Early pulmonary vascular disease in preterm infants at risk for bronchopulmonary dysplasia

Prostanoids and their analogues for the treatment of pulmonary hypertension in neonates

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is a disease entity that describes a physiology in which there is persistence of increased pulmonary arterial pressure. PPHN is characterised by failure to adapt to a functional postnatal circulation with a fall in pulmonary vascular resistance. PPHN is responsible for impairment in oxygenation and significant neonatal mortality and morbidity. Prostanoids and their analogues may be useful therapeutic interventions due to their pulmonary vasodilatory and immunomodulatory effects.

OBJECTIVES

Primary objective• To determine the efficacy and safety of prostanoids and their analogues (iloprost, treprostinil, and beraprost) in decreasing mortality and the need for extracorporeal membrane oxygenation (ECMO) among neonates with PHSecondary objective• To determine the efficacy and safety of prostanoids and their analogues (iloprost, treprostinil, and beraprost) in decreasing neonatal morbidity (necrotizing enterocolitis (NEC), chronic lung disease (CLD), retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), length of hospital stay, and duration of mechanical ventilation) and improving neurodevelopmental outcomes among neonates with PHComparisons• Prostanoids and their analogues at any dosage or duration used to treat PPHN versus 'standard treatment without these agents', placebo, or inhaled nitric oxide (iNO) therapy• Prostanoids and their analogues at any dosage or duration used to treat refractory PPHN as an 'add-on' therapy to iNO versus iNO alone SEARCH METHODS: We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 9), MEDLINE via PubMed (1966 to 16 September 2018), Embase (1980 to 16 September 2018), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 16 September 2018). We also searched clinical trials databases, conference proceedings of the Pediatric Academic Societies (1990 to 16 September 2018), and the reference lists of retrieved articles for randomized controlled trials and quasi-randomized trials. We contacted authors who have published in this field as discerned from the reference lists of identified clinical trials and review authors' personal files.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials evaluating prostanoids or their analogues (at any dose, route of administration, or duration) used in neonates at any gestational age less than 28 days' postnatal age for confirmed or suspected PPHN.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane Neonatal to conduct a systematic review and to assess the methodological quality of included studies (neonatal.cochrane.org/en/index.html). Three review authors independently assessed the titles and abstracts of studies identified by the search strategy and obtained full-text versions for assessment if necessary. We designed forms for trial inclusion or exclusion and for data extraction. We planned to use the GRADE approach to assess the quality of evidence.

MAIN RESULTS

We did not identify any eligible neonatal trials evaluating prostanoids or their analogues as sole agents in the treatment of PPHN.

AUTHORS' CONCLUSIONS

Implications for practiceCurrently, no evidence shows the use of prostanoids or their analogues as pulmonary vasodilators and sole therapeutic agents for the treatment of PPHN in neonates (age 28 days or less).Implications for researchThe safety and efficacy of different preparations and doses and routes of administration of prostacyclins and their analogues in neonates must be established. Well-designed, adequately powered, randomized, multi-center trials are needed to address the efficacy and safety of prostanoids and their analogues in the treatment of PPHN. These trials should evaluate long-term neurodevelopmental and pulmonary outcomes, in addition to short-term outcomes.

Hemodynamic management in chronically ventilated infants

Positive pressure ventilation can significantly alter hemodynamics. The reduction in systemic venous return and increase in right ventricular afterload in response to an inappropriately high mean airway pressure can decrease pulmonary blood flow and compromise systemic perfusion as a result. In addition to ventilator parameters, the degree of hemodynamic effects depends on the baseline cardiac function and lung compliance. Furthermore, the chronically ventilated infants often have a multitude of comorbidities which may also impact hemodynamics. These include pulmonary and systemic hypertension which can lead to myocardial dysfunction as a result of the increase in the right and left ventricular afterload, respectively. In this section, we aim to outline the hemodynamic changes associated with chronic lung disease and mechanical ventilation and discuss management options.

Correlating objective echocardiographic parameters in patients with pulmonary hypertension due to bronchopulmonary dysplasia

OBJECTIVE

Echocardiographic parameters assessing left and right heart function were evaluated in children with established pulmonary hypertension (PH) from bronchopulmonary dysplasia (BPD) to look for correlations with each other, and pulmonary artery pressure (PAPs) from right heart catheterizations (RHC).

STUDY DESIGN

Data were retrospectively collected on patients with BPD and PH and correlations were performed between various objective echocardiographic and RHC measurements.

RESULTS

A total of 31 patients with BPD were found to have PH by echocardiogram and RHC after chart review. Median age of evaluation was 0.58 years. Correlations were noted between measurements of right heart function, indirect measures of pulmonary artery pressures and left ventricular dimensions. A trend was noted between the tricuspid annular plane systolic excursion obtained at echocardiography and systolic pulmonary artery pressure, obtained during RHC.

CONCLUSION

Significant correlations were found between objective echocardiographic measurements of left and right heart function, in patients with PH from BPD.

Anti-sFlt-1 Therapy Preserves Lung Alveolar and Vascular Growth in Antenatal Models of Bronchopulmonary Dysplasia

RATIONALE

Pregnancies complicated by antenatal stress, including preeclampsia (PE) and chorioamnionitis (CA), increase the risk for bronchopulmonary dysplasia (BPD) in preterm infants, but biologic mechanisms linking prenatal factors with BPD are uncertain. Levels of sFlt-1 (soluble fms-like tyrosine kinase 1), an endogenous antagonist to VEGF (vascular endothelial growth factor), are increased in amniotic fluid and maternal blood in PE and associated with CA.

OBJECTIVES

Because impaired VEGF signaling has been implicated in the pathogenesis of BPD, we hypothesized that fetal exposure to sFlt-1 decreases lung growth and causes abnormal lung structure and pulmonary hypertension during infancy.

METHODS

To test this hypothesis, we studied the effects of anti-sFlt-1 monoclonal antibody (mAb) treatment on lung growth in two established antenatal models of BPD that mimic PE and CA induced by intraamniotic (i.a.) injections of sFlt-1 or endotoxin, respectively. In experimental PE, mAb was administered by three different approaches, including antenatal treatment by either i.a. instillation or maternal uterine artery infusion, or by postnatal intraperitoneal injections.

RESULTS

With each strategy, mAb therapy improved infant lung structure as assessed by radial alveolar count, vessel density, right ventricular hypertrophy, and lung function. As found in the PE model, the adverse lung effects of i.a. endotoxin were also reduced by antenatal or postnatal mAb therapy.

CONCLUSIONS

We conclude that treatment with anti-sFlt-1 mAb preserves lung structure and function and prevents right ventricular hypertrophy in two rat models of BPD of antenatal stress and speculate that early mAb therapy may provide a novel strategy for the prevention of BPD.

Pulmonary Vascular Underperfusion Score in Premature Infants with Bronchopulmonary Dysplasia and Pulmonary Hypertension

Pulmonary hypertension (PH) is a complication of bronchopulmonary dysplasia (BPD). The underlying pathophysiology of BPD-associated PH is complex and poorly understood. Echocardiogram may underestimate the severity of pulmonary hypertensive vascular disease in severe BPD. Digital subtraction pulmonary angiography (DSPA) is a potentially useful imaging modality for evaluating changes in the pulmonary vasculature of BPD-associated PH. In this study, we objectively quantified the pulmonary hypertensive vascular changes demonstrated by DSPA using a novel pulmonary vascular underperfusion score (PVUS) and correlated the scoring system with echocardiography parameters and cardiac hemodynamics by right heart catheterization.

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.

