis in day 5 lung lysates, namely vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1), no difference was detected in ex vivo pulmonary vascular reactivity between air and hyperoxia mice as measured in precision cut lung slices, or by immunohistochemistry in alpha-smooth muscle actin (α-SMA) and endothelin receptor type-A (ET_A) at day 28. Further, on day 28 of life we observed cardiac fibrosis by Sirius Red staining, which was accompanied by an increase in mRNA expression of galectin-3 and CCL2 (chemokine (C-C motif) ligand 2) in whole hearts of hyperoxic pups, which improved with IL-1Ra. In summary, our findings suggest that daily administration of the anti-inflammatory IL-1Ra prevents the increase in pulmonary vascular resistance and the pulmonary dysangiogenesis of murine BPD-PH, thus pointing to IL-1Ra as a promising candidate for the treatment of both BPD and BPD-PH.

Death or resolution: the "natural history" of pulmonary hypertension in bronchopulmonary dysplasia

OBJECTIVES

The primary objective was to describe the early "natural history" of pulmonary hypertension (PH) in the premature population. The secondary objective was to describe factors associated with poor outcomes in the premature population with PH at 36 weeks post-menstrual age (PMA).

STUDY DESIGN

Retrospective chart review of patients followed at our institution from 2000 to 2017 with echocardiographic (ECHO) evidence of PH at 36 weeks PMA, and born ≤ 32 weeks estimated gestational age (GA). Cox regression was used for survival analysis.

RESULTS

Sixty-one patients with PH (26.5 ± 1.5 weeks at birth) were included. All PH patients had bronchopulmonary dysplasia (BPD), with 89% considered severe; 38% were small for gestational age. Necrotizing enterocolitis requiring surgery was common (25%). Use of post-natal steroids (HR 11.02, p = 0.01) and increased severity of PH (HR 1.05, p < 0.001) were associated with mortality. Pulmonary vein stenosis (PVS) was documented in 26% of the PH cohort, but not associated with increased mortality. ECHO estimation of pulmonary artery pressure (PAP) was available in 84%. PAP was higher in those who died (sPAP/sBP ratio 1.09 ± 27 vs 0.83 ± 20 %, p = 0.0002). At follow-up (mean 250 ± 186 weeks PMA), 72% of the PH cohort was alive. Most survivors (66%) had resolution of their PH on their most recent ECHO; 31% remained on PH therapy.

CONCLUSION

PH resolved in most survivors in this study population. Mortality in those with BPD-PH was associated with male sex, post-natal steroid use, and increased severity of PH, but not with PVS.

An update on the diagnosis and management of bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension

The past decade of neonatal care has been highlighted by increased survival rates in smaller and more premature infants. Despite reduction in mortality associated with extreme prematurity, long term pulmonary morbidities remain a concern, with growing recognition of the clinical burden attributable to infants with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH). Recent publications shed light on the critical contributions of maternal placental pathology and compromised intrauterine growth to fetal pulmonary vascular development. A body of literature has further clarified postnatal risk factors for PH, most notably the severity of BPD but surprisingly the additional presence of non-pulmonary morbidities including necrotizing enterocolitis (NEC). Limitations of current diagnostics persist with growing consideration of novel echocardiographic approaches as well as complementary non-invasive biomarkers to better identify infants at risk. In 2015, a joint report published by the American Heart Association and American Thoracic Society provided the first guidelines for the care of children with PH with limited content to address BPD-associated PH. These guidelines were expanded upon in an expert consensus report produced by the Pediatric Pulmonary Hypertension Network (PPHNet). These recommendations encouraged the use of standardized screening protocols and emphasized the importance of evaluation and treatment of comorbidities when PH is identified. Cardiac catheterization was recommended prior to initiation of therapy for more accurate quantification of pulmonary pressures, clarification of anatomy and guidance in the use of pharmacotherapy. Despite these guidelines, significant practice variation persists and gaps remain with respect to optimal evaluation and management of BPD-associated PH.

Evidence of Echocardiographic Markers of Pulmonary Vascular Disease in Asymptomatic Infants Born Preterm at One Year of Age

OBJECTIVE

To test the hypothesis that echocardiographic markers of pulmonary vascular disease (PVD) exist in asymptomatic infants born preterm at 1-year corrected age.

STUDY DESIGN

We conducted a prospective cohort study of 80 infants born preterm (<29 weeks of gestation) and 100 age- and weight-matched infants born at term and compared broad-based conventional and quantitative echocardiographic measures of pulmonary hemodynamics at 1-year corrected age. Pulmonary artery acceleration time (PAAT), a validated index of pulmonary vascular resistance, arterial pressure, and compliance, was used to assess pulmonary hemodynamics. Lower PAAT is indicative of PVD. Subanalyses were performed in infants with bronchopulmonary dysplasia (BPD, n = 48, 59%) and/or late-onset pulmonary hypertension (n = 12, 15%).

RESULTS

At 1 year, there were no differences between conventional measures of pulmonary hypertension in the infants born at term and preterm. All infants born preterm had significantly lower values of PAAT than infants born at term (73 ± 8 milliseconds vs 98 ± 5 milliseconds, P < .001). Infants born preterm with BPD had even lower PAAT than those without BPD (69 ± 5 milliseconds vs 79 ± 4 milliseconds, P < .01). The degree of PVD at 1-year corrected age was inversely related to gestation in all infants born preterm. Data analysis included adjustment for ventricular function and other confounding factors.

