Primary pulmonary hypertension in children: clinical characterization and survival

Long-term outcome of children with newly diagnosed pulmonary arterial hypertension: results from the global TOPP registry

BACKGROUND AND AIMS

The Tracking Outcomes and Practice in Pediatric Pulmonary Hypertension (TOPP) registry is a global network established to gain insights into the disease course and long-term outcomes of paediatric pulmonary arterial hypertension (PAH). Previously published cohorts in paediatric PAH are obscured by survival bias due to the inclusion of both prevalent (previously diagnosed) and incident (newly diagnosed) patients. The current study aims to describe long-term outcome and its predictors in paediatric PAH, exclusively of newly diagnosed patients.

METHODS AND RESULTS

Five hundred thirty-one children with confirmed pulmonary hypertension, aged ≥3 months and <18 years, were enrolled in the real-world TOPP registry at 33 centres in 20 countries, from 2008 to 2015. Of these, 242 children with newly diagnosed PAH with at least one follow-up visit were included in the current outcome analyses. During long-term follow-up, 42 (17.4%) children died, 9 (3.7%) underwent lung transplantation, 3 (1.2%) atrial septostomy, and 9 (3.7%) Potts shunt palliation (event rates: 6.2, 1.3, 0.4, and 1.4 events per 100 person-years, respectively). One-, three-, and five-year survival free from adverse outcome was 83.9%, 75.2%, and 71.8%, respectively.Overall, children with open (unrepaired or residual) cardiac shunts had the best survival rates. Younger age, worse World Health Organization functional class, and higher pulmonary vascular resistance index were identified as independent predictors of long-term adverse outcome. Younger age, higher mean right atrial pressure, and lower systemic venous oxygen saturation were specifically identified as independent predictors of early adverse outcome (within 12 months after enrolment).

CONCLUSION

This comprehensive analysis of survival from time of diagnosis in a large exclusive cohort of children newly diagnosed with PAH describes current-era outcome and its predictors.

The Emerging Therapeutic Role of Prostaglandin E2 Signaling in Pulmonary Hypertension

Mild-to-moderate pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD). It is characterized by narrowing and thickening of the pulmonary arteries, resulting in increased pulmonary vascular resistance (PVR) and ultimately leading to right ventricular dysfunction. Pulmonary vascular remodeling in COPD is the main reason for the increase of pulmonary artery pressure (PAP). The pathogenesis of PH in COPD is complex and multifactorial, involving chronic inflammation, hypoxia, and oxidative stress. To date, prostacyclin and its analogues are widely used to prevent PH progression in clinical. These drugs have potent anti-proliferative, anti-inflammatory, and stimulating endothelial regeneration properties, bringing therapeutic benefits to the slowing, stabilization, and even some reversal of vascular remodeling. As another well-known and extensively researched prostaglandins, prostaglandin E2 (PGE2) and its downstream signaling have been found to play an important role in various biological processes. Emerging evidence has revealed that PGE2 and its receptors (i.e., EP1-4) are involved in the regulation of pulmonary vascular homeostasis and remodeling. This review focuses on the research progress of the PGE2 signaling pathway in PH and discusses the possibility of treating PH based on the PGE2 signaling pathway.

Prognostic Value of Change in Cardiac Index After Prostacyclin Initiation in Pediatric Pulmonary Hypertension

Invasive hemodynamic assessment remains the gold standard for the diagnosis of pediatric pulmonary hypertension and for longitudinal assessment of response to therapy. This analysis sought to describe the changes in hemodynamic variables after initiation of prostacyclin therapy and determine which changes bear predictive power of adverse clinical outcomes. A retrospective chart review of established patients at Cincinnati Children's Hospital with pulmonary arterial hypertension (PAH) who required prostacyclin therapy between 2004 and 2018 was performed. The baseline hemodynamic parameters at diagnosis as well as change in those parameters between initial catheterization and post-prostacyclin initiation catheterization were independent variables. Cox proportional hazard regression and recursive partitioning analysis were used to characterize which hemodynamic factors predicted the composite adverse outcome (CAO) defined as death, lung transplantation, or reverse Pott's shunt surgery. During the study period, 29 patients met inclusion criteria in which there were 7 CAOs: 4 deaths, 3 lung transplants, and 2 reverse Pott's shunts. Median time between catheterizations was 86 days and between the initiation of prostacyclin therapy and the second catheterization was 54 days. Cox regression revealed that only baseline pulmonary artery pressure (> 51 mmHg) and a failure to increase cardiac index illustrated statistically significant hazard for occurrence of the CAO (p < 0.01). These criteria significantly dichotomized the population in a Kaplan-Meier analysis into likelihoods of experiencing the CAO. While controlling for other hemodynamic variables, the absence of augmentation of cardiac index after the initiation of prostacyclin therapy is a valuable prognostic indicator of adverse PAH outcomes in pediatrics.