Persistence of right ventricular dysfunction and altered morphometry in asymptomatic preterm Infants through one year of age: Cardiac phenotype of prematurity

INTRODUCTION

Prematurity impacts myocardial development and may determine long-term outcomes. The objective of this study was to test the hypothesis that preterm neonates develop right ventricle dysfunction and adaptive remodelling by 32 weeks post-menstrual age that persists through 1 year corrected age.

MATERIALS AND METHODS

A subset of 80 preterm infants (born <29 weeks) was selected retrospectively from a prospectively enrolled cohort and measures of right ventricle systolic function and morphology by two-dimensional echocardiography were assessed at 32 weeks post-menstrual age and at 1 year of corrected age. Comparisons were made to 50 term infants at 1 month and 1 year of age. Sub-analyses were performed in preterm-born infants with bronchopulmonary dysplasia and/or pulmonary hypertension.

RESULT

In both term and preterm infants, right ventricle function and morphology increased over the first year (p < 0.01). The magnitudes of right ventricle function measures were lower in preterm-born infants at each time period (p < 0.01 for all) and right ventricle morphology indices were wider in all preterm infants by 1 year corrected age, irrespective of lung disease. Measures of a) right ventricle function were further decreased and b) morphology increased through 1 year in preterm infants with bronchopulmonary dysplasia and/or pulmonary hypertension (p < 0.01).

CONCLUSION

Preterm infants exhibit abnormal right ventricle performance with remodelling at 32 weeks post-menstrual age that persists through 1 year corrected age, suggesting a less developed intrinsic myocardial function response following preterm birth. The development of bronchopulmonary dysplasia and pulmonary hypertension leave a further negative impact on right ventricle mechanics over the first year of age.

Drugs for the Prevention and Treatment of Bronchopulmonary Dysplasia

Rates of bronchopulmonary dysplasia (BPD) are increasing. After preterm birth, there are important developmental periods in which neonates are more vulnerable to stressful events. These periods are opportunities for pharmacologic interventions. Many drugs remain inadequately tested and no new drugs have been approved in more than 25 years for BPD prevention or therapy. More progress is needed in defining appropriate end points based on the pathophysiology of BPD and postdischarge chronic pulmonary insufficiency of prematurity and to develop effective new drugs. In addition, much work is needed to better define perinatal factors, early postnatal findings, and physiologic phenotypes or endotypes.

Mortality in infants with bronchopulmonary dysplasia: Data from cardiac catheterization

RATIONALE

Pulmonary hypertension (PH) is relatively common in infants with severe bronchopulmonary dysplasia (BPD), however, hemodynamic data and factors associated with mortality in this patient group are sparsely described in the literature.

OBJECTIVES

To characterize the hemodynamics of former preterm infants with BPD and PH, as measured at cardiac catheterization, and to identify respiratory and cardiovascular predictors of mortality.

METHODS

Single-center, retrospective cohort study, including, 30 patients born at less than 32-week gestational age (GA), who had an oxygen requirement at 36 weeks postmenstrual age and underwent cardiac catheterization between July 2014 and December 2017.

RESULTS

Median GA at birth was 25 5/7 weeks (interquartile range [IQR], 24 4/7-26 6/7 weeks). Median birth weight was 620 g (IQR, 530-700 g). With a median of 23 months of follow up (IQR, 11-39 months), mortality as of July 2018 was 27% (8 of 30). The alveolar-arterial oxygen gradient as a measure of lung disease did not correlate with mortality (log-rank test P = 0.28). However, indexed pulmonary vascular resistance (PVR) of greater than 3 Woods units × m ² showed a trend toward increased mortality (log-rank test P =  0.12). Pulmonary vein stenosis was the only predictor significantly associated with mortality (log-rank test P =  0.005).

CONCLUSIONS

In this cohort, the severity of lung disease as assessed by impaired oxygenation at cardiac catheterization did not correlate with mortality. The only factor significantly associated with mortality was the presence of pulmonary vein stenosis on cardiac catheterization, although PVR may also be an important factor.

Screening Echocardiography and Brain Natriuretic Peptide Levels Predict Late Pulmonary Hypertension in Infants with Bronchopulmonary Dysplasia

Through this study, we aimed to assess the ability of routine neonatal screening at time of bronchopulmonary dysplasia (BPD) diagnosis to predict the development of late pulmonary hypertension (PHTN). This is a retrospective longitudinal cohort study of 37 premature infants with BPD assessing the utility of screening serum brain natriuretic peptide (BNP) and echocardiograms performed at the time of BPD diagnosis ('early PHTN') to predict 'late PHTN' at the last follow-up. Screening evaluation demonstrated early PHTN in 9/37 patients. At an average follow-up interval of 52.7 ± 38.7 weeks, 4/9 had late PHTN; one patient without early PHT had late PHT. At initial screening, infants with late PHTN were significantly more likely to have demonstrated elevated BNP values (p = 0.003), and echocardiographic evidence of right atrial dilatation (p = 0.01), right ventricular hypertrophy (p = 0.01), lower right ventricular area change percentage (p = 0.03), and larger main pulmonary artery Z-scores (p = 0.02). Serum BNP and echocardiographic evaluation performed at the time of BPD diagnosis can detect patients at increased risk of late PHTN. Large, prospective studies are necessary to further address this question.

Effect of oxygen saturation targets on the incidence of bronchopulmonary dysplasia and duration of respiratory supports in extremely preterm infants

Background

Recent clinical practice changes in neonatal care resulted in higher, narrower oxygen saturation target ranges for preterm infants. The effect of targeting higher or lower oxygen saturations on respiratory outcomes of preterm infants and duration of hospitalization has not been extensively reviewed in the context of current care, but could have significant implications.

Methods

A multicentre retrospective cohort of 145 preterm infants was conducted; 105 had lower oxygen saturation targets (88 to 92%), 40 had higher targets (90 to 95%). The primary outcome was bronchopulmonary dysplasia (BPD). Secondary outcomes included duration of invasive/noninvasive respiratory support, oxygen therapy, and hospitalization. The primary outcome was compared using Fisher's exact test. Secondary outcomes were evaluated with survival analysis and Wilcoxon rank sum test.

Results

The difference in incidence of BPD in the lower (N=56, 53.3%) and higher saturation groups (N=14, 35.0%) was not statistically significant (relative risk [RR]=0.66 [0.41, 1.04], P=0.06). The difference in duration of mechanical ventilation in the lower (median 7.8 days, interquartile range [IQR] 3.7 to 15.9) and higher saturation groups (median 4.5, IQR 1.9 to 12.3) approached statistical significance (P=0.05). There were no statistically significant differences in the durations of other respiratory supports or hospital stay between the two groups.

Conclusions

The results of this study approached statistical significance and suggest that higher, narrower oxygen saturation targets may result in a clinically important reduction in BPD incidence and duration of mechanical ventilation. These results require validation in a larger sample to refine optimal targets.

Effect of patent ductus arteriosus on pulmonary vascular disease

The hemodynamic effects of a patent ductus arteriosus (PDA) are well known including systemic hypoperfusion and volume overload on the left ventricle. This article aims to provide a review of the long-standing effect of a hemodynamically significant PDA on the pulmonary vasculature and the role of cardiac catheterization in preterm infants with a PDA and pulmonary hypertension.

Prenatal complications are associated with the postnatal airway host response and microbiota in intubated preterm infants

PURPOSE

To prospectively examine the relationship between prenatal events, postnatal airway host response and microbiota, and clinical outcomes.

