A consensus approach to the classification of pediatric pulmonary hypertensive vascular disease: Report from the PVRI Pediatric Taskforce, Panama 2011

Pulmonary hypertension in bronchopulmonary dysplasia: clinical findings, cardiovascular anomalies and outcomes

OBJECTIVE

Pulmonary hypertension (PH) worsens the prognosis of bronchopulmonary dysplasia (BPD). The following items have not been fully established for PH in BPD: clinical characterization, incidence of cardiovascular anomalies (CVAs), response to PH treatment, and outcome.

STUDY DESIGN

A review of clinical records, computed tomography (CT) images and catheterization data of 36 patients with PH-BPD referred to our PH Unit (March 2006 to December 2011) was performed. Twenty-nine patients without major congenital heart defects and with complete follow-up data were included.

RESULTS

The diagnosis of PH was made at a median age of 4.5 months (IQR 2.4-7.8), with an echocardiography estimated median right ventricular pressure/systemic pressure ratio of 70% (IQR 60-80%). CT scanning was performed in 21 patients and catheterization in 14 patients. CVAs were found in 19 patients (65.5%): aortopulmonary collaterals (n = 9), pulmonary vein stenosis (n = 7), ASD (n = 4), and PDA (n = 9). Hemodynamic data: PVRI 4.3 UW m(2) (2.7-7); PVRI/SVRI 0.44 (0.32-0.8); and transpulmonary gradient 28 mmHg (19-40). At a median follow-up of 35 months (IQR 21-91), 6 patients had undergone shunts closure, 22 received specific PH drugs, 3 spontaneously improved of their PH, and 8 (26%) had died.

CONCLUSION

PH in BPD is not always a transient condition; it can be diagnosed at later stages and can have a protracted course. The incidence of associated CVAs is high. Prompt diagnosis, detection, and treatment of CVAs, and specific drug therapy can improve the outcome in these patients, although the mortality rate remains high.

Looking beyond PPHN: the unmet challenge of chronic progressive pulmonary hypertension in the newborn

Abstract Infants with forms of pulmonary hypertension (PH) that persist or develop beyond the first week of life are an understudied group of patients with up to 40%-60% mortality. The clinical management of the progressive PH that develops in these infants is challenging because of the nonspecific signs and symptoms of clinical presentation, the limited diagnostic sensitivity of standard echocardiographic techniques, and the lack of proven therapies. The signaling mechanisms that underlie the structural and functional abnormalities in the pulmonary circulation of these infants are not yet clear. The ability to improve outcomes for these patients awaits technological advances to improve diagnostic capabilities and therapeutic discoveries made in basic science laboratories that can be tested in randomized clinical trials.

Diagnosis and treatment of pulmonary hypertension in infancy

Normal pulmonary vascular development in infancy requires maintenance of low pulmonary vascular resistance after birth, and is necessary for normal lung function and growth. The developing lung is subject to multiple genetic, pathological and/or environmental influences that can adversely affect lung adaptation, development, and growth, leading to pulmonary hypertension. New classifications of pulmonary hypertension are beginning to account for these diverse phenotypes, and or pulmonary hypertension in infants due to PPHN, congenital diaphragmatic hernia, and bronchopulmonary dysplasia (BPD). The most effective pharmacotherapeutic strategies for infants with PPHN are directed at selective reduction of PVR, and take advantage of a rapidly advancing understanding of the altered signaling pathways in the remodeled vasculature.

