Addressing the challenges of phenotyping pediatric pulmonary vascular disease

ATS core curriculum 2023. Pediatric pulmonary medicine: Respiratory disorders in infants

The American Thoracic Society Core Curriculum updates clinicians annually in pediatric pulmonary disease. This is a summary of the Pediatric Pulmonary Medicine Core Curriculum presented at the 2023 American Thoracic Society International Conference. The respiratory disorders of infancy discussed in this year's review include: the care of the patient with bronchopulmonary dysplasia in the neonatal intensive care unit, clinical phenotypes and comorbidities; diffuse lung disease; pulmonary hypertension; central and obstructive sleep apnea. The care of infants with respiratory disorders often poses significant challenges to the general pediatric pulmonologist, sleep clinician, and neonatologist. This review aims to highlight the most clinically relevant aspects of the evaluation, management, and outcomes of infants with these key respiratory disorders, while emphasizing the importance of multidisciplinary care. Furthermore, this document summarizes essential aspects of genetic testing, novel imaging and treatment modalities, and includes multiple resources for clinical practice.

Asphyxia, Therapeutic Hypothermia, and Pulmonary Hypertension

Neonates with a perinatal hypoxic insult and subsequent neonatal encephalopathy are at risk of acute pulmonary hypertension (aPH) in the transitional period. The phenotypic contributors to aPH following perinatal asphyxia include a combination of hypoxic vasoconstriction of the pulmonary vascular bed, right heart dysfunction, and left heart dysfunction. Therapeutic hypothermia is the standard of care for neonates with moderate-to-severe hypoxic ischemic encephalopathy. This review summarizes the underlying risk factors, causes of aPH in neonates with perinatal asphyxia, discusses the unique phenotypical contributors to disease, and explores the impact of the initial insult and subsequent therapeutic hypothermia on aPH.

Exercise and hypoxia unmask pulmonary vascular disease and right ventricular dysfunction in a 10-12 week old swine model of neonatal oxidative injury

Abstract

Prematurely born young adults who experienced neonatal oxidative injury (NOI) of the lungs have increased incidence of cardiovascular disease. Here, we investigated the long‐term effects of NOI on cardiopulmonary function in piglets at the age of 10–12 weeks. To induce NOI, term‐born piglets (1.81 ± 0.06 kg) were exposed to hypoxia (10–12% FiO2), within 2 days after birth, and maintained for 4 weeks or until symptoms of heart failure developed (range 16–28 days), while SHAM piglets were normoxia raised. Following recovery (>5 weeks), NOI piglets were surgically instrumented to measure haemodynamics during hypoxic challenge testing (HCT) and exercise with modulation of the nitric‐oxide system. During exercise, NOI piglets showed a normal increase in cardiac index, but an exaggerated increase in pulmonary artery pressure and a blunted increase in left atrial pressure – suggesting left atrial under‐filling – consistent with an elevated pulmonary vascular resistance (PVR), which correlated with the duration of hypoxia exposure. Moreover, hypoxia duration correlated inversely with stroke volume (SV) during exercise. Nitric oxide synthase inhibition and HCT resulted in an exaggerated increase in PVR, while the PVR reduction by phosphodiesterase‐5 inhibition was enhanced in NOI compared to SHAM piglets. Finally, within the NOI piglet group, prolonged duration of hypoxia was associated with a better maintenance of SV during HCT, likely due to the increase in RV mass. In conclusion, duration of neonatal hypoxia appears an important determinant of alterations in cardiopulmonary function that persist further into life. These changes encompass both pulmonary vascular and cardiac responses to hypoxia and exercise.

Key points

Children who suffered from neonatal oxidative injury, such as very preterm born infants, have increased risk of cardiopulmonary disease later in life.

Risk stratification requires knowledge of the mechanistic underpinning and the time course of progression into cardiopulmonary disease.

Exercise and hypoxic challenge testing showed that 10‐ to 12‐week‐old swine that previously experienced neonatal oxidative injury had increased pulmonary vascular resistance and nitric oxide dependency.

Duration of neonatal oxidative injury was a determinant of structural and functional cardiopulmonary remodelling later in life.

Remodelling of the right ventricle, as a result of prolonged neonatal oxidative injury, resulted in worse performance during exercise, but enabled better performance during the hypoxic challenge test.