MATERIALS AND METHODS

Tracheal aspirates collected at seven days of age from 71 mechanically ventilated infants (median gestational age (GA), 25 weeks [range 23-28]) were simultaneously processed for a 12-plex protein assay and bacterial identification by 16S rRNA sequencing. Phenotypes were determined by unsupervised clustering of the protein analytes. Subject characteristics, microbial communities and clinical factors and outcomes were compared across the phenotype groups.

RESULTS

Three clusters were identified: 1 (high protein levels), 2 (high proinflammatory proteins and low anti-inflammatory proteins), and 3 (low protein levels), respectively. Antenatal hemorrhage was most common in cluster 1, while chorioamnionitis characterized cluster 2 and preeclampsia was most prevalent in cluster 3, which was characterized by a predominance of Staphylococcus and relative absence of Ureaplasma. There were higher rates of adverse clinical outcomes in cluster 1.

CONCLUSIONS

Airway protein profiles in seven days old mechanically ventilated preterm infants are associated with important antenatal events and unique airway microbial communities. These relationships may reveal new mechanisms by which antenatal events impact the course and outcomes of preterm infants.

Cardiac mechanics in infants with Down syndrome in the early neonatal period

OBJECTIVE

The objective of this study is to test whether myocardial performance is impaired over the first week of age in infants with Down syndrome (DS) without congenital heart disease (CHD).

STUDY DESIGN

A prospective cohort study of 20 infants with DS without CHD and 17 healthy term infants comparing echocardiographic measures of left (LV) and right (RV) ventricular function and pulmonary hypertension (PH) on days 1, 2, and 5-7.

RESULTS

Indices of PH were higher in the DS group over the study period. Infants with DS had larger RV and smaller LV dimensions. Fractional area change and RV longitudinal strain values were lower in the DS group. LV shear strain values were lower in infants with DS driven by a lack of basal rotation.

CONCLUSION

Infants with DS without CHD and echocardiographic evidence of PH during the early neonatal period demonstrate reduced RV systolic function with impaired LV rotational mechanics, reflective of the ventricular interdependence.

Diagnosis and Pathophysiological Mechanisms of Group 3 Hypoxia-Induced Pulmonary Hypertension

PURPOSE OF REVIEW

Group 3 hypoxia-induced pulmonary hypertension (PH) is an important and increasingly diagnosed condition in both the pediatric and adult population. The majority of pulmonary hypertension studies to date and all three classes of drug therapies were designed to focus on group 1 PH. There is a clear unmet medical need for understanding the molecular mechanisms of group 3 PH and a need for novel non-invasive methods of assessing PH in neonates.

RECENT FINDINGS

Several growth factors are expressed in patients and in animal models of group 3 PH and are thought to contribute to the pathophysiology of this disease. Here, we review some of the findings on the roles of vascular endothelial growth factor A (VEGFA), platelet-derived growth factor B (PDGFB), transforming growth factor-beta (TGFB1), and fibroblast growth factors (FGF) in PH. Additionally, we discuss novel uses of echocardiographic parameters in assessing right ventricular form and function. FGF2, TGFB, PDGFB, and VEGFA may serve as biomarkers in group 3 PH along with echocardiographic methods to diagnose and follow right ventricle function. FGFs and VEGFs may also function in the pathophysiology of group 3 PH.

Exploring clinical, echocardiographic and molecular biomarkers to predict bronchopulmonary dysplasia

Introduction

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease in childhood, related to prematurity, and the most common cause of pulmonary hypertension (PH) secondary to pulmonary disease in children. Moderate and severe BPD have a worse outcome and relate more frequently with PH. The prediction of moderate or severe BPD development in extremely premature newborns is vital to implement preventive strategies. Starting with the hypothesis that molecular biomarkers were better than clinical and echocardiographic factors, this study aims to explore the ability of clinical, echocardiographic and analytical variables to predict moderate or severe BPD in a cohort of extremely preterm infants.

Patients and methods

We designed a prospective longitudinal study, in which we followed a cohort of preterm newborns (gestational age <28 weeks and weight ≤ 1250 grams). In these newborns we recorded weekly clinical and echocardiographic variables as well as blood and tracheal aspirate samples, to analyze molecular biomarkers (IL-6, IL-1, IP10, uric acid, HGF, endothelin-1, VEGF, CCL5). Variables and samples were collected since birth up to week 36 (postmenstrual age), time-point at which the diagnosis of BPD is established.

Results

We included 50 patients with a median gestational age of 26 weeks (IQR 25–27) and weight of 871 g (SD 161,0) (range 590-1200g). Three patients were excluded due to an early death. Thirty-five patients (74.5%) developed BPD (mild n = 14, moderate n = 15, severe n = 6). We performed a logistic regression in order to identify risk factors for moderate or severe BPD. We compared two predictive models, one with two variables (mechanical ventilation and inter-ventricular septum flattening), and another-one with an additional molecular biomarker (ET-1).

Conclusions

The combination of clinical and echocardiographic variables is a valuable tool for determining the risk of BPD. We find the two variable model (mechanical ventilation and echocardiographic signs of PH) more practical for clinical and research purposes. Future research on BPD prediction should be oriented to explore the potential role of ET-1.

Rapid development of pulmonary hypertension during treatment of paediatric cancer

Paediatric pulmonary hypertension has been described as a secondary complication of multiple diseases and their treatment. Limited information exists about the relationship between pulmonary hypertension and cancer in children. A review of charts was performed in all patients treated for cancer and developed pulmonary hypertension. A total of four patients developed pulmonary hypertension during treatment of cancer. All patients had solid tumors, had echocardiographic evidence of elevated right ventricular pressures, and required intensive care stays. Treatment courses included inhaled and oral pulmonary vasodilators along with systemic steroids. Each had normalisation of echocardiograms and resolution of pulmonary symptoms. Prompt diagnosis of pulmonary hypertension and treatment with pulmonary vasodilators and steroids are considered important measures followed by chemotherapy and radiation regimens.

Preventing bronchopulmonary dysplasia: new tools for an old challenge

Bronchopulmonary dysplasia (BPD) is the most prevalent chronic lung disease in infants and presents as a consequence of preterm birth. Due to the lack of effective preventive and treatment strategies, BPD currently represents a major therapeutic challenge that requires continued research efforts at the basic, translational, and clinical levels. However, not all very low birth weight premature babies develop BPD, which suggests that in addition to known gestational age and intrauterine and extrauterine risk factors, other unknown factors must be involved in this disease's development. One of the main goals in BPD research is the early prediction of very low birth weight infants who are at risk of developing BPD in order to initiate the adequate preventive strategies. Other benefits of determining the risk of BPD include providing prognostic information and stratifying infants for clinical trial enrollment. In this article, we describe new opportunities to address BPD's complex pathophysiology by identifying prognostic biomarkers and develop novel, complex in vitro human lung models in order to develop effective therapies. These therapies for protecting the immature lung from injury can be developed by taking advantage of recent scientific progress in -omics, 3D organoids, and regenerative medicine.

Comprehensive Evaluation of Right Heart Performance and Pulmonary Hemodynamics in Neonatal Pulmonary Hypertension : Evaluation of cardiopulmonary performance in neonatal pulmonary hypertension

PURPOSE OF REVIEW

Pulmonary hypertension is characterized by an elevation of pulmonary artery pressures and prolonged exposure of the right ventricle to high afterload that collectively contribute to morbidity and mortality in both the term and preterm infants. This review summarizes the pathogenesis, etiologies, and hemodynamic profiles of the conditions that result in pulmonary hypertension in neonates. We explore the application of echocardiographic techniques for the assessment of right ventricular performance and pulmonary hemodynamics that enhance and guide the diagnosis and management strategies in neonates.

