Pulmonary Hypertension in Preterm Infants with Bronchopulmonary Dysplasia

Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease, associated with premature birth, that arises during the infantile period. It is an evolving disease process with an unchanged incidence due to advancements in neonatal care which allow for the survival of premature infants of lower gestational ages and birth weights. Currently, there are few effective interventions to prevent BPD. However, careful attention to BPD phenotypes and comprehensive care provided by an interdisciplinary team have improved care. Interventions early in the disease course hold promise for improving long-term survival and outcomes in adulthood for this high-risk population.

Biomarker screening for pulmonary hypertension in VLBW infants at risk for bronchopulmonary dysplasia

BACKGROUND

Very low birth weight (VLBW) infants demonstrate altered alveolar and pulmonary vascular development and carry an increased risk of developing bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH). Risk stratification for BPD-associated PH (BPD-PH) in at-risk infants may help tailor management, improve outcomes, and optimize resource utilization.

METHODS

VLBW infants were screened for PH with blood gas measurements, serum NT-proBNP and bicarbonate (HCO3) levels, and echocardiograms if they remained on respiratory support at 34 weeks corrected gestational age. We then tested 11 models using different cutoffs for NT-proBNP and HCO3 to predict infants at low risk of BPD-PH.

RESULTS

We identified PH in 34 of 192 (17.6%) VLBW infants. The median NT-proBNP in VLBWs with PH was 2769 pg/mL versus 917 pg/mL in those without PH (p < 0.0001). A model with NT-proBNP < 950 pg/mL and HCO3 < 32 mmol/L had a sensitivity of 100%, specificity of 34.2%, and negative predictive value of 100%. Using this model, 54 of 192 (28%) of the patients in this study would have been categorized as low risk for PH and could have avoided a screening echocardiogram.

CONCLUSION

NT-proBNP and HCO3 together may serve as sensitive and cost-effective screening tools for BPD-PH in VLBW infants.

IMPACT

NT-proBNP and HCO3 concentrations obtained together may help identify very low birth weight infants at risk for bronchopulmonary dysplasia who should undergo screening for pulmonary hypertension with echocardiography. This large dataset demonstrates that NT-proBNP and HCO3 levels together are more sensitive than NT-proBNP alone in identifying VLBW infants to undergo echocardiography. The combination of NT-proBNP and HCO3 levels may identify VLBW infants at low risk for pulmonary hypertension and thus those who may be able to avoid screening echocardiography.

Cardiovascular Sequelae of Bronchopulmonary Dysplasia in Preterm Neonates Born before 32 Weeks of Gestational Age: Impact of Associated Pulmonary and Systemic Hypertension

Bronchopulmonary dysplasia (BPD) remains the most common respiratory disorder of prematurity for infants born before 32 weeks of gestational age (GA). Early and prolonged exposure to chronic hypoxia and inflammation induces pulmonary hypertension (PH) with the characteristic features of a reduced number and increased muscularisation of the pulmonary arteries resulting in an increase in the pulmonary vascular resistance (PVR) and a fall in their compliance. BPD and BPD-associated pulmonary hypertension (BPD-PH) together with systemic hypertension (sHTN) are chronic cardiopulmonary disorders which result in an increased mortality and long-term problems for these infants. Previous studies have predominantly focused on the pulmonary circulation (right ventricle and its function) and developing management strategies accordingly for BPD-PH. However, recent work has drawn attention to the importance of the left-sided cardiac function and its impact on BPD in a subset of infants arising from a unique pathophysiology termed postcapillary PH. BPD infants may have a mechanistic link arising from chronic inflammation, cytokines, oxidative stress, catecholamines, and renin-angiotensin system activation along with systemic arterial stiffness, all of which contribute to the development of BPD-sHTN. The focus for the treatment of BPD-PH has been improvement of the right heart function through pulmonary vasodilators. BPD-sHTN and a subset of postcapillary PH may benefit from afterload reducing agents such as angiotensin converting enzyme inhibitors. Preterm infants with BPD-PH are at risk of later cardiac and respiratory morbidities as young adults. This paper reviews the current knowledge of the pathophysiology, diagnosis, and treatment of BPD-PH and BPD-sHTN. Current knowledge gaps and emerging new therapies will also be discussed.

Approaches to Interdisciplinary Care for Infants with Severe Bronchopulmonary Dysplasia: A Survey of the Bronchopulmonary Dysplasia Collaborative

OBJECTIVE

Bronchopulmonary dysplasia (BPD) remains the most common late morbidity for extremely premature infants. Care of infants with BPD requires a longitudinal approach from the neonatal intensive care unit to ambulatory care though interdisciplinary programs. Current approaches for the development of optimal programs vary among centers.

STUDY DESIGN

We conducted a survey of 18 academic centers that are members of the BPD Collaborative, a consortium of institutions with an established interdisciplinary BPD program. We aimed to characterize the approach, composition, and current practices of the interdisciplinary teams in inpatient and outpatient domains.

RESULTS

Variations exist among centers, including composition of the interdisciplinary team, whether the team is the primary or consult service, timing of the first team assessment of the patient, frequency and nature of rounds during the hospitalization, and the timing of ambulatory visits postdischarge.

CONCLUSION

Further studies to assess long-term outcomes are needed to optimize interdisciplinary care of infants with severe BPD.

KEY POINTS

· Care of infants with BPD requires a longitudinal approach from the NICU to ambulatory care.. · Benefits of interdisciplinary care for children have been observed in other chronic conditions.. · Current approaches for the development of optimal interdisciplinary BPD programs vary among centers..

Serial tissue Doppler imaging in the evaluation of bronchopulmonary dysplasia-associated pulmonary hypertension among extremely preterm infants: a prospective observational study

Objectives

To evaluate serial tissue Doppler cardiac imaging (TDI) in the evolution of bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH) among extremely preterm infants.

Design

Prospective observational study.

Setting

Single-center, tertiary-level neonatal intensive care unit.

Patients

Infant born <28 weeks gestation.

Main outcome measures

Utility of TDI in the early diagnosis and prediction of BPD-PH and optimal timing for screening of BPD-PH.

Results

A total of 79 infants were included. Of them, 17 (23%) had BPD-PH. The mean gestational age was 25.9 ± 1.1 weeks, and mean birth weight was 830 ± 174 g. The BPD-PH group had a high incidence of hemodynamically significant patent ductus arteriosus (83% vs. 56%, p < 0.018), longer oxygen days (96.16 ± 68.09 vs. 59.35 ± 52.1, p < 0.008), and prolonged hospital stay (133.8 ± 45.9 vs. 106.5 ± 37.9 days, p < 0.005). The left ventricular eccentricity index (0.99 ± 0.1 vs. 1.1 ± 0.7, p < 0.01) and the ratio of acceleration time to right ventricular ejection time showed a statistically significant trend from 33 weeks (0.24 ± 0.05 vs. 0.28 ± 0.05, p < 0.05). At 33 weeks, the BPD-PH group showed prolonged isovolumetric contraction time (27.84 ± 5.5 vs. 22.77 ± 4, p < 0.001), prolonged isovolumetric relaxation time (40.3 ± 7.1 vs. 34.9 ± 5.3, p < 0.003), and abnormal myocardial performance index (0.39 ± 0.05 vs. 0.32 ± 0.03, p < 0.001). These differences persisted at 36 weeks after conceptional gestational age.

Conclusions

TDI parameters are sensitive in the early evolution of BPD-PH. Diagnostic accuracy can be increased by combining the TDI parameters with conventional echocardiographic parameters. BPD-PH can be recognizable as early as 33-34 weeks of gestation.

Outcomes of High-Dose Inhaled Nitric Oxide and Oxygen Administration for Severe Pulmonary Hypertension With Bronchopulmonary Dysplasia

Pulmonary hypertension (PH) with bronchopulmonary dysplasia (BPD) is fraught with high infant mortality rates. However, the intervention strategy for severe PH is unclear. This case report discusses the utility of long-term high-dose inhaled nitric oxide (iNO) administration and that of oxygen therapy for the prevention of PH deterioration. A male infant weighing 864 g was delivered at a gestational age of 24 weeks and three days. The patient who had severe BPD was diagnosed with PH at a corrected gestational age (CGA) of 43 weeks. Although oxygen was administered to prevent PH, the patient still developed severe PH. Despite long-term high-dose (iNO) administration, the patient could not survive. The abovementioned treatment may exacerbate PH, and oxygen administration is less effective for the prevention of PH deterioration with BPD.