CONCLUSIONS

In comparison with infants born at term, infants born preterm exhibit abnormal PAAT at 1-year corrected age irrespective of neonatal lung disease status, suggesting the existence of PVD beyond infancy. PAAT measurements offer a reliable, noninvasive tool for screening and longitudinal monitoring of pulmonary hemodynamics in infants.

Pulmonary hypertension associated with bronchopulmonary dysplasia in preterm infants

Bronchopulmonary dysplasia (BPD) and BPD-associated pulmonary hypertension (BPD-PH) are chronic inflammatory cardiopulmonary diseases with devastating short- and long-term consequences for infants born prematurely. The immature lungs of preterm infants are ill-prepared to achieve sufficient gas exchange, thus usually necessitating immediate commencement of respiratory support and oxygen supplementation. These therapies are life-saving, but they exacerbate the tissue damage that is inevitably inflicted on a preterm lung forced to perform gas exchange. Together, air-breathing and necessary therapeutic interventions disrupt normal lung development by aggravating pulmonary inflammation and vascular remodelling, thus frequently precipitating BPD and PH via an incompletely understood pathogenic cascade. BPD and BPD-PH share common risk factors, such as low gestational age at birth, fetal growth restriction and perinatal maternal inflammation; however, these risk factors are not unique to BPD or BPD-PH. Occurring in 17-24% of BPD patients, BPD-PH substantially worsens the morbidity and mortality attributable to BPD alone, thus darkening their outlook; for example, BPD-PH entails a mortality of up to 50%. The absence of a safe and effective therapy for BPD and BPD-PH renders neonatal cardiopulmonary disease an area of urgent unmet medical need. Besides the need to develop new therapeutic strategies, a major challenge for clinicians is the lack of a reliable method for identifying babies at risk of developing BPD and BPD-PH. In addition to discussing current knowledge on pathophysiology, diagnosis and treatment of BPD-PH, we highlight emerging biomarkers that could enable clinicians to predict disease-risk and also optimise treatment of BPD-PH in our tiniest patients.

CHD and respiratory syncytial virus: global expert exchange recommendations

BACKGROUND

Palivizumab is the standard immunoprophylaxis against serious disease due to respiratory syncytial virus infection. Current evidence-based prophylaxis guidelines may not address certain children with CHD within specific high-risk groups or clinical/management settings.

METHODS

An international steering committee of clinicians with expertise in paediatric heart disease identified key questions concerning palivizumab administration; in collaboration with an additional international expert faculty, evidence-based recommendations were formulated using a quasi-Delphi consensus methodology.

RESULTS

Palivizumab prophylaxis was recommended for children with the following conditions: <2 years with unoperated haemodynamically significant CHD, who are cyanotic, who have pulmonary hypertension, or symptomatic airway abnormalities; <1 year with cardiomyopathies requiring treatment; in the 1st year of life with surgically operated CHD with haemodynamically significant residual problems or aged 1-2 years up to 6 months postoperatively; and on heart transplant waiting lists or in their 1st year after heart transplant. Unanimous consensus was not reached for use of immunoprophylaxis in children with asymptomatic CHD and other co-morbid factors such as arrhythmias, Down syndrome, or immunodeficiency, or during a nosocomial outbreak. Challenges to effective immunoprophylaxis included the following: multidisciplinary variations in identifying candidates with CHD and prophylaxis compliance; limited awareness of severe disease risks/burden; and limited knowledge of respiratory syncytial virus seasonal patterns in subtropical/tropical regions.

CONCLUSION

Evidence-based immunoprophylaxis recommendations were formulated for subgroups of children with CHD, but more data are needed to guide use in tropical/subtropical countries and in children with certain co-morbidities.

Effectiveness of positive pressure ventilation during newborn care unit evacuation

OBJECTIVE

Assess the utility of high fidelity simulation in understanding effectiveness of bag-valve ventilation in a simulated newborn intensive care unit vertical evacuation.

PARTICIPANTS

A total of 70 participants, (13 teams of 4-6 staff) including physicians, nurses, respiratory therapists and other support personnel participated in a 90-min evacuation sessions.

METHODS

Two wireless high-fidelity newborn mannequins (Gaumand Scientific^R) provided real-time data of ventilation support during a NICU evacuation exercise. Trained evaluators also recorded data related to performance. Following the exercises, the simulator data were downloaded and analyzed for rate and consistency of respirations.

RESULTS

Using the data from the simulators and evaluator comments, it was found the infants received proper airway management during the evacuation only 58% of the time. This study highlights the need for ongoing training for NICU staff around safe, effective, coordinated, and timely care of these fragile newborns in the event of an evacuation.

Pathophysiology, screening and diagnosis of pulmonary hypertension in infants with bronchopulmonary dysplasia - A review of the literature

Bronchopulmonary dysplasia (BPD) is a common complication of extreme prematurity, which has increased over the last 20 years. BPD is associated with increased morbidities and mortality. It has been increasingly recognized that BPD affects overall lung development including the pulmonary vasculature. More recent studies have demonstrated an increased awareness of pulmonary arterial hypertension (PH) in BPD patients and recent international guidelines have advocated for better screening. This review will describe the current understanding of the pathophysiology of PH in infants with BPD, the in-depth assessment of the available literature linking PH and BPD, and propose an approach of screening and diagnosis of PH in infants with BPD.

