Recent advances in the treatment of pediatric pulmonary artery hypertension

Update on pediatric pulmonary arterial hypertension

PURPOSE OF REVIEW

Pulmonary arterial hypertension (PAH) causes high morbidity and mortality in children. In this review, we discuss advances in diagnosis and treatment of this disorder.

RECENT FINDINGS

Proceedings published from the 2018 World Symposium updated the definition of pulmonary hypertension to include all adults and children with mean pulmonary artery pressure more than 20 mmHg. Targeted PAH therapy is increasingly used off-label, but in 2017, bosentan became the first Food and Drug Administration-targeted PAH therapy approved for use in children.

SUMMARY

In recent years, advanced imaging and clinical monitoring have allowed improved risk stratification of pulmonary hypertension patients. New therapies, approved in adults and used off-label in pediatric patients, have led to improved outcomes for affected children.

Pediatric Pulmonary Arterial Hypertension

Pulmonary hypertension (PH), the syndrome of increased pressure in the pulmonary arteries, is associated with significant morbidity and mortality for affected children and is associated with a variety of potential underlying causes. Several pulmonary arterial hypertension-targeted therapies have become available to reduce pulmonary artery pressure and improve outcome, but there is still no cure for most patients. This review provides a description of select causes of PH encountered in pediatrics and an update on the most recent data pertaining to evaluation and management of children with PH. Available evidence for specific classes of PH-targeted therapies in pediatrics is discussed.

Diagnosis, Evaluation and Treatment of Pulmonary Arterial Hypertension in Children

Pulmonary Hypertension (PH), the syndrome of elevated pressure in the pulmonary arteries, is associated with significant morbidity and mortality for affected children. PH is associated with a wide variety of potential underlying causes, including cardiac, pulmonary, hematologic and rheumatologic abnormalities. Regardless of the cause, for many patients the natural history of PH involves progressive elevation in pulmonary arterial resistance and pressure, right ventricular dysfunction, and eventually heart failure. In recent years, a number of pulmonary arterial hypertension (PAH)-targeted therapies have become available to reduce pulmonary artery pressure and improve outcome. A growing body of evidence in both the adult and pediatric literature demonstrates enhanced quality of life, functional status, and survival among treated patients. This review provides a description of select etiologies of PH seen in pediatrics and an update on the most recent data pertaining to evaluation and management of children with PH/PAH. The available evidence for specific classes of PAH-targeted therapies in pediatrics is additionally discussed.

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.

A role for actin polymerization in persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is defined as the failure of normal pulmonary vascular relaxation at birth. Hypoxia is known to impede postnatal disassembly of the actin cytoskeleton in pulmonary arterial myocytes, resulting in elevation of smooth muscle α-actin and γ-actin content in elastic and resistance pulmonary arteries in PPHN compared with age-matched controls. This review examines the original histological characterization of PPHN with attention to cytoskeletal structural remodeling and actin isoform abundance, reviews the existing evidence for understanding the biophysical and biochemical forces at play during neonatal circulatory transition, and specifically addresses the role of the cortical actin architecture, primarily identified as γ-actin, in the transduction of mechanical force in the hypoxic PPHN pulmonary circuit.

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.

Endothelial and smooth muscle cell ion channels in pulmonary vasoconstriction and vascular remodeling

The pulmonary circulation is a low resistance and low pressure system. Sustained pulmonary vasoconstriction and excessive vascular remodeling often occur under pathophysiological conditions such as in patients with pulmonary hypertension. Pulmonary vasoconstriction is a consequence of smooth muscle contraction. Many factors released from the endothelium contribute to regulating pulmonary vascular tone, while the extracellular matrix in the adventitia is the major determinant of vascular wall compliance. Pulmonary vascular remodeling is characterized by adventitial and medial hypertrophy due to fibroblast and smooth muscle cell proliferation, neointimal proliferation, intimal, and plexiform lesions that obliterate the lumen, muscularization of precapillary arterioles, and in situ thrombosis. A rise in cytosolic free Ca(2+) concentration ([Ca(2+)]cyt) in pulmonary artery smooth muscle cells (PASMC) is a major trigger for pulmonary vasoconstriction, while increased release of mitogenic factors, upregulation (or downregulation) of ion channels and transporters, and abnormalities in intracellular signaling cascades are key to the remodeling of the pulmonary vasculature. Changes in the expression, function, and regulation of ion channels in PASMC and pulmonary arterial endothelial cells play an important role in the regulation of vascular tone and development of vascular remodeling. This article will focus on describing the ion channels and transporters that are involved in the regulation of pulmonary vascular function and structure and illustrating the potential pathogenic role of ion channels and transporters in the development of pulmonary vascular disease.