Association of the respiratory severity score with bronchopulmonary dysplasia-associated pulmonary hypertension in infants born extremely preterm

OBJECTIVE

To test the hypothesis that elevations in the respiratory severity score (RSS) are associated with increased probability of bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH).

STUDY DESIGN

Retrospective cohort study of infants born extremely preterm admitted to a BPD center between 2010 and 2018. Echocardiograms obtained ≥ 36 weeks' post-menstrual age (PMA) were independently adjudicated by two blinded cardiologists to determine the presence/absence of BPD-PH. Multivariable logistic regression estimated the association between RSS and BPD-PH.

RESULT

BPD-PH was observed in 68/223 (36%) of subjects. The median RSS at time of echocardiography was 3.04 (Range 0-18.3). A one-point increase in the RSS was associated with BPD-PH, aOR 1.3 (95% CI 1.2-1.4), after adjustment for gestational age and PMA at time of echocardiography.

CONCLUSION

Elevations in the RSS were associated with a greater probability of BPD-PH. Prospective studies are needed to determine the validity and performance of RSS as a clinical susceptibility/risk biomarker for BPD-PH.

Short term effect of intravenous treprostinil in term and preterm infants with pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening condition in newborns. We aimed to assess the clinical and echocardiographic responses of term and preterm infants to treprostinil.

METHODS

This retrospective study included newborns diagnosed with PH and treated with treprostinil as additional therapy after inhaled nitric oxide administration in the neonatal intensive care unit of a tertiary center. Term and preterm infants were compared in terms of echocardiographic findings and clinical findings 4 weeks after treprostinil treatment.

RESULTS

During the study period, 11 term and 18 preterm infants were diagnosed with PH and received treprostinil. There were no differences in the echocardiographic findings of interventricular septal deviation, direction of shunt, and ratio of estimated pulmonary artery pressure over systolic blood pressure. Congenital diaphragmatic hernia was the most common condition occurring upon PH diagnosis among term infants, while severe bronchopulmonary dysplasia was the most common in preterm infants. Improvements in echocardiographic findings were more pronounced in term infants than in preterm infants (100% vs. 55.6%, P = 0.012). The inhaled nitric oxide dose was gradually tapered for term infants and was lower than that for preterm infants at 1, 2, and 3 weeks after treprostinil.

CONCLUSION

Intravenous treprostinil could be an adjuvant therapy option for term and preterm infants with PH, especially for those who cannot receive oral medication. The efficacy and safety of treprostinil in this population with PH should be investigated further.

Association of the Respiratory Severity Score with Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension in Infants Born Extremely Preterm

Objective

To test the hypothesis that elevations in the respiratory severity score (RSS) are associated with increased risk of bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH).

Study Design

Retrospective cohort study of infants born extremely preterm admitted to a BPD center between 2010-2018. Echocardiograms obtained ≥36 weeks' post-menstrual age (PMA) were independently adjudicated by two blinded cardiologists to determine the presence/absence of BPD-PH. Multivariable logistic regression estimated the association between RSS with BPD-PH.

Result

BPD-PH was observed in 68/223 (36%) of subjects. The median RSS at time of echocardiography was 3.04 (Range 0-18.3). A one-point increase in RSS was associated with BPD-PH, aOR 1.3 (95% CI 1.2-1.4), after adjustment for gestational age and PMA at time of echocardiography.

Conclusion

Elevations in the RSS were associated with a greater risk of BPD-PH. Prospective studies are needed to determine the validity and performance of RSS as a clinical susceptibility/risk biomarker for BPD-PH.

Multiomics endotyping of preterm infants with bronchopulmonary dysplasia and pulmonary hypertension-A pilot study

Pulmonary hypertension associated with bronchopulmonary dysplasia is a severe complication of preterm birth resulting in high mortality of up to 50% within the first 2 years of life. There is a direct relationship between bronchopulmonary dysplasia severity and incidence of associated pulmonary hypertension. However, it is challenging to clinically characterize severe bronchopulmonary dysplasia with and without pulmonary hypertension and there is need for better understanding of the two entities. Our main objective is to identify markers to help understand biological processes and characterize infants with pulmonary hypertension associated with bronchopulmonary dysplasia using tracheal aspirates. We conducted an unbiased multiomic analysis of tracheal aspirates via microRNA (miRNA) polymerase chain reaction arrays, RNA sequencing, and mass spectrometry proteomics in preterm infants with severe bronchopulmonary dysplasia with and without pulmonary hypertension (n = 46). Our pilot study analysis revealed 12 miRNAs (hsa-miR-29a, has-miR-542-3p, has-miR-624, has-miR-183, hsa-miR-501-3p, hsa-miR-101, hsa-miR-3131, hsa-miR-3683, hsa-miR-3193, hsa-miR-3672, hsa-miR-3128, and hsa-miR-1287), 6 transcripts (IL6, RPL35P5, HSD3B7, RNA5SP215, OR2A1-AS1, and RNVU1-19), and 5 proteins (CAPS, AAT, KRT5, SFTPB, and LGALS3BP) with significant differential expression in preterm infants with severe lung disease with pulmonary hypertension when compared with infants with severe lung disease but no pulmonary hypertension. Pathway analysis of the integrated multiomic expression signatures revealed NFkB, VEGF, SERPINA1, IL6, and ERK1/2 as target molecules and cellular development, cellular growth and proliferation, and cellular movement as key affected molecular functions. Our multiomic analysis of tracheal aspirates revealed a comprehensive thumbprint of miRNAs, mRNAs, and proteins that could help endotype infants with severe lung disease and pulmonary hypertension.

Right ventricle speckle tracking in bronchopulmonary dysplasia: one-year follow-up

BACKGROUND

Bronchopulmonary dysplasia (BPD) is still a major concern in preterm infants and adequate screening methods for secondary right ventricle (RV) failure are needed. Early detection could be aided by taking measurements of RV deformation using speckle tracking echocardiography. A prospective longitudinal study was carried out over 28 months at a tertiary care pediatric cardiology center. Preterm infants < 32 weeks gestational age (GA) were eligible for the study. Enrolled patients were separated in two groups: NO-BPD or BPD. At three timepoints over the first year of life, echocardiogram measurements were performed. Right ventricle strain was studied using speckle tracking analysis and compared to conventional function parameters.

RESULTS

Fifty patients were enrolled in the study, 22 in the NO-BPD group and 28 in the BPD group. RV strain showed no statistical differences between groups. However, the BPD group showed worse RV function than the NO-BPD group, using speckle tracking analysis and other conventional parameters. During the study follow-up, an improvement trend is shown in RV strain.

CONCLUSIONS

RV longitudinal strain and strain rate derived by speckle tracking is feasible in preterm infants. Although there seems to be a good correlation between RV strain and BPD severity, the results of this study were not conclusive. More studies should be carried out to investigate the optimum echocardiographic screening model of RV dysfunction in BPD patients.

Prospective Risk Stratification Identifies Healthcare Utilization Associated with Home Oxygen Therapy for Infants with Bronchopulmonary Dysplasia

OBJECTIVE

To test whether prospective classification of infants with bronchopulmonary dysplasia identifies lower-risk infants for discharge with home oxygen who have fewer rehospitalizations by 1 year after neonatal intensive care unit discharge.

STUDY DESIGN

This is a prospective single-center cohort that included infants from 2016 to 2019 with bronchopulmonary dysplasia, defined as receiving respiratory support at 36 weeks of postmenstrual age. "Lower-risk" infants were receiving ≤2 L/min nasal cannula flow, did not have pulmonary hypertension or airway comorbidities, and had blood gas partial pressure of carbon dioxide <70 mm Hg. We compared 3 groups by discharge status: lower-risk room air, lower-risk home oxygen, and higher-risk home oxygen. The primary outcome was rehospitalization at 1 year postdischarge, and the secondary outcomes were determined by the chart review and parent questionnaire.

