Outcomes in Children With Idiopathic Pulmonary Arterial Hypertension

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.

Bilateral lung transplantation for pediatric idiopathic pulmonary arterial hypertension: a multi-center experience

Many children with idiopathic pulmonary arterial hypertension (IPAH) experience disease progression despite advanced medical therapy. In these children, heart-lung or bilateral lung transplantation (BLTx) remain the only therapeutic options when other treatments fail. Data on functional outcome after BLTx in children with IPAH are limited. We report a multi-center experience of BLTx for pediatric IPAH. We performed a retrospective study including 25 centers within the International Pediatric Lung Transplant Collaborative. Children with IPAH who underwent BLTx were included (1996-2006). Twenty-three children underwent BLTx for IPAH, most of whom were in WHO class III or IV level of function pre-transplantation. At 6 months post-transplantation, 82% of children reported improvement in level of function to WHO class I. The median FEV(1) was 89% (12-126) of predicted at 12 months post-transplantation. Ten patients (44%) developed BOS at a median of 42 months (3-85), of whom five died at a median of 27 months (4-86) post-transplantation. Overall mortality was 4% at 3 months post-transplantation. The median survival for children in this cohort was 45 months (2-123). Our data suggest that BLTx is a valuable therapeutic option for children with end-stage IPAH with outcomes comparable to that after heart-lung transplantation in children with pulmonary arterial hypertension or those patients undergoing lung transplantation for other indications. In the majority of children, a good cardiopulmonary function is possible following BLTx, making BLTx a good therapeutic option and maximizing donor organ utilization by allowing more hearts to be available for children needing cardiac transplantation.

Recent progress in understanding pediatric pulmonary hypertension

PURPOSE OF REVIEW

Pulmonary artery hypertension (PAH) in children contributes significantly to morbidity and mortality in diverse pediatric cardiac, lung, hematologic and other diseases. Advances in pulmonary vascular biology over the past few decades have significantly expanded therapeutic strategies; however, many unique issues persist regarding our understanding of pediatric PAH.

RECENT FINDINGS

Recent studies of pediatric PAH include those that highlight gaps in our understanding of pediatric diseases associated with PAH from those of adult onset, emphasizing the strong need for specific studies regarding unique aspects of the pathogenesis and treatment of children with PAH. Registries have begun to provide new data showing differences in physiology, course, and genetics between adult and pediatric forms of PAH. Unfortunately, therapeutic strategies in pediatric pulmonary hypertension are often limited to small observational studies in children and are dependent on results from larger adult studies. In addition, clinical endpoints for studies and care remain poorly defined in infants and children.

SUMMARY

Despite many advances, long-term outcomes for children with PAH remain guarded and substantial challenges persist, especially with regard to understanding mechanisms and approach to severe PAH. Future studies are needed to develop novel biomarkers, clinical endpoints and interventions for young children with diverse causes of PAH.

Pediatric pulmonary arterial hypertension: current and emerging therapeutic options

INTRODUCTION

Pulmonary arterial hypertension (PAH) is a rare disease in neonates, infants and children that is associated with significant morbidity and mortality. An adequate understanding of the controlling pathophysiologic mechanisms is lacking and although mortality has decreased as therapeutic options have increased over the past several decades, outcomes remain unacceptable.

AREAS COVERED

This review summarizes the currently available therapies for neonates, infants and children with PAH and describes emerging therapies in the context of what is known about the underlying pathophysiology of the disease.

EXPERT OPINION

All of the currently approved PAH therapies impact one of three endothelial-based pathways: nitric oxide-guanosine-3'-5'cyclic monophosphate, prostacyclin or endothelin-1. The beneficial effects of these agents may relate to their impact on pulmonary vascular tone, and/or their antiproliferative and antithrombotic properties. Fundamental advances in PAH therapy are likely to relate to: i) a better understanding of PAH subpopulations, allowing for therapies to be better tailored to individual patients and pathophysiologic processes; and ii) therapies that promote the regression of advanced structural remodeling.

Idiopathic and Heritable Pulmonary Hypertension in Children: New Insights into Causes, Evaluation, and Treatment

Over the past decade, major progress has occurred in the care of children and adults with pulmonary arterial hypertension (PAH). Recent insights into molecular mechanisms implicated in the development of pulmonary vascular disease have led to revised clinical classification and diagnostic strategies.1 Data from multicenter pulmonary hypertension registries have provided increased understanding of the clinical course and natural history of many subtypes of disease.2–4 Additionally, the development of multiple therapies targeting important pathways of disease and the translation of those treatments to pediatrics have led to improved life experience and survival for many children with PAH.5

Add-on therapy with subcutaneous treprostinil for refractory pediatric pulmonary hypertension

OBJECTIVE

To evaluate the efficacy and tolerability of subcutaneous (SC) treprostinil, a prostacyclin analogue, in young children with refractory pulmonary arterial hypertension.

STUDY DESIGN

Eight children (median age, 4 years) received SC treprostinil therapy after failure of combined oral treatment (n = 7) or because of severe complications with intravenous epoprostenol (n = 1). Treprostinil was delivered through an SC catheter at gradually increasing doses to an average of 40 ng/kg/min, depending on the presence of adverse effects.

