Pulmonary vascular disease in bronchopulmonary dysplasia: pulmonary hypertension and beyond

Placental effects and transfer of sildenafil in healthy and preeclamptic conditions

Background

The phosphodiesterase-5 inhibitor (PDE5) sildenafil has emerged as a promising treatment for preeclampsia (PE). However, a sildenafil trial was recently halted due to lack of effect and increased neonatal morbidity.

Methods

Ex vivo dual-sided perfusion of an isolated cotyledon and wire-myography on chorionic plate arteries were performed to study the effects of sildenafil and the non-selective PDE inhibitor vinpocetine on the response to the NO donor sodium nitroprusside (SNP) under healthy and PE conditions. Ex vivo perfusion was also used to study placental transfer of sildenafil in 6 healthy and 2 PE placentas. Furthermore, placental mRNA and protein levels of eNOS, iNOS, PDE5 and PDE1 were quantified.

Findings

Sildenafil and vinpocetine significantly enhanced SNP responses in chorionic plate arteries of healthy, but not PE placentas. Only sildenafil acutely decreased baseline tension in arteries of both healthy and PE placentas. At steady state, the foetal-to-maternal transfer ratio of sildenafil was 0·37 ± 0·03 in healthy placentas versus 0·66 and 0·47 in the 2 PE placentas. mRNA and protein levels of PDE5, eNOS and iNOS were comparable in both groups, while PDE1 levels were lower in PE.

Interpretation

The absence of sildenafil-induced NO potentiation in arteries of PE placentas, combined with the non-PDE-mediated effects of sildenafil and the lack of PDE5 upregulation in PE, argue against sildenafil as the preferred drug of use in PE. Moreover, increased placental transfer of sildenafil in PE might underlie the neonatal morbidity in the STRIDER trial.

Fund

This study was funded by an mRACE Erasmus MC grant.

Right ventricular myocardial performance index in pediatric patients with bronchopulmonary dysplasia-related pulmonary hypertension

INTRODUCTION

This study aims to assess the utility of right ventricular myocardial performance index (RVMPI) as a potential echocardiographic tool to evaluate and serially follow patients with bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH).

METHODS

We performed a retrospective chart review of all hemodynamic cardiac catheterizations performed January 2011 to December 2016 in patients born premature and with diagnosed BPD up to 4 years of age-excluding patients with significant congenital heart defects. Echocardiograms performed within 24 hours of the cardiac catheterization were reviewed, and a blinded RVMPI was calculated. The primary endpoint was correlation of invasive catheterization hemodynamics to noninvasive echocardiographic RVMPI measurement.

RESULTS

A total of 49 individual patients met complete study criteria, and 10 of those patients underwent repeat cardiac catheterization. Median age at the time of assessment was 8 months (25%-75%, 4-18 months), and the cohort had a calculated RVMPI mean of 0.39 (±0.19), with 73% (43/59) having a RVMPI >0.28. A statistically significant correlation was found between the RVMPI and the baseline hemodynamics during catheterization with regard to the initial mean pulmonary arterial pressure (r = 0.58; P < 0.01) as well as the calculated pulmonary vascular resistance (r = 0.34; P = 0.01).

CONCLUSIONS

This study demonstrates the utility of RVMPI for evaluation of PH in patients with prematurity and BPD. An increased RVMPI by noninvasive echocardiography was found to correlate with increased mean pulmonary arterial pressure and pulmonary vascular resistance measured during invasive cardiac catheterization. Large-scale validation of this study is being planned.

Pulmonary hypertension during respiratory syncytial virus bronchiolitis: a risk factor for severity of illness

BACKGROUND

Respiratory syncytial virus infection is the most frequent cause of acute lower respiratory tract disease in infants. A few reports have suggested that pulmonary hypertension is associated with increased severity of respiratory syncytial virus infection. We sought to determine the association between the pulmonary hypertension detected by echocardiography during respiratory syncytial virus bronchiolitis and clinical outcomes.

METHODS

We retrospectively reviewed 154 children admitted with respiratory syncytial virus bronchiolitis who had an echocardiography performed during the admission. The association between pulmonary hypertension and clinical outcomes including mortality, intensive care unit (ICU) admission, prolonged ICU stay (&gt;10 days), tracheal intubation, and need of high frequency oscillator ventilation was evaluated.

RESULTS

Echocardiography detected pulmonary hypertension in 29 patients (18.7%). Pulmonary hypertension was observed more frequently in patients with congenital heart disease (CHD) (n = 11/33, 33%), chronic lung disease of infancy (n = 12/25, 48%), prematurity (&lt;37 weeks gestational age, n = 17/59, 29%), and Down syndrome (n = 4/10, 40%). The presence of pulmonary hypertension was associated with morbidity (p &lt; 0.001) and mortality (p = 0.02). However, in patients without these risk factors (n = 68), pulmonary hypertension was detected in five patients who presented with shock or poor perfusion. Chronic lung disease was associated with pulmonary hypertension (OR = 5.9, 95% CI 2.2-16.3, p = 0.0005). Multivariate logistic analysis demonstrated that pulmonary hypertension is associated with ICU admission (OR = 6.4, 95% CI 2.2-18.8, p = 0.0007), intubation (OR = 4.7, 95% CI 1.8-12.3, p = 0.002), high frequency oscillator ventilation (OR = 8.4, 95% CI 2.95-23.98, p &lt; 0.0001), and prolonged ICU stay (OR = 4.9, 95% CI 2.0-11.7, p = 0.0004).

CONCLUSIONS

Pulmonary hypertension detected by echocardiography during respiratory syncytial virus infection was associated with increased morbidity and mortality. Chronic lung disease was associated with pulmonary hypertension detected during respiratory syncytial virus bronchiolitis. Routine echocardiography is not warranted for previously healthy, haemodynamically stable patients with respiratory syncytial virus bronchiolitis.

Respiratory Medications in Infants <29 Weeks during the First Year Postdischarge: The Prematurity and Respiratory Outcomes Program (PROP) Consortium

OBJECTIVE

To determine patterns of respiratory medications used in neonatal intensive care unit graduates.

STUDY DESIGN

The Prematurity Respiratory Outcomes Program enrolled 835 babies <29 weeks of gestation in the first week. Of 751 survivors, 738 (98%) completed at least 1, and 85% completed all 4, postdischarge medication usage in-person/telephone parental questionnaires requested at 3, 6, 9, and 12 months of corrected age. Respiratory drug usage over the first year of life after in neonatal intensive care unit discharge was analyzed.

RESULTS

During any given quarter, 66%-75% of the babies received no respiratory medication and 45% of the infants received no respiratory drug over the first year. The most common postdischarge medication was the inhaled bronchodilator albuterol; its use increased significantly from 13% to 31%. Diuretic usage decreased significantly from 11% to 2% over the first year. Systemic steroids (prednisone, most commonly) were used in approximately 5% of subjects in any one quarter. Inhaled steroids significantly increased over the first year from 9% to 14% at 12 months. Drug exposure changed significantly based on gestational age with 72% of babies born at 23-24 weeks receiving at least 1 respiratory medication but only 40% of babies born at 28 weeks. Overall, at some time in the first year, 55% of infants received at least 1 drug including an inhaled bronchodilator (45%), an inhaled steroid (22%), a systemic steroid (15%), or diuretic (12%).

CONCLUSION

Many babies born at <29 weeks have no respiratory medication exposure postdischarge during the first year of life. Inhaled medications, including bronchodilators and steroids, increase over the first year.

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.