Increased nitric oxide dependency together with age‐ or comorbidity‐related endothelial dysfunction may contribute to predisposition to pulmonary hypertension later in life.

Bronchopulmonary dysplasia from chest radiographs to magnetic resonance imaging and computed tomography: adding value

Bronchopulmonary dysplasia (BPD) is a common long-term complication of preterm birth. The chest radiograph appearance and survivability have evolved since the first description of BPD in 1967 because of improved ventilation and clinical strategies and the introduction of surfactant in the early 1990s. Contemporary imaging care is evolving with the recognition that comorbidities of tracheobronchomalacia and pulmonary hypertension have a great influence on outcomes and can be noninvasively evaluated with CT and MRI techniques, which provide a detailed evaluation of the lungs, trachea and to a lesser degree the heart. However, echocardiography remains the primary modality to evaluate and screen for pulmonary hypertension. This review is intended to highlight the important findings that chest radiograph, CT and MRI can contribute to precision diagnosis, phenotyping and prognosis resulting in optimal management and therapeutics.

Cardiovascular impact and sequelae of bronchopulmonary dysplasia

The development, growth, and function of the cardiac, pulmonary, and vascular systems are closely intertwined during both fetal and postnatal life. In utero, placental, environmental, and genetic insults may contribute to abnormal pulmonary alveolarization and vascularization that increase susceptibility to the development of bronchopulmonary dysplasia (BPD) in preterm infants. However, the shared milieu of stressors may also contribute to abnormal cardiac or vascular development in the fetus and neonate, leading to the potential for cardiovascular dysfunction. Further, cardiac or pulmonary maladaptation can potentiate dysfunction in the other organ, amplify the risk for BPD in the neonate, and increase the trajectory for overall neonatal morbidity. Beyond infancy, there is an increased risk for systemic and pulmonary vascular disease including hypertension, as well as potential cardiac dysfunction, particularly within the right ventricle. This review will focus on the cardiovascular antecedents of BPD in the fetus, cardiovascular consequences of preterm birth in the neonate including associations with BPD, and cardiovascular impact of prematurity and BPD throughout the lifespan.

Biomarkers of ageing in New Zealand VLBW young adults and controls

BACKGROUND

There is individual variation in physiological ageing. Former very low birthweight (VLBW; birthweight < 1500 g) young adults may have less satisfactory measurements on some physiological parameters than term controls. We hypothesized that a summation score of physiological biomarkers that change with age would show VLBW adults to have a more advanced physiologic age than controls.

METHODS

VLBW adults (229; 71% survivors of a national VLBW cohort) and term-born controls (100) were clinically assessed at 26-30 years. Ten measured physiological biomarkers were selected and measurements converted to z-scores using normative reference data. Between-group comparisons were tested for statistical significance for individual biomarker z-scores and a summation score.

RESULTS

Nine of 10 biomarkers showed a mean z-score suggestive of older physiological age in the VLBW group versus controls. The observed mean difference in the summation score was highly significant (p < 0.001), representing a mean shift of 0.47 SD in the distribution of test scores for VLBW relative to controls.

CONCLUSIONS

Utilizing a 10-biomarker score, VLBW young adults have a score indicative of poorer physiological functioning than term-born controls. Repeating these measures after an interval could provide insights into the comparative pace of ageing between VLBW and term-born adults.

IMPACT

A summation score of 10 physiological biomarkers that are known to change with age shows that former very low birthweight adults have significantly poorer physiological functioning by the end of their third decade than term-born controls. This result adds to existing literature showing very preterm and very low birthweight young adults often have physiological and metabolic test results that are less satisfactory than those from term controls, despite mostly being in the normal range for age; for instance, higher systolic blood pressure. Although the pace of ageing in later years is yet to be established, the implications of this study are that preventative measures and lifestyle choices that impact on physiological ageing might have even greater importance for very preterm and very low birthweight graduates.