RESULTS

Seven patients demonstrated early significant improvement (in functional class, hemodynamics, and/or 6-minute walk distance; P <.05), and 6 had a sustained good response. Site pain could be effectively managed in all but one child.

CONCLUSIONS

Treprostinil may be a potentially valuable rescue therapy in children with refractory pulmonary arterial hypertension, but further study in a larger number of patients is needed.

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).

How has epoprostenol changed the outcome for patients with pulmonary arterial hypertension?

AIMS

Pulmonary arterial hypertension (PAH), characterized by increased pulmonary vascular resistance and pulmonary artery pressure, is a significant cause of morbidity and mortality in children and adults. Prior to 1995, there were no approved therapies for PAH.

MATERIALS AND METHODS

Review of the clinical drug development of epoprostenol (synthetic prostacyclin) for the treatment of PAH.

RESULTS

Based on the results of a phase 2 and one phase 3 trial carried out between 1987 and 1992 in adult patients with PAH, epoprostenol was approved for the treatment of severe idiopathic PAH in 1995. Continuous intravenous infusion 24/7 of epoprotenol improved exercise capacity, hemodynamic parameters, functional capacity and survival. Epoprostenol was subsequently shown to be safe and efficacious in PAH associated with the scleroderma spectrum of disease and has now been utilized in PAH associated with congenital heart disease, HIV, portal hypertension, drugs and toxin and connective tissue diseases. Epoprostenol has also been used in children of all ages with similar safety and efficacy as shown in adult patients.

DISCUSSION

Due to the mode of delivery of epoprostenol, i.e. continuous intravenous infusion 24/7 via an indwelling central venous line, there are significant side effects than can occur with its use, e.g. bacteremia, sepsis, thromboembolic events, that can be fatal. Furthermore, there is significant variability in the optimal dose in both children and adult patients. It remains unclear why there is such dose variability between patients to achieve optimal efficacy. Furthermore, its mechanism(s) of action remain unclear.

Long-term outcomes in children with pulmonary arterial hypertension treated with bosentan in real-world clinical settings

Treatment algorithms in pediatric pulmonary arterial hypertension (PAH) are derived from clinical trials in adult populations and from clinical practice, but experience in children is limited. In this retrospective cohort study, we analyzed outcomes in a previously identified cohort of 86 consecutive children with PAH treated with bosentan as part of their treatment regimen. All children with idiopathic PAH or heritable PAH and PAH associated with congenital heart disease or connective tissue disease who started bosentan treatment from May 2001 to April 2003 in 2 tertiary pediatric referral centers were followed, with data collection ending August 2006. Eighty-six children (37 male, 49 female) 11 ± 5 years of age with idiopathic/heritable PAH (n = 36), PAH associated with congenital heart disease (n = 48), or PAH associated with connective tissue disease (n = 2) received bosentan as monotherapy (n = 42) or as an add-on to pre-existing continuous intravenous epoprostenol or subcutaneous treprostinil (n = 44). Median observation period was 39 months (range 2 to 60). Thirty-four patients (40%) received ≥1 additional PAH-specific therapy during follow-up. At end of data collection, 25 patients (29%) remained on bosentan, 43 (50%) had stopped bosentan, 11 (13%) had died while on bosentan, and 7 were lost to follow-up. At 4 years, the Kaplan-Meier estimate of disease progression in patients while on bosentan was 54% (7 patients at risk) with a survival estimate of 82% (16 patients at risk). Risk factors significantly associated with survival were World Health Organization functional class and indexed pulmonary vascular resistance. In conclusion, outcome in children with PAH managed with current treatment regimens appears favorable. However, despite current therapy options, disease progression remains a concern.

Vasodilator testing with nitric oxide and/or oxygen in pediatric pulmonary hypertension

The objective of this study was to determine whether a combination of inhaled nitric oxide (iNO) and O(2) is more effective than 100% O(2) or iNO alone for acute vasodilator testing in children. An open, prospective, randomized, controlled trial was conducted at 16 centers. Subjects were children 4 weeks to 18 years of age with pulmonary hypertension (PH) and increased pulmonary vascular resistance (PVR) undergoing right heart catheterization for acute vasodilator testing. All patients were tested with each of three agents (80 ppm iNO, 100% O(2), combination of 80 ppm iNO/100% O(2)) in three 10-min treatment periods, and hemodynamic measurements obtained. Primary outcome measures were percentages of acute responders with O(2) alone vs. iNO/O(2) and iNO alone vs. iNO/O(2). More patients on the combination were acute responders compared with O(2) or iNO alone (26% vs. 14%, P = 0.019, and 27% vs. 24%, P = 0.602, respectively). Changes in PVR index and mean pulmonary arterial pressure vs. baseline were greater with iNO/O(2) vs. either O(2) or iNO alone (P < 0.001). Survival at 1-year follow-up included (1) 90.9% of acute responders to the combination, compared with 77.8% of nonresponders to the combination, and (2) 85.7% of acute responders to O(2) alone, compared with 80.6% of nonresponders to O(2). Key conclusions are as follows. In children with PH and increased PVR, more acute responders were identified with the iNO/O(2) combination vs. O(2) alone. While there was no significant difference in acute responder rate with iNO alone vs. iNO/O(2), the combination improved pulmonary hemodynamics acutely better than iNO alone. One-year survival data show similar rates between the iNO/O(2) and the O(2) alone groups; however, the combination may be more effective than O(2) alone in discriminating survivors versus nonsurvivors at long-term follow-up.