Perioperative Complications After Spinal Fusion in Pediatric Patients With Congenital Heart Disease

BACKGROUND

Children with congenital heart disease (CHD) have been reported to be at increased risk of developing scoliosis following cardiac surgery. Previous sample studies have reported that these patients may safely undergo posterior spinal fusion (PSF) with low complication rates. The goal of this study is to provide an updated analysis of the perioperative complication profile for posterior spinal fusion in a large cohort of pediatric patients with CHD, using a nationwide database.

METHODS

A retrospective cohort study was conducted using 30-day perioperative outcomes data from the NSQIP-P database. Our inclusion criteria were all pediatric patients who underwent posterior spinal fusion by CPT code. Patients were subdivided into two groups: those with a history of cardiac surgery for CHD and those without. Postoperative complications were classified according to the Clavien-Dindo system. Risk factors were assessed in univariate and multivariate logistic regression analyses, with significance set at p < .05.

RESULTS

Our results included 3,426 pediatric patients (68.2% female, 31.8% male) with a median age at spinal fusion of 13.7 ± 2.87 years. A CHD diagnosis was present in 312 patients, with 128 having had prior cardiac surgery. The overall complication rate was 6.68%, with a 10.9% rate in the prior cardiac surgery cohort (p = .068). The most common overall perioperative complications were unplanned readmission (3.5%), reoperation (2.6%), and superficial wound dehiscence (2.5%). Patients with a history of cardiac surgery were not at increased risk for postoperative complications; however, blood transfusion (p < .001), bronchopulmonary dysplasia (p < .001), combined bronchopulmonary dysplasia and previous cardiac surgery (p = .004), and a neuromuscular diagnosis (p < .001) were all risk factors for major postoperative complications in this cohort.

CONCLUSIONS

Children with scoliosis who have undergone cardiac surgery to address CHD are not at an increased risk of perioperative complications within 30 days of undergoing a posterior spinal fusion. However, patients who underwent cardiac surgery for CHD who also had bronchopulmonary dysplasia or an associated neuromuscular diagnosis are at increased risk for perioperative complications. It is important for pediatric orthopedic spine surgeons to be familiar with an updated profile of potential perioperative obstacles they may face when treating these patients, as seen in a large and representative cohort.

LEVEL OF EVIDENCE

Level III.

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.

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.

[Clinical features and prognosis of bronchopulmonary dysplasia complicated by pulmonary hypertension in preterm infants]

OBJECTIVE

To study the clinical features and prognosis of bronchopulmonary dysplasia (BPD) complicated by pulmonary hypertension (PH) in preterm infants.

METHODS

A retrospective analysis was performed on the clinical data of 191 preterm infants with BPD.

RESULTS

In the 191 preterm infants with BPD, 37 (19.4%), all with moderate or severe BPD, developed PH beyond 36 weeks' corrected age. The incidence rates of PH in infants with moderate and severe BPD were 5.7% (5/87) and 47.8% (32/67) respectively. Gestational age and birth weight were lower in infants with PH than in those without PH (P<0.01). Infants with PH had higher incidence rates of small for gestational age (SGA), severe BPD, surgical ligation of patent ductus arteriosus (PDA), neonatal respiratory distress syndrome, hemodynamically significant PDA, and pneumonia than those without PH (P<0.01). Durations of oxygen therapy, intubation, and positive pressure ventilation were longer in infants with PH than in those without PH (P<0.01). Infants with PH had higher incidence rates of retinopathy of prematurity and extrauterine growth retardation, a higher mortality, and a longer length of hospital stay compared with those without PH (P<0.01). In the 37 infants with PH (6 with mild PH, 14 with moderate PH, and 17 with severe PH), those with mild or moderate PH all survived; 15(88%) out of 17 infants with severe PH died.

CONCLUSIONS

The incidence of PH is high in preterm infants with moderate or severe BPD. Regular screening of pulmonary artery pressure is recommended for infants with BPD. Infants with low gestational age and birth weight, SGA, and severe BPD are more likely to develop PH. Infants with BPD complicated by PH have relatively high incidence rates of complications, high mortality, and poor prognosis.

Sildenafil Use in the Treatment of Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension: A Case Series

Objective  This article studies the role of sildenafil in reducing myocardial stress (measured by serial N-terminal pro b-type natriuretic peptide [NTproBNP] levels) secondary to bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH). Study Design  This is a case series of three extremely low birth weight infants with severe BPD at 36 weeks' postmenstrual age. All infants had very elevated NTproBNP (> 2,000 ng/dL) levels and echocardiographic evidence of BPD-PH. Sildenafil was started and infants were followed up every 2 weeks clinically along with NTproBNP levels and echocardiograms. Results  After 4 weeks of sildenafil treatment, NTproBNP levels decreased significantly in all infants, echocardiograms showed significant improvement in one infant, and respiratory severity score improved significantly in one infant. All infants tolerated sildenafil. Conclusion  Sildenafil reduced NTproBNP levels in all infants with BPD-PH but the echocardiographic findings and respiratory scores did not improve consistently. We speculate that this may be due to a delay in diagnosis and initiation of therapy after irreversible pulmonary changes have set in.

Changes in the nitric oxide pathway of the pulmonary vasculature after exposure to hypoxia in swine model of neonatal pulmonary vascular disease

Neonatal pulmonary vascular disease (PVD) is increasingly recognized as a disease that complicates the cardiopulmonary adaptations after birth and predisposes to long-term cardiopulmonary disease. There is growing evidence that PVD is associated with disruptions in the nitric oxide (NO)-cGMP-phosphodiesterase 5 (PDE5) pathway. Examination of the functionality of different parts of this pathway is required for better understanding of the pathogenesis of neonatal PVD. For this purpose, the role of the NO-cGMP-PDE5 pathway in regulation of pulmonary vascular function was investigated in vivo, both at rest and during exercise, and in isolated pulmonary small arteries in vitro, in a neonatal swine model with hypoxia-induced PVD. Endothelium-dependent vasodilatation was impaired in piglets with hypoxia-induced PVD both in vivo at rest and in vitro. Moreover, the responsiveness to the NO-donor SNP was reduced in hypoxia-exposed piglets in vivo, while the relaxation to SNP and 8-bromo-cyclicGMP in vitro were unaltered. Finally, PDE5 inhibition-induced pulmonary vasodilatation was impaired in hypoxia-exposed piglets both in vitro and in vivo at rest. During exercise, however, the pulmonary vasodilator effect of PDE5 inhibition was significantly larger in hypoxia-exposed as compared to normoxia-exposed piglets. In conclusion, the impaired endothelium-dependent vasodilatation in piglets with hypoxia-induced PVD was accompanied by reduced responsiveness to NO, potentially caused by altered sensitivity and/or activity of soluble guanylyl cyclase (sGC), resulting in an impaired cGMP production. Our findings in a newborn animal model for neonatal PVD suggests that sGC stimulators/activators may be a novel treatment strategy to alleviate neonatal PVD.

The mechanosensitive ion channel TRPV4 is a regulator of lung development and pulmonary vasculature stabilization

Introduction –

Clinical observations and animal models suggest a critical role for the dynamic regulation of transmural pressure and peristaltic airway smooth muscle contractions for proper lung development. However, it is currently unclear how such mechanical signals are transduced into molecular and transcriptional changes at the cell level. To connect these physical findings to a mechanotransduction mechanism, we identified a known mechanosensor, TRPV4, as a component of this pathway.

Methods –

Embryonic mouse lung explants were cultured on membranes and in submersion culture to modulate explant transmural pressure. Time-lapse imaging was used to capture active changes in lung biology, and whole-mount images were used to visualize the organization of the epithelial, smooth muscle, and vascular compartments. TRPV4 activity was modulated by pharmacological agonism and inhibition.