RESULTS

Among 145 infants, 32 (22%) were lower-risk discharged in room air, 49 (32%) were lower-risk using home oxygen, and 64 (44%) were higher-risk. Lower-risk infants using home oxygen had rehospitalization rates similar to those of lower-risk infants on room air (18% vs 16%, P = .75) and lower rates than higher-risk infants (39%, P = .018). Lower-risk infants using home oxygen had more specialty visits (median 10, IQR 7-14 vs median 6, IQR 3-11, P = .028) than those on room air. Classification tree analysis identified risk status as significantly associated with rehospitalization, along with distance from home to hospital, inborn, parent-reported race, and siblings in the home.

CONCLUSIONS

Prospectively identified lower-risk infants discharged with home oxygen had fewer rehospitalizations than higher-risk infants and used more specialty care than lower-risk infants discharged in room air.

Early diagnosis and targeted approaches to pulmonary vascular disease in bronchopulmonary dysplasia

Pulmonary hypertension has emerged as a life-threatening disease in preterm infants suffering from bronchopulmonary dysplasia (BPD). Its development is closely linked to respiratory disease, as vasculogenesis and alveologenesis are closely interconnected. Once clinically significant, BPD-associated pulmonary hypertension (BPD-PH) can be challenging to manage, due to poor reversibility and multiple comorbidities frequently associated. The pulmonary vascular disease process underlying BPD-PH is the result of multiple innate and acquired factors, and emerging evidence suggests that it progressively develops since birth and, in certain instances, may begin as early as fetal life. Therefore, early recognition and intervention are of great importance in order to improve long-term outcomes. Based on the most recent knowledge of BPD-PH pathophysiology, we review state-of-the-art screening and diagnostic imaging techniques currently available, their utility for clinicians, and their applicability and limitations in this specific population. We also discuss some biochemical markers studied in humans as a possible complement to imaging for the detection of pulmonary vascular disease at its early stages and the monitoring of its progression. In the second part, we review pharmacological agents currently available for BPD-PH treatment or under preclinical investigation, and discuss their applicability, as well as possible approaches for early-stage interventions in fetuses and neonates. IMPACT: BPD-associated PH is a complex disease involving genetic and epigenetic factors, as well as environmental exposures starting from fetal life. The value of combining multiple imaging and biochemical biomarkers is emerging, but requires larger, multicenter studies for validation and diffusion. Since "single-bullet" approaches have proven elusive so far, combined pharmacological regimen and cell-based therapies may represent important avenues for research leading to future cure and prevention.

Bronchopulmonary dysplasia

Bronchopulmonary dysplasia is the most frequent adverse outcome of prematurity. Before implementation of antenatal steroids and surfactant therapy, bronchopulmonary dysplasia was mostly characterized by fibrotic, scarred, and hyper-inflated lungs due to pulmonary injury following mechanical ventilation and oxygen toxicity. With advances in neonatal medicine, this "old" bronchopulmonary dysplasia has changed to a "new" bronchopulmonary dysplasia characterized by an arrest in lung growth, leading to alveolar simplification and pulmonary vascular dysangiogenesis. While the old definition was based on the need for oxygen supplementation at a postnatal age of 28 days or at a corrected gestational age of 36 weeks, the newer definition looks at the mode of respiratory support required (eg, invasive versus noninvasive) and is then graded as mild, moderate, or severe. Patients with bronchopulmonary dysplasia may present with significantly impaired pulmonary function, reactive airway disease, or exercise intolerance. Over time, these patients may develop asthma or chronic obstructive pulmonary disease. The most serious long-term complication is the development of pulmonary vascular disease and pulmonary hypertension. Medical treatment often includes diuretics, steroids, bronchodilators, or oxygen supplementation and in the presence of pulmonary hypertension medication to decrease the pulmonary vascular resistance. Perioperative anesthetic risk is increased in children with pulmonary hypertension. These patients might require additional diagnostic imaging and plans for increased resource allocation such as postoperative intensive care admission.

Comprehensive assessments of pulmonary circulation in children with pulmonary hypertension associated with congenital heart disease

Pulmonary hypertension associated with congenital heart disease (CHD-PH) encompasses different conditions confounded by the left-to-right shunt, left heart obstruction, ventricular dysfunction, hypoxia due to airway obstruction, dysplasia/hypoplasia of the pulmonary vasculature, pulmonary vascular obstructive disease, and genetic variations of vasoactive mediators. Pulmonary input impedance consists of the pulmonary vascular resistance (Rp) and capacitance (Cp). Rp is calculated as the transpulmonary pressure divided by the pulmonary cardiac output, whereas Cp is calculated as the pulmonary stroke volume divided by the pulmonary arterial pulse pressure. The plots of Rp and Cp demonstrate a unique hyperbolic relationship, namely, the resistor-capacitor coupling curve, which represents the pulmonary vascular condition. The product of Rp and Cp is the exponential pressure decay, which refers to the time constant. Alterations in Cp are more considerable in CHD patients at an early stage of developing pulmonary hypertension or with excessive pulmonary blood flow due to a left-to-right shunt. The importance of Cp has gained attention because recent reports have shown that low Cp potentially reflects poor prognosis in patients with CHD-PH and idiopathic pulmonary hypertension. It is also known that Cp levels decrease in specific populations, such as preterm infants and trisomy 21. Therefore, both Rp and Cp should be individually evaluated in the management of children with CHD-PH who have different disease conditions.

DDAH1 SNP rs480414 that protects against the development of pulmonary hypertension in bronchopulmonary dysplasia results in lower nitric oxide production in neonatal cord blood-derived lymphoblastoid cell lines

BACKGROUND

Bronchopulmonary dysplasia (BPD) is chronic lung disease of prematurity and pulmonary hypertension (PH) is a major contributor to morbidity and mortality in BPD patients. Nitric oxide (NO) is a vasodilator and apoptotic mediator made by NO synthase (NOS). NOS is inhibited by asymmetric dimethylarginine (ADMA), and dimethylarginine dimethylaminohydrolase (DDAH) hydrolyzes ADMA. Previously, in a BPD patient cohort, we identified single nucleotide polymorphism (SNP) DDAH1 rs480414 (G > A) that was protective against developing PH. This study aims to determine functional consequences of the DDAH1 SNP in lymphoblastoid cell lines (LCLs) derived from neonatal cord blood. We tested the hypothesis that DDAH1 SNP (AA) results in DDAH1 gain of function, leading to greater NO-mediated apoptosis compared to DDAH1 wild-type (GG) in LCLs.

METHODS

LCLs were analyzed by Western blot (DDAH1, cleaved and total caspase-3 and -8, and β-actin), and RT-PCR (DDAH1, iNOS). Cell media assayed for nitrites with chemiluminescence NO analyzer, and conversion of ADMA to L-citrulline was measured by spectrophotometry.

RESULTS

LCLs with DDAH1 SNP had similar levels of DDAH1 protein and mRNA expression, as well as DDAH activity, compared to DDAH1 WT LCLs. There were also no changes in cleaved caspase-3 and -8 protein levels. LCLs with DDAH1 SNP had similar iNOS mRNA expression. Nitrite levels in media were lower for DDAH1 SNP LCLs compared to DDAH1 WT LCLs (p < 0.05).

CONCLUSION

Contrary to our hypothesis, we found that NO production was lower in DDAH1 SNP LCLs, indicative of a loss of function phenotype.

Pulmonary Function Tests in Very Low Birth Weight Infants Screened for Pulmonary Hypertension: A Pilot Study

OBJECTIVE

To compare pulmonary function tests (PFTs), specifically respiratory system resistance (Rrs) and compliance (Crs), in very low birth weight (VLBW) infants with and without pulmonary hypertension.

