Long-term safety and tolerability of ambrisentan treatment for pediatric patients with pulmonary arterial hypertension: An open-label extension study.

This open-label, extension study assessed long-term safety, tolerability, and efficacy of ambrisentan in a pediatric population (age 8- < 18 years) with pulmonary arterial hypertension (PAH). Following completion of a 6-month, randomized study, participants entered the long-term extension at individualized ambrisentan dosages (2.5/5/7.5 or 10 mg/day). Safety assessments included adverse events (AEs), AEs of special interest, and serious AEs (SAEs); efficacy outcomes included 6-min walking distance (6MWD) and World Health Organization functional class (WHO FC). Thirty-eight of 41 (93%) randomized study participants entered the extension; 21 (55%) completed (reaching age 18 years). Most participants received concomitant phosphodiesterase-5 inhibitors (n = 25/38, 66%). Median ambrisentan exposure was 3.5 years. Most participants experienced ≥ 1 AE (n = 34/38, 89%), and 21 (55%) experienced SAEs, most commonly worsening PAH (n = 3/38, 8%), acute cardiac failure, pneumonia, or anemia (n = 2/38; 5% each); none considered ambrisentan-related. Seven participants (18%) died, with recorded reasons (MedDRA preferred term): cardiac failure (n = 2), PAH (n = 2), COVID-19 (n = 1), acute right ventricular failure (n = 1), and failure to thrive (n = 1); median time to death: 5.2 years. Anemia and hepatotoxicity AEs were generally mild to moderate and did not require ambrisentan dose adjustment. Assessed at study end in 29 participants (76%), mean 6MWD improved by 17% (standard deviation: 34.3%), and all (29/29, 100%) had improved or unchanged WHO FC.    Conclusion: Long-term weight-based ambrisentan dosing, alone or combined with other PAH therapies in children with PAH aged 8- < 18 years, exhibited tolerability and clinical improvements consistent with prior randomized study results.    Trial registration: NCT01342952, April 27, 2011. What is Known: • The endothelin receptor antagonist, ambrisentan, is indicated for treatment of pulmonary arterial hypertension (PAH). Previous studies have shown similar efficacy and tolerability in pediatric patients as in adults. What is New: • This open-label extension study assessed the long-term use of ambrisentan in pediatric patients (8-<18 years) with PAH, most of whom were also receiving recommended background PAH treatment. • Weight-based dosing of ambrisentan, given alone or in combination with other PAH therapies, was well tolerated with clinical improvements consistent with prior randomized study results.

Computed tomographic findings in TBX4 mutation: a common cause of severe pulmonary artery hypertension in children.

BACKGROUND: Mutations in the T-Box 4 (TBX4) gene are a lesser-known cause of heritable pulmonary arterial hypertension (PAH). Patients with heritable PAH typically have worse outcomes when compared with patients with idiopathic PAH, yet little is known about the phenotypical presentation of this mutation. OBJECTIVE: This article reviews the pattern of chest CT findings in pediatric patients with PAH and TBX4 mutations and compares their radiographic presentation with those of age-matched patients with PAH but without TBX4 mutations. MATERIALS AND METHODS: A retrospective chart review of the pulmonary arterial hypertension database was performed. Pediatric patients with PAH-confirmed TBX4 mutations and an available high CT were included. Fifteen (9 females) patients met the inclusion criteria. Fourteen (8 females) age-matched controls with diagnosed PAH but without TBX4 mutations were also evaluated. The median age at diagnosis was 7.4 years (range: 0.1-16.4 years). Demographic information and clinical outcomes were collected. CTs of the chest were reviewed for multiple airway, parenchymal, and structural abnormalities (16 imaging findings in total). Chi-square tests were used to compare the prevalence of each imaging finding in the TBX4 cohort compared to the control group. RESULTS: Patients with TBX-4 mutations had increased presence of peripheral or subpleural irregularity (73% vs 0%, P < 0.01), cystic lucencies (67% vs 7%, P < 0.01), and linear or reticular opacity (53% vs 0%, P < 0.01) compared to the control group. Ground glass opacities, bronchiectasis, and centrilobular nodules were not significantly different between the two patient groups (P > 0.05). CONCLUSION: TBX4 mutations have distinct imaging phenotypes in pediatric patients with PAH. Compared to patients without this mutation, patients with TBX-4 genes typically present with peripheral or subpleural irregularity, cystic lucencies, and linear or reticular opacity.

Management of Complex Pulmonary Vein Stenosis at Altitude Combining Comprehensive Percutaneous Interventional Treatment with Sirolimus, Pulmonary Hypertension Medications and Intraluminal Imaging with Optical Coherence Tomography.