Results –

TRPV4 expression is present in the murine lung with strong localization to the epithelium and major pulmonary blood vessels. TRPV4 agonism and inhibition resulted in hyper- and hypoplastic airway branching, smooth muscle differentiation, and lung growth, respectively. Smooth muscle contractions also doubled in frequency with agonism and were reduced by 60% with inhibition demonstrating a functional role consistent with levels of smooth muscle differentiation. Activation of TRPV4 increased the vascular capillary density around the distal airways, and inhibition resulted in a near complete loss of the vasculature.

Conclusions –

These studies have identified TRPV4 as a potential mechanosensor involved in transducing mechanical forces on the airways to molecular and transcriptional events that regulate the morphogenesis of the three essential tissue compartments in the lung.

Novel therapeutics for bronchopulmonary dysplasia

PURPOSE OF REVIEW

This review provides a concise summary of recent literature pertaining to emerging therapies for bronchopulmonary dysplasia (BPD). To provide context for the presented therapies, a brief overview of recently proposed changes to the definition of BPD and the concept of expanded respiratory outcomes is included.

RECENT FINDINGS

New or redefined respiratory outcomes are required to improve accuracy in evaluating new therapies and correlating results with long-term clinical outcomes of importance. Dexamethasone is no longer the only steroid-based therapy showing promise for impacting BPD. Early trials indicate hydrocortisone, inhaled budesonide, and a budesonide-surfactant combination may be of benefit to preterm infants. Additionally, simple approaches like increasing utilization of mother's own milk may deserve more emphasis. Of significant interest is the traction stem cell therapies are acquiring as one of the more anticipated treatments for BPD. A new preclinical meta-analysis demonstrates the benefits of mesenchymal stromal cell therapy in animal models while the results of early clinical trials remain eagerly awaited.

SUMMARY

BPD continues to be the most frequently occurring significant morbidity for extremely preterm infants, yet highly effective therapies remain elusive. Promising new treatments are on the horizon, but only continued efforts to complete well-designed clinical trials will determine the true impact of these emerging therapies.

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.

Genotypes and Phenotypes: Making Progress Toward a Precision Medicine Approach in Pediatric Pulmonary Hypertension

Pediatric pulmonary hypertension (PH) is a heterogeneous disease that includes etiologies related to growth and development that are unique to children. Recent pediatric registry studies have characterized diverse phenotypes even within recognized PH subtypes, including PH associated with congenital heart disease and developmental lung disease. Advances in genetics are resulting in increased understanding of the genetic basis for PH, with recent discoveries such as TBX4 mutations specific for pediatric-onset pulmonary arterial hypertension (PAH) and SOX17 related to congenital heart disease–associated PAH. In addition to potential genetic underpinnings, PAH risk and clinical presentation in children with congenital heart disease may vary by cardiac condition, such as single-ventricle physiology or transposition of the great arteries. Growth and development of the pulmonary vasculature likely plays a role in all pediatric PH, which is highlighted by the disruption of normal lung growth in patients with PH related to prematurity and developmental lung disease. These diverse pediatric genotypes and phenotypes underscore a need for an individualized approach to diagnose and treat the complex pediatric PH population. Magnetic resonance imaging (MRI) is increasingly being used to improve clinical characterization of PH in children, with recent identification of specific MRI biomarkers associated with PH severity and outcomes. While much progress has been made, additional understanding of the important genetic causes and developmental concepts in pediatric PH is needed to develop a precision medicine approach to diagnosis and treatment of children with PH.

An Echocardiographic Screening Program Helps to Identify Pulmonary Hypertension in Extremely Low Birthweight Infants with and without Bronchopulmonary Dysplasia: A Single-Center Experience

BACKGROUND

Pulmonary hypertension (PH) affects 1 in 6 infants with a birthweight <1,000 g (extremely low birthweight; ELBW) and is frequently associated with bronchopulmonary dysplasia (BPD). If untreated, the mortality rates of the disease are high.

OBJECTIVES

The aim of this study was to characterize risk factors for PH in ELBW infants and to describe the timing of onset of the disease by setting up a screening program.

METHODS

ELBW infants treated at the Department of Neonatology (level III neonatal intensive care unit at the University of Cologne Medical Centre, Germany) between January 2010 and March 2015 were included. Echocardiography screening for PH was performed either before discharge or if BPD was diagnosed. Additionally, infants had at least 1 echocardiographic scan after discharge. Survival with PH, age at diagnosis of PH, and risk factors associated with PH were assessed.

RESULTS

In total, 34/188 (18%) infants had PH. Of these, 14 (41%) were identified after discharge. Another 11 (32%) were diagnosed with PH without suffering from moderate or severe BPD. The risk factors for diagnosis of PH were moderate (odds ratio, OR 4 [2-8]) or severe BPD (OR 13 [2-71]), prolonged rupture of membranes >7 days (OR 5 [1-19]), and birthweight below the 3rd percentile (OR 3 [1-9]). All infants with PH before discharge and 50% diagnosed after discharge were treated with sildenafil (2.0 mg/kg/day). PH resolved and sildenafil was discontinued in all patients after a median duration of 13 months (IQR 8-20).

CONCLUSIONS

An echocardiographic screening program may help to identify infants with PH. Examinations should include all ELBW infants irrespective of the presence of BPD and be continued after discharge.

Bronchopulmonary dysplasia-associated pulmonary hypertension: clues from placental pathology

OBJECTIVES

Bronchopulmonary dysplasia (BPD) and the associated complication of pulmonary hypertension (PH) leads to increased mortality and a longer length of stay among survivors. Placental histopathology may give early clues of subsequent events. The objective was to evaluate the relationship of maternal vascular underperfusion (MVU) changes on placental histopathology with subsequent development of BPD-associated PH in a cohort of extremely premature infants.

STUDY DESIGN

In a cohort of preterm infants '⩽28 weeks' gestational age (GA) and with 'severe' BPD, this retrospective study evaluated specific placental histopathological changes and assessed the relationship with subsequent development of PH. 'Severe' BPD was defined as the need for ⩾30% oxygen and/or positive pressure ventilation at 36 weeks postmenstrual age. Placental and echocardiographic assessments were done by investigators masked to the grouping and clinical outcomes.

RESULTS

Fifty six infants with severe BPD formed the cohort; PH was noted in 22 (39.3%) infants. The GA of the infants with and without PH was comparable (25.8±1.6 vs 25.8±1.3 weeks, P=0.9). On placental histopathological examination, 13 (23%) had features of MVU. On univariate logistic regression, the presence of changes consistent with MVU increased the relative risk of subsequent BPD-associated PH by 2.75 (95% confidence interval 1.56 to 4.85, P=0.004). The significance persisted after adjustment for GA. Stratification by the presence or absence of fetal growth restriction, yielded nonsignificant associations (P=0.17).

CONCLUSION

Based on the results of the present study, specific placental histopathological changes may give early clues to the subsequent development of BPD-associated PH.