Chronic hypoxia selectively enhances L- and T-type voltage-dependent Ca2+ channel activity in pulmonary artery by upregulating Cav1.2 and Cav3.2

Hypoxia-induced pulmonary hypertension (HPH) is characterized by sustained pulmonary vasoconstriction and vascular remodeling, both of which are mediated by pulmonary artery smooth muscle cell (PASMC) contraction and proliferation, respectively. An increase in cytosolic Ca²⁺ concentration ([Ca²⁺]cyt) is a major trigger for pulmonary vasoconstriction and an important stimulus for cell proliferation in PASMCs. Ca²⁺ influx through voltage-dependent Ca²⁺ channels (VDCC) is an important pathway for the regulation of [Ca²⁺]cyt. The potential role for L- and T-type VDCC in the development of HPH is still unclear. Using a hypoxic-induced pulmonary hypertension mouse model, we undertook this study to identify if VDCC in pulmonary artery (PA) are functionally upregulated and determine which type of VDCC are altered in HPH. Mice subjected to chronic hypoxia developed pulmonary hypertension within 4 wk, and high-K⁺- and U-46619-induced contraction of PA was greater in chronic hypoxic mice than that in normoxic control mice. Additionally, we demonstrate that high-K⁺- and U-46619-induced Ca²⁺ influx in PASMC is significantly increased in the hypoxic group. The VDCC activator, Bay K8864, induced greater contraction of the PA of hypoxic mice than in that of normoxic mice in isometric force measurements. L-type and T-type VDCC blockers significantly attenuated absolute contraction of the PA in hypoxic mice. Chronic hypoxia did not increase high-K⁺- and U-46619-induced contraction of mesenteric artery (MA). Compared with MA, PA displayed higher expression of calcium channel voltage-dependent L-type α1C-subunit (Cav1.2) and T-type α1H-subunit (Cav3.2) upon exposure to chronic hypoxia. In conclusion, both L-type and T-type VDCC were functionally upregulated in PA, but not MA, in HPH mice, which could result from selectively increased expression of Cav1.2 and Cav3.2.

Living-donor liver transplantation for moderate or severe porto-pulmonary hypertension accompanied by pulmonary arterial hypertension: a single-centre experience over 2 decades in Japan

BACKGROUND

Candidates for orthotopic liver transplantation (OLT) often have porto-pulmonary hypertension (PPHTN) with pulmonary arterial hypertension (PAH). Poor outcomes of PPHTN contraindicate OLT. There are no guidelines for living-donor liver transplantation (LDLT) in PPHTN patients.

METHODS

We present our experiences of LDLT in six patients with moderate or severe PPHTN, along with our institutional guidelines. Three had liver cirrhosis and three were non-cirrhotic. Catheterization studies were undertaken before, during and after LDLT, and the mean pulmonary arterial pressure (mPAP), cardiac output (CO), pulmonary vascular resistance and total peripheral resistance (TPR) were monitored.

RESULTS

The results showed significant differences in CO and TPR between cirrhotic and non-cirrhotic patients before, during and after LDLT. Cirrhotic patients showed systemic hyperdynamic state. Two cirrhotic patients showed poor responses to pre-transplant treatment, and continued to have increased PAH and poor clinical courses after LDLT. LDLT has an advantage of flexible timing of LT. Currently in our institution, PPHTN patients with mPAP <40 mmHg are registered for LDLT after treatment and catheterization. However, LDLT is performed when mPAP is ≤35 mmHg, leading to improved outcomes.

CONCLUSION

PPHTN patients with well-controlled PAH, or secondary PAH resulting from porto-systemic shunts, may be appropriate candidates for LDLT after careful considerations.