BACKGROUND: Pulmonary vein stenosis (PVS) is a growing problem for the pediatric congenital heart population. Sirolimus has previously been shown to improve survival and slow down the progression of in-stent stenosis in patients with PVS. We evaluated patients before and after initiation of sirolimus to evaluate its effects on re-intervention and vessel patency utilizing Optical Coherence Tomography (OCT). METHODS: We performed a retrospective study, reviewing the charts of patients with PVS, who had been prescribed sirolimus between October 2020 and December 2021. OCT was performed in the pulmonary vein of interest as per our published protocol. Angiographic and OCT imaging was retrospectively reviewed. Statistical analysis was performed using Chi square and Wilcoxon signed-rank test to compare pre-and post-sirolimus data. RESULTS: Ten patients had been started and followed on sirolimus. Median age at sirolimus initiation was 25 months with median weight of 10.6 kg and average follow-up of 1 year. Median total catheterizations were 7 for patients prior to starting sirolimus and 2 after starting treatment (p = 0.014). Comparing pre- and post-sirolimus, patients were catheterized every 3 months vs every 11 months (p = 0.011), median procedure time was 203 min vs 145 min (p = 0.036) and fluoroscopy time, 80 min vs 57.2 min (p = 0.036). 23 veins had severe in-stent tissue ingrowth prior to SST (luminal diameter < 30% of stent diameter). Post-sirolimus, 23 pulmonary veins had moderate to severe in-stent tissue ingrowth that responded to non-compliant balloon inflation only with stent luminal improvement of > 75%. CONCLUSION: Our study suggests that the addition of sirolimus in patients with moderate-severe PVS helps to decrease disease progression with decrease frequency of interventions. Reaching therapeutic levels for sirolimus is critical and medication interactions and side-effects need careful consideration. OCT continues to be important for evaluation and treatment guidance in this patient population.

Chest computed tomography findings of ground-glass nodules with enhancing central vessel/nodule in pediatric patients with BMPR2 mutations and plexogenic arteriopathy.

BACKGROUND: Germline mutation in bone morphogenetic protein type II (BMPR2) is the most common cause of idiopathic/heritable pulmonary hypertension in pediatric patients. Despite the discovery of this gene there are no known descriptions of the CT or CT angiography findings in these children. OBJECTIVE: To correlate the clinical presentation, pathology and chest CT findings in pediatric patients with pulmonary hypertension caused by mutations in the BMPR2 gene. MATERIALS AND METHODS: We performed a search to identify pediatric patients with a BMPR2 mutation and CT or CT angiography with the clinical history of pulmonary hypertension. Three pediatric radiologists reviewed the children's CT imaging findings and ranked the dominant findings in order of prevalence via consensus. RESULTS: We identified three children with pulmonary hypertension and confirmed germline BMPR2 mutations, two of whom had undergone lung biopsy. We then correlated the imaging findings with histopathology and clinical course. CONCLUSION: All of our patients with BMPR2 mutations demonstrated a distinct CT pattern of ground-glass nodules with a prominent central enhancing vessel/nodule. These findings correlated well with the pathological findings of plexogenic arteriopathy.

Technical Feasibility on the Use of Optical Coherence Tomography in the Evaluation of Pediatric Pulmonary Venous Stenosis.

Pulmonary vein stenosis (PVS) in children is a morbid disease and limited progress has been made in improving outcomes for this heterogenous group of patients. Evaluation is currently limited to imaging techniques that fail to provide an adequate overview of the intraluminal and luminal pathology perpetuating our limited understanding of this condition. Optical coherence tomography (OCT) is an imaging modality which provides intraluminal profiling with microstructural detail through optical reflective technology. We sought to evaluate whether its use was technically feasible in pediatric PVS and whether the imaging data provided potentially useful outputs for clinical utility. Eleven patients were prospectively selected from our cardiac catheterization for OCT evaluation of their pulmonary veins (PV) during elective catheterization for PVS. Measurements were taken both pre and post intervention using both manual and automated tools. Stent morphology was characterized. Eleven patients had evaluation of 34 pulmonary veins, with 7 patients having more than one assessment, for a total of 25 overall catheterizations. Most patients were female (75%). Median age at cardiac catheterization was 35 months (range 5-45 months). Median weight of subjects was 10.6 kg (3.7-14.2) with a median BSA documented at 0.505 m2 (0.21-0.57). Median number of pulmonary veins involved was 3, (range 1-5 veins) and median contrast volume of 2.9 mL/kg (0.7-3.7) given. Median radiation dose (DAP) was 6095 µGy·cm2 (1670-12,400). Median number of previous cardiac catheterizations was 7 (range 1-11). All of the vessels with a diameter < 5 mm were adequately visualized. Of all the OCT images acquired, in 15 vessels (44%) contrast was used to clear the vessels from blood as an angiogram was required at the time, in the other 19 vessels (56%), saline was used with adequate imaging. There were no complications related to OCT. OCT is technically feasible to use in pediatric patients without any directly related complications. It provides intraluminal anatomy in children with both native and treated pulmonary venous stenosis when vessel size is less than 5 mm.