Structural and functional changes of the pulmonary vasculature after hypoxia exposure in the neonatal period: a new swine model of pulmonary vascular disease

Pulmonary vascular disease (PVD) represents an underestimated and increasing clinical burden not only in the neonatal period but also later in life, when exercise tolerance is decreased. Animal models performing long-term followup after a perinatal insult are lacking. This study aimed to develop and characterize a neonatal swine model with hypoxia-induced PVD during long-term followup after reexposure to normoxia and to investigate the exercise response in this model. Piglets were exposed to a normoxic ( n = 10) or hypoxic environment ( n = 9) for 4 wk. Neonatal hypoxia exposure resulted in pulmonary hypertension. Mean pulmonary artery pressure was elevated 1 day after reexposure to normoxia (30.2 ± 3.3 vs. 14.3 ± 0.9 mmHg) and remained significantly higher in the second week (32.8 ± 3.8 vs. 21.4 ± 1.2 mmHg), accompanied by decreased exercise tolerance. Exercise resulted in a trend toward an exaggerated increase of pulmonary artery pressure in hypoxia-exposed animals ( week 6, P = 0.086). Although pulmonary hypertension was transient, thickening of pulmonary arterioles was found at the end of followup. Furthermore, right ventricular dilation, lower right ventricular fractional area change ( week 8, 40.0 ± 2.7% vs. 29.5 ± 4.7%), and tricuspid annular plane systolic excursion ( week 8, 27.0 ± 2.5 vs. 22.9 ± 2.1 mm) persisted during followup. Male animals showed more severe PVD than female animals. In conclusion, we developed a neonatal swine model that allows examination of the long-term sequelae of damage to the developing neonatal lung, the course of the disease and the effect of therapy on long-term outcome. NEW & NOTEWORTHY The swine model of neonatal pulmonary vascular disease developed in the present study is the first that allows exercise testing and examination of long-term sequelae of a perinatal hypoxic insult, the course of the disease, and the effect of therapy on long-term outcome.

Mid-childhood outcomes after pre-viable preterm premature rupture of membranes

OBJECTIVES

Investigate cardiorespiratory outcomes in children surviving previable preterm premature rupture of membranes (PV-PPROM) before 22 weeks' gestational age (GA) with minimum 2 weeks latency.

STUDY DESIGN

Single institution, follow-up of retrospectively identified children who were born after PV-PPROM during 2000-2004, and individually matched preterm-born controls.

RESULTS

Eleven PV-PPROM and matched control children were included at mean age of 10.5 and 10.7 years. Rupture of membranes occurred at mean GA 18² and 27⁶ weeks and birth at 28³ and 28⁶ weeks, respectively. Compared to controls, the PV-PPROM group had significantly poorer lung function, findings on echocardiography indicating mild pulmonary hypertension, and lower peak oxygen consumption. Chart reviews suggested more motor difficulties and a tendency towards more problems with learning and attention.

CONCLUSION

The findings highlight a preterm-born sub-group in need of targeted long-term monitoring and possibly interventions regarding future cardiorespiratory and neurodevelopmental function.

Persistent pulmonary hypertension of the newborn

Failure of the normal circulatory adaptation to extrauterine life results in persistent pulmonary hypertension of the newborn (PPHN). Although this condition is most often secondary to parenchymal lung disease or lung hypoplasia, it may also be idiopathic. PPHN is characterized by elevated pulmonary vascular resistance with resultant right-to-left shunting of blood and hypoxemia. Although the preliminary diagnosis of PPHN is often based on differential cyanosis and labile hypoxemia, the diagnosis is confirmed by echocardiography. Management strategies include optimal lung recruitment and use of surfactant in patients with parenchymal lung disease, maintaining optimal oxygenation and stable blood pressures, avoidance of respiratory and metabolic acidosis and alkalosis, and pulmonary vasodilator therapy. Extracorporeal membrane oxygenation is considered when medical management fails. Although mortality associated with PPHN has decreased significantly with improvements in medical care, there remains the potential risk for neurodevelopmental disability which warrants close follow-up of affected infants after discharge.

The significance of IL-1β +3953C>T, IL-6 -174G>C and -596G>A, TNF-α -308G>A gene polymorphisms and 86 bp variable number tandem repeat polymorphism of IL-1RN in bronchopulmonary dysplasia in infants born before 32 weeks of gestation

Introduction

Bronchopulmonary dysplasia (BPD) is a chronic lung disease that affects primarily preterm infants. Genetic factors are also taken into consideration in the pathogenesis of BPD. Genetic predispositions to higher production of inflammation mediators seem to be crucial.

Material and methods

The aim of this study was to evaluate the possible relationship between polymorphisms: interleukin-1β +3953 C>T, interleukin-6 -174 G>C and -596 G>A, tumour necrosis factor -308 G>A and interleukin-1RN VNTR 86bp and the occurrence of BPD in a population of 100 preterm infants born from singleton pregnancy, before 32+0 weeks of gestation, exposed to antenatal steroids therapy, and without congenital abnormalities.

Results

In the study population BPD was diagnosed in 36 (36%) newborns. Among the studied polymorphisms we found the higher prevalence for BPD developing of the following genotypes: 1/2 (OR 1.842 [0.673-5.025] and 2/2 IL-1RN (OR 1.75 [0.418-6.908] 86bpVNTR; GC (2.222 [0.658-8.706]) and CC IL-6 -174G>C (1.6 [0.315-8.314]) and GA (2.753 [0.828-10.64]) and AA (1.5 [0.275-8.067] IL-6 -596G>A), GA 1.509 (0.515-4.301) TNF-α -308G>A. However, these finding were not statistically significant.

Conclusions

Genetic factors are undeniably involved in the pathogenesis of BPD. In the times of individualised therapy finding genes responsible for BPD might allow the development of new treatment strategies. A new way of specific therapy could ensure the reduction of complications connected with BPD and treatment costs.

The evolution of modern respiratory care for preterm infants

Preterm birth rates are rising, and many preterm infants have breathing difficulty after birth. Treatments for infants with prolonged breathing difficulty include oxygen therapy, exogenous surfactant, various modes of respiratory support, and postnatal corticosteroids. In this Series paper, we review the history of neonatal respiratory care and its effect on long-term outcomes, and we outline the future direction of the research field. The delivery and monitoring of oxygen therapy remains controversial, despite being in use for more than 50 years. Exogenous surfactant replacement has been used for 25 years and has dramatically reduced mortality and morbidity, but more research on when and how it is administered is needed. Methods and techniques of neonatal respiratory support are evolving. Clinicians are moving away from routine intubation and ventilation, and new modes of non-invasive support are being investigated. Postnatal corticosteroids have a limited role in infants with evolving bronchopulmonary dysplasia, but more research is needed to identify the best timing, type, dose, and method of administration. Despite advances in neonatal care in the past 50 years, bronchopulmonary dysplasia, with all its adverse short-term and long-term consequences, is still a serious problem in neonatal care. The challenge remains to support breathing in preterm infants, with special attention to risk factors in the subpopulation of infants that are at highest risk of bronchopulmonary dysplasia, without damaging their lungs or adversely affecting their long-term health.

Bronchopulmonary dysplasia and pulmonary hypertension: a meta-analysis

OBJECTIVE

Pulmonary hypertension (PH) is a complication of bronchopulmonary dysplasia (BPD) but the true impact of PH in patients with BPD remains unclear. We sought to systematically review and meta-analyze incidence of PH in BPD and compare clinical outcomes of BPD patients with PH to those without PH in preterm infants.

STUDY DESIGN

Medline, Embase, PsychINFO and CINAHL were searched from January 2000 through December 2015. Cohort, case-control and randomized studies were included. Case-reports, case-series and letters to editors and studies with high risk of bias were excluded. Study design, inclusion/exclusion criteria, diagnostic criteria for BPD and PH and outcomes were extracted independently by two co-authors.