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.

PRX-08066, a novel 5-hydroxytryptamine receptor 2B antagonist, reduces monocrotaline-induced pulmonary arterial hypertension and right ventricular hypertrophy in rats

Pulmonary arterial hypertension (PAH) is a life-threatening disease that results in right ventricular failure. 5-((4-(6-Chlorothieno[2,3-d]pyrimidin-4-ylamino)piperidin-1-yl)methyl)-2-fluorobenzonitrile monofumarate (PRX-08066) is a selective 5-hydroxytryptamine receptor 2B (5-HT2BR) antagonist that causes selective vasodilation of pulmonary arteries. In the current study, the effects of PRX-08066 were assessed by using the monocrotaline (MCT)-induced PAH rat model. Male rats received 40 mg/kg MCT or phosphate-buffered saline and were treated orally twice a day with vehicle or 50 or 100 mg/kg PRX-08066 for 5 weeks. Pulmonary and cardiac functions were evaluated by hemodynamics, heart weight, magnetic resonance imaging (MRI), pulmonary artery (PA) morphology, and histology. Cardiac MRI demonstrated that PRX-08066 (100 mg/kg) significantly (P < 0.05) improved right ventricular ejection fraction. PRX-08066 significantly reduced peak PA pressure at 50 and 100 mg/kg (P < 0.05 and < 0.01, respectively) compared with MCT control animals. PRX-08066 therapy also significantly reduced right ventricle (RV)/body weight and RV/left ventricle + septum (P < 0.01 and < 0.001, respectively) compared with MCT-treated animals. Morphometric assessment of pulmonary arterioles revealed a significant reduction in medial wall thickening and lumen occlusion associated with both doses of PRX-08066 (P < 0.01). The 5-HT2BR antagonist PRX-08066 significantly attenuated the elevation in PA pressure and RV hypertrophy and maintained cardiac function. Pulmonary vascular remodeling was also diminished compared with MCT control rats. PRX-08066 prevents the severity of PAH in the MCT rat model.

Lung transplantation in children with idiopathic pulmonary arterial hypertension

BACKGROUND

Despite improved medical therapy, transplantation (Tx) represents the only option for end-stage pulmonary vascular disease.

METHODS

Clinical data of children with idiopathic pulmonary arterial hypertension (IPAH) referred for Tx assessment between January 2002 and June 2007 were related to listing decision and outcome.

RESULTS

Seven of the 14 children assessed for Tx were listed. Five were transplanted (lung Tx, n = 3; heart-lung Tx, n = 2) and two died on the waiting list. Mean age at diagnosis was 3.7 (0.4-9.5) years. Time from diagnosis to listing was 3.6 years (range 1.4-9.3). Children listed were in a worse functional class (WHO 3.5 vs. 2.5; P = 0.0006), had a lower SpO(2) on exercise (76.5% vs. 89%; P = 0.0001) and a shorter 6-min walk distance (154 m vs. 330 m; P < 0.01) than those not listed. Right ventricular function was worse in those listed (P = 0.03), as was pulmonary vascular resistance index (PVRI) on vasodilator testing (34 U m(2) vs. 14.6 U m(2); P = 0.03). Age at diagnosis and at assessment, weight, height, mean pulmonary artery pressure, baseline PVRI, B-type natriuretic peptide, spirometry and resting-SO(2) did not differ between the two groups. For the five children transplanted, median waiting time was 81 days. Age at Tx was 5.4 years. After 2.8 years all transplanted children are alive with a good functional outcome. Two patients died on the active waiting list. All children considered too well for listing are still alive and stable on treatment.

CONCLUSIONS

Outcome after transplantation in children with IPAH has been encouraging. Defining listing criteria for these patients remains a challenge.

Prostacyclin in the intensive care setting

The prostacyclins-prostanoids were one of the first medications used to treat pulmonary arterial hypertension (PAH). Three prostanoids have been developed to treat PAH: epoprostenol, treprostinil, and iloprost. In the acute setting, experience is growing, using the inhaled forms of these three medications. Inhalation may improve ventilation/perfusion matching, whereas in the intravenous form these medications may cause nonselective pulmonary vasodilation and may worsen ventilation/perfusion matching. Currently, there are no universal recommendations for dosing delivery of inhaled prostanoids to intubated patients in the intensive care unit setting.