RECENT FINDINGS

Clinical assessments based on the determinants of mean pulmonary artery pressures (pulmonary vascular resistance, pulmonary blood flow, and pulmonary capillary wedge pressure) provide a physiologic approach in determining the acute and chronic etiologies of pulmonary hypertension in neonates. In addition, advances in neonatal echocardiography now afford the capability to obtain quantitative information that often precedes the qualitative information acquired by conventional methods and also provide sensitive markers of right ventricle performance for prognostic information based on the determinants of mean pulmonary artery pressures. Neonatal pulmonary hypertension represents a physiologic spectrum that accounts for the variance in clinical presentation and response to therapies. Physiology-based approaches to etiological identification, coupled with the emerging echocardiographic methods for the assessment of pulmonary hypertension in neonates will likely help to identify cardiovascular compromise earlier, guide therapeutic intervention, monitor therapeutic effectiveness, and improve overall outcome.

Prospective study of pulmonary hypertension in preterm infants with bronchopulmonary dysplasia

OBJECTIVE

To evaluate the prevalence, risk factors, and optimal timing of echocardiogram for pulmonary hypertension (PH) in infants with bronchopulmonary dysplasia (BPD).

DESIGN

In this prospective study, infants with gestational age (GA) <30 weeks admitted to a tertiary NICU between July 2015 and June 2017 who required positive pressure ventilation or oxygen therapy at ≥28 days of life were evaluated with serial echocardiograms at study enrollment (4-6 weeks of age), 32 weeks (only for ≤25 weeks), 36, and 40 weeks post-menstrual age (PMA) for PH.

RESULTS

Of 126 infants (mean birth weight 858 ± 221 g; mean GA 26.1 ± 1.6 wks), 48 (38%) developed PH at any time during their hospital stay. The first study echocardiogram was performed at a median age of 31 weeks PMA. The prevalence of PH was 36/126 (28.5%) at enrollment, at 6/30 (20%) at 32 weeks, 24/111 (21.6%) at 36 weeks, and 10/59 (17%) at 40 weeks. No new cases of PH were identified at 40 weeks. At 36 weeks, none of the infants with mild BPD had PH, whereas 20% of moderate and 32% of severe BPD infants had PH. After controlling for confounding variables severe BPD (OR 3.31, 95%CI 1.12, 9.74), and ventilator associated pneumonia (VAP) (OR 17.9, 95%CI 3.9, 82.11) remained independent risk factors for BPD-associated PH.

CONCLUSION

Echocardiographic screening for PH can be safely restricted to infants with moderate or severe BPD at 36 weeks PMA. We identified VAP as an independent risk factor for PH.

Bronchoscopy in neonates with severe bronchopulmonary dysplasia in the NICU

OBJECTIVES

To describe the findings, resulting changes in management, and safety profile of flexible bronchoscopy in the neonates with severe bronchopulmonary dysplasia.

STUDY DESIGN

This was a retrospective case series of twenty-seven neonates with severe bronchopulmonary dysplasia who underwent flexible bronchoscopy in the neonatal intensive care unit.

RESULTS

Flexible bronchoscopy revealed airway pathology in 20/27 (74%) patients. Tracheomalacia 13/27 (48%), bronchomalacia 11/27 (40.7%), and airway edema 13/27 (48%) were the most common findings. Bronchoalveolar lavage (BAL) was performed in 17 patients. BAL culture revealed a microorganism in 12/17 (70.5%) cases. Findings from bronchoscopy resulted in change in clinical management in 17/27 (63%) patients. Common interventions included initiation of antibiotics (37%) and treatment of tracheobronchomalacia with bethanechol (22.2%), atrovent (18.5%), and PEEP titration (18.5%). Bronchoscopy was performed without significant complication in 26/27 (97%) patients.

CONCLUSION

Flexible bronchoscopy can be a safe and useful tool for the management of neonates with severe bronchopulmonary dysplasia.

Ceramide and Regulation of Vascular Tone

In addition to playing a role as a structural component of cellular membranes, ceramide is now clearly recognized as a bioactive lipid implicated in a variety of physiological functions. This review aims to provide updated information on the role of ceramide in the regulation of vascular tone. Ceramide may induce vasodilator or vasoconstrictor effects by interacting with several signaling pathways in endothelial and smooth muscle cells. There is a clear, albeit complex, interaction between ceramide and redox signaling. In fact, reactive oxygen species (ROS) activate different ceramide generating pathways and, conversely, ceramide is known to increase ROS production. In recent years, ceramide has emerged as a novel key player in oxygen sensing in vascular cells and mediating vascular responses of crucial physiological relevance such as hypoxic pulmonary vasoconstriction (HPV) or normoxic ductus arteriosus constriction. Likewise, a growing body of evidence over the last years suggests that exaggerated production of vascular ceramide may have detrimental effects in a number of pathological processes including cardiovascular and lung diseases.

Developmental outcomes of preterm infants with bronchopulmonary dysplasia-associated pulmonary hypertension at 18-24 months of corrected age

Background

Owing to advances in the critical care of premature infants with bronchopulmonary dysplasia (BPD), BPD-associated pulmonary hypertension (PH) is becoming a growing concern. However, only few investigations were available on neurodevelopmental outcomes in preterm infants with PH. Therefore, this study aimed to identify the impact of PH on growth and neurodevelopment at 18–24 months of corrected age (CA).

Methods

We retrospectively analyzed the medical records of 394 infants (aged < 28 weeks of gestation) admitted to the neonatal intensive care unit between 2005 and 2014. Among the surviving infants, 123 returned for follow-up evaluations including the Bayley Scales of Infant and Toddler Development, third Edition (Bayley-III) screening tests and growth assessment at 18–24 months of CA. Among the 81 infants with moderate or severe BPD, 20 met the criteria for PH. Baseline characteristics and outcomes were compared in infants who developed BPD-associated PH (PH group, n = 20) and moderate or severe BPD infants who did not develop PH (non-PH group, n = 61).

Results

Compared to the non-PH group, the PH group showed significantly lower cognitive (85 vs. 95, p = 0.004), language (81 vs. 89, p = 0.040), and motor (88 vs. 94, p = 0.010) scores of the Bayley-III at 18–24 months of CA. Cognitive delay was found in 45.0% (9/20) of PH infants. In addition, z-scores of weight (− 1.4 ± 1.3 vs. -0.6 ± 1.1%, p = 0.011) and HC (− 1.2 ± 1.8 vs. 0.53 ± 1.0%, p = 0.035) were significantly lower in the BPD with PH group. With the subgroup analysis in infants with severe BPD only, the cognitive score was consistently lower and poorer and weight gain after discharge was identified in infants with PH and severe BPD.

Conclusion

PH was a worsening factor of non-optimal growth and poor neurodevelopmental outcome in preterm infants with BPD at 18–24 months of CA. Our findings suggest the importance of close developmental follow-up and recognition of that risk to help optimize the outcome of preterm infants with PH.