Children and Adolescents with Pulmonary Arterial Hypertension: Baseline and Follow-Up Data from the Polish Registry of Pulmonary Hypertension (BNP-PL)

We present the results from the pediatric arm of the Polish Registry of Pulmonary Hypertension. We prospectively enrolled all pulmonary arterial hypertension (PAH) patients, between the ages of 3 months and 18 years, who had been under the care of each PAH center in Poland between 1 March 2018 and 30 September 2018. The mean prevalence of PAH was 11.6 per million, and the estimated incidence rate was 2.4 per million/year, but it was geographically heterogeneous. Among 80 enrolled children (females, n = 40; 50%), 54 (67.5%) had PAH associated with congenital heart disease (CHD-PAH), 25 (31.25%) had idiopathic PAH (IPAH), and 1 (1.25%) had portopulmonary PAH. At the time of enrolment, 31% of the patients had significant impairment of physical capacity (WHO-FC III). The most frequent comorbidities included shortage of growth (n = 20; 25%), mental retardation (n = 32; 40%), hypothyroidism (n = 19; 23.8%) and Down syndrome (n = 24; 30%). The majority of children were treated with PAH-specific medications, but only half of them with double combination therapy, which improved after changing the reimbursement policy. The underrepresentation of PAH classes other than IPAH and CHD-PAH, and the geographically heterogeneous distribution of PAH prevalence, indicate the need for building awareness of PAH among pediatricians, while a frequent coexistence of PAH with other comorbidities calls for a multidisciplinary approach to the management of PAH children.

Drug Treatment of Pulmonary Hypertension in Children

Pulmonary arterial hypertension (PAH) is a rare disease in infants and children that is associated with significant morbidity and mortality. The disease is characterized by progressive pulmonary vascular functional and structural changes resulting in increased pulmonary vascular resistance and eventual right heart failure and death. In many pediatric patients, PAH is idiopathic or associated with congenital heart disease and rarely is associated with other conditions such as connective tissue or thromboembolic disease. PAH associated with developmental lung diseases such as bronchopulmonary dysplasia or congenital diaphragmatic hernia is increasingly more recognized in infants and children. Although treatment of the underlying disease and reversal of advanced structural changes have not yet been achieved with current therapy, quality of life and survival have improved significantly. Targeted pulmonary vasodilator therapies, including endothelin receptor antagonists, prostacyclin analogs, and phosphodiesterase type 5 inhibitors have resulted in hemodynamic and functional improvement in children. The management of pediatric PAH remains challenging as treatment decisions depend largely on results from evidence-based adult studies and the clinical experience of pediatric experts. This article reviews the current drug therapies and their use in the management of PAH in children.

Diminished right ventricular function at diagnosis of pulmonary hypertension is associated with mortality in bronchopulmonary dysplasia

Pulmonary vascular disease and resultant pulmonary hypertension (PH) have been increasingly recognized in the preterm population, particularly among patients with bronchopulmonary dysplasia (BPD). Limited data exist on the impact of PH severity and right ventricular (RV) dysfunction at PH diagnosis on outcome. The purpose of this study was to evaluate if echocardiography measures of cardiac dysfunction and PH severity in BPD-PH were associated with mortality. The study is a retrospective analysis of the echocardiography at three months or less from time of PH diagnosis. Survival analysis using a univariate Cox proportional hazard model is presented and expressed using hazard ratios (HR). We included 52 patients with BPD and PH of which 16 (31%) died at follow-up. Average gestational age at birth was 26.3 ± 2.3 weeks. Echocardiography was performed at a median of 43.3 weeks (IQR: 39.0–54.7). The median time between PH diagnosis and death was 117 days (range: 49–262 days). Multiple measures of PH severity and RV performance were associated with mortality (sPAP/sBP: HR 1.02, eccentricity index: HR 2.02, tricuspid annular plane systolic excursion Z-score: HR 0.65, fractional area change: HR 0.88, peak longitudinal strain: HR 1.22). Hence, PH severity and underlying RV dysfunction at PH diagnosis were associated with mortality in BPD-PH patients. While absolute estimation of pulmonary pressures is not feasible in every screening echocardiography, thorough evaluation of RV function and other markers of PH may allow to discriminate the most at-risk population and should be considered as standard add-ons to the current screening at 36 weeks.

Intensive Care Mortality Prognostic Model for Pediatric Pulmonary Hypertension

OBJECTIVES

The disease burden and mortality of children with pulmonary hypertension are significantly higher than for the general PICU population. We aimed to develop a risk-adjustment tool predicting PICU mortality for pediatric pulmonary hypertension patients: the Pediatric Index of Pulmonary Hypertension Intensive Care Mortality score.

DESIGN

Retrospective analysis of prospectively collected multicenter pediatric critical care data.

SETTING

One-hundred forty-three centers submitting data to Virtual Pediatric Systems database between January 1, 2009, and December 31, 2015.

PATIENTS

Patients 21 years old or younger with a diagnosis of pulmonary hypertension.

INTERVENTIONS

Twenty-one demographic, diagnostic, and physiologic variables obtained within 12 hours of PICU admission were assessed for inclusion. Multivariable logistic regression with stepwise selection was performed to develop the final model. Receiver operating characteristic curves were used to compare the Pediatric Index of Pulmonary Hypertension Intensive Care Mortality score with Pediatric Risk of Mortality 3 and Pediatric Index of Mortality 2 scores.