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.

Pulmonary arterial banding in mice may be a suitable model for studies on ventricular mechanics in pediatric pulmonary arterial hypertension.

BACKGROUND: The role of interventricular mechanics in pediatric pulmonary arterial hypertension (PAH) and its relation to right ventricular (RV) dysfunction has been largely overlooked. Here, we characterize the impact of maintained pressure overload in the RV-pulmonary artery (PA) axis on myocardial strain and left ventricular (LV) mechanics in pediatric PAH patients in comparison to a preclinical PA-banding (PAB) mouse model. We hypothesize that the PAB mouse model mimics important aspects of interventricular mechanics of pediatric PAH and may be beneficial as a surrogate model for some longitudinal and interventional studies not possible in children. METHODS: Balanced steady-state free precession (bSSFP) cardiovascular magnetic resonance (CMR) images of 18 PAH and 17 healthy (control) pediatric subjects were retrospectively analyzed using CMR feature-tracking (FT) software to compute measurements of myocardial strain. Furthermore, myocardial tagged-CMR images were also analyzed for each subject using harmonic phase flow analysis to derive LV torsion rate. Within 48 h of CMR, PAH patients underwent right heart catheterization (RHC) for measurement of PA/RV pressures, and to compute RV end-systolic elastance (RV_Ees, a measure of load-independent contractility). Surgical PAB was performed on mice to induce RV pressure overload and myocardial remodeling. bSSFP-CMR, tagged CMR, and intra-cardiac catheterization were performed on 12 PAB and 9 control mice (Sham) 7 weeks after surgery with identical post-processing as in the aforementioned patient studies. RV_Ees was assessed via the single beat method. RESULTS: LV torsion rate was significantly reduced under hypertensive conditions in both PAB mice (p = 0.004) and pediatric PAH patients (p < 0.001). This decrease in LV torsion rate correlated significantly with a decrease in RV_Ees in PAB (r = 0.91, p = 0.05) and PAH subjects (r = 0.51, p = 0.04). In order to compare combined metrics of LV torsion rate and strain parameters principal component analysis (PCA) was used. PCA revealed grouping of PAH patients with PAB mice and control subjects with Sham mice. Similar to LV torsion rate, LV global peak circumferential, radial, and longitudinal strain were significantly (p < 0.05) reduced under hypertensive conditions in both PAB mice and children with PAH. CONCLUSIONS: The PAB mouse model resembles PAH-associated myocardial mechanics and may provide a potential model to study mechanisms of RV/LV interdependency.

Cellular sources of interleukin-6 and associations with clinical phenotypes and outcomes in pulmonary arterial hypertension.

The pro-inflammatory cytokine interleukin (IL)-6 has been associated with outcomes in small pulmonary arterial hypertension (PAH) cohorts composed largely of patients with severe idiopathic PAH (IPAH). It is unclear whether IL-6 is a marker of critical illness or a mechanistic biomarker of pulmonary vascular remodelling. We hypothesised that IL-6 is produced by pulmonary vascular cells and sought to explore IL-6 associations with phenotypes and outcomes across diverse subtypes in a large PAH cohort.IL-6 protein and gene expression levels were measured in cultured pulmonary artery smooth muscle cells (PASMCs) and endothelial cells (PAECs) from PAH patients and healthy controls. Serum IL-6 was measured in 2017 well-characterised PAH subjects representing each PAH subgroup. Relationships between IL-6 levels, clinical variables, and mortality were analysed using regression models.Significantly higher IL-6 protein and gene expression levels were produced by PASMCs than by PAECs in PAH (p<0.001), while there was no difference in IL-6 between cell types in controls. Serum IL-6 was highest in PAH related to portal hypertension and connective tissue diseases (CTD-PAH). In multivariable modelling, serum IL-6 was associated with survival in the overall cohort (hazard ratio 1.22, 95% CI 1.08-1.38; p<0.01) and in IPAH, but not in CTD-PAH. IL-6 remained associated with survival in low-risk subgroups of subjects with mild disease.IL-6 is released from PASMCs, and circulating IL-6 is associated with specific clinical phenotypes and outcomes in various PAH subgroups, including subjects with less severe disease. IL-6 is a mechanistic biomarker, and thus a potential therapeutic target, in certain PAH subgroups.