STUDY DESIGN

Infants were included who underwent PFTs at 34-38 weeks postmenstrual age (PMA) as part of our pulmonary hypertension screening guidelines for infants born at ≤1500 g requiring respiratory support at ≥34 weeks PMA. One pediatric cardiologist reviewed and estimated right ventricular or pulmonary arterial pressure and defined pulmonary hypertension as an estimated pulmonary arterial pressure or right ventricular pressure greater than one-half the systemic pressure. Rrs and Crs were measured with the single breath occlusion technique and functional residual capacity with the nitrogen washout method according to standardized criteria.

RESULTS

Twelve VLBW infants with pulmonary hypertension and 39 without pulmonary hypertension were studied. Those with pulmonary hypertension had significantly lower birth weight and a trend toward a lower gestational age. There were no other demographic differences between the groups. The infants with pulmonary hypertension had significantly higher Rrs (119 vs 78 cmH₂O/L/s; adjusted P = .012) and significantly lower Crs/kg (0.71 vs 0.92 mL/cmH₂O/kg; P = .04).

CONCLUSIONS

In this pilot study of VLBW infants screened for pulmonary hypertension at 34-38 weeks PMA, those with pulmonary hypertension had significantly increased Rrs and decreased Crs compared with those without pulmonary hypertension. Additional studies are needed to further phenotype infants with evolving BPD and pulmonary hypertension.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

Short and long-term outcomes of chronic pulmonary hypertension in preterm infants managed using a standardized algorithm

BACKGROUND

There is limited data on management strategies for chronic pulmonary hypertension (cPH) in chronic lung disease (CLD) of prematurity. Our objective was to evaluate clinical outcomes following a standardized policy, wherein only cPH with right-ventricular (RV) dilatation was treated and diuretics were employed as first-line therapy; cPH without RV-dilatation was managed expectantly.

METHOD

In this retrospective cohort study, all infants with CLD were categorized as "CLD-only" or "CLD-cPH," using echocardiography at ≥36 weeks postmenstrual age. Intergroup comparison was performed. Regression analysis examined the association between cPH and primary outcome of death or disability at 18-24 months.

RESULTS

Of 128 CLD infants, 48 (38%) had cPH, of which 29 (60%) received diuretics. Symptomatic improvement within 1-week was recorded in 90%. Although CLD-cPH had worse in-hospital respiratory course than CLD-only, all post-discharge respiratory and neurodevelopmental outcomes were similar. cPH was not associated with death or disability (adjusted odds ratio, 1.02; 95% confidence interval, 0.32-3.27). Disease progression treated with sildenafil occurred in 2 (4%) cases. There was no death from respiratory or RV failure.

CONCLUSION

Primary treatment of CLD-cPH with diuretics using RV-dilatation as therapeutic threshold, may result in symptomatic improvement, disease stabilization and post-discharge outcomes comparable to infants without cPH.

Children with Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension Treated with Pulmonary Vasodilators-The Pediatric Cardiologist Point of View

Pulmonary hypertension in children with bronchopulmonary dysplasia (BPD-PH) significantly worsens the prognosis. Pulmonary vasodilators are often used in BPD-PH but the short-term outcome of treatment is not well described. The aim of this study was to evaluate BPD-PH children diagnosed beyond 36 weeks postmenstrual age treated with pulmonary vasodilators (sildenafil, bosentan, or both) and to assess the short and long-term effect of oral pulmonary vasodilators treatment. Twenty patients were included in the study. Cardiology evaluation (WHO-FC, NTproBNP, oxygen saturation, pulmonary to systemic pressure ratio PAP/SAP) was performed at diagnosis and after treatment initiation. In the majority of patients improvement in all evaluated factors was observed. No side effects of vasodilators were observed. PH resolved in 10 patients after a mean of 21.4 months of treatment. Six patients died. The number of poor prognostic factors commonly used to assess patients with pulmonary arterial hypertension (PAH) decreased significantly during BPD-PH treatment. The influence of BPD-PH perinatal risk factors on prognosis was considered but was not confirmed. In conclusion, the treatment of BPD-PH with pulmonary vasodilators was well tolerated and led to a clinical improvement with the possibility of discontinuation without recurrence of PH. Prognostic factors used in pediatric PAH risk stratification also seem to be useful in assessing treatment efficacy and prognosis in patients with BPD-PH.

Exaggerated Cardiac Contractile Response to Hypoxia in Adults Born Preterm

Individuals born prematurely have smaller hearts, cardiac limitations to exercise, and increased overall cardiometabolic risk. The cardiac effects of acute hypoxia exposure as another physiologic stressor remain under explored. The purpose of this study was to determine the effects of hypoxia on ventricular function in adults born preterm. Adults born moderately to extremely preterm (≤32 weeks gestation or <1500 g, N = 32) and born at term (N = 18) underwent cardiac magnetic resonance imaging under normoxic (21% O₂) and hypoxic (12% O₂) conditions to assess cardiovascular function. In normoxia, cardiac function parameters were similar between groups. During hypoxia, the right ventricular (RV) contractile response was significantly greater in participants born premature, demonstrated by greater increases in RV ejection fraction (EF) (p = 0.002), ventricular-vascular coupling (VVC) (p = 0.004), and strain (p < 0.0001) measures compared to term-born participants, respectively. Left ventricular contractile reserve was similar to term-born participants. Adults born preterm exhibit an exaggerated contractile response to acute hypoxia, particularly in the RV. This suggests that adults born preterm may have contractile reserve, despite the lack of volume reserve identified in previous exercise studies. However, this exaggerated and hyper-adapted response may also increase their risk for late RV failure.

Interaction between pulmonary vasculature and the patent ductus arteriosus in very premature infants

BACKGROUND

The benefits of closing the ductus arteriosus in very preterm infants have not been convincingly shown in numerous clinical trials. Because a large untreated ductus arteriosus can cause death from congestive heart failure in infants born at term, we need to explain why this might not occur in premature infants born at <28 weeks' gestation.

METHODS

Based on information in the literature, I have commented on the possible relationship between the pulmonary vasculature and the shunt through the patent ductus arteriosus.

RESULTS

Many of these infants have bronchopulmonary dysplasia, in which animal and human studies have shown a reduced number of capillaries and small pulmonary arteries as well as reduction in vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (PECAM-1). Both of these import angiogenic factors. Some who do not have bronchopulmonary dysplasia may have a restricted pulmonary vascular bed.

CONCLUSIONS

The increased pulmonary vascular resistance in very premature infants may restrict pulmonary blood flow even if the ductus is large, thus reducing the urgency for ductus closure.

Interactive and independent effects of early lipopolysaccharide and hyperoxia exposure on developing murine lungs

Bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) is a chronic infantile lung disease that lacks curative therapies. Infants with BPD-associated PH are often exposed to hyperoxia and additional insults such as sepsis that contribute to disease pathogenesis. Animal models that simulate these scenarios are necessary to develop effective therapies; therefore, we investigated whether lipopolysaccharide (LPS) and hyperoxia exposure during saccular lung development cooperatively induce experimental BPD-PH in mice. C57BL/6J mice were exposed to normoxia or 70% O₂ (hyperoxia) during postnatal days (PNDs) 1-5 and intraperitoneally injected with varying LPS doses or a vehicle on PNDs 3-5. On PND 14, we performed morphometry, echocardiography, and gene and protein expression studies to determine the effects of hyperoxia and LPS on lung development, vascular remodeling and function, inflammation, oxidative stress, cell proliferation, and apoptosis. LPS and hyperoxia independently and cooperatively affected lung development, inflammation, and apoptosis. Growth rate and antioxidant enzyme expression were predominantly affected by LPS and hyperoxia, respectively, while cell proliferation and vascular remodeling and function were mainly affected by combined exposure to LPS and hyperoxia. Mice treated with lower LPS doses developed adaptive responses and hyperoxia exposure did not worsen their BPD phenotype, whereas those mice treated with higher LPS doses displayed the most severe BPD phenotype when exposed to hyperoxia and were the only group that developed PH. Collectively, our data suggest that an additional insult such as LPS may be necessary for models utilizing short-term exposure to moderate hyperoxia to recapitulate human BPD-PH.