Clinical Utility of Echocardiography for the Diagnosis and Prognosis in Children with Bronchopulmonary Dsyplasia

Background

Bronchopulmonary dysplasia (BPD) may result in chronic pulmonary artery hypertension and right ventricular (RV) dysfunction. Various echocardiographic assessments of RV dysfunction have been used to determine whether echocardiographic measurements of premature infants with BPD could provide sensitive measures of RV function that correlates with BPD severity.

Methods

Twenty-eight control subjects without BPD (non BPD group), 28 patients with mild BPD, 11 patients with moderate BPD, and six patients with severe BPD underwent echocardiograms with standard measurement such as ejection fraction by M-mode, tricuspid regurgitation pressure gradient, myocardial performance index (MPI) derived from pulse Doppler, and tissue Doppler imaging (TDI) measurements. BPD severity was classified by the NICHD/NHLBI/ORD workshop rating scale. Twenty-eight control subjects without BPD (non BPD group), 28 patients with mild BPD, 11 patients with moderate BPD, and six patients with severe BPD underwent echocardiograms with standard measurement such as ejection fraction by M-mode, tricuspid regurgitation pressure gradient, myocardial performance index (MPI) derived from pulse Doppler, and TDI measurements. BPD severity was classified by the NICHD/NHLBI/ORD workshop rating scale.

Results

None of the standard echocardiographic findings was significantly different between the control group and BPD groups. However, mean septal TDI-MPI of the severe BPD group (0.68 ± 0.06) was significantly (p < 0.01) higher than that of the non-BPD (0.58 ± 0.10) or the mild BPD group (0.59 ± 0.12). In addition, mean RV TDI-MPI of the severe BPD group (0.71 ± 0.13) was significantly (p < 0.05) higher than that of the non-BPD group (0.56 ± 0.08) or the mild BPD group (0.60 ± 0.125). Linear regression showed a good correlation between the severity of BPD and RV TDI-MPI (p = 0.01, R = 0.30) or septal TDI-MPI (p = 0.04, R = 0.24).

Conclusion

Echocardiographic evaluation of RV function based on an assessment of RV TDI-MPI can provide RV dysfunction parameter in premature infants with BPD.

Bronchopulmonary Dysplasia in Preterm Infants Born at Less Than 32 Weeks Gestation

Objectives: Bronchopulmonary dysplasia (BPD) is a chronic pulmonary disorder affecting preterm infants. We studied the factors and echocardiographic evidence of early pulmonary hypertension (PH) associated with moderate or severe BPD. Methods: We retrospectively reviewed preterm infants who were born at <32 weeks gestation and admitted to the neonatal intensive care unit at the Children’s Hospital of Zhejiang University School of Medicine between July 2013 and July 2015. Results: Forty-two preterm infants were enrolled in the study. All the patients received oxygen treatment for a mean of 62.5 ± 28.0 days. The grades of BPD were classified as follows: severe, 35.7%; moderate, 40.5%; and mild, 23.8%. The time of ventilator and oxygen supplementation was longer in infants who developed PH. Severe BPD was related to PH at 28 days. Conclusions: These findings support the notion that early pulmonary vascular disease and long-term infection in preterm infants contributes to increased susceptibility for severe BPD.

Leukotriene B4 mediates macrophage influx and pulmonary hypertension in bleomycin-induced chronic neonatal lung injury

Systemically-administered bleomycin causes inflammation, arrested lung growth, and pulmonary hypertension (PHT) in the neonatal rat, similar to human infants with severe bronchopulmonary dysplasia (BPD). Leukotrienes (LTs) are inflammatory lipid mediators produced by multiple cell types in the lung. The major LTs, LTB4 and cysteinyl LTs, are suggested to contribute to BPD, but their specific roles remain largely unexplored in experimental models. We hypothesized that LTs are increased in bleomycin-induced BPD-like injury, and that inhibition of LT production would prevent inflammatory cell influx and thereby ameliorate lung injury. Rat pups were exposed to bleomycin (1 mg·kg(-1)·day(-1) ip) or vehicle (control) from postnatal days 1-14 and were treated with either zileuton (5-lipoxygenase inhibitor), montelukast (cysteinyl LT1 receptor antagonist), or SC57461A (LTA4 hydrolase inhibitor) 10 mg·kg(-1)·day(-1) ip. Bleomycin led to increased lung content of LTB4, but not cysteinyl LTs. Bleomycin-induced increases in tissue neutrophils and macrophages and lung contents of LTB4 and tumor necrosis factor-α were all prevented by treatment with zileuton. Treatment with zileuton or SC57461A also prevented the hemodynamic and structural markers of chronic PHT, including raised pulmonary vascular resistance, increased Fulton index, and arterial wall remodeling. However, neither treatment prevented impaired alveolarization or vascular hypoplasia secondary to bleomycin. Treatment with montelukast had no effect on macrophage influx, PHT, or on abnormal lung structure. We conclude that LTB4 plays a crucial role in lung inflammation and PHT in experimental BPD. Agents targeting LTB4 or LTB4-mediated signaling may have utility in infants at risk of developing BPD-associated PHT.

The genetic predisposition to bronchopulmonary dysplasia

PURPOSE OF REVIEW

Bronchopulmonary dysplasia (BPD) is a prevalent chronic lung disease in premature infants. Twin studies have shown strong heritability underlying this disease; however, the genetic architecture of BPD remains unclear.