Pediatric pulmonary hypertension: insulin-like growth factor-binding protein 2 is a novel marker associated with disease severity and survival.

BACKGROUND: Insulin-like growth factors (IGFs), and their binding proteins (IGFBPs), play a significant role in cardiovascular function and may influence the pathobiology of PAH. We determined the diagnostic and prognostic value of IGF1 and IGFBP2 in pediatric PAH. METHODS: Serum was analyzed by ELISA for IGF1 and IGFBP2 in pediatric PAH subjects from the NHLBI PAH Biobank (PAHB, n = 175) and a cohort of asthmatic subjects (n = 46, age 0-21 years) as a chronic pediatric pulmonary disease control. Biomarkers were analyzed with demographic and clinical variables for PAH severity. RESULTS: Serum IGF1 was significantly lower in PAH compared to controls, while IGFBP2 was elevated in PAH subjects compared to controls. In the PAHB, IGF1 was negatively associated with mPAP and PVR, while IGFBP2 was positively associated with PVR and negatively associated with cardiac output and 6-min walk distance. Higher IGFBP2 levels were associated with use of prostacyclin therapy. IGFBP2 was associated with death, transplant, or palliative shunt with a Cox proportional hazard ratio of 8.8 (p < 0.001) but not IGF1 (p = 0.13). CONCLUSIONS: Circulating IGFBP2 is a novel marker for pediatric PAH, which is associated with worse functional status, and survival. IGF axis dysregulation may be an important mechanistic target in pediatric pulmonary arterial hypertension. IMPACT: Pediatric pulmonary hypertension is a severe disease, with poorly understood pathobiology. There are few studies looking at the pathobiology of pulmonary hypertension only in children. The IGF axis is dysregulated in pediatric pulmonary arterial hypertension. IGF axis dysregulation, with increased IGFBP2, is associated with worse clinical outcomes in pediatric pulmonary artery hypertension. IGF axis dysregulation gives new insight into the disease process and may be a mechanistic or therapeutic target.

Segmental Pulmonary Hypertension in Children with Congenital Heart Disease.

Segmental pulmonary hypertension is a complex condition in children that encompasses many congenital heart diseases including pulmonary atresia with ventricular septal defect, hemitruncus/truncus arteriosus with branch pulmonary artery stenosis, unilateral absent pulmonary artery, and several post-tricuspid shunt lesions. Multimodality imaging is required to confirm and assess pulmonary vascular disease in subjects with major aorto-pulmonary collaterals. We describe 3 children with complex congenital heart defects who have a variable degree of segmental pulmonary hypertension and discuss management strategies and the role of interventional and/or pulmonary hypertension targeted therapies.

Phenotype characterisation of TBX4 mutation and deletion carriers with neonatal and paediatric pulmonary hypertension.

Rare variants in the T-box transcription factor 4 gene (TBX4) have recently been recognised as an emerging cause of paediatric pulmonary hypertension (PH). Their pathophysiology and contribution to persistent pulmonary hypertension in neonates (PPHN) are unknown. We sought to define the spectrum of clinical manifestations and histopathology associated with TBX4 variants in neonates and children with PH.We assessed clinical data and lung tissue in 19 children with PH, including PPHN, carrying TBX4 rare variants identified by next-generation sequencing and copy number variation arrays.Variants included six 17q23 deletions encompassing the entire TBX4 locus and neighbouring genes, and 12 likely damaging mutations. 10 infants presented with neonatal hypoxic respiratory failure and PPHN, and were subsequently discharged home. PH was diagnosed later in infancy or childhood. Three children died and two required lung transplantation. Associated anomalies included patent ductus arteriosus, septal defects, foot anomalies and developmental disability, the latter with a higher prevalence in deletion carriers. Histology in seven infants showed abnormal distal lung development and pulmonary hypertensive remodelling.TBX4 mutations and 17q23 deletions underlie a new form of developmental lung disease manifesting with severe, often biphasic PH at birth and/or later in infancy and childhood, often associated with skeletal anomalies, cardiac defects, neurodevelopmental disability and other anomalies.

Structural and Biomechanical Adaptations of Right Ventricular Remodeling-In Pulmonary Arterial Hypertension-Reduces Left Ventricular Rotation During Contraction: A Computational Study.