The role of calcium channel blockers, steroids, anticoagulation, antiplatelet drugs, and endothelin receptor antagonists

The rationale for the drug therapy of pulmonary artery hypertension is to reduce mortality and morbidity caused by failure of right ventricular adaptation to an elevated pulmonary vascular resistance. We review the evidence for the use of calcium-channel blockers, steroids, anticoagulation, antiplatelet drugs, and endothelin receptor antagonists in the management of pulmonary artery hypertension. The drugs we discuss are more suited to long-term outpatient therapy. These drugs have not found a routine place in intensive care management, and calcium-channel blockers are contraindicated in patients with right-heart failure. The efficacy of many agents has been extrapolated from data acquired in adult patients and applied to children. All of us involved in the care of young patients with pulmonary artery hypertension should advocate for both the inclusion of younger patients in clinical trials and the design of distinctly pediatric trials with pharmaceutical and drug administration agencies. It is only with data derived from pediatric inclusive studies that we shall be able to recommend therapy with strong evidence. However, it is important to point out that the use of newer agents for the treatment of chronic pulmonary artery hypertension (prostacyclin, endothelin receptor antagonists, nitric oxide, and sildenafil) have not been shown to improve survival unequivocally and have relied on surrogates, such as exercise capacity. There are no long-term studies of survival benefit. Recent studies have included data on time to clinical worsening, which may be a more predictive surrogate of survival.

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.

Potts anastomosis for children with idiopathic pulmonary hypertension

Mortality in children with idiopathic pulmonary arterial hypertension is high, emphasizing the need for novel therapeutic approaches. A surgical approach consisting in the creation of anastomosis between descending aorta and left pulmonary artery, the Potts shunt, has been proposed to decompress right ventricle. We reported two cases of severe idiopathic pulmonary hypertension in children with right heart failure refractory to medical treatment who benefited of Potts shunt.

Clinical characterization of pediatric pulmonary hypertension: complex presentation and diagnosis

OBJECTIVES

To describe the clinical presentation of pediatric pulmonary arterial hypertension (PAH) and the intricacies of how to classify pediatric PAH according to the Venice classification.

STUDY DESIGN

Children (n = 63) seen at a national referral center for pediatric PAH underwent a diagnostic work-up for diagnosis of pulmonary hypertension (PH) and associated conditions and for assessment of the explanatory role of associated conditions for the PH. Subsequently, PH was classified.

RESULTS

In 18 patients (29%), no associated conditions were identified; they were classified as having idiopathic PAH. In 45 patients (71%), > or = 1 associated conditions were detected: congenital heart defects (CHD, n = 40), connective tissue disease (CTD, n = 2), disorders of respiratory system and/or hypoxemia (RSH, n = 17), and chronic thromboembolic disease (CTE, n = 1). Patients were classified according to the condition judged to be primarily explanatory for the PH. In 11 of 45 patients with associated conditions, the PH was not sufficiently explained by these conditions; these patients were classified as having idiopathic-like PAH. In 17 of 40 cases of CHD and 9 of 17 cases of RSH, these conditions were not sufficiently explanatory for the PH. Syndromal abnormalities were frequent (43%). Ultimately, classification revealed idiopathic (-like) PAH (n = 29; 46%), PAH-CHD (n = 23; 37%), PAH-CTD (n = 2; 3%), PH-RSH (n = 8; 12%), and CTE-PH (n = 1; 2%).

CONCLUSION

Pediatric PH frequently presents with associated conditions and syndromal abnormalities. However, detailed evaluation of this complex presentation reveals that associated conditions are not always explanatory for the PH.

Updated evidence-based treatment algorithm in pulmonary arterial hypertension

Uncontrolled and controlled clinical trials with different compounds and procedures are reviewed to define the risk-benefit profiles for therapeutic options in pulmonary arterial hypertension (PAH). A grading system for the level of evidence of treatments based on the controlled clinical trials performed with each compound is used to propose an evidence-based treatment algorithm. The algorithm includes drugs approved by regulatory agencies for the treatment of PAH and/or drugs available for other indications. The different treatments have been evaluated mainly in idiopathic PAH, heritable PAH, and in PAH associated with the scleroderma spectrum of diseases or with anorexigen use. Extrapolation of these recommendations to other PAH subgroups should be done with caution. Oral anticoagulation is proposed for most patients; diuretic treatment and supplemental oxygen are indicated in cases of fluid retention and hypoxemia, respectively. High doses of calcium-channel blockers are indicated only in the minority of patients who respond to acute vasoreactivity testing. Nonresponders to acute vasoreactivity testing or responders who remain in World Health Organization (WHO) functional class III, should be considered candidates for treatment with either an oral phosphodiesterase-5 inhibitor or an oral endothelin-receptor antagonist. Continuous intravenous administration of epoprostenol remains the treatment of choice in WHO functional class IV patients. Combination therapy is recommended for patients treated with PAH monotherapy who remain in WHO functional class III. Atrial septostomy and lung transplantation are indicated for refractory patients or where medical treatment is unavailable.

Clinical practice: pulmonary hypertension in children

INTRODUCTION

Pulmonary arterial hypertension is a rare disorder in childhood, the two most common types being idiopathic pulmonary arterial hypertension and pulmonary hypertension associated with congenital left-to-right shunt lesions, together accounting for almost 90% of cases.