Transitioning From Intravenous to Subcutaneous Prostacyclin Therapy in Neonates With Severe Pulmonary Hypertension

This article aims to present our neonatal intensive care unit experience transitioning from intravenous epoprostenol to IV and subcutaneous treprostinil in patients with persistent pulmonary hypertension of the neonate. This was a retrospective chart review at an academic teaching hospital. Neonates with a diagnosis of persistent pulmonary hypertension of the neonate (PPHN) who were started on IV prostacyclin therapy while admitted to the NICU between August 2017 and October 2019 were included. Of the 5 patients included, gestational ages ranged from 24 to 38 weeks. All patients were treated with inhaled nitric oxide and sildenafil before being initiated on IV or SQ prostacyclin therapy. Intravenous epoprostenol dosing was initiated at 1 ng/kg/min and was increased by 1 ng/kg/min every 12 hours until the provider was satisfied with the clinical response. Once the dose was stable for a few days epoprostenol was transitioned to IV treprostinil using double the last epoprostenol dose. A few days later infants were switched to SQ treprostinil using the same dose by stopping the IV infusion and starting the SQ infusion. All patients survived to hospital discharge and were sent home on SQ treprostinil. Minimal adverse effects were seen; patients experienced some slight hypotension, tachycardia, and diarrhea. Severe pulmonary hypertension is a common occurrence and a significant cause of mortality in the NICU. Our patients demonstrate that IV and SQ prostacyclin therapy is a therapeutic option for PPHN. Additionally, rapid high-dose transition from IV epoprostenol to IV treprostinil and then to SQ treprostinil is well tolerated in neonates, with minimal adverse effects.

Survey of practices in relation to chronic pulmonary hypertension in neonates in the Canadian Neonatal Network and the National Institute of Child Health and Human Development Neonatal Research Network

Current knowledge gaps pertaining to diagnosis and management of neonatal chronic pulmonary hypertension (cPH) may result in significant variability in clinical practice. The objective of the study is to understand cPH management practices in neonatal intensive care units affiliated with the Canadian Neonatal Network (CNN) and National Institute of Child Health and Human Development Neonatal Research Network (NRN). A 32-question survey seeking practice details for cPH evaluation, diagnostic criteria, conservative measures, pharmacotherapeutics, and follow-up was e-mailed to a designated physician at each center. Responses were described as frequency (percentage) and compared between CNN and NRN, where appropriate. Overall response rate was 67% (CNN 20/28 (71%), NRN 9/15 (60%)). While 8 (28%) centers had standardized management protocols, 17 (59%) routinely evaluate high-risk patients; moderate-severe chronic lung disease being the commonest indication. While interventricular septal flattening on echocardiography was the commonest listed diagnostic criterion, several adjunctive indices were also identified. Asymptomatic neonates with cPH were managed expectantly (routine care) in 50% of sites, and using various conservative measures in others. Pulmonary vasodilators were prescribed for symptomatic cases, with 60% of sites using them early (86% reporting any use). Seventy-five percent of sites use inhaled nitric oxide and sildenafil citrate as first- and second-line agents, respectively. Use of standard protocols, cardiac catheterization, and conservative measures for asymptomatic cases was more common in NRN units (p < 0.05). While there is relative homogeneity in patient identification and diagnostic criteria used for neonatal cPH, significant interunit inconsistencies still exists in routine evaluation, use of additional investigations, management of asymptomatic cases, frequency and type of conservative measures, and choice of pulmonary vasodilators.

Early Pulmonary Vascular Disease in Young Adults Born Preterm

Rationale: Premature birth affects 10% of live births in the United States and is associated with alveolar simplification and altered pulmonary microvascular development. However, little is known about the long-term impact prematurity has on the pulmonary vasculature.Objectives: Determine the long-term effects of prematurity on right ventricular and pulmonary vascular hemodynamics.Methods: Preterm subjects (n = 11) were recruited from the Newborn Lung Project, a prospectively followed cohort at the University of Wisconsin-Madison, born preterm with very low birth weight (≤1,500 g; average gestational age, 28 wk) between 1988 and 1991. Control subjects (n = 10) from the same birth years were recruited from the general population. All subjects had no known adult cardiopulmonary disease. Right heart catheterization was performed to assess right ventricular and pulmonary vascular hemodynamics at rest and during hypoxic and exercise stress.Measurements and Main Results: Preterm subjects had higher mean pulmonary arterial pressures (mPAPs), with 27% (3 of 11) meeting criteria for borderline pulmonary hypertension (mPAP, 19-24 mm Hg) and 18% (2 of 11) meeting criteria for overt pulmonary hypertension (mPAP ≥ 25 mm Hg). Pulmonary vascular resistance and elastance were higher at rest and during exercise, suggesting a stiffer vascular bed. Preterm subjects were significantly less able to augment cardiac index or right ventricular stroke work during exercise. Among neonatal characteristics, total ventilatory support days was the strongest predictor of adult pulmonary pressure.Conclusions: Young adults born preterm demonstrate early pulmonary vascular disease, characterized by elevated pulmonary pressures, a stiffer pulmonary vascular bed, and right ventricular dysfunction, consistent with an increased risk of developing pulmonary hypertension.

DDAH1 regulates apoptosis and angiogenesis in human fetal pulmonary microvascular endothelial cells

Nitric Oxide (NO) is an endogenous pulmonary vasodilator produced by endothelial NO synthase (eNOS). Asymmetric dimethyl L‐arginine (ADMA) is an endogenous inhibitor of eNOS activity. In endothelial cells, ADMA is hydrolyzed to L‐citrulline primarily by dimethylarginine dimethyl‐aminohydrolase‐1 (DDAH1). We tested the hypothesis that DDAH1 expression is essential for maintaining NO production in human fetal pulmonary microvascular endothelial cells (hfPMVEC), such that knockdown of DDAH1 expression will lead to decreased NO production resulting in less caspase‐3 activation and less tube formation. We found that hfPMVEC transfected with DDAH1 siRNA had lower NO production than control, with no difference in eNOS protein levels between groups. hfPMVEC transfected with DDAH1 siRNA had lower protein levels of cleaved caspase‐3 and ‐8 than control. Both DDAH1 siRNA‐ and ADMA‐treated hfPMVEC had greater numbers of viable cells than controls. Angiogenesis was assessed using tube formation assays in matrigel, and tube formation was lower after either DDAH1 siRNA transfection or ADMA treatment than controls. Addition of an NO donor restored cleaved caspase‐3 and ‐8 protein levels after DDAH1 siRNA transfection in hfPMVEC to essentially the levels seen in scramble control. Addition of a putative caspase‐3 inhibitor to DDAH1 siRNA transfected and NO‐donor treated cells led to greater numbers of viable cells and far less angiogenesis than in any other group studied. We conclude that in hfPMVEC, DDAH1 is central to the regulation of NO‐mediated caspase‐3 activation and the resultant apoptosis and angiogenesis. Our findings suggest that DDAH1 may be a potential therapeutic target in pulmonary hypertensive disorders.

Tie-2 Cre-Mediated Deficiency of Extracellular Signal-Regulated Kinase 2 Potentiates Experimental Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension in Neonatal Mice

Bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) is a significant lung morbidity of infants, and disrupted lung angiogenesis is a hallmark of this disease. We observed that extracellular signal-regulated kinases (ERK) 1/2 support angiogenesis in vitro, and hyperoxia activates ERK1/2 in fetal human pulmonary microvascular endothelial cells (HPMECs) and in neonatal murine lungs; however, their role in experimental BPD and PH is unknown. Therefore, we hypothesized that Tie2 Cre-mediated deficiency of ERK2 in the endothelial cells of neonatal murine lungs would potentiate hyperoxia-induced BPD and PH. We initially determined the role of ERK2 in in vitro angiogenesis using fetal HPMECs. To disrupt endothelial ERK2 signaling in the lungs, we decreased ERK2 expression by breeding ERK2^flox/flox mice with Tie-Cre mice. One-day-old endothelial ERK2-sufficient (eERK2^+/+) or –deficient (eERK2^+/−) mice were exposed to normoxia or hyperoxia (FiO₂ 70%) for 14 d. We then performed lung morphometry, gene and protein expression studies, and echocardiography to determine the extent of inflammation, oxidative stress, and development of lungs and PH. The knockdown of ERK2 in HPMECs decreased in vitro angiogenesis. Hyperoxia increased lung inflammation and oxidative stress, decreased lung angiogenesis and alveolarization, and induced PH in neonatal mice; however, these effects were augmented in the presence of Tie2-Cre mediated endothelial ERK2 deficiency. Therefore, we conclude that endothelial ERK2 signaling is necessary to mitigate hyperoxia-induced experimental BPD and PH in neonatal mice. Our results indicate that endothelial ERK2 is a potential therapeutic target for the management of BPD and PH in infants.