RECENT FINDINGS

A number of studies employed different approaches to characterize the genetic aberrations associated with BPD, including candidate gene studies, genome-wide association studies, exome sequencing, integrative omics analysis, and pathway analysis. Candidate gene studies identified a number of genes potentially involved with the development of BPD, but the etiological contribution from each gene is not substantial. Copy number variation studies and three independent genome-wide association studies did not identify genetic variations significantly and consistently associated with BPD. A recent exome-sequencing study pointed to rare variants implicated in the disease. In this review, we summarize these studies' methodology and findings, and suggest future research directions to better understand the genetic underpinnings of this potentially life-long lung disease.

SUMMARY

Genetic factors play a significant role in the development of BPD. Recent studies suggested that rare variants in genes participating in lung development pathways could contribute to BPD susceptibility.

Evaluation of the maternal and fetal risk factors associated with neonatal care unit hospitalization time

OBJECTIVE

To evaluate maternal and neonatal risk factors associated with the length of hospital stay in the neonatal intensive care unit (NICU).

MATERIAL AND METHOD

This retrospective observational study was based on 3607 newborns who were admitted to the NICU of a tertiary teaching hospital from January 2012 through December 2014. Known obstetric risk factors associated with duration of hospitalization in NICUs were assessed including intrauterine growth restriction, maternal diabetes, oligohydramnios, chorioamnionitis, premeture rupture of membranes, preeclampsia, congenital malformations, neonatal sepsis, premature retinopathy, intracranial bleeding, necrotizing enterocolitis, meconium aspiration, maternal hypertension, fetal congenital cardiac malformations, congenital metabolic diseases, congenital hypothyroidism, pneumonia, pulmonary hypertension, bronchopulmonary dysplasia, pneumothorax and respiratory distress syndrome.

RESULTS

Gestational age (beta coefficient: -0.244, p<0.001) and birth weight (beta coefficient: -0.237, p<0.001) were significant confounders for duration of hospitalization in newborns.

CONCLUSION

Gestational age and the birth weight were the most important confounders for duration of hospitalization. Neonate care in developing countries would further benefit from additional large population-based long-term studies with broad parameters.

Some neonatal risk factors for adult pulmonary arterial hypertension remain unknown

AIM

Pulmonary hypertension has been linked to premature birth, chronic lung disease, bronchopulmonary dysplasia and congenital heart disease. This national population-based registry study assessed the risk of adult pulmonary hypertension following premature birth, adjusted for known risk factors.

METHODS

We focused on adults in the Swedish Pulmonary Arterial Hypertension Registry, who were born prematurely, and controls randomly selected from the Swedish medical birth register and matched to each case by birth year and delivery hospital. Information on perinatal factors was also retrieved from the medical birth register. Conditional multiple logistic regression was used to evaluate the association between premature birth and adult pulmonary hypertension, taking into account the potential confounding factors.

RESULTS

The study population comprised 427 adults born between 1973 and 1996, with 61 cases and 366 controls. Adult pulmonary hypertension was associated with premature birth, with an odds ratio of 3.08 and 95% confidence interval of 1.21-7.87. The association did not alter after adjusting for potential confounders.

CONCLUSION

By adjusting for factors linked to adult pulmonary hypertension, namely congenital heart defects, pulmonary diseases and premature birth, we were able to show that other unknown factors may influence the risk for pulmonary hypertension among adults who were born premature.

The Impact of Atrial Left-to-Right Shunt on Pulmonary Hypertension in Preterm Infants with Moderate or Severe Bronchopulmonary Dysplasia

BACKGROUND

Bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) is a well-known complication of prematurity; however, the additional impact of a left-to-right interatrial shunt on this condition remains poorly understood. The aim of the present study was to identify the significance of atrial left-to-right shunt lesions in PH infants with moderate or severe BPD.

METHODS

The medical records of 383 preterm infants (gestational age of < 32 weeks) who were diagnosed with BPD between 2005 and 2013 were retrospectively reviewed. Baseline characteristics such as interatrial shunts and outcomes were compared between the infants who developed PH (n = 50) and infants who did not (n = 144). Infants with hemodynamically significant residual patent ductus arteriosus were excluded. Among the infants diagnosed with PH (n = 50), the outcomes were compared between the patients with (n = 21) and without atrial shunts (n = 29) at 36 weeks corrected postmenstrual age.

RESULTS

Fifty (15%) preterm infants with BPD were diagnosed with PH. The number of infants with a history of atrial shunt lesions was significantly higher in the PH group than in the non-PH group (42% vs. 15.3%, respectively). The adjusted odds ratio for PH in the atrial shunt group was 3.8 (95% confidence interval, 1.8-8.0), compared to PH-BPD infants without an atrial shunt.

CONCLUSION

The presence of an atrial left-to-right shunt was associated with PH in preterm infants with moderate or severe BPD. Close follow up is needed for infants with interatrial shunts, and a more tailored prognostic evaluation and treatment are recommended.

Pulmonary hypertension in preterm infants: prevalence and association with bronchopulmonary dysplasia

OBJECTIVE

To determine whether early pulmonary hypertension (PH) at 10-14 days of life in preterm infants is associated with bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age (PMA).