Functional characterization of voltage-dependent Ca(2+) channels in mouse pulmonary arterial smooth muscle cells: divergent effect of ROS

Electromechanical coupling via membrane depolarization-mediated activation of voltage-dependent Ca(2+) channels (VDCC) is an important mechanism in regulating pulmonary vascular tone, while mouse is an animal model often used to study pathogenic mechanisms of pulmonary vascular disease. The function of VDCC in mouse pulmonary artery (PA) smooth muscle cells (PASMC), however, has not been characterized, and their functional role in reactive oxygen species (ROS)-mediated regulation of vascular function remains unclear. In this study, we characterized the electrophysiological and pharmacological properties of VDCC in PASMC and the divergent effects of ROS produced by xanthine oxidase (XO) and hypoxanthine (HX) on VDCC in PA and mesenteric artery (MA). Our data show that removal of extracellular Ca(2+) or application of nifedipine, a dihydropyridine VDCC blocker, both significantly inhibited 80 mM K(+)-mediated PA contraction. In freshly dissociated PASMC, the maximum inward Ca(2+) currents were -2.6 ± 0.2 pA/pF at +10 mV (with a holding potential of -70 mV). Window currents were between -40 and +10 mV with a peak at -15.4 mV. Nifedipine inhibited currents with an IC(50) of 0.023 μM, and 1 μM Bay K8644, a dihydropyridine VDCC agonist, increased the inward currents by 61%. XO/HX attenuated 60 mM K(+)-mediated increase in cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)) due to Ca(2+) influx through VDCC in PASMC. Exposure to XO/HX caused relaxation in PA preconstricted by 80 mM K(+) but not in aorta and MA. In contrast, H(2)O(2) inhibited high K(+)-mediated increase in [Ca(2+)](cyt) and caused relaxation in both PA and MA. Indeed, RT-PCR and Western blot analysis revealed significantly lower expression of Ca(V)1.3 in MA compared with PA. Thus our study characterized the properties of VDCC and demonstrates that ROS differentially regulate vascular contraction by regulating VDCC in PA and systemic arteries.

Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Neonates and children differ from adults in physiology, pharmacologic responses to drugs, epidemiology, and long-term consequences of thrombosis. This guideline addresses optimal strategies for the management of thrombosis in neonates and children.

METHODS

The methods of this guideline follow those described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that where possible, pediatric hematologists with experience in thromboembolism manage pediatric patients with thromboembolism (Grade 2C). When this is not possible, we suggest a combination of a neonatologist/pediatrician and adult hematologist supported by consultation with an experienced pediatric hematologist (Grade 2C). We suggest that therapeutic unfractionated heparin in children is titrated to achieve a target anti-Xa range of 0.35 to 0.7 units/mL or an activated partial thromboplastin time range that correlates to this anti-Xa range or to a protamine titration range of 0.2 to 0.4 units/mL (Grade 2C). For neonates and children receiving either daily or bid therapeutic low-molecular-weight heparin, we suggest that the drug be monitored to a target range of 0.5 to 1.0 units/mL in a sample taken 4 to 6 h after subcutaneous injection or, alternatively, 0.5 to 0.8 units/mL in a sample taken 2 to 6 h after subcutaneous injection (Grade 2C).

CONCLUSIONS

The evidence supporting most recommendations for antithrombotic therapy in neonates and children remains weak. Studies addressing appropriate drug target ranges and monitoring requirements are urgently required in addition to site- and clinical situation-specific thrombosis management strategies.

New approaches to the treatment of pulmonary hypertension: from bench to bedside

Pulmonary hypertension (PH) is a severe, life-threatening disease for which there are no effective curative therapies. A diverse group of agents such as prostacyclins, endothelin antagonists, phosphodiesterase inhibitors, calcium channel blockers, diuretics, inotropic agents, and anticoagulants are used to treat PH; however, none of these agents have a marked effect upon survival. Among the new agents that promise treatment of PH are rho-kinase inhibitors and soluble guanylate cyclase stimulators. Although these new classes of agents have beneficial effects in experimental animal models and clinical studies, they are not selective in their actions on the pulmonary vascular bed. This manuscript reviews the actions of rho-kinase inhibitors and soluble guanylate cyclase stimulators on the pulmonary vascular bed. It is our hypothesis that these new agents may be more effective than current therapies in the treatment of PH. Moreover, new methods in the delivery of these agents to the lung need to be developed so that their main effects will be exerted in the pulmonary vascular bed and their systemic effects can be minimized or avoided.