Pulmonary vascular disease is evident in gene regulation of experimental bronchopulmonary dysplasia

Objective: To examine the gene expression regarding pulmonary vascular disease in experimental bronchopulmonary dysplasia in young mice. Premature delivery puts babies at risk of severe complications. Bronchopulmonary dysplasia (BPD) is a common complication of premature birth leading to lifelong affection of pulmonary function. BPD is recognized as a disease of arrested alveolar development. The disease process is not fully described and no complete cure or prevention is known. The focus of interest in the search for treatment and prevention of BPD has traditionally been at airspace level; however, the pulmonary vasculature is increasingly acknowledged in the pathology of BPD. The aim of the investigation was to study the gene expression in lungs with BPD with regards to pulmonary vascular disease (PVD).Methods: We employed a murine model of hyperoxia-induced BPD and gene expression microarray technique to determine the mRNA expression in lung tissue from young mice. We combined gene expression pathway analysis and analyzed the biological function of multiple single gene transcripts from lung homogenate to study the PVD relevant gene expression.Results: There were n = 117 significantly differentially regulated genes related to PVD through down-regulation of contractile elements, up- and down-regulation of factors involved in vascular tone and tissue-specific genes. Several genes also allowed for pinpointing gene expression differences to the pulmonary vasculature. The gene Nppa coding for a natriuretic peptide, a potent vasodilator, was significantly down-regulated and there was a significant up-regulation of Pde1a (phosphodiesterase 1A), Ptger3 (prostaglandin e receptor 3), and Ptgs1 (prostaglandin-endoperoxide synthase one).Conclusion: The pulmonary vasculature is affected by the arrest of secondary alveolarization as seen by differentially regulated genes involved in vascular tone and pulmonary vasculature suggesting BPD is not purely an airspace disease. Clues to prevention and treatment may lie in the pulmonary vascular system.

Accuracy of Brain Natriuretic Peptide for Diagnosing Pulmonary Hypertension in Severe Bronchopulmonary Dysplasia

BACKGROUND

Premature infants with severe bronchopulmonary dysplasia (sBPD) are at risk of pulmonary hypertension (PH). Serum brain natriuretic peptide (BNP) is used to predict disease severity in adult PH. Its diagnostic utility in sBPD-associated PH is unknown.

OBJECTIVE

The aim of this paper was to determine the accuracy of BNP, against echocardiogram (echo), to diagnose PH in infants born <32 weeks' gestation with sBPD.

METHODS

We conducted a retrospective cohort study of all infants with sBPD with an echo and BNP within a 24-h period, at ≥36 weeks postmenstrual age. PH was defined as: right ventricular pressure >½ systemic blood pressure estimated from tricuspid regurgitant jet or patent ductus arteriosus (PDA) velocity, bidirectional or right-to left-PDA, and/or flat/bowing ventricular septum at end-systole. Receiver-operating characteristic (ROC) curves were constructed to test the diagnostic accuracy of BNP.

RESULTS

Of 128 infants, 68 (53%) had echo evidence of PH. BNP was higher among the infants with PH (median [interquartile range]: 127 pg/mL [39-290] vs. 35 [20-76], p < 0.001). The area under the ROC curve for diagnosing PH using BNP was 0.74 (95% CI 0.66-0.83). At an optimal cutpoint of 130 pg/mL, BNP correctly classified the presence or absence of PH in 70% of the infants (specificity: 92, sensitivity: 50%).

CONCLUSIONS

BNP, relative to concurrent echo, demonstrated moderate accuracy for diagnosing PH in this cohort of preterm infants with sBPD. BNP may help rule in PH in this population but has low utility to rule out the disease.

Paediatric pulmonary arterial hypertension: updates on definition, classification, diagnostics and management

Paediatric pulmonary arterial hypertension (PAH) shares common features of adult disease, but is associated with several additional disorders and challenges that require unique approaches. This article discusses recent advances, ongoing challenges and distinct approaches for the care of children with PAH, as presented by the Paediatric Task Force of the 6th World Symposium on Pulmonary Hypertension. We provide updates of the current definition, epidemiology, classification, diagnostics and treatment of paediatric PAH, and identify critical knowledge gaps. Several features of paediatric PAH including the prominence of neonatal PAH, especially in pre-term infants with developmental lung diseases, and novel genetic causes of paediatric PAH are highlighted. The use of cardiac catheterisation as a diagnostic modality and haemodynamic definitions of PAH, including acute vasoreactivity, are addressed. Updates are provided on issues related to utility of the previous classification system to reflect paediatric-specific aetiologies and approaches to medical and interventional management of PAH, including the Potts shunt. Although a lack of clinical trial data for the use of PAH-targeted therapy persists, emerging data are improving the identification of appropriate targets for goal-oriented therapy in children. Such data will likely improve future clinical trial design to enhance outcomes in paediatric PAH.

Intratracheal administration of clinical-grade mesenchymal stem cell-derived extracellular vesicles reduces lung injury in a rat model of bronchopulmonary dysplasia

Mesenchymal stem cells (MSCs) prevent the onset of bronchopulmonary dysplasia (BPD) in animal models, an effect that seems to be mediated by their secreted extracellular vesicles (EVs). The aim of this study was to compare the protective effects of intratracheally (IT) administered MSCs versus MSC-EVs in a hyperoxia-induced rat model of BPD. At birth, rats were distributed as follows: animals raised in ambient air for 2 wk ( n = 10), and animals exposed to 60% oxygen for 2 wk and treated with IT-administered physiological solution ( n = 10), MSCs ( n = 10), or MSC-EVs ( n = 10) on postnatal days 3, 7, and 10. The sham-treated hyperoxia-exposed animals showed reductions in total surface area of alveolar air spaces, and total number of alveoli ( Nalv), and an increased mean alveolar volume (Valv). EVs prompted a significant increase in Nalv ( P < 0.01) and a significant decrease in Valv ( P < 0.05) compared with sham-treated animals, whereas MSCs only significantly improved Nalv ( P < 0.05). Small pulmonary vessels of the sham-treated hyperoxia-exposed rats also showed an increase in medial thickness, which only EVs succeeded in preventing significantly ( P < 0.05). In conclusion, both EVs and MSCs reduce hyperoxia-induced damage, with EVs obtaining better results in terms of alveolarization and lung vascularization parameters. This suggests that IT-administered EVs could be an effective approach to BPD treatment.

Target oxygen saturation and development of pulmonary hypertension and increased pulmonary vascular resistance in preterm infants

OBJECTIVE

Determine whether higher targeted oxygen levels are associated with reduced incidence of pulmonary hypertension (PH) and elevated pulmonary vascular resistance (PVR) in extremely premature infants.

STUDY DESIGN

Retrospective chart review of 252 extremely preterm infants (<29 weeks), who underwent echocardiogram prior to discharge. PH rates were compared during periods (June 2012-May 2015 and June 2015-April 2016) when lower (88-92%) or higher (90-95%) oxygen saturation targets were used. PH was determined on echocardiography. The ratio of pulmonary artery acceleration time to right ventricular ejection time was computed, with values <0.31 indicative of elevated PVR. Survival analysis compared the effects of oxygen saturation group on development/resolution of PH and elevated PVR.

RESULTS

The higher saturation group had significantly lower risk of developing PH (hazard ratio (HR) = 0.50, 95%CI 0.26-0.95; P = 0.03) or elevated PVR (HR = 0.55, 95%CI 0.38-0.81; P = 0.002), compared to the lower oxygen saturation group. Median time to PH development was significantly shorter in the lower saturation group than in the higher saturation group (5 days vs 12 days; P = 0.02), as was time to development of elevated PVR (4 days vs 6 days; P < 0.001). Duration of PH (P = 0.12) and elevated PVR (P = 0.86) did not differ significantly between groups. Cumulative incidence of PH (P = 0.04) and elevated PVR (P = 0.01) at 36 weeks post-menstrual age was significantly lower in the high saturation group compared to the lower saturation group.

CONCLUSION

Higher targeted oxygen saturation was associated with reduced risk of PH or elevated PVR in extremely preterm infants compared to lower oxygen saturation target.