STUDY DESIGN

This was a prospective observational cohort study of infants <28 weeks' gestation. Exclusion criteria were any major anomaly, genetic syndrome, or death before the initial echocardiogram. Echocardiograms were performed between 10 and 14 days of life and at 36 weeks' PMA to assess PH. BPD and its severity were determined at 36 weeks PMA by the National Institutes of Health workshop definition.

RESULTS

From March 2011 to April 2013, of 146 consecutively admitted infants <28 weeks, 120 were enrolled. One infant was excluded, 17 did not consent, and 8 died before undergoing a study echocardiogram. At 10-14 days of life, 10 infants had early PH (8%). Male sex (56% vs 40%), gestational age (26(+2) ± 1(+2) vs 25(+6) ± 1(+4) weeks), birth weight (837 ± 205 g vs 763 ± 182 g), and small for gestational age (14% vs 20%) were not significantly different among infants with no PH and early PH, respectively. Infants with early PH required >0.3 fraction of inspired oxygen by day 10 of life (70% vs 27%, P < .01). Moderate/severe BPD or death was greater among infants with early PH (90%) compared with no PH (47%, relative risk 1.9, 95% CI 1.43-2.53).

CONCLUSION

In this prospective, single-center cohort, early PH was associated with moderate/severe BPD or death at 36 weeks' PMA.

[Update on pediatric cardiology and congenital heart disease: imaging techniques, pulmonary arterial hypertension, hybrid treatment, and surgical treatment]

This article contains a review of the most significant contributions to pediatric cardiology and congenital heart disease reported in publications between September 2009 and August 2010. The review focuses on imaging techniques, new treatment for pulmonary arterial hypertension in pediatric patients, and therapy in general (e.g. hybrid treatment and surgical treatment). With regard to imaging techniques, the review highlights the increasing application of congenital heart disease diagnosis during fetal life, the introduction of new echocardiographic techniques (e.g. tissue Doppler imaging, two-dimensional speckle-tracking imaging and three-dimensional echocardiography) into routine clinical practice, and the growing use of cardiac CT and magnetic resonance imaging in diagnosis and the assessment of cardiac function, respectively. The role played by cardiac interventions continues to increase and cardiac surgery is becoming more advanced and has, in some cases, been combined with hybrid techniques. However, there are still a number of controversial issues in cardiac surgery that have not yet been resolved, such as whether or not fenestration should be used with Fontan surgery, the optimum type of correction for hypoplastic left heart syndrome, and the best conduit for pulmonary artery replacement.

Cardiovascular function in children who had chronic lung disease of prematurity

OBJECTIVES

Although increased pulmonary arterial pressure is common in infancy in preterm infants who develop chronic lung disease of prematurity (CLD), it is unknown if the increase persists into childhood. We, therefore, assessed if 8-12-year-old children with documented CLD in infancy had evidence of right ventricular dysfunction or pulmonary arterial hypertension at rest or in response to acute hypoxia when compared to preterm and term-born controls.

METHODS

We studied 90 children: 60 born at ≤32 weeks of gestation (28 with CLD and 32 preterm controls), and 30 term-born controls. All had echocardiography including myocardial velocity imaging, at rest and while breathing 15% oxygen and 12% oxygen for 20 min each.

RESULTS

Baseline oxygen saturation, heart rate, blood pressure and echocardiographic markers of left and right ventricular function were similar in all three groups. While breathing 12% oxygen, the oxygen saturation decreased to 81.9% in the CLD group compared to 85.1% (p<0.05) and 84.7% (p<0.01) in the preterm and term controls, respectively. In response to hypoxia, all three groups showed increases in velocity of tricuspid regurgitation, end-diastolic velocity of pulmonary regurgitation, and right ventricular relaxation time; and decreases in pulmonary arterial acceleration time and the ratio of right ventricular acceleration time to ejection time. However, there were no differences between groups.

CONCLUSIONS

Childhood survivors of CLD have comparable left and right ventricular function at 8-12 years of age to preterm and term-born children, and no evidence of increased pulmonary arterial pressure even after hypoxic exposure.

Prevention of hyperoxia-induced bronchial hyperreactivity by sildenafil and vasoactive intestinal peptide: impact of preserved lung function and structure

Objective

Hyperoxia exposure leads to the development of lung injury and bronchial hyperreactivity (BHR) via involvement of nitric oxide (NO) pathway. We aimed at characterizing whether the stimulation of the NO pathway by sildenafil or vasoactive intestinal peptide (VIP) is able to prevent the hyperoxia-induced development of BHR. The respective roles of the preserved lung volume and alveolar architecture, the anti-inflammatory and anti-apoptotic potentials of these treatments in the diminished lung responsiveness were also characterized.

Materials and methods

Immature (28-day-old) rats were exposed for 72 hours to room air (Group C), hyperoxia (>95%, Group HC), or hyperoxia with the concomitant administration of vasoactive intestinal peptide (VIP, Group HV) or sildenafil (Group HS). Following exposure, the end-expiratory lung volume (EELV) was assessed plethysmographically. Airway and respiratory tissue mechanics were measured under baseline conditions and following incremental doses of methacholine to assess BHR. Inflammation was assessed by analyzing the bronchoalveolar lavage fluid (BALF), while biochemical and histological analyses were used to characterize the apoptotic and structural changes in the lungs.