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).

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.

Advances in diagnosis and treatment of pulmonary arterial hypertension in neonates and children with congenital heart disease

BACKGROUND

This article aims to review recent advances in the diagnosis and treatment of pulmonary arterial hypertension in neonates and children with congenital heart disease.

DATA SOURCES

Articles on pulmonary arterial hypertension in congenital heart disease were retrieved from PubMed and MEDLINE published after 1958.

RESULTS

A diagnosis of primary (or idiopathic) pulmonary arterial hypertension is made when no known risk factor is identified. Pulmonary arterial hypertension associated with congenital heart disease constitutes a heterogenous group of conditions and has been characterized by congenital systemic-to-pulmonary shunts. Despite the similarities in histologic appearance of pulmonary vascular disease, there are differences between pulmonary arterial hypertension secondary to congenital systemic-to-pulmonary shunts and those with other conditions with respect to pathophysiology, therapeutic strategies, and prognosis. Revision and subclassification within the category of secondary pulmonary arterial hypertension based on pathophysiology were conducted to improve specific treatments. The timing of surgical repair is crucial to prevent and minimize risk of postoperative pulmonary arterial hypertension. Drug therapies including prostacyclin, endothelin-receptor antagonist, phosphodiesterase inhibitor, and nitric oxide have been evolved with promising results in neonates and children.

CONCLUSIONS

Among the different forms of congenital heart diseases, an early correction generally prevents subsequent development of pulmonary arterial hypertension. Emerging therapies for treatment of patients with idiopathic pulmonary arterial hypertension also improve quality of life and survival in neonates and children with congenital heart disease associated with pulmonary arterial hypertension. Heart and lung transplantation or lung transplantation in combination with repair of the underlying cardiac defect is a therapeutic option in a minority of patients. Partial repair options are also beneficial in some selected cases. Randomized controlled trials are needed to evaluate the safety and efficacy of these therapies including survival and long-term outcome.

Pediatric Pulmonary Hypertension: A Pharmacotherapeutic Review

Pulmonary hypertension in children is a disorder associated with increased pulmonary vascular resistance and arterial pressure, decreased cardiac output, and right-sided cardiac dysfunction that is caused by numerous etiologies. Although treatment will vary with underlying cause, pharmacological treatment has historically included inhaled nitric oxide and prostacyclin analogues. Over the past several years new agents have been added to the treatment armamentarium, including phosphodiesterase V inhibitors (eg sildenafil) and endothelin antagonists (eg bosentan). Further, more agents are currently under investigation for pulmonary hypertension in children including immunosuppressives and other endothelin antagonist entities. Limitations to treatment include the availability of appropriate, robust pediatric pharmacological data and constraints with dosage forms.

Antithrombotic therapy in neonates and children: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter about antithrombotic therapy in neonates and children is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs, and Grade 2 suggests that individual patient values may lead to different choices (for a full understanding of the grading, see Guyatt et al in this supplement, pages 123S-131S). In this chapter, many recommendations are based on extrapolation of adult data, and the reader is referred to the appropriate chapters relating to guidelines for adult populations. Within this chapter, the majority of recommendations are separate for neonates and children, reflecting the significant differences in epidemiology of thrombosis and safety and efficacy of therapy in these two populations. Among the key recommendations in this chapter are the following: In children with first episode of venous thromboembolism (VTE), we recommend anticoagulant therapy with either unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) [Grade 1B]. Dosing of IV UFH should prolong the activated partial thromboplastin time (aPTT) to a range that corresponds to an anti-factor Xa assay (anti-FXa) level of 0.35 to 0.7 U/mL, whereas LMWH should achieve an anti-FXa level of 0.5 to 1.0 U/mL 4 h after an injection for twice-daily dosing. In neonates with first VTE, we suggest either anticoagulation or supportive care with radiologic monitoring and subsequent anticoagulation if extension of the thrombosis occurs during supportive care (Grade 2C). We recommend against the use of routine systemic thromboprophylaxis for children with central venous lines (Grade 1B). For children with cerebral sinovenous thrombosis (CSVT) without significant intracranial hemorrhage (ICH), we recommend anticoagulation initially with UFH, or LMWH and subsequently with LMWH or vitamin K antagonists (VKAs) for a minimum of 3 months (Grade 1B). For children with non-sickle-cell disease-related acute arterial ischemic stroke (AIS), we recommend UFH or LMWH or aspirin (1 to 5 mg/kg/d) as initial therapy until dissection and embolic causes have been excluded (Grade 1B). For neonates with a first AIS, in the absence of a documented ongoing cardioembolic source, we recommend against anticoagulation or aspirin therapy (Grade 1B).