DISCUSSION

The clinical presentation of idiopathic pulmonary arterial hypertension (familial and non familial) is essentially non-specific and varies with age. Pulmonary vasoreactivity testing identifies responders and non-responders. Responders are treated with calcium channel blockers and have a better prognosis. Non-responders have a very limited survival beyond diagnosis if not treated with more selective pulmonary arterial vasodilators. Prostacyclin, endothelin receptor antagonists and phosphodiesterase-5 inhibitors improve haemodynamics, functional class and exercise tolerance and delay deterioration. Patients with congenital left-to-right shunts and irreversible pulmonary arterial hypertension leading to Eisenmenger's syndrome have multiple organ disease. Despite a very pronounced exercise intolerance, their clinical course is rather stable with survival up to 40-60 years, depending on the complexity of their underlying cardiac defect. Treatment is based on general measures along with the same three types of selective pulmonary vasodilators as in idiopathic pulmonary arterial disease. Improvement in haemodynamics, functional class and exercise tolerance are comparable for both patient groups.

CONCLUSION

Pulmonary hypertension in children is idiopathic or associated with congenital heart disease in the majority of patients. Treatment with new selective pulmonary vasodilators offers haemodynamic and functional improvement.

Review of inhaled iloprost for the control of pulmonary artery hypertension in children

In the pediatric population, pulmonary hypertension may present as an acute event in the setting of lung or cardiac pathology or as a chronic disease, mainly as idiopathic pulmonary hypertension or associated with congenital heart disease. Recently, new pharmacologic approaches have demonstrated significant efficacy in the management of adults with pulmonary arterial hypertension; these include intravenous epoprostenol, prostacyclin analogs, endothelin receptor antagonists and phosphodiesterase type 5 inhibitors. The same treatment strategies are currently used in children. There are only few reports of the use of inhaled iloprost in pediatrics, only one of which reported the use of chronic inhaled iloprost in a significant number of children. This report showed that 1) the acute pulmonary vasodilator response to inhaled iloprost is equivalent to that of inhaled nitric oxide; 2) acute inhalation of iloprost can induce bronchoconstriction 3) the addition of inhaled iloprost can reduce the need for intravenous prostanoid therapy in some patients; 4) most children tolerated the combination of inhaled iloprost and endothelin receptor antagonist or phosphodiesterase inhibitors; 5) Several patients had clinical deterioration during chronic inhaled iloprost therapy and required rescue therapy with intravenous prostanoids. In this review we will discuss the role of inhaled iloprost in acute and chronic pulmonary hypertension in children.

Pulmonary arterial hypertension in children: a medical update

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a progressive pulmonary vasculopathy with ensuing right heart failure if left untreated. In the 1980's, prior to the current treatment era, idiopathic pulmonary arterial hypertension (IPAH) carried a poor prognosis with a 10 month median survival for children after diagnosis. However, in 1995 continuous intravenous epoprostenol was approved for the treatment of severe PAH, improving hemodynamics, quality of life, exercise capacity, functional class and survival. In the past decade there have been further advances in the treatment of PAH; however, there is still no cure. While much of the groundbreaking clinical research has been performed in adults, children have also seen the benefits of PAH novel therapies. The target population among pediatric patients is expanding with the recent recognition of pulmonary hypertension as a risk factor for sickle cell disease patients. With rapid advances, navigating the literature becomes challenging. A comprehensive review of the most recent literature over the past year on available and emerging novel therapies as well as an approach to target pediatric populations provides insights into the management of pediatric PAH patients.

Safety and efficacy of autologous endothelial progenitor cells transplantation in children with idiopathic pulmonary arterial hypertension: open-label pilot study

Experimental data suggest that transplantation of EPCs attenuates monocrotaline-induced pulmonary hypertension in rats and dogs. In addition, our previous studies suggested that autologous EPC transplantation was feasible, safe, and might have beneficial effects on exercise capacity and pulmonary hemodynamics in adults with IPAH. Thus, we hypothesized that transplantation of EPCs would improve exercise capacity and pulmonary hemodynamics in children with IPAH. Thirteen children with IPAH received intravenous infusion of autologous EPCs. The right-sided heart catheterization and 6-MWD test were performed at baseline and at the time of 12 wk after cell infusion. At the time of 12 wk, mPAP decreased by 6.4 mmHg from 70.3 +/- 19.0 to 63.9 +/- 19.3 mmHg (p = 0.015). PVR decreased by approximately 19% from 1118 +/- 537 to 906 +/- 377 dyn s/cm(5) (p = 0.047). CO increased from 3.39 +/- 0.79 to 3.85 +/- 0.42 L/min (p = 0.048). The 6-MWD increased by 39 m from 359 +/- 82 to 399 +/- 74 m (p = 0.012). NYHA functional class also improved. There were no severe adverse events with cell infusion. The small pilot study suggested that intravenous infusion of autologous EPCs was feasible, safe, and associated with significant improvements in exercise capacity, NYHA functional class, and pulmonary hemodynamics in children with IPAH. Confirmation of these results in a randomized controlled trial are essential.