Results

The BHR, the increased EELV, the aberrant alveolarization, and the infiltration of inflammatory cells into the BALF that developed in Group HC were all suppressed significantly by VIP or sildenafil treatment. The number of apoptotic cells increased significantly in Group HC, with no evidence of statistically significant effects on this adverse change in Groups HS and HV.

Conclusions

These findings suggest that stimulating the NO pathway by sildenafil and VIP exert their beneficial effect against hyperoxia-induced BHR via preserving normal EELV, inhibiting airway inflammation and preserving the physiological lung structure, whereas the antiapoptotic potential of these treatments were not apparent in this process.

Prescription of home oxygen therapy to very low birth weight infants in Germany: a nationwide survey

OBJECTIVE

There is no consensus on prescription of home oxygen therapy to infants in Germany. We hypothesized that this causes considerable variability in prescribing home oxygen to infants.

STUDY DESIGN

A structured questionnaire involving management of home oxygen therapy was sent to all German pediatric departments (n = 293).

RESULTS

Response rate was 84% (247/293). SpO2 cutoff values below which oxygen therapy was considered indicated showed a wide range (80% to 94%, mean 90%). Respondents admitting >50 very low birth weight infants annually significantly more frequently prescribed home oxygen (P < .001) and aimed for SpO2 levels closer to the physiological range than those admitting less very low birth weight infants (P = .046).

CONCLUSION

Management of pediatric home oxygen therapy is diverse in Germany. Optimal SpO2 targets have to be further investigated by controlled studies and German guidelines should be established. Until then practice should abide by existing foreign guidelines.

Rho-kinase inhibitor prevents bleomycin-induced injury in neonatal rats independent of effects on lung inflammation

Bleomycin-induced lung injury is characterized in the neonatal rat by inflammation dominated by neutrophils and macrophages, inhibited distal airway and vascular development, and pulmonary hypertension, similar to human infants with severe bronchopulmonary dysplasia. Rho-kinase (ROCK) is known to mediate lung injury in adult animals via stimulatory effects on inflammation. We therefore hypothesized that inhibition of ROCK may ameliorate bleomycin-induced lung injury in the neonatal rat. Pups received daily intraperitoneal bleomycin or saline from Postnatal Days 1 through 14 with or without Y-27632, a ROCK inhibitor. Treatment with Y-27632 prevented bleomycin-induced pulmonary hypertension, as evidenced by normalized pulmonary vascular resistance, decreased right-ventricular hypertrophy, and attenuated remodeling of pulmonary resistance arteries. Bleomycin-induced changes in distal lung architecture, including septal thinning, inhibited alveolarization, and decreased numbers of peripheral arteries and capillaries, were partially or completely normalized by Y-27632. Treatment with Y-27632 or a CXCR2 antagonist, SB265610, also abrogated tissue neutrophil influx, while having no effect on macrophages. However, treatment with SB265610 did not prevent bleomycin-induced lung injury. Lung content of angiostatic thrombospondin-1 (TSP1) was increased significantly in the lungs of bleomycin-exposed animals, and was completely attenuated by treatment with Y-27632. Thrombin-stimulated TSP1 production by primary cultured rat pulmonary artery endothelial cells was also attenuated by Y-27632. Taken together, our findings suggest a preventive effect of Y-27632 on bleomycin-mediated injury by a mechanism unrelated to inflammatory cells. Our data suggest that improvements in lung morphology may have been related to indirect stimulatory effects on angiogenesis via down-regulation of TSP1.

Therapeutic hypercapnia prevents inhaled nitric oxide-induced right-ventricular systolic dysfunction in juvenile rats

Chronic pulmonary hypertension in the neonate and infant frequently presents with right-ventricular (RV) failure. Current clinical management may include protracted treatment with inhaled nitric oxide (iNO), with the goal of reducing RV afterload. We have previously reported that prolonged exposure to iNO causes RV systolic dysfunction in the chronic hypoxia-exposed juvenile rat, which was prevented by a peroxynitrite decomposition catalyst. Given that inhalation of CO2 (therapeutic hypercapnia) may limit oxidative stress and upregulated cytokine expression in the lung and other organs, we hypothesized that therapeutic hypercapnia would attenuate cytokine-mediated nitric oxide synthase (NOS) upregulation, thus limiting peroxynitrite generation. Sprague-Dawley rat pups were exposed to chronic hypoxia (13% O2) from postnatal day 1 to 21, while receiving iNO (20 ppm) from day 14 to 21, with or without therapeutic hypercapnia (10% CO2). Therapeutic hypercapnia completely normalized RV systolic function, RV hypertrophy, and remodeling of pulmonary resistance arteries in animals exposed to iNO. Inhaled nitric oxide-mediated increases in RV peroxynitrite, apoptosis, and contents of tumor necrosis factor (TNF)-α, interleukin (IL)-1α, and NOS-2 were all attenuated by therapeutic hypercapnia. Inhibition of NOS-2 activity with 1400 W (1 mg/kg/day) prevented iNO-mediated upregulation of peroxynitrite and led to improved RV systolic function. Blockade of IL-1 receptor signaling with anakinra (500 mg/kg/day) decreased NOS-2 content and had similar effects compared to NOS-2 inhibition on iNO-mediated effects, whereas blockade of TNF-α signaling with etanercept (0.4 mg/kg on alternate days) had no effects on these parameters. We conclude that therapeutic hypercapnia prevents the adverse effects of sustained exposure to iNO on RV systolic function by limiting IL-1-mediated NOS-2 upregulation and consequent nitration. Therapeutic hypercapnia also acts synergistically with iNO in normalizing RV hypertrophy, vascular remodeling, and raised pulmonary vascular resistance secondary to chronic hypoxia.