Highly Efficient In Vivo Targeting of the Pulmonary Endothelium Using Novel Modifications of Polyethylenimine: An Importance of Charge

Pulmonary vascular disease encompasses a wide range of serious afflictions with important clinical implications. There is critical need for the development of efficient, nonviral gene therapy delivery systems. Here, a promising avenue to overcome critical issues in efficient cell targeting within the lung via a uniquely designed nanosystem is reported. Polyplexes are created by functionalizing hyperbranched polyethylenimine (PEI) with biological fatty acids and carboxylate-terminated poly(ethylene glycol) (PEG) through a one-pot 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride/N-hydroxysuccinimide reaction. Following intravenous injection, polyplexes show an exceptionally high specificity to the pulmonary microvascular endothelium, allowing for the successful delivery of stabilized enhanced green fluorescent protein (eGFP) expressing messenger ribonucleic acid (mRNA). It is further shown, quantitatively, that positive surface charge is the main mechanism behind such high targeting efficiency for these polyplexes. Live in vivo imaging, flow cytometry of single cell suspensions, and confocal microscopy are used to demonstrate that positive polyplexes are enriched in the lung tissue and disseminated in 85-90% of the alveolar capillary endothelium, whilst being sparse in large vessels. Charge modification, achieved through poly(acrylic acid) or heparin coating, drives a highly significant reduction in both targeting percentage and targeting strength, highlighting the importance of specific surface charge, derived from chemical formulation, for efficient targeting of the pulmonary microvascular endothelium.

Echocardiographic Measurements of Right Ventricular Mechanics in Infants with Bronchopulmonary Dysplasia at 36 Weeks Postmenstrual Age

OBJECTIVE

To test the hypothesis that specific echocardiographic measurements of right ventricular (RV) mechanics at 36 weeks postmenstrual age (PMA) are associated with the severity of bronchopulmonary dysplasia (BPD).

STUDY DESIGN

A subset of 93 preterm infants (born between 27 and 29 weeks of gestation) was selected retrospectively from a prospectively enrolled cohort. BPD was defined using the National Institutes of Health workshop definition, with modifications for oxygen reduction testing and altitude. The cohort was divided into no-BPD and BPD groups using previously published methodology for analyses. Echocardiographic measurements of RV function (ie, tricuspid annular plane systolic excursion, fractional area of change, systolic-to-diastolic ratio, tissue Doppler myocardial performance index, and RV strain), RV remodeling/morphology (end-systolic left ventricular eccentricity index), and RV afterload (pulmonary artery acceleration time measure) were evaluated at 36 weeks PMA. Multivariable logistic regression determined associations between RV measurements and BPD severity.

RESULTS

Compared with the no-BPD cohort, the BPD group had lower birth weight z-scores (P = .04) and trended toward a male predominance (P = .08). After adjusting for birth weight z-score, gestational age, and sex, there were no between-group differences in echocardiographic measurements except for the eccentricity index (scaled OR [0.1-unit increase], 1.49; 95% CI, 1.13-2.12; P = .01).

CONCLUSIONS

Among conventional and emerging echocardiographic measurements of RV mechanics, eccentricity index was the sole variable independently associated with BPD severity in this study. The eccentricity index may be a useful echocardiographic measurement for characterizing RV mechanics in patients with BPD at 36 weeks PMA.

The Impact of Pulmonary Hypertension in Preterm Infants with Severe Bronchopulmonary Dysplasia through 1 Year

OBJECTIVES

To assess the effect of pulmonary hypertension on neonatal intensive care unit mortality and hospital readmission through 1 year of corrected age in a large multicenter cohort of infants with severe bronchopulmonary dysplasia.

STUDY DESIGN

This was a multicenter, retrospective cohort study of 1677 infants born <32 weeks of gestation with severe bronchopulmonary dysplasia enrolled in the Children's Hospital Neonatal Consortium with records linked to the Pediatric Health Information System.

RESULTS

Pulmonary hypertension occurred in 370 out of 1677 (22%) infants. During the neonatal admission, pulmonary hypertension was associated with mortality (OR 3.15, 95% CI 2.10-4.73, P < .001), ventilator support at 36 weeks of postmenstrual age (60% vs 40%, P < .001), duration of ventilation (72 IQR 30-124 vs 41 IQR 17-74 days, P < .001), and higher respiratory severity score (3.6 IQR 0.4-7.0 vs 0.8 IQR 0.3-3.3, P < .001). At discharge, pulmonary hypertension was associated with tracheostomy (27% vs 9%, P < .001), supplemental oxygen use (84% vs 61%, P < .001), and tube feeds (80% vs 46%, P < .001). Through 1 year of corrected age, pulmonary hypertension was associated with increased frequency of readmission (incidence rate ratio [IRR] = 1.38, 95% CI 1.18-1.63, P < .001).

CONCLUSIONS

Infants with severe bronchopulmonary dysplasia-associated pulmonary hypertension have increased morbidity and mortality through 1 year of corrected age. This highlights the need for improved diagnostic practices and prospective studies evaluating treatments for this high-risk population.

Right ventricular function in infants with bronchopulmonary dysplasia and pulmonary hypertension: a pilot study

Premature birth and bronchopulmonary dysplasia (BPD) are risk factors for the development of echocardiographic signs of pulmonary hypertension (PH) and are associated with changes in cardiac structure and function. It is unclear whether this association persists beyond early infancy. The aims of this study are to prospectively investigate the prevalence of PH in children with severe BPD and to investigate the effect of BPD and PH on myocardial structure and function at six months corrected age. Preterm infants (gestational age ≤ 32 weeks) with severe BPD were included. Echocardiography was used to define PH and to measure speckle tracking derived longitudinal and circumferential strain of the left ventricle (LV) and right ventricle (RV). Sixty-nine infants with a median (interquartile range [IQR]) gestational age of 25.6 (24.9–26.4) weeks and a median birthweight of 770 (645–945) gram were included. Eight (12%) infants had signs of PH at six months corrected age. RV fractional area change was lower in infants with severe BPD and PH at six months compared to infants without PH (35% ± 9% vs. 43% ± 9%, P = 0.03). RV mean longitudinal systolic strain was lower in infants with severe BPD and PH compared to infants without PH (17.6% [−19.5%/−16.1%] vs. −20.9% [−25.9%/−17.9%], P = 0.04). RV size and LV longitudinal and circumferential strain in children with BPD with or without PH were similar. Signs of PH were found in 12% of infants with severe BPD at six months corrected age and the presence of PH is associated with reduced RV systolic function.

Persistent pulmonary hypertension of the newborn in extremely preterm infants: a Japanese cohort study

OBJECTIVE

To investigate the characteristics of persistent pulmonary hypertension of the newborn (PPHN) in extremely preterm infants and its impact on neurodevelopmental outcomes at 3 years of age.

DESIGN

A retrospective multicentre cohort study.

SETTINGS

202 tertiary perinatal centres registered in the Neonatal Research Network of Japan (NRNJ).

PATIENTS

Infants born at <28 weeks of gestational age (GA), between 2003 and 2012, were extracted from tertiary perinatal centres participating in NRNJ.

MAIN OUTCOME MEASURES

Demographic characteristics, morbidity, interventions and mortality were compared for infants with and without PPHN. Multivariable logistic analysis was performed to evaluate the impact of PPHN on long-term neurodevelopmental outcomes (the prevalence rate of cerebral palsy, need for home oxygen therapy, and visual, hearing and cognitive impairment) at 3 years of age.