Safety experience with bosentan in 146 children 2-11 years old with pulmonary arterial hypertension: results from the European Postmarketing Surveillance program

The oral dual endothelin receptor antagonist bosentan has been shown to improve the short- and medium-term course of adult pulmonary arterial hypertension (PAH); however, data from clinical studies in children are limited. This analysis investigated the safety profile of bosentan in pediatric patients in a European, prospective, noninterventional, Internet-based postmarketing surveillance database (Tracleer PMS). Pediatric patients (aged 2-11 y) were compared with patients aged > or =12 y. Over a 30-mo period, 4994 patients, including 146 bosentan-naïve pediatric patients (51.4% males), were captured in the database. Predominant etiologies in children were idiopathic PAH (40.4%) and PAH related to congenital heart disease (45.2%). The majority of children were in New York Heart Association functional class II (28.1%) or III (50.7%), and median exposure to bosentan was 29.1 wk. Elevated aminotransferases were reported in 2.7% of children versus 7.8% of patients > or =12 y. The discontinuation rate was 14.4% in children versus 28.1% in patients > or =12 y. The Tracleer PMS results provide unique information on pediatric PAH in Europe. They also suggest that Tracleer may be better tolerated in children than in adults. This observation confirms the value of monthly monitoring of liver function for the duration of bosentan treatment.

Pulmonary arterial hypertension in children: a medical update

PURPOSE OF REVIEW

With rapid advances in the understanding and treatment of pulmonary arterial hypertension, navigating the pediatric literature becomes challenging. A comprehensive review of the most recent literature over the past year on available and emerging novel therapies as well as an approach to target pediatric populations will provide insight into the current management of pediatric pulmonary hypertension patients.

RECENT FINDINGS

Recent therapeutic advances have significantly improved the prognosis for children with pulmonary arterial hypertension. Pediatric pulmonary arterial hypertension continues to be a serious condition, however, which is extremely challenging to manage. There are also new target groups, such as those with sickle cell disease, congenital diaphragmatic hernia and Eisenmenger syndrome who may be candidates for treatments previously used for idiopathic pulmonary arterial hypertension patients.

SUMMARY

The data in children are often limited to case reports as many of those described here. Thus, the reader needs to be cautious about the interpretation of such small uncontrolled studies. While many of these data support the rationale for using novel agents for children with pulmonary arterial hypertension, further controlled and well designed studies are necessary to assess the true impact of these agents on various subgroups of children with pulmonary arterial hypertension.

Short- and long-term effects of inhaled iloprost therapy in children with pulmonary arterial hypertension

OBJECTIVES

This study investigated the short- and long-term outcome of children with pulmonary arterial hypertension (PAH) treated with inhaled iloprost.

BACKGROUND

Inhaled iloprost has been approved for the treatment of adults with PAH, but little is known about the effects in children with PAH.

METHODS

We evaluated the acute effects of inhaled iloprost on hemodynamic status and lung function and the response to long-term therapy in 22 children (range 4.5 to 17.7 years) with PAH (idiopathic, n = 12; congenital heart disease, n = 10). Cardiac catheterization, standard lung function testing before and after iloprost inhalation, 6-min walk test, World Health Organization functional class, and hemodynamic parameters were monitored.

RESULTS

Acute administration of inhaled iloprost lowered mean pulmonary artery pressure equivalent to the response to inhaled nitric oxide with oxygen. Acute iloprost inhalation reduced forced expiratory volume in 1 s and mid-volume forced expiratory flow by 5% and 10%, respectively, consistent with acute bronchoconstriction. At 6 months, functional class improved in 35%, decreased in 15%, and remained unchanged in 50% of children. Sixty-four percent of patients continued receiving long-term iloprost therapy, 36% stopped iloprost, due to lower airway reactivity, clinical deterioration, or death. In 9 patients on chronic intravenous prostanoids, 8 transitioned from intravenous prostanoids to inhaled iloprost, which continued during follow-up.

CONCLUSIONS

Inhaled iloprost caused sustained functional improvement in some children with PAH, although inhaled iloprost occasionally induced bronchoconstriction. Most patients tolerated the transition from intravenous to inhaled prostanoid therapy. Clinical deterioration, side effects, and poor compliance, owing to the frequency of treatments, could limit chronic treatment in children.

Living-donor lobar lung transplantation for pulmonary arterial hypertension after failure of epoprostenol therapy

OBJECTIVES

The aim of this study was to evaluate the long-term effects of living-donor lobar lung transplantation (LDLLT) for critically ill patients with pulmonary arterial hypertension (PAH) who failed in epoprostenol treatment.

BACKGROUND

Although continuous epoprostenol infusion has markedly improved survival in patients with PAH, some patients do not benefit from this therapy.

METHODS

From July 1998 to December 2003, 28 consecutive PAH patients who were treated with epoprostenol and accepted as candidates for lung transplantation were enrolled. All data were prospectively collected. As of July 2006, LDLLT was performed in 11 of those patients whose condition was deteriorating. Cadaveric lung transplantation (CLT) was performed in 2 patients. Medical treatment was continued in 15 patients.