Long term cardiovascular consequences of chronic lung disease of prematurity

Pulmonary arterial (PA) hypertension in preterm infant is an important consequence of chronic lung disease of prematurity (CLD) arising mainly due to impaired alveolar development and dysregulated angiogenesis of the pulmonary circulation. Although PA pressure and resistance in these children normalise by school age, their pulmonary vasculature remains hyper-reactive to hypoxia until early childhood. Furthermore, there is evidence that systemic blood pressure in preterm born children with or without CLD is mildly increased at school age and in young adulthood when compared to term-born children. Arterial stiffness may be increased in CLD survivors due to increased smooth muscle tone of the pre-resistance and resistance vessels rather than the loss of elasticity in the large arteries. This review explores the long term effects of CLD on the pulmonary and systemic circulations along with their clinical correlates and therapeutic approaches.

Pulmonary hypertension in bronchopulmonary dysplasia

Pulmonary hypertension (PH) is a common complication of neonatal respiratory diseases, including bronchopulmonary dysplasia (BPD), and recent studies have increased awareness that PH worsens the clinical course, morbidity and mortality of BPD. Recent evidence indicates that up to 18% of all extremely low-birth-weight infants will develop some degree of PH during their hospitalization, and the incidence rises to 25-40% of the infants with established BPD. Risk factors are not yet well understood, but new evidence shows that fetal growth restriction is a significant predictor of PH. Echocardiography remains the primary method for evaluation of BPD-associated PH, and the development of standardized screening timelines and techniques for identification of infants with BPD-associated PH remains an important ongoing topic of investigation. The use of pulmonary vasodilator medications, such as nitric oxide, sildenafil, and others, in the BPD population is steadily growing, but additional studies are needed regarding their long-term safety and efficacy.

Associated inflammation or increased flow-mediated shear stress, but not pressure alone, disrupts endothelial caveolin-1 in infants with pulmonary hypertension

Endothelial caveolin-1 loss is an important feature of pulmonary hypertension (PH); the rescue of caveolin-1 abrogates experimental PH. Recent studies in human PH suggest that the endothelial caveolin-1 loss is followed by an enhanced expression of caveolin-1 in smooth muscle cells (SMC) with subsequent neointima formation. In order to evaluate caveolin-1 expression in infants with PH, we examined the available clinical histories, hemodynamic data, and the expression of caveolin-1, PECAM-1, vWF, and smooth muscle α-actin in the lung biopsy/autopsy specimens obtained from infants with congenital heart disease (CHD, n = 8) and lung disease (n = 9). In CHD group, PH associated with increased pulmonary blood flow exhibited loss of endothelial caveolin-1 and PECAM-1 in pulmonary arteries; additional vWF loss was associated with enhanced expression of caveolin-1 in SMC. In the absence of PH, increased or decreased pulmonary blood flow did not disrupt endothelial caveolin-1, PECAM-1, or vWF; nor was there any enhanced expression of caveolin-1 in SMC. In Lung Disease + PH group, caveolin-1, PECAM-1, and vWF were well preserved in seven infants, and importantly, SMC in these arteries did not exhibit enhanced caveolin-1 expression. Two infants with associated inflammatory disease exhibited loss of endothelial caveolin-1 and PECAM-1; additional loss of vWF was accompanied by enhanced expression of caveolin-1 in SMC. Thus, associated flow-induced shear stress or inflammation, but not elevated pulmonary artery pressure alone, disrupts endothelial caveolin-1. Subsequent vWF loss, indicative of extensive endothelial damage is associated with enhanced expression of caveolin-1 in SMC, which may worsen the disease.

Associated inflammation or increased flow-mediated shear stress, but not pressure alone, disrupts endothelial caveolin-1 in infants with pulmonary hypertension

Endothelial caveolin-1 loss is an important feature of pulmonary hypertension (PH); the rescue of caveolin-1 abrogates experimental PH. Recent studies in human PH suggest that the endothelial caveolin-1 loss is followed by an enhanced expression of caveolin-1 in smooth muscle cells (SMC) with subsequent neointima formation. In order to evaluate caveolin-1 expression in infants with PH, we examined the available clinical histories, hemodynamic data, and the expression of caveolin-1, PECAM-1, vWF, and smooth muscle α-actin in the lung biopsy/autopsy specimens obtained from infants with congenital heart disease (CHD, n = 8) and lung disease (n = 9). In CHD group, PH associated with increased pulmonary blood flow exhibited loss of endothelial caveolin-1 and PECAM-1 in pulmonary arteries; additional vWF loss was associated with enhanced expression of caveolin-1 in SMC. In the absence of PH, increased or decreased pulmonary blood flow did not disrupt endothelial caveolin-1, PECAM-1, or vWF; nor was there any enhanced expression of caveolin-1 in SMC. In Lung Disease + PH group, caveolin-1, PECAM-1, and vWF were well preserved in seven infants, and importantly, SMC in these arteries did not exhibit enhanced caveolin-1 expression. Two infants with associated inflammatory disease exhibited loss of endothelial caveolin-1 and PECAM-1; additional loss of vWF was accompanied by enhanced expression of caveolin-1 in SMC. Thus, associated flow-induced shear stress or inflammation, but not elevated pulmonary artery pressure alone, disrupts endothelial caveolin-1. Subsequent vWF loss, indicative of extensive endothelial damage is associated with enhanced expression of caveolin-1 in SMC, which may worsen the disease.