Updates on Management for Acute and Chronic Phenotypes of Neonatal Pulmonary Hypertension

Neonatal pulmonary hypertension is a heterogeneous disease in term and preterm neonates. It is characterized by persistent increase of pulmonary artery pressures after birth (acute) or an increase in pulmonary artery pressures after approximately 4 weeks of age (chronic); both phenotypes result in exposure of the right ventricle to sustained high afterload. In-depth clinical assessment plus echocardiographic measures evaluating pulmonary blood flow, pulmonary vascular resistance, pulmonary capillary wedge pressure, and myocardial contractility are needed to determine the cause and provide individualized targeted therapies. This article summarizes the causes, risk factors, hemodynamic assessment, and management of neonatal pulmonary hypertension.

Variation in the use of pulmonary vasodilators in children and adolescents with pulmonary hypertension: a study using data from the MarketScan® insurance claims database

Despite progress in pharmacotherapy in pediatric pulmonary hypertension, real-world patterns of directed pulmonary hypertension therapy have not been studied in the current era. A retrospective observational study of children (≤18 years) with pulmonary hypertension was performed using data from the MarketScan® Commercial and Medicaid claims databases. Associations between etiology of pulmonary hypertension and pharmaceutical regimen were evaluated, as were the associations between subject social and geographic characteristics (insurance-type, race, and/or census region) and regimen. Annualized costs of single- and multi-class regimens were calculated. In total, 873 subjects were studied, of which 94% received phosphodiesterase-5 inhibitors, 31% endothelin receptor antagonist, 9% prostacyclin analogs, and 7% calcium channel blockers. Monotherapy was used in 72% of subjects. Phosphodiesterase-5 inhibitors monotherapy was the most common regimen (93%). Subjects with idiopathic pulmonary hypertension, congenital heart disease, and unclassified pulmonary hypertension receive more than one agent and were more likely to receive both endothelin receptor antagonist and prostacyclin analogs than other forms of pulmonary hypertension. Compared to recipients of public insurance, subjects with commercial insurance were more likely to receive more intense therapy (p = 0.003), which was confirmed in multivariable analysis (OR: 1.4, p = 0.03). Receipt of commercial insurance was also associated with increased annual costs across all subjects (p < 0.001) and for the most common specific regimens. The majority of children with pulmonary hypertension receive phosphodiesterase monotherapy, followed by phosphodiesterase–endothelin receptor antagonist two drug regimens, and finally the addition of prostacyclin analogs for three-drug therapy. However, even after adjustment for measurable confounders, commercial insurance was associated with higher intensity care and higher costs (even within specific classes of pulmonary vasodilators). The effect of these associations on clinical outcome cannot be discerned from the current data set, but patterns of treatment deserve further attention.

Cardiac Magnetic Resonance Imaging Evaluation of Neonatal Bronchopulmonary Dysplasia-associated Pulmonary Hypertension

Rationale: Patients with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) have increased morbidity and mortality. Noninvasive assessment relies on echocardiograms (echos), which are technically challenging in this population. Improved assessment could augment decisions regarding PH therapies.Objectives: We hypothesized that neonatal cardiac magnetic resonance imaging (MRI) will correlate with BPD severity and predict short-term clinical outcomes, including need for PH therapies for infants with BPD.Methods: A total of 52 infants (31 severe BPD, 9 moderate BPD, and 12 with either mild or no BPD) were imaged between 39 and 47 weeks postmenstrual age on a neonatal-sized, neonatal ICU-sited 1.5-T magnetic resonance (MR) scanner. MR left ventricular eccentricity index (EI), main pulmonary artery-to-aorta (PA/AO) diameter ratio, and pulmonary arterial blood flow were determined. Echos obtained for clinical indications were reviewed. MRI and echo indices were compared with BPD severity and clinical outcomes, including length of stay (LOS), duration of respiratory support, respiratory support at discharge, and PH therapy.Measurements and Main Results: PA/AO ratio increased with BPD severity. Increased PA/AO ratio, MR-EI, and echo-EIs were associated with increased LOS and duration of respiratory support. No correlation was seen between pulmonary arterial blood flow and BPD outcomes. Controlling for gestational age, birth weight, and BPD severity, MR-EI was associated with LOS and duration of respiratory support. Increased PA/AO ratio and MR-EI were associated with PH therapy during hospitalization and at discharge.Conclusions: MRI can provide important image-based measures of cardiac morphology that relate to disease severity and clinical outcomes in neonates with BPD.

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

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

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

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.