RESULTS

There was no mortality in patients receiving LDLLT during a follow-up period of 11 to 66 months (average 48 months), and all patients returned to World Health Organization functional class I. Mean pulmonary artery pressure decreased from 62 +/- 4 mm Hg to 15 +/- 2 mm Hg (p < 0.001) at discharge and remained normal at 3 years. One CLT patient died of primary graft failure. Among medically treated patients, 6 patients died of disease progression. The survival rate was 100% at 5 years for patients receiving LDLLT, and 80% at 1 year, 67% at 3 years, and 53% at 5 years for patients medically treated (p = 0.028). All living donors have returned to their previous lifestyles.

CONCLUSIONS

These follow-up data support the option of LDLLT in patients with PAH who would die soon otherwise.

Atrial septostomy improves survival in select patients with pulmonary hypertension

BACKGROUND

Atrial septostomy is a palliative treatment for patients with pulmonary hypertension (PHTN) refractory to vasodilator therapy. Limited data exist in the pediatric population and in patients with repaired congenital heart defects.

METHODS

We performed a retrospective analysis of hemodynamic and symptomatic changes in patients with PHTN who underwent an atrial septostomy at our institution.

RESULTS

Forty-six atrial septostomies were performed on 43 patients. Patient ages ranged from 0.3 to 30 years (median 12.5). Of 43 patients, 29 had primary PHTN, 10 had PHTN associated with repaired congenital heart defects, and 4 had other secondary causes of PHTN. Mean baseline pulmonary vascular resistance was 35 +/- 17 Wood units, and mean pulmonary artery pressure was 74 +/- 19 mm Hg. Patients surviving > or = 30 days had immediate improvement in cardiac index (from 2.3 to 2.9 L x min(-1) x m(-2), P < .0001), right atrial pressure (RAp) (from 9.9 to 8.3 mm Hg, P < .05), and oxygen delivery (from 424 to 491 mL O2 per minute, P < .01), with a decrease in systemic oxygen saturation (from 93% to 86%, P < .001). Pulmonary artery pressure was unchanged (P = .3). New York Heart Association class and symptoms of syncope improved (P < .01). Event-free survival at 1, 2, and 3 years was 84%, 77%, and 69%, respectively. Using the National Institutes of Health Registry model, predicted survival probability significantly improved (P < .001). Ten patients (22%) died within 30 days of catheterization. Mortality was associated with preceding decompensations in the intensive care unit (6/10, P < .001) and a higher RAp (21.4 vs 9.8 mm Hg, P < .001).

CONCLUSIONS

Atrial septostomy provides symptomatic and hemodynamic improvement in cardiac index and RAp. Risk of septostomy is increased in patients with preceding decompensation or a RAp > 18 mm Hg.

Pulmonary arterial hypertension in the pediatric age

Pulmonary hypertension is defined as a mean pulmonary artery pressure more than 25 mmHg at rest or 30 mmHg on exercise. Pathogenesis of pulmonary hypertension is recognized to be multifactorial: vasoconstriction, proliferation, inflammation, and thrombosis. The main point in the clinical management is to assess the potential causes, the degree of functional and hemodynamic impairment and the available therapeutic options. Treatment of children with idiopathic pulmonary hypertension is similar to that of adults, but the results are often difficult to predict, with clinical deterioration being very rapid in early symptomatic patients. However, the availability of chronic vasodilator therapy, in particular epoprostenol, has led to a significant improvement in survival of children with idiopathic pulmonary hypertension and oral vasodilator agents are currently being evaluated. Moreover, lung transplantation is, nowadays, a reality even in children. Survival for patients with idiopathic pulmonary hypertension undergoing lung transplantation is approximately 65% at 1 year and 45% at 5 years. Accepted indications are severe clinical deterioration (New York Heart Association class III or IV) despite available medical treatments including intravenous epoprostenol. Timing for listing the patient is a difficult issue that should take into account possible markers of poor prognosis on medical therapy together with mortality rate of lung transplantation, local organ availability and mean waiting time on the list before transplantation.

Sitaxsentan: a selective endothelin-A receptor antagonist, for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive, life-threatening condition. Sitaxsentan, a selective endothelin-A receptor antagonist, is an effective, safe and well-tolerated endothelin receptor antagonist for the treatment of PAH in adult patients. Multi-center, randomized, placebo-controlled clinical trials have demonstrated that sitaxsentan has beneficial effects on exercise capacity (i.e., 6-min walk distance), functional class and hemodynamic parameters in PAH patients. Sitaxsentan has a low incidence of acute hepatotoxicity. Patients on concomitant warfarin require a decrease in warfarin dose to maintain a therapeutic international normalized ratio. The demonstration of clinical efficacy and low incidence of acute hepatotoxicity support the potential use of sitaxsentan for the treatment of PAH.

Epoprostenol treatment in children with severe pulmonary hypertension

INTRODUCTION

Severe, sustained pulmonary arterial hypertension leads to a progressive reduction in exercise capacity, right heart failure and death. Use of intravenous epoprostenol has improved survival in adults, but data are limited in children.