RESULTS

The pooled incidence of PH in patients with BPD (any severity) was 17% (95% confidence interval (CI) 12 to 21; 7 studies) and 24% (95% CI 17 to 30; 9 studies) in moderate-severe BPD. Patients with BPD have higher unadjusted odds of developing PH compared to those without BPD (odds ratio (OR) 3.00; 95% CI 1.18 to 7.66; 4 studies). Patients with BPD and PH were at higher odds of mortality (OR 5.29; 95% CI 2.07 to 13.56; 3 studies) compared with BPD without PH, but there was no significant difference in duration of initial hospitalization, duration of supplemental oxygen requirement or need for home oxygen. No studies included in this review reported on long-term pulmonary or neurodevelopmental outcomes.

CONCLUSIONS

PH occurs in one out of 4 to 5 preterm neonates with BPD. Patients with BPD and PH may have higher odds of mortality; however, there is urgent need for high quality studies that control for confounders and provide data on long-term outcomes.

Early Use of Inhaled Nitric Oxide in Preterm Infants: Is there a Rationale for Selective Approach?

Background Inhaled nitric oxide (iNO) is being increasingly used in preterm infants < 34 weeks with hypoxemic respiratory failure (HRF) and/or pulmonary hypertension (PH). Objective To evaluate the risk factors, survival characteristics, and lung histopathology in preterm infants with PH/HRF. Methods Retrospective chart review was conducted to determine characteristics of 93 preterm infants treated with iNO in the first 28 days and compared with 930 matched controls. Factors associated with survival with preterm HRF and smooth muscle actin from nine autopsies were evaluated. Results Preterm neonates treated with iNO had a higher incidence of preterm prolonged rupture of membrane (pPROM ≥ 18 hours), oligohydramnios and delivered by C-section. In infants treated with iNO, antenatal steroids (odds ratio [OR],3.7; confidence interval [CI], 1.2-11.3; p = 0.02), pPROM (OR, 1.001; CI, 1.0-1.004; p = 0.3), and oxygenation response to iNO (OR, 3.7; CI, 1.08-13.1; p = 0.037) were associated with survival. Thirteen infants with all three characteristics had 100% (13/13) survival without severe intraventricular hemorrhage (IVH)/periventricular leukomalacia (PVL) compared with 48% survival (12/25, p = 0.004) and 16% severe IVH/PVL without any of these factors. Severity of HRF correlated with increased smooth muscle in pulmonary vasculature. Conclusion Preterm infants with HRF exposed to antenatal steroids and pPROM had improved oxygenation with iNO and survival without severe IVH/PVL. Precisely targeting this subset may be beneficial in future trials of iNO.

Pulmonary hypertension's variegated landscape: a snapshot

The many types of pulmonary hypertension (PH) are so protean in their biological origin, histological expression, and natural history that it is difficult to create a summary picture of the disease, or to easily compare and contrast characteristics of one type of PH with another. For newcomers to the field, however, such a picture would facilitate a broad understanding of PH. In this paper, we suggest that four characteristics are fundamental to describing the nature of various types of PH, and that taken together they define a number of patterns of PH expression. These characteristics are histopathology, developmental origin, associated clinical conditions, and potential for resolution. The “snapshot” is a way to concisely display the ways that these signal characteristics intersect in select specific types of PH, and is an effort to summarize these patterns in a way that facilitates a “big picture” comprehension of this disease.

Very low birthweight bronchopulmonary dysplasia survivors had similar cardiac outcomes to controls at six years to 14 years of age

AIM

This study evaluated cardiac function and its associations with lung function and neonatal pulmonary morbidity in very low birthweight (VLBW) children, with and without severe radiographic bronchopulmonary dysplasia (radBPD), at school age.

METHODS

We examined 18 VLBW children with radBPD, 17 VLBW children without radBPD and 18 healthy term-born children using conventional echocardiography, tissue Doppler imaging, speckle tracking echocardiography and real-time three-dimensional echocardiography at six years to 14 years of age. Lung function was studied by impulse oscillometry. Plasma N-terminal-proBNP concentrations were measured.

RESULTS

Cardiac function and N-terminal-proBNP concentrations did not differ between the groups. No associations were found between cardiac function and neonatal dexamethasone, oxygen or ventilator therapies. In VLBW children, poorer reactance correlated with larger left ventricle (LV) end-systolic (Spearman's ρ = -0.45) and end-diastolic (ρ = -0.50) volumes and higher resistance correlated with higher LV dyssynchrony indexes, with ρ ranging from 0.37 to 0.48. Greater bronchodilation responses correlated with lower early diastolic myocardial relaxation velocities, with ρ ranging from 0.39 to 0.42.

CONCLUSION

BPD survivors had normal cardiac function at the age of six years to 14 years. No associations were found between neonatal pulmonary morbidity and cardiac parameters. Poorer lung function correlated modestly with LV echocardiographic parameters in VLBW children.

Bronchopulmonary dysplasia: new becomes old again!

Despite the many advances in neonatology, bronchopulmonary dysplasia (BPD) continues to be a frustrating disease of prematurity. BPD is a disease which is defined oddly by its treatment rather than its pathophysiology, leading to frequently changing nomenclature which has widespread implications on our ability to both understand and follow the progression of BPD. As various treatment modalities for BPD were developed and a larger number of extremely preterm infants survived, the "old" BPD based on lung injury from oxygen therapy and mechanical ventilation transitioned into a "new" BPD focused more on the interruption of normal development. However, the interruption of normal development does not solely apply to lung development. The effects of prematurity on vascular development cannot be overstated and pulmonary vascular disease has become the new frontier of BPD. As we begin to better understand the complex, multifactorial pathophysiology of BPD, it is necessary to again focus on appropriate, pathology-driven nomenclature that can effectively describe the multiple clinical phenotypes of BPD.

Simvastatin prevents and reverses chronic pulmonary hypertension in newborn rats via pleiotropic inhibition of RhoA signaling

Chronic neonatal pulmonary hypertension (PHT) frequently results in early death. Systemically administered Rho-kinase (ROCK) inhibitors prevent and reverse chronic PHT in neonatal rats, but at the cost of severe adverse effects, including systemic hypotension and growth restriction. Simvastatin has pleiotropic inhibitory effects on isoprenoid intermediates that may limit activity of RhoA, which signals upstream of ROCK. We therefore hypothesized that statin treatment would safely limit pulmonary vascular RhoA activity and prevent and reverse experimental chronic neonatal PHT via downstream inhibitory effects on pathological ROCK activity. Sprague-Dawley rats in normoxia (room air) or moderate normobaric hypoxia (13% O2) received simvastatin (2 mg·kg−1·day−1 ip) or vehicle from postnatal days 1–14 (prevention protocol) or from days 14–21 (rescue protocol). Chronic hypoxia increased RhoA and ROCK activity in lung tissue. Simvastatin reduced lung content of the isoprenoid intermediate farnesyl pyrophosphate and decreased RhoA/ROCK signaling in the hypoxia-exposed lung. Preventive or rescue treatment of chronic hypoxia-exposed animals with simvastatin decreased pulmonary vascular resistance, right ventricular hypertrophy, and pulmonary arterial remodeling. Preventive simvastatin treatment improved weight gain, did not lower systemic blood pressure, and did not cause apparent toxic effects on skeletal muscle, liver or brain. Rescue therapy with simvastatin improved exercise capacity. We conclude that simvastatin limits RhoA/ROCK activity in the chronic hypoxia-exposed lung, thus preventing or ameliorating hemodynamic and structural markers of chronic PHT and improving long-term outcome, without causing adverse effects.