MEASUREMENTS AND MAIN RESULTS

Fourteen-thousand two-hundred sixty-eight admissions with a diagnosis of pulmonary hypertension were included. Primary outcome was PICU mortality. Fourteen variables were selected for the final model: age, bradycardia, systolic hypotension, tachypnea, pH, FIO2, hemoglobin, blood urea nitrogen, creatinine, mechanical ventilation, nonelective admission, previous PICU admission, PICU admission due to nonsurgical cardiovascular disease, and cardiac arrest immediately prior to admission. The receiver operating characteristic curve for the Pediatric Index of Pulmonary Hypertension Intensive Care Mortality model (area under the curve = 0.77) performed significantly better than the receiver operating characteristic curves for Pediatric Risk of Mortality 3 (area under the curve = 0.71; p < 0.001) and Pediatric Index of Mortality 2 (area under the curve = 0.69; p < 0.001), respectively.

CONCLUSIONS

The Pediatric Index of Pulmonary Hypertension Intensive Care Mortality score is a parsimonious model that performs better than Pediatric Risk of Mortality 3 and Pediatric Index of Mortality 2 for mortality in a multicenter cohort of pediatric pulmonary hypertension patients admitted to PICUs. Application of the Pediatric Index of Pulmonary Hypertension Intensive Care Mortality model to pulmonary hypertension patients in the PICU might facilitate earlier identification of patients at high risk for mortality and improve the ability to prognosticate for patients and families.

Central line replacement following infection does not improve reinfection rates in pediatric pulmonary hypertension patients receiving intravenous prostanoid therapy

Treatment of pediatric pulmonary hypertension (PH) with IV prostanoids has greatly improved outcomes but requires a central line, posing inherent infection risk. This study examines the types of infections, infection rates, and importantly the effect of line management strategies on reinfection in children receiving IV prostanoids for PH. This study is a retrospective review of all pediatric PH patients receiving intravenous epoprostenol (EPO) or treprostinil (TRE) at one academic tertiary care center between 2000 and 2014. No patients declined participation in the study or were otherwise excluded. Infectious complications were characterized by organism(s), infection rates, time to next infection, and line management decisions (salvage vs. replace). Of the 40 patients followed, 13 sustained 38 infections involving 49 pathogens, with a predominance of gram-positive (GP) organisms (n = 35). The pooled infection rate was 1.06 per 1000 prostanoid days with no difference between EPO and TRE. No significant difference in reinfection rate was observed when comparing line salvage to replacement, regardless of organism type. Both overall and organism-type comparisons suggest longer time between line infections following line salvage compared with line replacement (732 vs. 410 days overall; 793 vs. 363 days for GP; 611 vs. 581 days for gram-negative [GN]; P > 0.05 for all comparisons). Central line replacement following blood stream infections in pediatric PH patients does not improve subsequent infection rates or time to next infection, and may lead to unnecessary risks associated with line replacement, including potential loss of vascular access. A revised approach to central line infections in pediatric PH is proposed.

Multicenter mortality and morbidity associated with pulmonary hypertension in the pediatric intensive care unit

Despite advances in the diagnosis and management of pediatric pulmonary hypertension (PH), children with PH represent a growing inpatient population with significant morbidity and mortality. To date, no studies have described the clinical characteristics of children with PH in the pediatric intensive care unit (PICU). A retrospective multicenter cohort study of 153 centers in the Virtual PICU Systems database who submitted data between 1 January 2009 and 31 December 2015 was performed. A total of 14,880/670,098 admissions (2.2%) with a diagnosis of PH were identified. Of these, 2190 (14.7%) had primary PH and 12,690 (85.3%) had secondary PH. Mortality for PH admissions was 6.8% compared to 2.3% in those admitted without PH (odds ratio = 3.1; 95% confidence interval = 2.9–3.4). Compared to patients admitted to the PICU without PH, those with PH were younger, had longer length of stay, higher illness severity scores, were more likely to receive invasive mechanical ventilation, cardiopulmonary resuscitation, extracorporeal membrane oxygenation, and more likely to have co-diagnoses of sepsis, heart failure, and respiratory failure. In a multivariate model, factors significantly associated with mortality for children with PH included age < 6 months or > 16 years, invasive mechanical ventilation, and co-diagnoses of heart failure, sepsis, hemoptysis, disseminated intravascular coagulation, stroke, and multi-organ dysfunction syndrome. Despite therapeutic advances, the disease burden and mortality of children with PH remains significant. Further investigation of the risk factors associated with clinical deterioration and mortality in this population could improve the ability to prognosticate and inform clinical decision-making.

Change in Pediatric Functional Classification During Treatment and Morbidity and Mortality in Children with Pulmonary Hypertension

Despite advances in therapy, outcomes for children with pulmonary hypertension remain poor. We sought to assess the validity of a pediatric-specific functional classification system for pulmonary hypertension (PH) in a heterogeneous population of children with PH diagnosed by echocardiogram or cardiac catheterization. A single-center, retrospective study of 65 infants and children with PH was performed. Pediatric Functional Class (FC) at diagnosis, at last visit, and change in FC over time were evaluated for their association with mortality and PH-associated morbidity in univariate, time-to-event, and multivariate regression analyses. Median age at PH diagnosis was 5.3 months (0 days-12.7 years). Twenty-five children (38 %) had idiopathic PH or PH secondary to congenital heart disease, one (2 %) had left heart disease, and 39 (60 %) had PH secondary to respiratory disease. Mortality was 25 % (16/63), primarily in the first year of follow-up. FC at diagnosis was not significantly associated with survival (p = 0.22), but higher FC (more impaired) at last visit (p < 0.001) and change in FC over time (HR 2.3, 95 % confidence interval 1.3-4, p = 0.0003) were associated with mortality. Higher FC at last visit was associated with greater days of hospitalization in the intensive care unit per year (p = 0.006) and history of cardiac arrest (p = 0.012) and syncope (p = 0.02). Although pediatric FC at diagnosis was not predictive of mortality, response to therapy (as assessed by change in FC over time and FC at last visit) was associated with morbidity and mortality in this heterogeneous cohort. Multicenter prospective studies are necessary to further validate these findings.