Mesenchymal stem/stromal cells stably transduced with an inhibitor of CC chemokine ligand 2 ameliorate bronchopulmonary dysplasia and pulmonary hypertension

Perinatal bronchopulmonary dysplasia (BPD) is defined as lung injury in preterm infants caused by various factors, resulting in serious respiratory dysfunction and high mortality. The administration of mesenchymal stem/stromal cells (MSCs) to treat/prevent BPD has proven to have certain therapeutic effects. However, MSCs can only weakly regulate macrophage function, which is strongly involved in the development of BPD. 7ND-MSCs are MSCs transfected with 7ND, a truncated version of CC chemokine ligand 2 (CCL2) that promotes macrophage activation, using a lentiviral vector. In the present study, we show in a BPD rat model that 7ND-MSC administration, but not MSCs alone, ameliorated the impaired alveolarization evaluated by volume density and surface area in the lung tissue, as well as pulmonary artery remodeling and pulmonary hypertension induced by BPD. In addition, 7ND-MSCs, but not MSCs alone, reduced M1 macrophages and the messenger RNA expressions of interleukin-6 and CCL2 in the lung tissue. Thus, the present study showed the treatment effect of 7ND-MSCs in a BPD rat model, which was more effective than that of MSCs alone.

Serum and Urinary N-Terminal Pro-brain Natriuretic Peptides as Biomarkers for Bronchopulmonary Dysplasia of Preterm Neonates

Bronchopulmonary dysplasia (BPD) is a common cause of respiratory illness in preterm newborns with high morbidity and mortality rates. At present, there are no early prognostic biomarkers that can be used in clinical practice to predict the development of BPD. In this review, we critically appraise evidence regarding the use of serum N-terminal pro-brain natriuretic peptide (NTproBNP) levels as a biomarker for BPD in neonates. Furthermore, we summarize studies assessing the feasibility of urinary NTproBNP levels as a non-invasive method to predict BPD in preterm infants. Multiple studies reported a strong association between NTproBNP serum levels and the onset of BPD. For urinary NTproBNP there is scarce evidence showing an association with BPD. Given the promising data obtained by preliminary studies, further assessment of this biomarker in both serum and urine is needed. Standardized reference values should be defined before conducting any further clinical studies.

Novel Strategies to Reduce Pulmonary Hypertension in Infants With Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a developmental lung disorder of preterm infants primarily caused by the failure of host defense mechanisms to prevent tissue injury and facilitate repair. This disorder is the most common complication of premature birth, and its incidence remains unchanged over the past few decades. Additionally, BPD increases long-term cardiopulmonary and neurodevelopmental morbidities of preterm infants. Pulmonary hypertension (PH) is a common morbidity of BPD. Importantly, the presence of PH increases both the short- and long-term morbidities and mortality in BPD infants. Further, there are no curative therapies for this complex disease. Besides providing an overview of the pathogenesis and diagnosis of PH associated with BPD, we have attempted to comprehensively review and summarize the current literature on the interventions to prevent and/or mitigate BPD and PH in preclinical studies. Our goal was to provide insight into the therapies that have a high translational potential to meaningfully manage BPD patients with PH.

Utility of echocardiography in predicting mortality in infants with severe bronchopulmonary dysplasia

OBJECTIVE

To determine the relationship between interventricular septal position (SP) and right ventricular systolic pressure (RVSP) and mortality in infants with severe BPD (sBPD).

STUDY DESIGN

Infants with sBPD in the Children's Hospitals Neonatal Database who had echocardiograms 34-44 weeks' postmenstrual age (PMA) were included. SP and RVSP were categorized normal, abnormal (flattened/bowed SP or RVSP > 40 mmHg) or missing.

RESULTS

Of 1157 infants, 115 infants (10%) died. Abnormal SP or RVSP increased mortality (SP 19% vs. 8% normal/missing, RVSP 20% vs. 9% normal/missing, both p < 0.01) in unadjusted and multivariable models, adjusted for significant covariates (SP OR 1.9, 95% CI 1.2-3.0; RVSP OR 2.2, 95% CI 1.1-4.7). Abnormal parameters had high specificity (SP 82%; RVSP 94%), and negative predictive value (SP 94%, NPV 91%) for mortality.

CONCLUSIONS

Abnormal SP or RVSP is independently associated with mortality in sBPD infants. Negative predictive values distinguish infants most likely to survive.

Dual-specificity phosphatase (DUSP) genetic variants predict pulmonary hypertension in patients with bronchopulmonary dysplasia

BACKGROUND

Pulmonary hypertension (PH) in patients with bronchopulmonary dysplasia (BPD) results from vasoconstriction and/or vascular remodeling, which can be regulated by mitogen-activated protein kinases (MAPKs). MAPKs are deactivated by dual-specificity phosphatases (DUSPs). We hypothesized that single-nucleotide polymorphisms (SNPs) in DUSP genes could be used to predict PH in BPD.

METHODS

Preterm infants diagnosed with BPD (n = 188) were studied. PH was defined by echocardiographic criteria. Genomic DNA isolated from patient blood samples was analyzed for 31 SNPs in DUSP genes. Clinical characteristics and minor allele frequencies were compared between BPD-PH (cases) and BPD-without PH (control) groups. Biomarker models to predict PH in BPD using clinical and SNP data were tested by calculations of area under the ROC curve.

RESULTS

In our BPD cohort, 32% (n = 61) had PH. Of the DUSP SNPs evaluated, DUSP1 SNP rs322351 was less common, and DUSP5 SNPs rs1042606 and rs3793892 were more common in cases than in controls. The best fit biomarker model combines clinical and DUSP genetic data with an area under the ROC curve of 0.76.

CONCLUSION

We identified three DUSP SNPs as potential BPD-PH biomarkers. Combining clinical and DUSP genetic data yields the most robust predictor for PH in BPD.

Initial Experience With Patent Ductus Arteriosus Ligation in Pre-term Infants With Bidirectional Shunt Pattern

Background: Patent ductus arteriosus (PDA) with a bidirectional shunt reflects critical clinical conditions. The operability of PDA with a bidirectional shunt in pre-term infants is still not clearly clarified. This study aimed to investigate the feasibility and the outcomes of PDA ligation in pre-term infants with a bidirectional shunt PDA. Methods: All pre-term infants receiving PDA ligation between 2013 and 2019 were enrolled in this prospective study. Patients were allocated into two groups based on the shunting direction of PDA, which were the left-to-right group (group A) and the bidirectional group (group B). Clinical characteristics and pre-op comorbidities were analyzed. Intraoperative complications, post-op neurological sequelae, necrotizing enterocolitis, survival, and mortality were compared between these two groups. Results: Thirty-seven pre-term infants were enrolled (18 in group A, 19 in group B). The mean post-menstrual age at PDA surgery was 32.0 ± 1.3 and 32.8 ± 1.5 weeks, respectively. Before surgery, 44.4 and 89.5% (group A vs. B) of the patients were using invasive mechanical ventilator (p < 0.01). The requirement of high-frequency oscillatory ventilatory support was significantly higher in group B. PDA rupture-related bleeding during exposing PDA or ligating PDA occurred in four infants, and all were all in group B, including one with delayed hemothorax. Early surgical mortality within 30 days of surgery was higher in group B (0 vs. 21.1%, p < 0.05), but only one death could be attributed to the surgery, which was caused by a pain-induced pulmonary hypertension crisis. The 5-year survival was 100% in group A, and 73.7% in group B (p < 0.05). Conclusion: We did not recommend routine PDA ligation in pre-term infants with a bidirectional shunt. However, a bidirectional shunt should not be an absolute contraindication if they fulfill indications of PDA closure. Unexpected intraoperative PDA rupture and delayed hemothorax in a bidirectional shunt PDA should be carefully monitored. Aggressive post-op pain control is also warranted to avoid pulmonary hypertension crisis. The post-op early mortality rate was higher in the bidirectional group, which could be inherent to their poor pre-operative lung condition. Only one death was directly related to the surgery.