Pulmonary hypertension in congenital diaphragmatic hernia

Clinically significant pulmonary hypertension (PHTN) is a common finding in newborn infants with congenital diaphragmatic hernia (CDH) resulting in right to left shunting at pre- and postductal level, hypoxemia, and acute right heart failure in those most severely affected. Even in those without clinical manifestations of ductal shunting, cardiac echo studies would suggest that increased pulmonary vascular resistance and right ventricular pressures are almost a universal finding in this disease, and in some instances, may persist well into the postnatal period. The lung is small and structurally abnormal, and the pulmonary vascular bed is not only reduced in size, but responds abnormally to vasodilators. During the last 20 years, "gentle" ventilation, delayed surgery, and improved peri-operative care have made the greatest impact in decreasing mortality in this condition. Use of PGE1 should be considered early if there is hemodynamically significant PHTN, right ventricular dysfunction, and the patent ductus arteriosus (PDA) is becoming restrictive. In individual patients, inhaled nitric oxide (iNO) might be helpful, but the response to iNO should be confirmed using echocardiography. In patients who survive operation and leave the hospital, there are chronic causes of morbidity that need to be looked for and managed in a multi-disciplinary follow-up clinic.

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.

Electrocardiography in the diagnosis of right ventricular hypertrophy in children

OBJECTIVE

Although the electrocardiogram is commonly obtained in the evaluation of patients with pulmonary hypertension, its value as a screening test for right ventricular hypertrophy or pulmonary hypertension is unclear. Therefore, we sought to determine the value of an electrocardiogram in the diagnosis of right ventricular hypertrophy using echocardiography as the gold standard.

METHODS

We identified children without congenital heart disease who underwent evaluation for suspected pulmonary hypertension that included both an electrocardiogram and echocardiography within a specified time frame.

RESULTS

A total of 76 echocardiography-electrocardiogram pairs for pulmonary hypertension were identified. Although there was a significant relationship between electrocardiogram and echocardiography evidence of right ventricular hypertrophy, the sensitivity of an electrocardiogram in diagnosing echocardiography-documented right ventricular hypertrophy was only 69%, and the positive predictive value was 67%. There was no relationship between electrocardiogram changes and Doppler tricuspid regurgitation gradient.

CONCLUSION

Despite a statistically significant relationship between an electrocardiogram and echocardiography in the diagnosis of right ventricular hypertrophy, an electrocardiogram has limited value as a screening tool for right ventricular hypertrophy because of its relatively low sensitivity and positive predictive value.

Transplantation as a treatment for end-stage pulmonary hypertension in childhood

Despite advances in drug therapy, severe sustained pulmonary arterial hypertension can be a fatal disease. When medical therapy is exhausted, transplantation may be an option. The most common approaches are heart-lung transplantation or double-lung transplantation, with repair of the cardiac defect if necessary. Single-lung transplantation optimises the use of scarce donors but leads to particular management problems. Heterotopic cardiac transplantation has occasionally been employed in subjects with pulmonary vascular disease secondary to cardiac disease. Timing of transplantation is a difficult decision and depends largely on the aetiology of pulmonary arterial hypertension and the rate of decline. Outcomes following transplantation are steadily improving but remain poorer than for other solid organ transplants, mainly because of the high incidence of post-transplant bronchiolitis obliterans syndrome.

Use of myocardial performance index in pediatric patients with idiopathic pulmonary arterial hypertension

BACKGROUND

The myocardial performance index (MPI) correlates with clinical status in adults with idiopathic pulmonary arterial (PA) hypertension (IPAH). This pediatric study used MPI to assess response to bosentan therapy.