Tetrahydrobiopterin oral therapy recouples eNOS and ameliorates chronic hypoxia-induced pulmonary hypertension in newborn pigs

We previously showed that newborn piglets who develop pulmonary hypertension during exposure to chronic hypoxia have diminished pulmonary vascular nitric oxide (NO) production and evidence of endothelial NO synthase (eNOS) uncoupling (Fike CD, Dikalova A, Kaplowitz MR, Cunningham G, Summar M, Aschner JL. Am J Respir Cell Mol Biol 53: 255-264, 2015). Tetrahydrobiopterin (BH4) is a cofactor that promotes eNOS coupling. Current clinical strategies typically invoke initiating treatment after the diagnosis of pulmonary hypertension, rather than prophylactically. The major purpose of this study was to determine whether starting treatment with an oral BH4 compound, sapropterin dihydrochloride (sapropterin), after the onset of pulmonary hypertension would recouple eNOS in the pulmonary vasculature and ameliorate disease progression in chronically hypoxic piglets. Normoxic (control) and hypoxic piglets were studied. Some hypoxic piglets received oral sapropterin starting on day 3 of hypoxia and continued throughout an additional 7 days of hypoxic exposure. Catheters were placed for hemodynamic measurements, and pulmonary arteries were dissected to assess eNOS dimer-to-monomer ratios (a measure of eNOS coupling), NO production, and superoxide (O2·-) generation. Although higher than in normoxic controls, pulmonary vascular resistance was lower in sapropterin-treated hypoxic piglets than in untreated hypoxic piglets. Consistent with eNOS recoupling, eNOS dimer-to-monomer ratios and NO production were greater and O2·- generation was less in pulmonary arteries from sapropterin-treated than untreated hypoxic animals. When started after disease onset, oral sapropterin treatment inhibits chronic hypoxia-induced pulmonary hypertension at least in part by recoupling eNOS in the pulmonary vasculature of newborn piglets. Rescue treatment with sapropterin may be an effective strategy to inhibit further development of pulmonary hypertension in newborn infants suffering from chronic cardiopulmonary conditions associated with episodes of prolonged hypoxia.

Pulmonary Hypertension in Children

The prevalence of PH is increasing in the pediatric population, because of improved recognition and increased survival of patients, and remains a significant cause of morbidity and mortality. Recent studies have improved the understanding of pediatric PH, but management remains challenging because of a lack of evidence-based clinical trials. The growing contribution of developmental lung disease requires dedicated research to explore the use of existing therapies as well as the creation of novel therapies. Adequate study of pediatric PH will require multicenter collaboration due to the small numbers of patients, multifactorial disease causes, and practice variability.

A single nucleotide polymorphism in the dimethylarginine dimethylaminohydrolase gene is associated with lower risk of pulmonary hypertension in bronchopulmonary dysplasia

AIM

Pulmonary hypertension (PH) develops in 25-40% of bronchopulmonary dysplasia (BPD) patients, substantially increasing mortality. We have previously found that asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) production, is elevated in patients with BPD-associated PH. ADMA is metabolised by N(ᴳ) ,N(ᴳ) -dimethylarginine dimethylaminohydrolase (DDAH). Presently, we test the hypothesis that there are single nucleotide polymorphisms (SNPs) in DDAH1 and/or DDAH2 associated with the development of PH in BPD patients.

METHODS

BPD patients were enrolled (n = 98) at Nationwide Children's Hospital. Clinical characteristics and 36 SNPs in DDAH1 and DDAH2 were compared between BPD-associated PH patients (cases) and BPD-alone patients (controls).

RESULTS

In BPD patients, 25 (26%) had echocardiographic evidence of PH (cases). In this cohort, DDAH1 wild-type rs480414 was 92% sensitive and 53% specific for PH in BPD, and the DDAH1 SNP rs480414 decreased the risk of PH in an additive model of inheritance (OR = 0.39; 95% CI [0.18-0.88], p = 0.01).

CONCLUSION

The rs480414 SNP in DDAH1 may be protective against the development of PH in patients with BPD. Furthermore, the DDAH1 rs480414 may be a useful biomarker in developing predictive models for PH in patients with BPD.

Right Ventricular Function in Infants with Bronchopulmonary Dysplasia: Association with Respiratory Sequelae

BACKGROUND

While cor pulmonale has been noted in infants with bronchopulmonary dysplasia (BPD), information on right ventricular (RV) function is limited.

OBJECTIVE

To assess RV function in infants with severe BPD and ascertain correlation with respiratory outcomes.

METHODS

We prospectively assessed RV function using tissue Doppler imaging (TDI), 2D fractional area change (FAC), M-mode tricuspid annular plane systolic excursion (TAPSE) and myocardial performance index (MPI) using echocardiography. Additionally, we compared RV function with preterm infants with no BPD.

RESULTS

Eighteen preterm infants with severe BPD were enrolled at 36 weeks' gestation. Higher E/E' (r = 0.78, p < 0.0001) and lower FAC (r = 0.8, p < 0.0001) showed strong correlations with the subsequent duration of respiratory support. Correlations with TDI isovolumic velocity and Tei index were significant (-0.69, p = 0.002 and 0.58, p = 0.011, respectively). On comparison with infants with no BPD, TDI peak systolic velocities (0.06 ± 0.01 vs. 0.09 ± 0.01 m/s, p < 0.0001), peak isovolumic systolic velocities (0.05 ± 0.009 vs. 0.07 ± 0.008 m/s, p < 0.0001) and RV FAC (31 ± 4.7 vs. 36 ± 3.6%, p = 0.019) were significantly lower. Cardiac relaxation was impaired [higher TDI E/E' ratio (9.6 ± 1.8 vs. 5.2 ± 0.5, p < 0.0001) and higher RV MPI (0.33 ± 0.03 vs. 0.25 ± 0.03, p < 0.0001)].

CONCLUSIONS

Impaired RV performance in the infants with severe BPD at 36 weeks' corrected gestation correlated with a longer duration of subsequent respiratory support.

Cardiac Mechanics in Children with Bronchopulmonary Dysplasia

BACKGROUND

Disruption of pulmonary vasculogenesis occurs in bronchopulmonary dysplasia (BPD). Increased impedance to pulmonary flow secondary to abnormal vascular development may affect ventricular mechanics.

OBJECTIVES

We aimed to test the hypothesis that cardiac mechanics are altered in prematurely born children with BPD.

METHODS

A cohort of 47 children was studied: 22 aged 48.9 ± 6.4 months born preterm with BPD (group I), 13 aged 46.3 ± 8.1 months born preterm without BPD (group II), and 12 healthy children aged 53.4 ± 12.2 months born at term (group III). Left (LV) and right ventricular (RV) strain and strain rate were assessed by speckle-tracking echocardiography.

RESULTS

The global RV systolic strain rate (p = 0.022) was significantly lower, while RV systolic strain (p = 0.05) and early diastolic strain rate (p = 0.05) and LV longitudinal systolic strain rate (p = 0.06) also tended to be lower in group I than group III. Group I also tended to have lower RV systolic strain (p = 0.09) and early diastolic strain rate (p = 0.049) and LV longitudinal systolic strain rate (p = 0.08) than group II. An increasing trend from group I to III was observed for RV lateral wall and septal systolic strain and strain rate (all p < 0.05). The LV but not RV size was significantly smaller in group I compared with group III (p < 0.05). Multiple regression identified duration of invasive ventilation (β = -0.66, p = 0.032) as an independent determinant of RV systolic strain after adjustment for perinatal risk factors.

CONCLUSION

Impairment of RV myocardial deformation occurs in children with BPD, the magnitude of which is associated negatively with the duration of invasive ventilation.