Current challenges in pediatric pulmonary hypertension

Pulmonary arterial hypertension (PAH) in the pediatric population is associated with a variety of underlying diseases and causes, significantly morbidity and mortality. In the majority of patients, PAH in children is idiopathic or associated with congenital heart disease (CHD), with pulmonary hypertension (PH) associated with connective tissue disease, a rare cause in children. Classification of pediatric PH has generally followed the WHO classification, but recognition of the importance of fetal origins of PH and developmental abnormalities have led to the formation of a new pediatric-specific classification. Incidence data from the Netherlands has revealed an annual incidence and point prevalence of 0.7 and 4.4 for idiopathic PAH and 2.2 and 15.6 for associated pulmonary arterial hypertension-CHD cases per million children. Although the treatment with new selective pulmonary vasodilators offers hemodynamic and functional improvement in pediatric populations, the treatments in children largely depend on results from evidence-based adult studies and experience of clinicians treating children. A recent randomized clinical trial of sildenafil and its long-term extension has led to disparate recommendations in the United States and Europe.

Clinical trials in neonates and children: Report of the pulmonary hypertension academic research consortium pediatric advisory committee

Drug trials in neonates and children with pulmonary hypertensive vascular disease pose unique but not insurmountable challenges. Childhood is defined by growth and development. Both may influence disease and outcomes of drug trials. The developing pulmonary vascular bed and airways may be subjected to maldevelopment, maladaptation, growth arrest, or dysregulation that influence the disease phenotype. Drug therapy is influenced by developmental changes in renal and hepatic blood flow, as well as in metabolic systems such as cytochrome P450. Drugs may affect children differently from adults, with different clearance, therapeutic levels and toxicities. Toxicity may not be manifested until the child reaches physical, endocrine and neurodevelopmental maturity. Adverse effects may be revealed in the next generation, should the development of ova or spermatozoa be affected. Consideration of safe, age-appropriate tablets and liquid formulations is an obvious but often neglected prerequisite to any pediatric drug trial. In designing a clinical trial, precise phenotyping and genotyping of disease is required to ensure appropriate and accurate inclusion and exclusion criteria. We need to explore physiologically based pharmacokinetic modeling and simulations together with statistical techniques to reduce sample size requirements. Clinical endpoints such as exercise capacity, using traditional classifications and testing cannot be applied routinely to children. Many lack the necessary neurodevelopmental skills and equipment may not be appropriate for use in children. Selection of endpoints appropriate to encompass the developmental spectrum from neonate to adolescent is particularly challenging. One possible solution is the development of composite outcome scores that include age and a developmentally specific functional classification, growth and development scores, exercise data, biomarkers and hemodynamics with repeated evaluation throughout the period of growth and development. In addition, although potentially costly, we recommend long-term continuation of blinded dose ranging after completion of the short-term, double-blind, placebo-controlled trial for side-effect surveillance, which should include neurodevelopmental and peripubertal monitoring. The search for robust evidence to guide safe therapy of children and neonates with pulmonary hypertensive vascular disease is a crucial and necessary goal.

Frontiers in pulmonary hypertension in infants and children with bronchopulmonary dysplasia

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

Pharmacotherapy for pulmonary hypertension

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

Mesenchymal stem cell-mediated reversal of bronchopulmonary dysplasia and associated pulmonary hypertension

Clinical trials have failed to demonstrate an effective preventative or therapeutic strategy for bronchopulmonary dysplasia (BPD), a multifactorial chronic lung disease in preterm infants frequently complicated by pulmonary hypertension (PH). Mesenchymal stem cells (MSCs) and their secreted components have been shown to prevent BPD and pulmonary fibrosis in rodent models. We hypothesized that treatment with conditioned media (CM) from cultured mouse bone marrow-derived MSCs could reverse hyperoxia-induced BPD and PH. Newborn mice were exposed to hyperoxia (FiO₂=0.75) for two weeks, were then treated with one intravenous dose of CM from either MSCs or primary mouse lung fibroblasts (MLFs), and placed in room air for two to four weeks. Histological analysis of lungs harvested at four weeks of age was performed to determine the degree of alveolar injury, blood vessel number, and vascular remodeling. At age six weeks, pulmonary artery pressure (PA acceleration time) and right ventricular hypertrophy (RVH; RV wall thickness) were assessed by echocardiography, and pulmonary function tests were conducted. When compared to MLF-CM, a single dose of MSC-CM-treatment (1) reversed the hyperoxia-induced parenchymal fibrosis and peripheral PA devascularization (pruning), (2) partially reversed alveolar injury, (3) normalized lung function (airway resistance, dynamic lung compliance), (4) fully reversed the moderate PH and RVH, and (5) attenuated peripheral PA muscularization associated with hyperoxia-induced BPD. Reversal of key features of hyperoxia-induced BPD and its long-term adverse effects on lung function can be achieved by a single intravenous dose of MSC-CM, thereby pointing toward a new therapeutic intervention for chronic lung diseases.