METHODS

The study included 12 children with IPAH and 12 healthy control subjects. MPI was correlated with catheterization data at initiation of bosentan and at a median follow-up of 9 months. Therapy responders were defined by a greater than 20% decrease in mean PA pressure.

RESULTS

Right ventricular MPI for patients with IPAH was 0.64 +/- 0.30 versus 0.28 +/- 0.03 in control subjects (P < .01). It had a strong correlation with mean PA pressure (R = 0.94; P < .001). Right ventricular MPI decreased significantly in responders (range 20%-44%, mean 25%) with a 5% increase in nonresponders.

CONCLUSIONS

Right ventricular MPI in pediatric IPAH correlates with mean PA pressure and response to therapy. This study suggests that this noninvasive Doppler index may be useful to follow up children with IPAH, particularly when tricuspid regurgitation data are insufficient.

Epoprostenol and home mechanical ventilation for pulmonary hypertension associated with chronic lung disease

Pulmonary hypertension (PH) can be associated with bronchopulmonary dysplasia (BPD) of infancy, and mortality in these pediatric patients is high without aggressive medical treatment. Continuous intravenous epoprostenol (prostacyclin) was shown to lower pulmonary artery pressures (PAP) in children with idiopathic pulmonary arterial hypertension (PAH), formerly referred to as primary pulmonary hypertension. We report on the first case of long-term home ventilation in combination with chronic intravenous epoprostenol in a child with severe pulmonary hypertension associated with chronic lung disease. This aggressive combination resulted in significant improvement in pulmonary artery pressures, substantial improvement in quality of life, and eventual discontinuation of home ventilation.

Pathophysiologic mechanisms of persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN), among the most rapidly progressive and potentially fatal of vasculopathies, is a disorder of vascular transition from fetal to neonatal circulation, manifesting as hypoxemic respiratory failure. PPHN represents a common pathway of vascular injury activated by numerous perinatal stresses: hypoxia, hypoglycemia, cold stress, sepsis, and direct lung injury. As with other multifactorial diseases, a single inciting event may be augmented by multiple concurrent/subsequent phenomena that result in differing courses of disease progression. I review the various mechanisms of vascular injury involved in neonatal pulmonary hypertension: endothelial dysfunction, inflammation, hypoxia, and mechanical strain, in the context of downstream effects on pulmonary vascular endothelial-myocyte interactions and myocyte phenotypic plasticity.

Pediatric transplantation, 1994-2003

This article uses OPTN/SRTR data to review trends in pediatric transplantation over the last decade. In 2003, children younger than 18 made up 3% of the 82,885 candidates for organ transplantation and 7% of the 25,469 organ transplant recipients. Children accounted for 14% of the 6,455 deceased organ donors. Pediatric organ transplant recipients differ from their adult counterparts in several important aspects, including the underlying etiology of organ failure, the complexity of the surgical procedures, the pharmacokinetic properties of common immunosuppressants, the immune response following transplantation, the number and degree of comorbid conditions, and the susceptibility to post-transplant complications, especially infectious diseases. Specialized pediatric organ transplant programs have been developed to address these special problems. The transplant community has responded to the particular needs of children and has provided them special consideration in the allocation of deceased donor organs. As a result of these programs and protocols, children are now frequently the most successful recipients of organ transplantation; their outcomes following kidney, liver, and heart transplantation rank among the best. This article demonstrates that substantial improvement is needed in several areas: adolescent outcomes, outcomes following intestine transplants, and waiting list mortality among pediatric heart and lung candidates.

Severe paediatric pulmonary hypertension: new management strategies

Pulmonary hypertension is a significant complication in many paediatric disease states. This article discusses current understanding of pulmonary hypertension and includes definition, diagnosis, and management. A description of the latest advances in targeted pharmacological therapy in children is also provided as well as impact on morbidity and mortality.