Pulmonary Hypertension Associated with Bronchopulmonary Dysplasia: A Review

Early pulmonary vascular disease (PVD) and established pulmonary hypertension (PH) are common associations of bronchopulmonary dysplasia (BPD). Diagnosis of PH is often made by echocardiography because of technical and logistic difficulties with the neonatal population. Optimization of respiratory support is the focus of treatment, however, medical therapies are being used with increased frequency. The prognosis for PH associated with BPD (PH-BPD) is tied to the child's respiratory status. PH is associated with increased risk of death in this population, so active screening and treatment is recommended to minimize morbidity and mortality. In this review, we discuss the pathophysiology of PH in infants with BPD, evaluate the current understanding of screening, diagnosis, and follow-up evaluation; describe comorbid conditions; and provide a framework for targeted physiology-based management strategies.

Role of HIF-1α-miR30a-Snai1 Axis in Neonatal Hyperoxic Lung Injury

Bronchopulmonary dysplasia (BPD) is characterized by a severe impairment in lung alveolarization and vascular development. We have previously shown that pulmonary angiogenesis is preserved in hyperoxia-exposed female mice accompanied by increased miR-30a expression, which is a proangiogenic miRNA. Also, miR-30a expression is decreased in human BPD. HIF-1α plays an essential role in postnatal lung development, especially in recovery from hyperoxic injury. Snai1 activation promotes pathological fibrosis through many mechanisms including Endo-MT, which may in turn adversely impact lung vascular development. Our objective was to test the hypothesis that higher miR-30a expression through HIF-1α decreases Snai1 expression in females and attenuates injury in the developing lung. Neonatal male and female mice (C57BL/6) were exposed to hyperoxia (P1-5, 0.95 FiO₂) and euthanized on P21. Neonatal human pulmonary microvascular endothelial cells (HPMECs; 18-24-week gestation donors; 3/group either sex) were subjected to hyperoxia (95% O₂ and 5% CO₂) or normoxia (air and 5% CO₂) up to 72 h. Snai1 expression was measured in HPMECs in vitro and in neonatal mouse lungs in vivo. Also, Snai1 expression was measured in HPMECs after miR-30a mimic and miR-30a inhibitor treatment. To further establish the potential regulation of miR-30a by Hif-1α, miR-30a expression after Hif-1α inhibition was measured in HPMECs. In vivo, Snai1 expression was decreased in neonatal female lungs compared to males at P7. Increased Snai1 expression was seen in male HPMECs upon exposure to hyperoxia in vitro. Treatment with the miR-30a mimic decreased Snai1 expression in HPMECs, while miR-30a inhibition significantly increased Snai1 expression in HPMECs. siRNA-mediated loss of Hif-1α expression in HPMECs decreased miR-30a expression. Hif-1α may lead to differential sex-specific miR-30a expression and may contribute to protection from hyperoxic lung injury in female neonatal mice through decreased Snai1 expression.

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.

Advances in treating bronchopulmonary dysplasia

Introduction: Bronchopulmonary dysplasia (BPD) is a common long-term adverse complication of very premature delivery. Affected infants can suffer chronic respiratory morbidities including lung function abnormalities and reduced exercise capacity even as young adults. Many studies have investigated possible preventative strategies; however, it is equally important to identify optimum management strategies for infants with evolving or established BPD. Areas covered: Respiratory support modalities and established and novel pharmacological treatments. Expert opinion: Respiratory support modalities including proportional assist ventilation and neurally adjusted ventilatory assist are associated with short term improvements in oxygenation indices. Such modalities need to be investigated in appropriate RCTs. Many pharmacological treatments are routinely used with a limited evidence base, for example diuretics. Stem cell therapies in small case series are associated with promising results. More research is required before it is possible to determine if such therapies should be investigated in large RCTs with long-term outcomes.

Clinical and echocardiography predictors of response to inhaled nitric oxide in hypoxic preterm neonates

AIM

To evaluate the clinical and echocardiography modulators of treatment response in hypoxemic preterm infants exposed to inhaled nitric oxide (iNO).

METHODS

In this multicentre retrospective study, clinical parameters, including oxygenation, ventilation and haemodynamics, were collected for preterm infants <36 weeks gestation before and 2 h after initiation of iNO for acute hypoxemia. Comprehensive echocardiography, performed near the time iNO initiation, was analysed by experts blind to the clinical course. Multiple logistic regression analysis was used to identify factors associated with iNO response as defined by a reduction in the fraction of inspired oxygen by >0.20.

RESULTS

A total of 213 infants met eligibility criteria, of which 73 had echocardiography data available and formed the study cohort. Response to iNO was demonstrated in 56% of patients. Younger post-natal age (odds ratio (OR) 0.94; 95% confidence interval (CI) 0.89, 0.99) and the presence of pulmonary hypertension (PH) (OR 4.47; 95% CI 1.23-11.9) were independently predictive of iNO response regardless of gestational age. Among neonates <72 h old with documented PH, iNO response was seen in 82%. The onset of a new diagnosis of severe (grade III/IV) intraventricular haemorrhage (IVH) after iNO treatment was seen in 6 of 40 patients <28 weeks' gestational age, with a greater frequency in responders (32 vs. 0%, P = 0.02).

CONCLUSIONS

Positive response to iNO is greatest in the first 3 days of life and in patients with echo-confirmed PH, independent of gestational age. The association between critical illness, iNO administration and IVH in extremely premature infants may merit prospective delineation.

Hyperoxia-induced lung structure-function relation, vessel rarefaction, and cardiac hypertrophy in an infant rat model

BACKGROUND

Hyperoxia-induced bronchopulmonary dysplasia (BPD) models are essential for better understanding and impacting on long-term pulmonary, cardiovascular, and neurological sequelae of this chronic disease. Only few experimental studies have systematically compared structural alterations with lung function measurements.

METHODS

In three separate and consecutive series, Sprague-Dawley infant rats were exposed from day of life (DOL) 1 to 19 to either room air (0.21; controls) or to fractions of inspired oxygen (FiO2) of 0.6, 0.8, and 1.0. Our primary outcome parameters were histopathologic analyses of heart, lungs, and respiratory system mechanics, assessed via image analysis tools and the forced oscillation technique, respectively.

RESULTS

Exposure to FiO2 of 0.8 and 1.0 resulted in significantly lower body weights and elevated coefficients of lung tissue damping (G) and elastance (H) when compared with controls. Hysteresivity (η) was lower due to a more pronounced increase of H when compared with G. A positive structure-function relation was demonstrated between H and the lung parenchymal content of α-smooth muscle actin (α-SMA) under hyperoxic conditions. Moreover, histology and morphometric analyses revealed alveolar simplification, fewer pulmonary arterioles, increased α-SMA content in pulmonary vessels, and right heart hypertrophy following hyperoxia. Also, in comparison to controls, hyperoxia resulted in significantly lower plasma levels of vascular endothelial growth factor (VEGF). Lastly, rats in hyperoxia showed hyperactive and a more explorative behaviour.

CONCLUSIONS

Our in vivo infant rat model mimics clinical key features of BPD. To the best of our knowledge, this is the first BPD rat model demonstrating an association between lung structure and function. Moreover, we provide additional evidence that infant rats subjected to hyperoxia develop rarefaction of pulmonary vessels, augmented vascular α-SMA, and adaptive cardiac hypertrophy. Thus, our model provides a clinically relevant tool to further investigate diseases related to O2 toxicity and to evaluate novel pharmacological treatment strategies.

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.

Pulmonary interstitial glycogenosis: Diagnostic evaluation and clinical course

OBJECTIVES

We sought to describe the phenotype for patients with P.I.G. including presentation, evaluation, cardiac co-morbidities, high resolution computed tomography findings, and outcomes.