Modulation of pulmonary vascular resistance as a target for therapeutic interventions in Fontan patients: focus on phosphodiesterase inhibitors

Despite advancements in surgical techniques over the past 20 years, Fontan patients have decreased exercise capacity as a consequence of an inherent inability to adequately increase cardiac output during exercise. They are also affected by several complications that are associated with considerable morbidity and mortality. As the systemic and pulmonary circulations are placed in series without a subpulmonary ventricle propelling blood through the pulmonary vasculature, the systemic venous pressure and the respiratory mechanics are the only forces driving pulmonary blood flow. In Fontan circulation, pulmonary vascular resistance is the single most important factor involved in the limitation of cardiac output and treatments able to decrease pulmonary vascular resistance might conversely improve cardiac output and exercise capacity. In this article we discuss the initial experience with the use of sildenafil in Fontan patients and we discuss the possible mechanisms through which sildenafil might positively act in Fontan circulation.

Advances in pediatric pulmonary arterial hypertension

PURPOSE OF REVIEW

Pulmonary arterial hypertension (PAH) is an important cause of morbidity and mortality in children. Approved medications for the treatment of adult PAH have been used to treat children, but evidence-based treatment algorithms for children are lacking.

RECENT FINDINGS

Pediatric PAH registries have begun to define the incidence and prevalence of idiopathic PAH and PAH associated with congenital heart disease. A pediatric-specific classification of pulmonary hypertensive vascular disease has been proposed. Furthermore, the first randomized placebo-controlled trial of type-5 phosphodiesterase therapy in treatment-naïve children with PAH has been completed and reported. This trial highlights the importance of the difficulties of performing clinical trials in children with targeted PAH therapy as well as the importance of long-term follow-up of adverse events.

SUMMARY

Classification, clinical trials, and therapy for children with PAH must take into account the unique aspects of PAH in children.

Improving outcomes for pulmonary vascular disease

Recognizing the importance of improving lung health through lung disease research, the National Heart, Lung, and Blood Institute (NHLBI) convened a workshop of multidisciplinary experts for the following purpose: (1) to review the current scientific knowledge underlying the basis for treatment of adults and children with pulmonary vascular diseases (PVDs); (2) to identify gaps, barriers, and emerging scientific opportunities in translational PVD research and the means to capitalize on these opportunities; (3) to prioritize new research directions that would be expected to affect the clinical course of PVDs; and (4) to make recommendations to the NHLBI on how to fill identified gaps in adult and pediatric PVD clinical research. Workshop participants reviewed experiences from previous PVD clinical trials and ongoing clinical research networks with other lung disorders, including acute respiratory distress syndrome, chronic obstructive lung disease, and idiopathic pulmonary fibrosis, as well. Bioinformatics experts discussed strategies for applying cutting-edge health information technology to clinical studies. Participants in the workshop considered approaches in the following broad concept areas: (1) improved phenotyping to identify potential subjects for appropriate PVD clinical studies; (2) identification of potential new end points for assessing key outcomes and developing better-designed PVD clinical trials; and (3) the establishment of priorities for specific clinical research needed to advance care of patients with various subsets of PVDs from childhood through adulthood. This report provides a summary of the objectives and recommendations to the NHLBI concentrating on clinical research efforts that are needed to better diagnose and treat PVDs.