Effect of continuous subcutaneous treprostinil therapy on the pharmacodynamics and pharmacokinetics of warfarin

Treprostinil sodium was recently approved in the United States for continuous subcutaneous infusion in the treatment of pulmonary arterial hypertension (PAH). Anticoagulation with warfarin is recommended in PAH therapy. Given the likelihood for treprostinil and warfarin coadministration, a single-blind, controlled, crossover study was conducted to evaluate the effect of treprostinil infusion on the pharmacodynamics and pharmacokinetics of a single dose of warfarin. Area under the effect-time curve (AUEC(0-1)) and maximum effect over the entire sampling phase (E(max)) for warfarin INR were 219.58 and 2.071 with treprostinil and 218.93 and 2.041 with vehicle, respectively. Mean time to attain the peak concentration of R-enantiomer of warfarin (T(max)), half-life, and elimination rate constant (k(el)) were 1.9 hours, 51.688 hours, and 0.0137 per hour, respectively, in the presence of treprostinil and 1.5 hours, 52.579 hours, and 0.0137 per hour, respectively, in the presence of vehicle (control). Results were similar for the S-enantiomer. The 90% confidence intervals for warfarin INR and warfarin R- and S-enantiomer pharmacokinetic parameter (C(max) and AUC( infinity )) ratios were within 0.80-1.25, which was established as the no-effect criterion for treprostinil coadministration. No serious or severe adverse events, anticoagulation-related events, or clinically significant physical or laboratory findings were reported. These findings suggest that a clinically important interaction between treprostinil and warfarin during therapy is unlikely.

Acute pulmonary edema caused by epoprostenol infusion in a child with scimitar syndrome and pulmonary hypertension

INTRODUCTION

Intravenous epoprostenol is frequently administered in adults and children for treatment of pulmonary hypertension. Although generally safe, pulmonary edema has been described in a few case reports of adult patients with pulmonary veno-occlusive disease.

CASE REPORT

We present an infant who had an operation for scimitar syndrome and abnormal drainage of the right pulmonary veins into the inferior vena cava who developed pulmonary edema while receiving a prostacyclin infusion. The typical partial anomalous pulmonary venous drainage was operatively corrected at 6 days of age, and an accompanying coarctation was resected. At 7 months of age, diagnostic cardiac catheterization was performed to evaluate suspected pulmonary hypertension. Pulmonary pressure was elevated to supra-systemic values, and obstructed venous drainage of the right hypoplastic lung was demonstrated. To decrease pulmonary hypertension during weaning and extubation, epoprostenol infusion was initiated. Sixty minutes after extubation, massive acute pulmonary edema lead to reintubation. Mean airway pressure of 16 mm Hg (21 mbar) with pure oxygen ventilation was initially required, with an oxygenation index of 14, a ventilation index of 36, and an alveolar-arterial oxygen tension difference of 541 mm Hg. After discontinuation of epoprostenol, weaning and extubation was successful.

CONCLUSION

Pulmonary edema caused by prostacyclin infusion in patients with impaired postcapillary pulmonary drainage may also be encountered in children and has to be anticipated.

Eisenmenger's syndrome: current management

Eisenmenger's syndrome describes the elevation of pulmonary arterial pressure to the systemic level caused by increased pulmonary vascular resistance with reversal or bi-directional shunting through a large intracardiac or extracardiac congenital heart defect. This article reviews the natural history and pathophysiology of Eisenmenger's syndrome untreated and medical and surgical treatment options presently available. Although there is no cure for this condition at present, recent advances in management have improved the quality of life for many patients with Eisenmenger's syndrome.

Cardiac risk factors and participation guidelines for youth sports

Accurate assessment of the cardiac system in pediatric and adolescent youth is important. The hemodynamic demands associated with exercise, training, and sport participation are usually positive and beneficial; however, when an underlying cardiac problem exists, it is imperative that such cardiac problems be identified. Safe sport-related cardiac participation guidelines should be provided for young athletes and their families and coaches. This chapter provides a physician perspective on the recognition and current cardiac management considerations for young athletes participating in both static and dynamic types of sports. The most recent guidelines for hypertension in youth are also provided.