Safety and tolerability considerations in the use of sildenafil for children with pulmonary arterial hypertension

Sildenafil is a phosphodiesterase type-5 inhibitor approved for treatment of pulmonary arterial hypertension (PAH) in adults. Data from pediatric trials demonstrate a similar acute safety profile to the adult population but have raised concerns regarding the safety of long-term use in children. Interpretation of these trials remains controversial with major regulatory agencies differing in their recommendations – the US Food and Drug Administration recommends against the use of sildenafil for treatment of PAH in children, while the European Medicines Agency supports its use at “low doses”. Here, we review the available pediatric data regarding dosing, acute, and long-term safety and efficacy of sildenafil for the treatment of PAH in children.

FUTURE-2: Results from an open-label, long-term safety and tolerability extension study using the pediatric FormUlation of bosenTan in pUlmonary arterial hypeRtEnsion

BACKGROUND

A novel formulation of bosentan was evaluated in children with pulmonary arterial hypertension (PAH) in FUTURE-1, which characterized its pharmacokinetic and clinical profile. The subsequent phase III, open-label, long-term extension study, FUTURE-2, aimed to provide long-term tolerability, safety and exploratory efficacy data.

METHODS

Children (≥2 and <12 years) with idiopathic or heritable PAH, who completed 12-week treatment in FUTURE-1 and for whom bosentan was considered beneficial were enrolled, and continued to receive bosentan 4 mg/kg twice-daily, which could be down-titrated to 2mg/kg if not tolerated. Safety and tolerability were evaluated via treatment-emergent adverse events (AEs), serious AEs, growth, and laboratory measurements. Exploratory efficacy endpoints included time to PAH worsening and long-term survival. All analyses were conducted on pooled data of both studies.

RESULTS

36 patients were enrolled in FUTURE-1 and 33 continued in FUTURE-2. The overall median duration of exposure to bosentan was 27.7 (range 1.9-59.6) months. Treatment-emergent AEs occurred in 32 (88.9%) patients; AEs considered treatment-related in 15 (41.7%) patients. Of 51 serious AEs, three were considered treatment-related: two incidences of reported PAH worsening and one of autoimmune hepatitis. Six deaths occurred; none were considered treatment-related. Kaplan-Meier event-free estimates of PAH worsening were 78.9% and 73.6% at 2 and 4 years, respectively.

CONCLUSIONS

The pediatric bosentan formulation was generally well tolerated, its safety profile comparable to that of the adult formulation when used in children. The results are in line with the efficacy profile of bosentan in previous pediatric and adult PAH studies of shorter duration.

The challenges in paediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare, progressive disease affecting both adults and children. While overall survival has improved in recent years, the need for improved therapeutic approaches remains. Treatments for paediatric PAH have not yet been sufficiently examined, particularly regarding potential toxicities and optimal dosing, and there is a lack of appropriate clinical trial end-points and validated treatment goals that might enable a goal-oriented therapeutic approach. Adult randomised controlled trials in PAH are demonstrating a shift towards more long-term designs, focusing on mortality and morbidity end-points rather than changes in 6-min walking distance. However, such trial designs may not be feasible within the paediatric setting due to challenges such as sufficient recruitment and retention of paediatric patients. Consideration should, therefore, be given towards identifying optimal end-points for the paediatric population, allowing sufficient duration to evaluate efficacy and safety of potential treatments. Herein we consider some of the complexities involved in the management of paediatric PAH, specifically presenting diagnostic challenges as well as reflecting on the lack of evidence currently available to support various therapeutic approaches within the paediatric population.

The mechanistic basis of prostacyclin and its stable analogues in pulmonary arterial hypertension: Role of membrane versus nuclear receptors

Pulmonary arterial hypertension (PAH) is a progressive disease of distal pulmonary arteries in which patients suffer from elevated pulmonary arterial pressure, extensive vascular remodelling and right ventricular failure. To date prostacyclin (PGI2) therapy remains the most efficacious treatment for PAH and is the only approved monotherapy to have a positive impact on long-term survival. A key thing to note is that improvement exceeds that predicted from vasodilator testing strongly suggesting that additional mechanisms contribute to the therapeutic benefit of prostacyclins in PAH. Given these agents have potent antiproliferative, anti-inflammatory and endothelial regenerating properties suggests therapeutic benefit might result from a slowing, stabilization or even some reversal of vascular remodelling in vivo. This review discusses evidence that the pharmacology of each prostacyclin (IP) receptor agonist so far developed is distinct, with non-IP receptor targets clearly contributing to the therapeutic and side effect profile of PGI2 (EP3), iloprost (EP1), treprostinil (EP2, DP1) along with a family of nuclear receptors known as peroxisome proliferator-activated receptors (PPARs), to which PGI2 and some analogues directly bind. These targets are functionally expressed to varying degrees in arteries, veins, platelets, fibroblasts and inflammatory cells and are likely to be involved in the biological actions of prostacylins. Recently, a highly selective IP agonist, selexipag has been developed for PAH. This agent should prove useful in distinguishing IP from other prostanoid receptors or PPAR binding effects in human tissue. It remains to be determined whether selectivity for the IP receptor gives rise to a superior or inferior clinical benefit in PAH.