RESULTS

The prevalence of PPHN among the 12 954 extremely preterm infants enrolled was 8.1% (95% CI 7.7% to 8.6%), with the trend increasing annually, and a higher proportion as GA decreased: 18.5% (range, 15.2% to 22.4%) for infants born at 22 weeks compared with 4.4% (range, 3.8% to 5.2%) for those born at 27 weeks. Clinical chorioamnionitis and premature rupture of membranes were associated with PPHN. On multivariate analysis of the data from 5923 infants followed up for 3 years, PPHN was a significant independent risk factor for visual impairment (adjusted OR, 1.42, 95% CI 1.03 to 1.97).

CONCLUSIONS

The prevalence of PPHN in extremely preterm infants has been increasing over the past decade in Japan. Clinicians should be aware of visual impairments as a neurodevelopmental abnormality among infants with PPHN.

Recent advances in antenatal factors predisposing to bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) remains a major cause of late morbidities and death after preterm birth. BPD is characterized by an arrest of vascular and alveolar growth and high risk for pulmonary hypertension; yet mechanisms contributing to its pathogenesis and early strategies to prevent BPD are poorly understood. Strong epidemiologic studies have shown that the "new BPD" reflects the long-lasting impact of antenatal factors on lung development, partly due to placental dysfunction, as reflected in recent data from animal models. Improved understanding of mechanisms through which antenatal stress alters placental function and contributes to BPD may lead to preventive therapies.

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.

Neonatal hyperoxia promotes asthma-like features through IL-33-dependent ILC2 responses

BACKGROUND

Premature infants often require oxygen supplementation and, therefore, are exposed to oxidative stress. Following oxygen exposure, preterm infants frequently develop chronic lung disease and have a significantly increased risk of asthma.

OBJECTIVE

We sought to identify the underlying mechanisms by which neonatal hyperoxia promotes asthma development.

METHODS

Mice were exposed to neonatal hyperoxia followed by a period of room air recovery. A group of mice was also intranasally exposed to house dust mite antigen. Assessments were performed at various time points for evaluation of airway hyperresponsiveness, eosinophilia, mucus production, inflammatory gene expression, and TH and group 2 innate lymphoid cell (ILC2) responses. Sera from term- and preterm-born infants were also collected and levels of IL-33 and type 2 cytokines were measured.

RESULTS

Neonatal hyperoxia induced asthma-like features including airway hyperresponsiveness, mucus hyperplasia, airway eosinophilia, and type 2 pulmonary inflammation. In addition, neonatal hyperoxia promoted allergic TH responses to house dust mite exposure. Elevated IL-33 levels and ILC2 responses were observed in the lungs most likely due to oxidative stress caused by neonatal hyperoxia. IL-33 receptor signaling and ILC2s were vital for the induction of asthma-like features following neonatal hyperoxia. Serum IL-33 levels correlated significantly with serum levels of IL-5 and IL-13 but not IL-4 in preterm infants.

CONCLUSIONS

These data demonstrate that an axis involving IL-33 and ILC2s is important for the development of asthma-like features following neonatal hyperoxia and suggest therapeutic potential for targeting IL-33, ILC2s, and oxidative stress to prevent and/or treat asthma development related to prematurity.

Long-term pulmonary vascular consequences of perinatal insults

Development of the pulmonary circulation is a critical component of fetal lung development, and continues throughout infancy and childhood, marking an extended window of susceptibility to vascular maldevelopment and maladaptation. Perinatal vascular insults may result in abnormal vascular structure or function, including decreased angiogenic signaling and vascular endowment, impaired vasoreactivity through increased pulmonary artery endothelial dysfunction and remodeling, or enhanced genetic susceptibility to pulmonary vascular disease through epigenetic modifications or germline mutations. Although some infants develop early onset pulmonary hypertension, due to the unique adaptive capabilities of the immature host many do not have clinically evident early pulmonary vascular dysfunction. These individuals remain at increased risk for development of late-onset pulmonary hypertension, and may be particularly susceptible to secondary insults. This review will address the role of perinatal vascular insults in the development of late pulmonary vascular dysfunction with an effort to highlight areas of critical research need.

Sildenafil and Retinopathy of Prematurity in Preterm Infants with Bronchopulmonary Dysplasia

OBJECTIVE

To assess whether sildenafil is associated with worsening retinopathy of prematurity (ROP) in very low birth weight (VLBW) infants (≤1500 g) with bronchopulmonary dysplasia (BPD).

STUDY DESIGN

This retrospective case-control study included VLBW infants admitted to the neonatal intensive care unit between January 1, 2006, and December 31, 2012. Each infant treated with sildenafil was assigned 3 unexposed controls matched for gestational age, birth weight, and BPD diagnosis. Severe ROP was defined as stage ≥3 ROP. Worsening ROP was defined as increased stage of ROP within 8 weeks + 4 days after initiation of sildenafil or matched postmenstrual age.

RESULTS

Twenty-three exposed infants and 69 matched controls met the inclusion criteria for the study (mean birth weight, 715 ± 210 g; mean gestational age, 25 ± 1 weeks). The mean postmenstrual age at sildenafil treatment was 42 ± 8 weeks. Exposed infants had more days of respiratory support (mean, 208 ± 101 days vs 102 ± 33 days; P < .001). Exposed infants had a higher prevalence of severe ROP (26% [6 of 23] vs 7% [5 of 69]; OR, 6.4; 95% CI, 1.2-32.9; P = .026). Five exposed infants and 2 unexposed infants had severe ROP before starting sildenafil and were excluded from the analysis for worsening ROP. The rate of worsening ROP did not differ significantly between exposed infants and unexposed infants ((41% [7 of 17] vs 24% [12 of 51]; OR, 8.4; 95% CI, 0.9-78.6; P = .061).

CONCLUSION

Although sildenafil treatment was not statistically significantly associated with worsening of ROP, the raw difference in ROP rate is concerning. Larger studies are warranted to confirm this finding.

Natural History of Postnatal Cardiopulmonary Adaptation in Infants Born Extremely Preterm and Risk for Death or Bronchopulmonary Dysplasia

OBJECTIVE

To study the natural history of postnatal cardiopulmonary adaptation in infants born extremely preterm and establish its association with death or bronchopulmonary dysplasia (BPD).

STUDY DESIGN

This was a prospective, observational, cohort study of infants born extremely preterm (<29 weeks). Initial echocardiogram was performed at <48 hours of life, followed by serial echocardiograms every 24-48 hours until 14 days of life. Resolution or no resolution of pulmonary hypertension (PH) at 72-96 hours was considered normal or delayed postnatal cardiopulmonary adaptation, respectively. PH between 96 hours and 14 days was defined as subsequent PH. Elevated pulmonary artery pressure throughout the 14 days of life was considered persistent PH. BPD was assessed at 36 weeks of postmenstrual age.

RESULTS

Sixty infants were enrolled; 2 died before a sequential echocardiogram could be done at 72-96 hours. Normal and delayed cardiopulmonary adaptation were noted in 26 (45%) and 32 (55%) infants, respectively. Five patterns of postnatal cardiopulmonary adaptation were recognized: normal without subsequent PH (n = 20), normal with subsequent PH (n = 6), delayed adaptation without subsequent PH (n = 6), delayed adaptation with subsequent PH (n = 16), and persistent PH (n = 10). Infants with delayed cardiopulmonary adaptation were of lower gestation and birth weight and required prolonged ventilation and supplemental oxygen (P < .05). On multivariate analysis, the incidence of death or BPD was significantly greater among infants with delayed adaptation (P < .001).

CONCLUSION

Infants born extremely preterm have normal or delayed postnatal cardiopulmonary adaptation that can be complicated by subsequent or persistent PH. Delayed cardiopulmonary adaptation is associated independently with death or BPD.

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.