Pediatric Primary Pulmonary Hypertension

Primary pulmonary hypertension is a disease for which there is no single best therapy. Rather, it is a process that progresses inexorably to disability and death, for which there are a variety of palliative therapies, all with significant side effects, and none curative. Nevertheless, it is clear that the available therapies improve the quality of life and prolong life; failure to offer therapy for patients with this disease in the current era is indefensible. As primary pulmonary hypertension progresses, one must chose from among the available therapies the regimen that provides the most benefit for the patient with the least associated morbidity. Organ replacement is appropriate only after all other available therapies have been exhausted. The recommended hierarchy of therapy is 1) anticongestive therapy, anticoagulation, and supplemental oxygen, 2) calcium channel blockade, 3) continuous intravenous prostacyclin, 4) beta-receptor agonists for cardiac support, and 5) lung transplantation. Newer therapies, described in this review, soon will be incorporated into this hierarchy.

Diagnosis and treatment of severe pediatric pulmonary hypertension

Advances in the treatment of pulmonary hypertension during the past decade have dramatically improved patient survival. Many of these advances are based on improved understanding of the vascular biology of the normal and hypertensive pulmonary circulations. Pulmonary hypertension is an important determinant of morbidity and mortality in patients with many pediatric diseases, including congenital heart disease. This article describes current diagnostic strategies and treatments for patients with primary and secondary pulmonary hypertension.

Characterization of the pulmonary arterial response to endothelin-1 and bosentan in neonatal pigs

BACKGROUND

This study determined the pulmonary vascular responses to intravenous (IV) administration of endothelin-1 (ET-1) before and after an IV bolus of bosentan (Ro 47-0203), an endothelin receptor antagonist, in anesthetized open-chest 48-hour-old and 2-week-old Yorkshire pigs.

METHODS

Eighteen 48-hour-old and 25 2-week-old pigs were randomly allocated to receive either (1) 400 ng x kg(-1) x min(-1) of ET-1 or (2) 5 mg/kg or 10 mg/kg of Ro 47-0203 followed by 400 ng x kg(-1) x min(-1) of ET-1 over a 10-minute interval. Pulmonary vascular resistance (PVR, dyne sec/cm(-5)), elastic modulus (E(Yo), dyne/cm2), and characteristic impedance (Zo) were determined (+/- SEM).

RESULTS

In 48-hour-old pigs, ET-1 decreased pulmonary artery pressure (PAP, dyne/cm2; 21,317 +/- 1,833 versus 17,757 +/- 1,823; p = 0.003). In 2-week-old pigs, ET-1 elevated PAP (19,009 +/- 1,834 versus 21,935 +/- 2,104; p = 0.003) and PVR (1,624 +/- 254 versus 2,302 +/- 416; p = 0.001), whereas bosentan abolished the ET-1 induced pulmonary and systemic vasoconstriction. Neither agent altered E(Y) or Z(o).

CONCLUSIONS

ET-1 caused a pulmonary depressor response in 48-hour-old pigs and a constrictor response in 2-week-old pigs, whereas bosentan inhibited the ET-1 induced pulmonary arteriolar vasoconstriction in 2-week-old pigs. The response to ET-1 changes from dilation in 48-hour-old pigs (neonates) to constriction in 2-week-old pigs (infants) suggests a maturational dependent alteration in ET receptors during the first 2 weeks of life. These data suggest that bosentan may have potential clinical application in the treatment of newborn pulmonary hypertensive episodes as it ablated ET-1 induced pulmonary vasoconstriction, while maintaining systemic pressure.

Treatment with epoprostenol reverts nitric oxide non-responsiveness in patients with primary pulmonary hypertension

OBJECTIVE

To assess whether long term treatment with epoprostenol might restore primary non-responsiveness to nitric oxide (NO) in patients with primary pulmonary hypertension.

METHODS

Seven patients with primary pulmonary hypertension receiving intravenous epoprostenol continuously because of failure of NO to influence pulmonary haemodynamics during initial testing were followed over a period of 13-29 months. Afterwards, acute vascular reactivity towards NO was tested again during right heart catheterisation.

RESULTS

Administration of NO after continuous epoprostenol treatment for a mean period of 18 months improved arterial oxygen saturation (p < 0.01) and cardiac index (p < 0.05), and decreased mean pulmonary artery pressure (p < 0.01) and total pulmonary vascular resistance (p < 0.01) in patients previously unresponsive to NO.

CONCLUSIONS

Long term treatment with epoprostenol reverts initial refractoriness to NO in patients with primary pulmonary hypertension. Thus the addition of NO to epoprostenol treatment might cause further improvement in the course of the disease.