Treating pulmonary hypertension in pediatrics

INTRODUCTION

Pulmonary hypertension is a hemodynamic condition occurring rarely in pediatrics. Nevertheless, it is associated with significant morbidity and mortality. When characterized by progressive pulmonary vascular structural changes, the disease is called pulmonary arterial hypertension (PAH). It results in increased pulmonary vascular resistance and eventual right ventricular failure. In the vast majority of cases, pediatric PAH is idiopathic or associated with congenital heart disease, and, contrary to adult PAH, is rarely associated with connective tissue, portal hypertension, HIV infection or thromboembolic disease.

AREAS COVERED

This article reviews the current drug therapies available for the management of pediatric PAH. These treatments target the recognized pathophysiological pathways of PAH with endothelin-1 receptor antagonists, prostacyclin analogs and PDE type 5 inhibitors. New treatments and explored pathways are briefly discussed.

EXPERT OPINION

Although there is still no cure for PAH, quality of life and survival have been improved significantly with specific drug therapies. Nevertheless, management of pediatric PAH remains challenging, and depends mainly on results from adult clinical trials and pediatric experts. Further research on PAH-specific treatments in the pediatric population and data from international registries are needed to identify optimal therapeutic strategies and treatment goals in the pediatric population.

Waiting for transplant: physical, psychosocial, and nutritional status considerations for pediatric candidates and implications for care

The waiting period for an organ transplant has been described as a time of tremendous uncertainty and vulnerability, posing unique challenges and stressors for pediatric transplant candidates and their families. It has been identified as the most stressful stage of the transplant journey, yet little attention has been given to the physical, psychological, or social impact of the waiting period in the literature. In this review, we discuss the physical, nutritional, and psychosocial implications of the waiting period for child and adolescent transplant candidates and the impact on their parents and siblings. We identify areas for future research and provide recommendations for clinical practice to support children, adolescents, and families during the waiting period.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Pulmonary hypertension in children

Pulmonary hypertension (PH) is relatively uncommon in children. Pulmonary arterial hypertension (PAH) in pediatric comprises a wide spectrum of diseases, from a transient neonatal condition to a progressive disease associated with morbidity and mortality. Most common PAH in pediatric are idiopathic (IPAH) or PAH associated with congenital heart disease (PAH-CHD), while other associated conditions, such as connective tissue disease (CTD), are less common in pediatrics. Despite better understanding of PH and the availability of new medications during recent decades; the diagnosis, investigation and choice of therapy remain a challenge in children, as evidence-based recommendations depend mainly on adult studies. In this review, we provide a detailed discussion about the distinctive features of PAH in pediatric, mainly emphacysing on classification and diagnostic algorithm.

Drug treatment of pulmonary hypertension in children

Pulmonary arterial hypertension (PAH) is a rare disease in infants and children that is associated with significant morbidity and mortality. The disease is characterized by progressive pulmonary vascular functional and structural changes resulting in increased pulmonary vascular resistance and eventual right heart failure and death. In the majority of pediatric patients, PAH is idiopathic or associated with congenital heart disease and rarely is associated with other conditions such as connective tissue or thromboembolic disease. Although treatment of the underlying disease and reversal of advanced structural changes has not yet been achieved with current therapy, quality of life and survival have been improved significantly. Targeted pulmonary vasodilator therapies, including endothelin receptor antagonists, prostacyclin analogs, and phosphodiesterase type 5 inhibitors, have demonstrated hemodynamic and functional improvement in children. The management of pediatric PAH remains challenging, as treatment decisions continue to depend largely on results from evidence-based adult studies and the clinical experience of pediatric experts. This article reviews the current drug therapies and their use in the management of PAH in children.

Evaluation of circulating proteins and hemodynamics towards predicting mortality in children with pulmonary arterial hypertension

BACKGROUND

Although many predictors have been evaluated, a set of strong independent prognostic mortality indicators has not been established in children with pediatric pulmonary arterial hypertension (PAH). The aim of this study was to identify a combination of clinical and molecular predictors of survival in PAH.

METHODS

This single-center, retrospective cohort study was performed from children with PAH between 2001 and 2008 at Children's Hospital Colorado. Blood samples from 83 patients (median age of 8.3 years-old) were obtained. We retrospectively analyzed 46 variables, which included 27 circulating proteins, 7 demographic variables and 12 hemodynamic and echocardiographic variables for establishing the best predictors of mortality. A data mining approach was utilized to evaluate predictor variables and to uncover complex data structures while performing variable selection in high dimensional problems.