PATIENTS AND METHODS

This study included all 39 children treated with continuous intravenous epoprostenol since November 1997 at Great Ormond Street Hospital for Children (London, UK). Patients were aged 4 months to 17 years (median 5.4 years) at the onset of therapy. The male:female ratio was 1:1.3. 25 patients had idiopathic pulmonary arterial hypertension and 14 had pulmonary arterial hypertension associated with congenital heart disease, connective tissue disease, chronic lung disease or HIV. All were in WHO functional class III and IV. Mean pulmonary arterial pressure (SD) was 59 (17) mmHg and mean pulmonary vascular resistance was 23.3 (11.6) units x m(2). Patients were assessed regularly (2-3 monthly intervals) by physical examination, electrocardiography, transthoracic echocardiography and a 6-min walk test, when practicable.

RESULTS

The mean duration of follow-up was 27 (21) months. 7 patients died and 8 underwent transplantation. Cumulative survival at 1, 2 and 3 years was 94, 90 and 84%. The 6-min walking distance improved by a mean of 77 m (p<0.003). WHO functional class improved during the first year (p<0.001) and improvement was maintained for up to 3 years. Weight improved significantly from a baseline z score of -1.55 (1.74) to -1.16 (1.8) (p<0.03). 28 children had additional oral specific therapy. Hickman line changes were 0.33/patient year.

CONCLUSIONS

Epoprostenol therapy improved survival, WHO functional class, exercise tolerance and ability to thrive in children with severe pulmonary arterial hypertension. Epoprostenol represents an effective and feasible therapy even in young children.

Current treatment options in children with pulmonary arterial hypertension and experiences with oral bosentan

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by vasoconstriction and progressive remodelling of the pulmonary arterial wall leading to right ventricular failure and death. Idiopathic PAH (IPAH) and PAH associated with congenital heart defects account for the majority of paediatric patients with PAH. During the last few decades, several pharmacological approaches have been introduced, including calcium channel-blockers (CCBs), prostacyclin analogues, endothelin receptor antagonists and, most recently, phosphodiesterase inhibitors. This paper reviews the treatment options available to children with a special focus on the initial experience with bosentan. Although CCBs have been shown to increase survival in IPAH, the beneficial effect appears to be limited to a small number of patients, defined as 'responders' to the vasoreactivity testing. With the availability of prostacyclin (intravenous epoprostenol) and then prostacyclin analogues, the treatment options have increased markedly and particularly in patients who have not responded to conventional therapy. Although epoprostenol has been shown to be efficacious in PAH, the drug is not ideal owing to serious complications arising from the invasive mode of application, particularly in children. Phosphodiesterase-5 inhibitors have also shown beneficial effects. Targeting the endothelin (ET) system with the oral, dual ET(A)/ET(B) receptor antagonist, bosentan has been demonstrated to improve the cardiopulmonary haemodynamics, exercise capacity, quality-of-life and survival in adult patients with PAH. Specific ET(A) antagonists may also present the same beneficial profile. Recent experience with bosentan in paediatric patients with PAH indicates that the results obtained in adult patients may be extrapolated to children, thus offering a safe and effective therapy that is easy to administer.

Survival in patients with pulmonary arterial hypertension treated with first-line bosentan

BACKGROUND

Pulmonary arterial hypertension (PAH) is a devastating disease of the small pulmonary arteries and arterioles, characterized by intimal fibrosis, medial hypertrophy and plexiform lesions. When untreated both the idiopathic form (IPAH, formerly termed primary pulmonary hypertension, PPH) and PAH related to various other conditions such as scleroderma (SSc) often take a progressive course with high mortality. There is ongoing search for disease-specific treatments that are able to improve survival in these patients. The oral dual endothelin (ET(A)/ET(B)) antagonist bosentan has been shown to improve exercise capacity, time to clinical worsening, haemodynamics and quality of life in short-term studies.

MATERIALS AND METHODS

To determine the long-term effects of bosentan on survival, patients from the two double-blind, randomized trials and their open-label extensions, treated with first-line bosentan, were followed for up to 3 years. Data on survival were collected between September 1999 (first patient included in the placebo-controlled trials) and December 2002. Vital status was verified in each patient. The survival cohorts of these patients were compared with either the predicted survival for each patient based on an equation from the National Institutes of Health (NIH) PPH registry or with historical controls.

RESULTS

Observed survival up to 36 months was reported as a Kaplan-Meier estimate in three cohorts: (1) In 169 PPH patients treated with first-line bosentan, 1- and 2-year survival was 96% and 89%, respectively, vs. predicted untreated survival at 1 and 2 years of 69% and 57%, respectively; (2) in 50 patients with PAH associated with SSc (PAH-SSc), 1-, 2- and 3-year survival was 82%, 67% and 64%, respectively, vs. approximately 45%, approximately 35% and approximately 28%, respectively, from registry data of untreated PAH-SSc patients; and (3) in 139 PPH patients in WHO functional class III, 1- and 2-year survival was 97% and 91%, respectively, vs. 91% and 84% in a historical cohort of 346 patients treated with epoprostenol in five major referral centres.

CONCLUSIONS

The present analyses suggest that first-line bosentan therapy, followed by the addition of other disease-specific therapies as required, improves survival in patients with advanced PAH.