Lack of EC-SOD worsens alveolar and vascular development in a neonatal mouse model of bleomycin-induced bronchopulmonary dysplasia and pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) worsens clinical outcomes in former preterm infants with bronchopulmonary dysplasia (BPD). Oxidant stress disrupts alveolar and vascular development in models of BPD. Bleomycin causes oxidative stress and induces BPD and PAH in neonatal rats. Disruption in the vascular endothelial growth factor (VEGF) and nitric oxide signaling pathways contributes to BPD. We hypothesized that loss of EC-SOD would worsen PAH associated with BPD in a neonatal mouse model of bleomycin-induced BPD by disrupting the VEGF/NO signaling pathway.

METHODS

Neonatal wild-type mice (WT), and mice lacking EC-SOD (EC-SOD KO) received intraperitoneal bleomycin (2 units/kg) or phosphate-buffered saline (PBS) three times weekly and were evaluated at weeks 3 or 4.

RESULTS

Lack of EC-SOD impaired alveolar development and resulted in PH (elevated right ventricular systolic pressures, right ventricular hypertrophy (RVH)), decreased vessel density, and increased small vessel muscularization. Exposure to bleomycin further impaired alveolar development, worsened RVH and vascular remodeling. Lack of EC-SOD and bleomycin treatment decreased lung total and phosphorylated VEGFR2 and eNOS protein expression.

CONCLUSION

EC-SOD is critical in preserving normal lung development and loss of EC-SOD results in disrupted alveolar development, PAH and vascular remodeling at baseline, which is further worsened with bleomycin and associated with decreased activation of VEGFR2.

Persistent Pulmonary Hypertension of the Newborn

Persistent pulmonary hypertension of the newborn (PPHN) is often secondary to parenchymal lung disease (such as meconium aspiration syndrome) or lung hypoplasia (with congenital diaphragmatic hernia) but can also be idiopathic. PPHN is characterized by elevated pulmonary vascular resistance, resulting in right-to-left shunting of blood and hypoxemia. The diagnosis of PPHN is based on clinical evidence of labile hypoxemia often associated with differential cyanosis and confirmed by echocardiography. Lung volume recruitment with optimal use of positive end-expiratory pressure or mean airway pressure and/or surfactant is very important in secondary PPHN due to parenchymal lung disease. Other management strategies include optimal oxygenation, avoiding respiratory and metabolic acidosis, blood pressure stabilization, sedation, and pulmonary vasodilator therapy. Failure of these measures leads to consideration of extracorporeal membrane oxygenation, although this rescue therapy is needed less frequently with advances in medical management. Randomized clinical trials with long-term follow-up are required to evaluate various therapeutic strategies in PPHN.

Rescue Treatment with L-Citrulline Inhibits Hypoxia-Induced Pulmonary Hypertension in Newborn Pigs

Infants with cardiopulmonary disorders associated with hypoxia develop pulmonary hypertension. We previously showed that initiation of oral L-citrulline before and continued throughout hypoxic exposure improves nitric oxide (NO) production and ameliorates pulmonary hypertension in newborn piglets. Rescue treatments, initiated after the onset of pulmonary hypertension, better approximate clinical strategies. Mechanisms by which L-citrulline improves NO production merit elucidation. The objective of this study was to determine whether starting L-citrulline after the onset of pulmonary hypertension inhibits disease progression and improves NO production by recoupling endothelial NO synthase (eNOS). Hypoxic and normoxic (control) piglets were studied. Some hypoxic piglets received oral L-citrulline starting on Day 3 of hypoxia and continuing throughout the remaining 7 days of hypoxic exposure. Catheters were placed for hemodynamic measurements, and pulmonary arteries were dissected to assess NO production and eNOS dimer-to-monomer ratios (a measure of eNOS coupling). Pulmonary vascular resistance was lower in L-citrulline-treated hypoxic piglets than in untreated hypoxic piglets but was higher than in normoxic controls. NO production and eNOS dimer-to-monomer ratios were greater in pulmonary arteries from L-citrulline-treated than from untreated hypoxic animals but were lower than in normoxic controls. When started after disease onset, oral L-citrulline treatment improves NO production by recoupling eNOS and inhibits the further development of chronic hypoxia-induced pulmonary hypertension in newborn piglets. Oral L-citrulline may be a novel strategy to halt or reverse pulmonary hypertension in infants suffering from cardiopulmonary conditions associated with hypoxia.

Correlation of radiographic thoracic area and oxygenation impairment in bronchopulmonary dysplasia

We hypothesized that radiographically-assessed hyperinflation in bronchopulmonary dysplasia (BPD) is related to the degree of oxygenation impairment. Our objective was to explore the relation of chest radiographic thoracic area (CRTA) with right-to-left shunt, right shift of the oxyhemoglobin dissociation curve and ventilation/perfusion ratio (VA/Q) in infants with BPD. Twenty-two infants born at median (IQR) gestation of 26 (24-28) weeks with BPD were prospectively studied at 39 (30-69) days. Inspired oxygen (FiO2) was varied to obtain transcutaneous oxygen saturation (SpO2) values between 85 and 96%. Shunt, shift and VA/Q were derived by plotting and analysing pairs of SpO2 and FiO2. CRTA was measured by free hand-tracing the perimeter of the thoracic area in anterio-posterior chest radiographs. Median (IQR) shunt was 8 (1-14)%, shift was 13 (11-19)kPa and VA/Q 0.42 (0.30-0.48). Median (IQR) CRTA/kg was 2495 (1962-2838)mm(2) and was significantly related to shift (r=0.674, p<0.001), VA/Q (r=-0.633, p<0.001), weight at study (r=-0.457, p=0.003) and day of life (r=-0.406, p=0.009), but not to shunt. CRTA in BPD is significantly related to oxygenation impairment as quantified by shift and VA/Q. CRTA can be used as a simple radiographic test to quantify BPD severity.

Recent advances in the mechanisms of lung alveolarization and the pathogenesis of bronchopulmonary dysplasia

Alveolarization is the process by which the alveoli, the principal gas exchange units of the lung, are formed. Along with the maturation of the pulmonary vasculature, alveolarization is the objective of late lung development. The terminal airspaces that were formed during early lung development are divided by the process of secondary septation, progressively generating an increasing number of alveoli that are of smaller size, which substantially increases the surface area over which gas exchange can take place. Disturbances to alveolarization occur in bronchopulmonary dysplasia (BPD), which can be complicated by perturbations to the pulmonary vasculature that are associated with the development of pulmonary hypertension. Disturbances to lung development may also occur in persistent pulmonary hypertension of the newborn in term newborn infants, as well as in patients with congenital diaphragmatic hernia. These disturbances can lead to the formation of lungs with fewer and larger alveoli and a dysmorphic pulmonary vasculature. Consequently, affected lungs exhibit a reduced capacity for gas exchange, with important implications for morbidity and mortality in the immediate postnatal period and respiratory health consequences that may persist into adulthood. It is the objective of this Perspectives article to update the reader about recent developments in our understanding of the molecular mechanisms of alveolarization and the pathogenesis of BPD.