RESULTS

Thirteen children (16%) died during follow-up (median; 3.1 years) and survival rates from time of sample collection at 1 year, 3 years and 5 years were 95%, 85% and 79%, respectively. A subset of potentially informative predictors were identified, the top four are listed here in order of importance: Tissue inhibitors of metalloproteinases-1 (TIMP-1), apolipoprotein-AI, RV/LV diastolic dimension ratio and age at diagnosis. In univariate analysis, TIMP-1 and apolipoprotein-AI had significant association with survival time (hazard ratio [95% confidence interval]: 1.25 [1.03, 1.51] and 0.70 [0.54-0.90], respectively). Patients grouped by TIMP-1 and apolipoprotein-AI values had significantly different survival risks (p<0.01).

CONCLUSION

Important predictors of mortality were identified from a large number of circulating proteins and clinical markers in this cohort. If confirmed in other populations, measurement of a subset of these predictors could aid in management of pediatric PAH by identifying patients at risk for death. These findings also further support a role for the clinical utility of measuring circulating proteins.

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.

Survival in childhood pulmonary arterial hypertension: insights from the registry to evaluate early and long-term pulmonary arterial hypertension disease management

BACKGROUND

Pulmonary arterial hypertension (PAH) is a rare but important cause of morbidity and mortality in children.

METHODS AND RESULTS

We analyzed data from 216 patients ≤18 years of age at diagnosis who were enrolled in the Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL). Median age at diagnosis and enrollment was 7 and 15 years, respectively. The most frequent presenting symptom was dyspnea (idiopathic/familial PAH, 53%; PAH associated with congenital heart disease, 30%). Presyncope/syncope was more frequent in patients with idiopathic PAH/familial PAH (36%) than in those with PAH associated with congenital heart disease (4%). At diagnosis, mean pulmonary artery pressure and pulmonary vascular resistance index were 56 mm Hg and 17 Wood units · m(2), respectively. Five-year survival from diagnosis for the overall cohort was 74±6%, with no significant difference between the idiopathic PAH/familial PAH (n=122, 75±7%) and PAH associated with congenital heart disease (n=77, 71±13%) cohorts (P=0.53). Older age at diagnosis was the only variable significantly associated with decreased survival from diagnosis. Variables at enrollment that were significantly associated with decreased survival from enrollment included higher pulmonary vascular resistance index, lower-weight z scores, and familial PAH. Additional variables at enrollment, identified in a secondary analysis, that were marginally associated with increased survival from enrollment included acute vasoreactivity (adaptation of conventional pediatric definition; P=0.087) and lower brain natriuretic peptide (P=0.060). None of the 22 patients who were acute responders treated with high-dose calcium channel blockade as monotherapy or combination therapy died within 5 years of diagnosis.

CONCLUSION

Using REVEAL, we identified key predictors of survival in childhood PAH. Refining these prognostic parameters should help clinicians improve outcomes.

CLINICAL TRIAL REGISTRATION

URL: www.clinicaltrials.gov. Unique identifier: NCT00370214.

Treatment of pediatric pulmonary hypertension with simvastatin: an observational study

BACKGROUND

Animal studies and an adult human case series suggest that statins may have a role in the treatment of pulmonary hypertension. We reviewed the results of empirical therapy for children at Primary Children's Medical Center to determine whether simvastatin had a favorable effect on non-invasive estimates of pulmonary arterial pressure.

MATERIALS AND METHODS

The medical records of children with pulmonary hypertension who were treated with simvastatin were reviewed. Mean measurements of the gradient of tricuspid valve regurgitation before and after treatment were compared by a paired t-test. A favorable response to simvastatin was defined as a 20% decrease in the average measurement of the gradient of tricuspid valve regurgitation or a 20% decrease in right ventricular anterior wall thickness when tricuspid valve regurgitation resolved during treatment. Potential factors associated with a favorable response to simvastatin were identified with a Fisher exact test.

RESULTS

Twelve children, 4-15 years of age, had adequate Doppler velocity waveforms to reliably measure gradients of tricuspid valve regurgitation during a period of 1 year before treatment. Eleven patients had gradients of tricuspid valve regurgitation that could be measured during a period of 1 year after treatment. Patients were treated with simvastatin 0.09-0.28 mg/kg/day. Collectively, there was no difference between the average measurements of the gradient of tricuspid valve regurgitation before and after treatment (66 ± 21 mmHg vs. 63 ± 28 mmHg). Three of the five patients with clinical findings consistent with alveolar hypoxia and none of the seven patients without clinical findings consistent with alveolar hypoxia had a favorable response to treatment with simvastatin (P = 0.05).

CONCLUSION

Simvastatin may decrease pulmonary arterial pressure in a subset of patients with pulmonary hypertension.

Pulmonary arterial hypertension: a comparison between children and adults

The characteristics of pulmonary arterial hypertension (PAH), including pathology, symptoms, diagnosis and treatment are reviewed in children and adults. The histopathology seen in adults is also observed in children, although children have more medial hypertrophy at presentation. Both populations have vascular and endothelial dysfunction. Several unique disease states are present in children, as lung growth abnormalities contribute to pulmonary hypertension. Although both children and adults present at diagnosis with elevations in pulmonary vascular resistance and pulmonary artery pressure, children have less heart failure. Dyspnoea on exertion is the most frequent symptom in children and adults with PAH, but heart failure with oedema occurs more frequently in adults. However, in idiopathic PAH, syncope is more common in children. Haemodynamic assessment remains the gold standard for diagnosis, but the definition of vasoreactivity in adults may not apply to young children. Targeted PAH therapies approved for adults are associated with clinically meaningful effects in paediatric observational studies; children now survive as long as adults with current treatment guidelines. In conclusion, there are more similarities than differences in the characteristics of PAH in children and adults, resulting in guidelines recommending similar diagnostic and therapeutic algorithms in children (based on expert opinion) and adults (evidence-based).