METHODS

With institutional review board approval, we performed a retrospective review of patients with biopsy-proven P.I.G. Biopsies, high resolution chest computed tomography, and cardiac evaluations were reviewed and characterized by experts in each field.

RESULTS

Sixty-two percent of the patients were male. The median gestational age was 37 weeks (range 27-40). The median age at biopsy was 1.6 months (range 0.3-6 months). Structural heart disease was present in 63% of patients. Pulmonary hypertension (diagnosed by echocardiogram and/or cardiac catheterization) was noted in 38% of patients. Alveolar simplification was present in 79% of patients. Fifty percent of available biopsies revealed patchy disease. An increase in age at biopsy was associated with patchy (vs diffuse) disease. Ninety-two percent of patients were treated with systemic corticosteroids. Median age at last follow-up was 1234 days with a range of 37 days to 15 years. At the time of last follow-up, 12 patients were off all support, eight were on supplemental oxygen, two were mechanically ventilated, one underwent lung transplantation, and one died. CT findings commonly included ground glass opacities (86%) and cystic change (50%).

CONCLUSIONS

The P.I.G. phenotype has not been comprehensively described, and poor recognition and misconceptions about P.I.G. persist. P.I.G. is a disease that presents in early infancy, requires significant medical intervention, and frequently is seen in association with alveolar simplification and/or cardiovascular disease. CT findings include ground glass opacities and cysts. Patients should be monitored for pulmonary hypertension. Without life-threatening comorbidities, many patients do well over time, although respiratory symptoms may persist into adolescence.

Using clinical and genetic data to predict pulmonary hypertension in bronchopulmonary dysplasia

AIM

Pulmonary hypertension significantly increases morbidity and mortality in infants with bronchopulmonary dysplasia. The frequency of single nucleotide polymorphisms in arginase-1 (ARG1 rs2781666) and dimethylarginine dimethylaminohydrolase-1 (DDAH1 rs480414) genes has been found to differ in a cohort of bronchopulmonary dysplasia patients with pulmonary hypertension (cases) and without pulmonary hypertension (controls). Therefore, we tested the hypothesis that combining these genotypes with phenotypic data would better predict pulmonary hypertension in bronchopulmonary dysplasia patients.

METHODS

Bronchopulmonary dysplasia patients (n = 79) born at <35 weeks gestation were studied. Pulmonary hypertension was diagnosed by echocardiographic criteria (n = 20). ROC curves to predict pulmonary hypertension in bronchopulmonary dysplasia were generated from genotype and/or clinical data.

RESULTS

Cases were born at an earlier gestation and weighed less at birth than did controls. ROC curves for rs2781666 had an AUC of 0.61, while rs480414 had an AUC of 0.66. Together, the AUC was 0.70. When clinical data were added to the genetic model, AUC was 0.73.

CONCLUSION

These findings demonstrate that ROC predictive modelling of pulmonary hypertension in bronchopulmonary dysplasia improves with inclusion of both genotypic and phenotypic data. Further refinement of these types of models could facilitate the implementation of precision medicine approaches to pulmonary hypertension in bronchopulmonary dysplasia.

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.

Efficacy of inhaled nitric oxide in neonates with hypoxic respiratory failure and pulmonary hypertension: the Japanese experience

OBJECTIVE

To analyze data from a registry of Japanese neonates with hypoxic respiratory failure associated with pulmonary hypertension (PH) to compare the effectiveness of inhaled nitric oxide (iNO) in neonates born <34 weeks vs. ≥34 weeks gestational age (GA).

MATERIALS AND METHODS

iNO was administered according to approved Japanese product labeling. Study data were collected before iNO administration and at predefined intervals until discontinuation.

RESULTS

A total of 1,114 neonates were included (n=431, <34 weeks GA; n=675, ≥34 weeks GA; n=8, missing age data). Mean decrease from baseline oxygenation index (OI) was similar in both age groups. OI reduction was more pronounced in the <34 weeks subgroups with baseline OI ≥25. Survival rates were similar in the <34 weeks GA and ≥34 weeks GA groups stratified by baseline OI (OI<15, 89% vs. 93%; 15≤OI<25, 85% vs. 91%; 25≤OI≤40, 73% vs. 79%; OI>40, 64% vs. 66%).

CONCLUSION

iNO improved oxygenation in preterm neonates as effectively as in late preterm and term neonates, without negative impact on survival. If clinically significant PH is present, as measured by pulse oximetry or echocardiography, a therapeutic trial of iNO might be indicated for preterm neonates.

N-terminal-probrain natriuretic peptide as a biomarker of moderate to severe bronchopulmonary dysplasia in preterm infants: A prospective observational study

OBJECTIVE

N-terminal-probrain natriuretic peptide (NT-proBNP) is a marker of hemodynamically significant patent ductus arteriosus (HsPDA) in preterm infants. In this study, we assessed whether NT-proBNP levels could predict the risk of moderate to severe bronchopulmonary dysplasia (BPD) and/or death.

METHODS

This was an observational prospective study of preterm infants with GA ≤32 weeks. Infants who died within the first 48 h or who had major congenital malformations or incomplete information were excluded. NT-proBNP was determined at 48-96 h of life and at 5-10 days of life. The predictive capacity of NT-proBNP for the combined outcome of BPD and/or death was evaluated using receiver operator characteristic (ROC) curves and multivariate regression.

RESULTS

Of the 125 eligible patients, 110 completed the analysis. Twenty-eight developed BPD (n = 15) and/or died (n = 13). Infants who developed BPD and/or died had higher NT-proBNP levels ​​at 48-96 h (26,848 ng/L, interquartile range [IQR] 7818-60,684 vs 3008 ng/L, IQR 1425-9876) and at 5-10 days (8849 ng/L, IQR 3796-19,526 vs 1427 ng/L, IQR 907-2889). The NT-proBNP levels at 5-10 days, but not at 48-96 h, were independently associated with BPD and/or death after adjustments for HsPDA and other confounders (OR = 3.36; 95%CI: 1.52-7.4, P = 0.006). For the prediction of this result, a cutoff of 3348 ng/L had a sensitivity and specificity of 82% and 83%, respectively (area under the curve [AUC] = 0.87; 95%CI: 0.79-0.95).

CONCLUSION

The NT-proBNP levels at 5-10 days of life may identify preterm infants with an HsPDA who are at high risk of BPD or death and may be useful for individualized preventive and therapeutic strategies.

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.

Is the fibroblast growth factor signaling pathway a victim of receptor tyrosine kinase inhibition in pulmonary parenchymal and vascular remodeling?

Idiopathic pulmonary arterial hypertension (IPAH), pulmonary hypertension (PH) due to lung disease and/or hypoxia and idiopathic pulmonary fibrosis (IPF) are increasingly recognized as important contributors to mortality and morbidity worldwide. Among others, the current treatment paradigm considers broad inhibition of receptor tyrosine kinases, a strategy that likely leads to collateral inhibition of signaling pathways that are critical for lung repair and regeneration. Fibroblast growth factor 7 (FGF7) and FGF10 signaling in the lung through FGF receptor 2 (FGFR2) are involved in epithelial cell protection and renewal, and mutations in their corresponding genes in humans are linked to increased susceptibility to lung pathologies, such as chronic obstructive pulmonary disease and bronchopulmonary dysplasia. In this report, we present data demonstrating significant upregulation of FGF7, FGF10, and FGFR2 in IPF and IPAH lungs compared with donor lungs. These ligands and their cognate receptor converged on the remodeled parenchyma and vasculature of IPF and IPAH lungs. Interestingly, the expression levels of FGFR1, which has been previously shown to play a pathological role in PH development, were not significantly changed in either disease state. Intriguingly, the expression levels of FGF7, FGF10, and FGFR2 were lower in IPF lung regions undergoing active remodeling, and inversely correlated with IPAH severity, indicating that increased expression might reflect lung repair rather than lung pathology, and warranting further research on the precise role of FGF signaling in pulmonary parenchymal and vascular remodeling.

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.