Persistent pulmonary hypertension of the newborn: Advances in diagnosis and treatment

Persistent pulmonary hypertension of the newborn (PPHN) is a frequent cause for admission to the neonatal intensive care unit and is associated with mortality and variable morbidities. It is primarily a state of oxygenation failure representing a failure of the normal postnatal decline in pulmonary vascular resistance that may be associated with right ventricular dysfunction. Enhanced knowledge of the pathophysiologic contributors to this syndrome helps clinicians understand its phenotypic expression and facilitates more focused intensive care decision-making. The approach to treatment should be based on alleviation of the elevation in pulmonary vascular resistance and should include optimization of lung recruitment and judicious use of pulmonary vasodilators. When response to inhaled nitric oxide is suboptimal, the physiologic contributors to impaired oxygenation need further investigation. Targeted neonatal echocardiography provides novel physiologic insights; in particular, it may help assess the adequacy of right ventricular performance, the relative contribution of the fetal shunts and the magnitude of the overall impairment to cardiac output. This information may facilitate therapeutic next steps and whether adjunctive vasodilators or drugs to augment ventricular function are preferable. This article provides a comprehensive overview of the pathological contributors to PPHN, the physiologic constituents of its phenotypic expression, standard approach to therapeutic intervention, and the role of bedside echocardiography in enhancing the decision-making process.

Impaired pulmonary vascular development in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), the chronic lung disease associated with preterm birth, results from the disruption of normal pulmonary vascular and alveolar growth. Though BPD was once described as primarily due to postnatal injury from mechanical ventilation and oxygen therapy after preterm birth, it is increasingly appreciated that BPD results from antenatal and perinatal factors that interrupt lung development in infants born at the extremes of prematurity. The lung in BPD consists of a simplified parenchymal architecture that limits gas exchange and leads to increased cardiopulmonary morbidity and mortality. This review outlines recent advances in the understanding of pulmonary vascular development and describes how the disruption of these mechanisms results in BPD. We point to future therapies that may augment postnatal vascular growth to prevent and treat this severe chronic lung disease.

Persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by elevated pulmonary vascular resistance resulting in right-to-left shunting of blood and hypoxemia. PPHN is often secondary to parenchymal lung disease (such as meconium aspiration syndrome, pneumonia or respiratory distress syndrome) or lung hypoplasia (with congenital diaphragmatic hernia or oligohydramnios) but can also be idiopathic. The diagnosis of PPHN is based on clinical evidence of labile hypoxemia often associated with differential cyanosis. The diagnosis is confirmed by the echocardiographic demonstration of - (a) right-to-left or bidirectional shunt at the ductus or foramen ovale and/or, (b) flattening or leftward deviation of the interventricular septum and/or, (c) tricuspid regurgitation, and finally (d) absence of structural heart disease. Management strategies include optimal oxygenation, avoiding respiratory and metabolic acidosis, blood pressure stabilization, sedation and pulmonary vasodilator therapy. Failure of these measures would lead to consideration of extracorporeal membrane oxygenation (ECMO); however decreased need for this rescue therapy has been documented with advances in medical management. While trends also note improved survival, long-term neurodevelopmental disabilities such as deafness and learning disabilities remain a concern in many infants with severe PPHN. Funded by: 1R01HD072929-0 (SL).

Outcomes for extremely premature infants

Premature birth is a significant cause of infant and child morbidity and mortality. In the United States, the premature birth rate, which had steadily increased during the 1990s and early 2000s, has decreased annually for 7 years and is now approximately 11.39%. Human viability, defined as gestational age at which the chance of survival is 50%, is currently approximately 23 to 24 weeks in developed countries. Infant girls, on average, have better outcomes than infant boys. A relatively uncomplicated course in the intensive care nursery for an extremely premature infant results in a discharge date close to the prenatal estimated date of confinement. Despite technological advances and efforts of child health experts during the last generation, the extremely premature infant (less than 28 weeks gestation) and extremely low birth weight infant (<1000 g) remain at high risk for death and disability with 30% to 50% mortality and, in survivors, at least 20% to 50% risk of morbidity. The introduction of continuous positive airway pressure, mechanical ventilation, and exogenous surfactant increased survival and spurred the development of neonatal intensive care in the 1970s through the early 1990s. Routine administration of antenatal steroids during premature labor improved neonatal mortality and morbidity in the late 1990s. The recognition that chronic postnatal administration of steroids to infants should be avoided may have improved outcomes in the early 2000s. Evidence from recent trials attempting to define the appropriate target for oxygen saturation in preterm infants suggests arterial oxygen saturation between 91% and 95% (compared with 85%-89%) avoids excess mortality; however, final analyses of data from these trials have not been published, so definitive recommendations are still pending. The development of neonatal neurocritical intensive care units may improve neurocognitive outcomes in this high-risk group. Long-term follow-up to detect and address developmental, learning, behavioral, and social problems is critical for children born at these early gestational ages.The striking similarities in response to extreme prematurity in the lung and brain imply that agents and techniques that benefit one organ are likely to also benefit the other. Finally, because therapy and supportive care continue to change, the outcomes of extremely low birth weight infants are ever evolving. Efforts to minimize injury, preserve growth, and identify interventions focused on antioxidant and anti-inflammatory pathways are now being evaluated. Thus, treating and preventing long-term deficits must be developed in the context of a "moving target."

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

RATIONALE

Pulmonary hypertension (PH) is associated with poor outcomes among preterm infants with bronchopulmonary dysplasia (BPD), but whether early signs of pulmonary vascular disease are associated with the subsequent development of BPD or PH at 36 weeks post-menstrual age (PMA) is unknown.

OBJECTIVES

To prospectively evaluate the relationship of early echocardiogram signs of pulmonary vascular disease in preterm infants to the subsequent development of BPD and late PH (at 36 wk PMA).

METHODS

Prospectively enrolled preterm infants with birthweights 500-1,250 g underwent echocardiogram evaluations at 7 days of age (early) and 36 weeks PMA (late). Clinical and echocardiographic data were analyzed to identify early risk factors for BPD and late PH.

MEASUREMENTS AND MAIN RESULTS

A total of 277 preterm infants completed echocardiogram and BPD assessments at 36 weeks PMA. The median gestational age at birth and birthweight of the infants were 27 weeks and 909 g, respectively. Early PH was identified in 42% of infants, and 14% were diagnosed with late PH. Early PH was a risk factor for increased BPD severity (relative risk, 1.12; 95% confidence interval, 1.03-1.23) and late PH (relative risk, 2.85; 95% confidence interval, 1.28-6.33). Infants with late PH had greater duration of oxygen therapy and increased mortality in the first year of life (P < 0.05).

CONCLUSIONS

Early pulmonary vascular disease is associated with the development of BPD and with late PH in preterm infants. Echocardiograms at 7 days of age may be a useful tool to identify infants at high risk for BPD and PH.

Plasma asymmetric dimethylarginine levels are increased in neonates with bronchopulmonary dysplasia-associated pulmonary hypertension

OBJECTIVE

To test the hypothesis that levels of the endogenous inhibitor of nitric oxide production, asymmetric dimethylarginine (ADMA), would be greater in preterm infants with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) than in infants with BPD alone.

STUDY DESIGN

A case-control study of 23 patients with both BPD and PH (cases) and 95 patients with BPD but no evidence of PH (controls). Levels of ADMA were compared between cases and controls by t test.

RESULTS

Patients with both BPD and PH had greater plasma levels of ADMA than patients with BPD alone (P = .04). In samples drawn before 28 days of life, greater levels of ADMA were again found in cases compared with controls (P = .02). The plasma arginine-to-ADMA ratio was lower in cases than in controls (P = .03), suggesting a greater likelihood of inhibition of nitric oxide production in patients with both BPD and PH than in patients with BPD alone.

CONCLUSION

In this neonatal BPD cohort, ADMA levels are increased in patients with BPD who develop PH. We speculate that ADMA may be both a biomarker and a potential therapeutic target for preterm infants with BPD-associated PH.