Smooth muscle proliferation and role of the prostacyclin (IP) receptor in idiopathic pulmonary arterial hypertension

RATIONALE

Prostacyclin analogs, used to treat idiopathic pulmonary arterial hypertension (IPAH), are assumed to work through prostacyclin (IP) receptors linked to cyclic AMP (cAMP) generation, although the potential to signal through peroxisome proliferator-activated receptor-γ (PPARγ) exists.

OBJECTIVES

IP receptor and PPARγ expression may be depressed in IPAH. We wished to determine if pathways remain functional and if analogs continue to inhibit smooth muscle proliferation.

METHODS

We used Western blotting to determine IP receptor expression in peripheral pulmonary arterial smooth muscle cells (PASMCs) from normal and IPAH lungs and immunohistochemistry to evaluate IP receptor and PPARγ expression in distal arteries.

MEASUREMENTS AND MAIN RESULTS

Cell proliferation and cAMP assays assessed analog responses in human and mouse PASMCs and HEK-293 cells. Proliferative rates of IPAH cells were greater than normal human PASMCs. IP receptor protein levels were lower in PASMCs from patients with IPAH, but treprostinil reduced replication and treprostinil-induced cAMP elevation appeared normal. Responses to prostacyclin analogs were largely dependent on the IP receptor and cAMP in normal PASMCs, although in IP(-/-) receptor cells analogs inhibited growth in a cAMP-independent, PPARγ-dependent manner. In IPAH cells, antiproliferative responses to analogs were insensitive to IP receptor or adenylyl cyclase antagonists but were potentiated by a PPARγ agonist and inhibited (∼ 60%) by the PPARγ antagonist GW9662. This coincided with increased PPARγ expression in the medial layer of acinar arteries.

CONCLUSIONS

The antiproliferative effects of prostacyclin analogs are preserved in IPAH despite IP receptor down-regulation and abnormal coupling. PPARγ may represent a previously unrecognized pathway by which these agents inhibit smooth muscle proliferation.

Outcome of pediatric patients with pulmonary arterial hypertension in the era of new medical therapies

Little is known about the effects of "second-generation drugs" (prostanoids, endothelin receptor antagonists, 5-phosphodiesterase inhibitors) in children with pulmonary arterial hypertension (PAH). This study describes the outcome of a national cohort of children with PAH in an era when these drugs became available. From 1993 to 2008, 52 consecutive children with idiopathic PAH (n = 29) or systemic-to-pulmonary shunt-associated PAH (n = 23) underwent baseline and follow-up assessments. Treatment was initiated depending on functional class, acute pulmonary vasoreactivity response, and drug availability. Observed survival was evaluated depending on time of diagnosis in relation to second-generation drug availability and subsequently compared to calculated predicted survival. Children for whom second-generation drugs were available had improved survival compared to their predicted survival (1-, 3-, and 5-year survival rates 93%, 83%, and 66% vs 79%, 61%, and 50%, respectively). However, this improved survival was observed only in patients for whom second-generation drugs became available during their disease course. No improved survival was observed in patients for whom drugs were available already at diagnosis. Baseline variables associated with decreased survival included higher functional class, higher pulmonary-to-systemic arterial pressure ratio, lower cardiac index, and higher serum levels of N-terminal pro-brain natriuretic peptide and uric acid. After start of second-generation drugs, functional class, 6-minute walking distance, and N-terminal pro-brain natriuretic peptide improved but gradually decreased after longer follow-up. In conclusion, survival of pediatric PAH seemed improved since the introduction of second-generation drugs only in selected patients for whom these drugs became available during their disease course. Start of second-generation drugs initially induced clinical improvements, but these effects decreased after longer follow-up.

Advances in therapies for pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by progressive obliteration of the pulmonary vasculature, leading to right heart failure and death if left untreated. Prior to the current treatment era, pulmonary hypertension carried a poor prognosis with a high mortality rate, but its prognosis has changed over the past decades in relation to new therapeutic agents. Nevertheless, pulmonary hypertension continues to be a serious condition, which is extremely challenging to manage. The data in children are often limited owing to the small number of patients, and extrapolation from adults to children is not straightforward. While none of these new therapeutic agents have been specifically approved for children, there is evidence that each can appropriately benefit the PAH child. We review the current understanding of pediatric pulmonary hypertension, classification, diagnostic evaluation and available treatment. A description of targeted pharmacological therapy and new treatments in children is outlined.