Identification of gaps in the current knowledge on pulmonary hypertension in extremely preterm infants: A systematic review and meta-analysis

BACKGROUND

Pulmonary hypertension complicates the clinical course of extremely preterm infants and is associated with bronchopulmonary dysplasia (BPD). However, prevalence, risk factors, and outcome of pulmonary hypertension in these infants are insufficiently known. This systematic review and meta-analysis aims to provide an up-to-date overview of available data on prevalence, risk factors, and outcome of pulmonary hypertension and to identify current knowledge gaps.

METHODS

Medline, EMBASE, and the Cochrane Library databases were searched in July 2017. Two authors reviewed titles/abstracts and full-texts. Eligible studies reported prevalence, patient characteristics or mortality of infants with/without pulmonary hypertension. Studies were excluded if they did not include extremely preterm infants. Only similar study samples (selected infants with BPD or infants both with/without BPD) were compared in the meta-analyses.

RESULTS

Of 1829 unique articles identified, 25 were eligible for inclusion. Pulmonary hypertension was observed in infants with BPD (20%, 95% confidence interval [CI] 14, 25), but also in those without BPD (2%, 95% CI 0, 8). Infants with severe BPD were most at risk of pulmonary hypertension (risk ratio [RR] 2.7, 95% CI 1.7, 4.2). Infants with pulmonary hypertension were more at risk of mortality (RR 4.7, 95% CI 2.7, 8.3).

CONCLUSIONS

Pulmonary hypertension occurs in particularly in infants with severe BPD, and increases risk of mortality. Due to selected study populations, heterogeneous pulmonary hypertension-definitions and poorly reported timing of pulmonary hypertension assessments, however, data available in current reports are insufficient to allow accurate assessment of true prevalence, risk factors, and time-related outcome. Prospective studies, with standardised methodology and follow-up are needed to determine these factors.

Serotonin 2A receptor inhibition protects against the development of pulmonary hypertension and pulmonary vascular remodeling in neonatal mice

Pulmonary hypertension (PH) complicating bronchopulmonary dysplasia (BPD) worsens clinical outcomes in former preterm infants. Increased serotonin (5-hydroxytryptamine, 5-HT) signaling plays a prominent role in PH pathogenesis and progression in adults. We hypothesized that increased 5-HT signaling contributes to the pathogenesis of neonatal PH, complicating BPD and neonatal lung injury. Thus, we investigated 5-HT signaling in neonatal mice exposed to bleomycin, previously demonstrated to induce PH and alveolar simplification. Newborn wild-type mice received intraperitoneal PBS, ketanserin (1 mg/kg), bleomycin (3 U/kg) or bleomycin (3 U/kg) plus ketanserin (1 mg/kg) three times weekly for 3 wk. Following treatment with bleomycin, pulmonary expression of the rate-limiting enzyme of 5-HT synthesis, tryptophan hydroxylase-1 (Tph1), was significantly increased. Bleomycin did not affect pulmonary 5-HT 2A receptor (R) expression, but did increase pulmonary gene expression of the 5-HT 2BR and serotonin transporter. Treatment with ketanserin attenuated bleomycin-induced PH (increased RVSP and RVH) and pulmonary vascular remodeling (decreased vessel density and increased muscularization of small vessels). In addition, we found that treatment with ketanserin activated pulmonary MAPK and Akt signaling in mice exposed to bleomycin. We conclude that 5-HT signaling is increased in a murine model of neonatal PH and pharmacological inhibition of the 5-HT 2AR protects against the development of PH in neonatal lung injury. We speculate this occurs through restoration of MAPK signaling and increased Akt signaling.

Practices surrounding pulmonary hypertension and bronchopulmonary dysplasia amongst neonatologists caring for premature infants

OBJECTIVE

Pulmonary hypertension (PH) is associated with bronchopulmonary dysplasia (BPD). Screening strategies, a thorough investigation of co-morbidities, and multidisciplinary involvement prior to anti-PH medications have been advocated by recent guidelines. We sought to evaluate current practices of neonatologists caring for premature infants with PH.

DESIGN

Electronic survey of American Academy of Pediatrics neonatology members.

RESULTS

Among 306 neonatologist respondents, 38% had an institutional screening protocol for patients with BPD; 83% screened at 36 weeks for premature neonates on oxygen/mechanical ventilation. In those practicing more than 5 years, 54% noted increasing numbers of premature infants diagnosed with PH. Evaluation for PH in BPD patients included evaluations for micro-aspiration (41%), airways anomalies (29%), and catheterization (10%). Some degree of acquired pulmonary vein stenosis was encountered in 47%. A majority (90%) utilized anti-PH medications during the neonatal hospitalization.

CONCLUSIONS

Screening for PH in BPD, and subsequent evaluation and management is highly variable.

A Translational Model of Incomplete Catch-Up Growth: Early-Life Hypoxia and the Effect of Physical Activity

Advances in therapies have led to prolonged survival from many previously lethal health threats in children, notably among prematurely born babies and those with congenital heart disease. Evidence for catch‐up growth is common in these children, but in many cases the adult phenotype is never achieved. A translational animal model is required in which specific tissues can be studied over a reasonable time interval. We investigated the impact of postnatal hypoxia (HY) (12%O₂ (HY12) or 10% O₂ (HY10)) on growth in rats relative to animals raised in room air. Subgroups had access to running wheels following the HY period. Growth was fully compensated in adult HY12 rats but not HY10 rats. The results of this study indicate that neonatal hypoxia can be a useful model for the elucidation of mechanisms that mediate successful catch‐up growth following neonatal insults and identify the critical factors that prevent successful catch‐up growth.

Maternal omega-3 PUFA supplementation prevents hyperoxia-induced pulmonary hypertension in the offspring

Pulmonary hypertension (PH) and right ventricular hypertrophy (RVH) affect 16-25% of premature infants with bronchopulmonary dysplasia (BPD), contributing significantly to perinatal morbidity and mortality. Omega-3 polyunsaturated fatty acids (PUFA ω-3) can improve vascular remodeling, angiogenesis, and inflammation under pathophysiological conditions. However, the effects of PUFA ω-3 supplementation in BPD-associated PH are unknown. The present study aimed to evaluate the effects of PUFA ω-3 on pulmonary vascular remodeling, angiogenesis, and inflammatory response in a hyperoxia-induced rat model of PH. From embryonic day 15, pregnant Sprague-Dawley rats were supplemented daily with PUFA ω-3, PUFA ω-6, or normal saline (0.2 ml/day). After birth, pups were pooled, assigned as 12 per litter, randomly assigned to either air or continuous oxygen exposure (fraction of inspired oxygen = 85%) for 20 days, and then euthanized for pulmonary hemodynamic and morphometric analysis. We found that PUFA ω-3 supplementation improved survival, decreased right ventricular systolic pressure and RVH caused by hyperoxia, and significantly improved alveolarization, vascular remodeling, and vascular density. PUFA ω-3 supplementation produced a higher level of total ω-3 in lung tissue and breast milk and was found to reverse the reduced levels of VEGFA, VEGF receptor 2, angiopoietin-1 (ANGPT1), endothelial TEK tyrosine kinase, endothelial nitric oxide synthase, and nitric oxide concentrations in lung tissue and the increased ANGPT2 levels in hyperoxia-exposed rats. The beneficial effects of PUFA ω-3 in improving lung injuries were also associated with an inhibition of leukocyte infiltration and reduced expression of the proinflammatory cytokines IL-1β, IL-6, and TNF-α. These data indicate that maternal PUFA ω-3 supplementation strategies could effectively protect against infant PH induced by hyperoxia.