Frontiers in pulmonary hypertension in infants and children with bronchopulmonary dysplasia

Pulmonary hypertension (PH) is an increasingly recognized complication of premature birth and bronchopulmonary dysplasia (BPD), and is associated with increased morbidity and mortality. Extreme phenotypic variability exists among preterm infants of similar gestational ages, making it difficult to predict which infants are at increased risk for developing PH. Intrauterine growth retardation or drug exposures, postnatal therapy with prolonged positive pressure ventilation, cardiovascular shunts, poor postnatal lung and somatic growth, and genetic or epigenetic factors may all contribute to the development of PH in preterm infants with BPD. In addition to the variability of severity of PH, there is also qualitative variability seen in PH, such as the variable responses to vasoactive medications. To reduce the morbidity and mortality associated with PH, a multi-pronged approach is needed. First, improved screening for and increased recognition of PH may allow for earlier treatment and better clinical outcomes. Second, identification of both prenatal and postnatal risk factors for the development of PH may allow targeting of therapy and resources for those at highest risk. Third, understanding the pathophysiology of the preterm pulmonary vascular bed may help improve outcomes through recognizing pathways that are dysregulated in PH, identifying novel biomarkers, and testing novel treatments. Finally, the recognition of conditions and exposures that may exacerbate or lead to recurrent PH is needed to help with developing treatment guidelines and preventative strategies that can be used to reduce the burden of disease.

Pharmacotherapy for pulmonary hypertension

Pulmonary arterial hypertension is a serious disease with significant morbidity and mortality. Although it can occur idiopathically, it is more commonly associated with other cardiac or lung diseases. While most of the available therapies have been tested in adult populations and most therapies in children remain off-label, new reports and randomized trials are emerging that inform the treatment of pediatric populations. This review discusses currently available therapies for pediatric pulmonary hypertension, their biological rationales, and evidence for their clinical effectiveness.

Use of cardiac biomarkers in neonatology

Cardiac biomarkers are used to identify cardiac disease in term and preterm infants. This review discusses the roles of natriuretic peptides and cardiac troponins. Natriuretic peptide levels are elevated during atrial strain (atrial natriuretic peptide (ANP)) or ventricular strain (B-type natriuretic peptide (BNP)). These markers correspond well with cardiac function and can be used to identify cardiac disease. Cardiac troponins are used to assess cardiomyocyte compromise. Affected cardiomyocytes release troponin into the bloodstream, resulting in elevated levels of cardiac troponin. Cardiac biomarkers are being increasingly incorporated into clinical trials as indicators of myocardial strain. Furthermore, cardiac biomarkers can possibly be used to guide therapy and improve outcome. Natriuretic peptides and cardiac troponins are potential tools in the diagnosis and treatment of neonatal disease that is complicated by circulatory compromise. However, clear reference ranges need to be set and validation needs to be carried out in a population of interest.

Therapeutic hypercapnia prevents bleomycin-induced pulmonary hypertension in neonatal rats by limiting macrophage-derived tumor necrosis factor-α

Bleomycin-induced lung injury is characterized in the neonatal rat by inflammation, arrested lung growth, and pulmonary hypertension (PHT), as observed in human infants with severe bronchopulmonary dysplasia. Inhalation of CO2 (therapeutic hypercapnia) has been described to limit cytokine production and to have anti-inflammatory effects on the injured lung; we therefore hypothesized that therapeutic hypercapnia would prevent bleomycin-induced lung injury. Spontaneously breathing rat pups were treated with bleomycin (1 mg/kg/d ip) or saline vehicle from postnatal days 1–14 while being continuously exposed to 5% CO2 (PaCO2 elevated by 15–20 mmHg), 7% CO2 (PaCO2 elevated by 35 mmHg), or normocapnia. Bleomycin-treated animals exposed to 7%, but not 5%, CO2, had significantly attenuated lung tissue macrophage influx and PHT, as evidenced by normalized pulmonary vascular resistance and right ventricular systolic function, decreased right ventricular hypertrophy, and attenuated remodeling of pulmonary resistance arteries. The level of CO2 neither prevented increased tissue neutrophil influx nor led to improvements in decreased lung weight, septal thinning, impaired alveolarization, or decreased numbers of peripheral arteries. Bleomycin led to increased expression and content of lung tumor necrosis factor (TNF)-α, which was found to colocalize with tissue macrophages and to be attenuated by exposure to 7% CO2. Inhibition of TNF-α signaling with the soluble TNF-2 receptor etanercept (0.4 mg/kg ip from days 1–14 on alternate days) prevented bleomycin-induced PHT without decreasing tissue macrophages and, similar to CO2, had no effect on arrested alveolar development. Our findings are consistent with a preventive effect of therapeutic hypercapnia with 7% CO2 on bleomycin-induced PHT via attenuation of macrophage-derived TNF-α. Neither tissue macrophages nor TNF-α appeared to contribute to arrested lung development induced by bleomycin. That 7% CO2 normalized pulmonary vascular resistance and right ventricular function without improving inhibited airway and vascular development suggests that vascular hypoplasia does not contribute significantly to functional changes of PHT in this model.