Effectiveness of transition from intravenous epoprostenol to oral/inhaled targeted pulmonary arterial hypertension therapy in pediatric idiopathic and familial pulmonary arterial hypertension

Before 2001, intravenous epoprostenol was the only approved drug for patients with idiopathic pulmonary arterial hypertension (IPAH) or familial pulmonary arterial hypertension (FPAH) who were nonresponsive to high-dose calcium channel blockade. The investigators report transitioning select pediatric patients with IPAH or FPAH from intravenous epoprostenol to oral and/or inhaled agents for pulmonary arterial hypertension. A retrospective review was performed on all pediatric patients with IPAH or FPAH treated at Columbia University (1987 to 2008) who transitioned off epoprostenol to oral or inhaled drugs. Criteria for transition included functional class I or II, mean pulmonary arterial pressure <35 mm Hg, normal cardiac index, and age >6 years. Hemodynamic and clinical data were obtained at baseline (before epoprostenol), at peak epoprostenol dose, and after epoprostenol discontinuation. Fourteen of 104 pediatric patients with IPAH or FPAH transitioned off epoprostenol to oral or inhaled drugs from April 2003 to July 2008. Of the 14 subjects, 13 transitioned off epoprostenol successfully to oral or inhaled drugs. No significant changes in functional class, hemodynamics, or exercise data were seen after epoprostenol (mean follow-up duration 7.0 +/- 5.8 months) compared to peak epoprostenol, but further improvement was reported in World Health Organization functional class (p <0.005) after epoprostenol discontinuation. After successful epoprostenol discontinuation, 77% of patients were treated with endothelin receptor antagonists, 69% with phosphodiesterase-5 inhibitors, 38% with calcium channel blockers, and 8% inhaled iloprost. At the cut-off date (May 2009), there was 100% survival and 93% transition success. In conclusion, in carefully selected children with IPAH or FPAH initiated on intravenous epoprostenol before the availability of nonparenteral therapy, transition to oral or inhaled therapy for pulmonary arterial hypertension appears safe, with efficacy maintained when performed with close follow-up at a pulmonary hypertension specialty center.

Pulmonary hypertension in children: a historical overview

Pulmonary arterial hypertension in children contributes significantly to morbidity and mortality in diverse pediatric cardiac, lung, hematologic, and other diseases. Pulmonary arterial hypertension is generally a disease of small pulmonary arteries characterized by vascular narrowing due to high-tone and abnormal vasoreactivity, structural remodeling of the vessel wall, intraluminal obstruction, and decreased vascular growth and surface area. Without therapy, high pulmonary vascular resistance contributes to progressive right ventricular failure, low cardiac output, and death. Advances in basic pulmonary vascular biology over the last few decades have led directly to several novel therapies, which have significantly expanded therapeutic choices and have led to improved survival and quality of life of many children with pulmonary arterial hypertension. Despite these improvements, long-term outcomes in many settings remain guarded and substantial challenges persist, especially with regard to understanding mechanisms and approach to structural remodeling of severe pulmonary arterial hypertension.

Non-congenital heart disease associated pediatric pulmonary arterial hypertension

Recognition of causes of pulmonary hypertension other than congenital heart disease is increasing in children. Diagnosis and treatment of any underlying cause of pulmonary hypertension is crucial for optimal management of pulmonary hypertension. This article discusses the available knowledge regarding several disorders associated with pulmonary hypertension in children: idiopathic pulmonary arterial hypertension (IPAH), pulmonary capillary hemangiomatosis, pulmonary veno-occlusive disease, hemoglobinopathies, hepatopulmonary syndrome, portopulmonary hypertension and HIV. Three classes of drugs have been extensively studied for the treatment of IPAH in adults: prostanoids (epoprostenol, treprostinil, iloprost, beraprost), endothelin receptor antagonists (bosentan, sitaxsentan, ambrisentan), and phosphodiesterase inhibitors (Sildenafil, tadalafil). These medications have been used in treatment of children with pulmonary arterial hypertension, although randomized clinical trial data is lacking. As pulmonary vasodilator therapy in certain diseases may be associated with adverse outcomes, further study of these medications is needed before widespread use is encouraged.

Bosentan and sildenafil: should the combination therapy be a valid alternative in childhood to prostacyclin infusion?

We report a case of a seven-yr-old girl with a PAH treated with continuation therapy of bosentan and sildenafil. The combination therapy revealed safety and efficacy in long-term follow up.

Use of Amplatzer fenestrated atrial septal defect device in a child with familial pulmonary hypertension

In a 4.5-year-old child with refractory pulmonary arterial hypertension, we performed atrial septostomy with the application of an Amplatzer fenestrated device designed to maintain patency. Continuous intravenous epoprostenol infusion was started concomitantly. Forty-two months after the procedure, the patient had no recurrent syncope and remained in New York Heart Association functional class II. Fenestration of the atrial septum is feasible in children with pulmonary artery hypertension. No conclusion regarding the patient's need for an atrial septal defect can be drawn since concomitant prostanoid therapy was administered. The long-term patency of the atrial communication needs further confirmation and the optimal timing for its application has to be determined.

Pulmonary hypertension in children: the twenty-first century

Pulmonary hypertension is an elevation in pulmonary artery pressure that is associated with a spectrum of diseases and causes. Its clinical severity and presentation are widely varied. The field of study has changed immensely over the past several years. Significant knowledge has been gained in the pathophysiology, genetics, and vascular biology associated with pulmonary hypertension. These discoveries have contributed to medical interventions that have improved outcomes associated with pulmonary hypertension. This article reviews pulmonary hypertension in children, focusing on idiopathic pulmonary hypertension. Because most information is associated with children who have this form of the disease, formerly classified as primary pulmonary hypertension, medical therapy is discussed with a focus on this patient group. Additional therapeutic concepts relevant to other causes of pulmonary hypertension are highlighted.