Pulmonary hypertension (PH) is a degenerative disease characterized by progressively increased right ventricular (RV) afterload that leads to ultimate functional decline. Recent observational studies have documented a decrease in left ventricular (LV) torsion during ejection, with preserved LV ejection fraction (EF) in pediatric and adult PH patients. The objective of this study was to develop a computational model of the biventricular heart and use it to evaluate changes in LV torsion mechanics in response to mechanical, structural, and hemodynamic changes in the RV free wall. The heart model revealed that LV torsion and apical rotation were decreased when increasing RV mechanical rigidity and during re-orientation of RV myocardial fibers, both of which have been demonstrated in PH. Furthermore, structural changes to the RV appear to have a notable impact on RV EF, but little influence on LV EF. Finally, RV pressure overload exponentially increased LV myocardial stress. The computational results found in this study are consistent with clinical observations in adult and pediatric PH patients, which reveal a decrease in LV torsion with preserved LV EF. Furthermore, discovered causes of decreased LV torsion are consistent with RV structural adaptations seen in PH rodent studies, which might also explain suspected stress-induced changes in LV myocardial gene and protein expression.

Usefulness of 4D-Flow MRI in Mapping Flow Distribution Through Failing Fontan Circulation Prior to Cardiac Intervention.

We report a case of a 23-year-old male with failing Fontan circulation who was taken to the catheterization lab to better evaluate the Fontan circulation and hemodynamics. Catheterization revealed arteriovenous malformations exclusively present in the right lung leading to the consideration of placing stents to direct the inferior vena cava flow through the Fontan circuit to the right pulmonary artery (RPA), thus increasing the RPA concentration of the hepatic factor. However, comprehensive 4D-Flow MRI analyses indicated sufficient distribution of the hepatic flow between branch pulmonary arteries, and consequently no further invasive intervention to redirect hepatic flow was performed.

A bosentan pharmacokinetic study to investigate dosing regimens in paediatric patients with pulmonary arterial hypertension: FUTURE-3.

AIM: The aim of the present study was to investigate whether increasing the bosentan dosing frequency from 2 mg kg-1 twice daily (b.i.d.) to 2 mg kg-1 three times daily (t.i.d.) in children with pulmonary arterial hypertension (PAH) (from ≥3 months to <12 years of age) would increase exposure. METHODS: An open-label, prospective, randomized, multicentre, multiple-dose, phase III study was conducted. Patients (n = 64) were randomized 1:1 to receive oral doses of bosentan of 2 mg kg-1 b.i.d. or t.i.d. The main pharmacokinetic endpoint was the daily exposure to bosentan over 24 h corrected to the 2 mg kg-1 dose (AUC0-24C ). The maximum plasma concentration corrected to the 2 mg kg-1 dose (CmaxC ), the time to reach the maximum plasma concentration (tmax ) and safety endpoints were also assessed. RESULTS: The geometric mean [95% confidence interval (CI)] for AUC0-24C was 8535 h.ng ml-1 (6936, 10 504) and 7275 h.ng ml-1 (5468, 9679) for 2 mg kg-1 b.i.d. and t.i.d., respectively [geometric mean ratio (95% CI) 0.85 (0.61, 1.20)]. The geometric mean (95% CI) for CmaxC was 743 ng ml-1 (573, 963) and 528 ng ml-1 (386, 722) for 2 mg kg-1 b.i.d. and t.i.d., respectively [geometric mean ratio (95% CI) 0.71 (0.48, 1.05)]. The median (range) for tmax was 3.0 h (0.0-7.5) and 3.0 h (1.0-8.0) for 2 mg kg-1 b.i.d. and t.i.d., respectively. The proportions of patients who experienced ≥1 adverse event were similar in the b.i.d. (66.7%) and t.i.d. (67.7%) groups. CONCLUSIONS: There appeared to be no clinically relevant difference in exposure to bosentan, or in safety, when increasing the frequency of bosentan dosing from b.i.d. to t.i.d. Therefore, the present study provides no indication that the dosing recommendation should be changed, and 2 mg kg-1 b.i.d. remains the recommended dosing regimen for bosentan in paediatric PAH patients.

Treatment initiation in paediatric pulmonary hypertension: insights from a multinational registry.

Different treatment options for pulmonary hypertension have emerged in recent years, and evidence-based management strategies have improved quality of life and survival in adults. In children with pulmonary vascular disease, therapeutic algorithms are not so clearly defined; this study determined current treatment initiation in children with pulmonary hypertension in participating centres of a registry. Through the multinational Tracking Outcomes and Practice in Pediatric Pulmonary Hypertension registry, patient demographics, diagnosis, and treatment as judged and executed by the local physician were collected. Inclusion criteria were >3 months and <18 years of age and diagnostic cardiac catheterisation consistent with pulmonary hypertension (mean pulmonary arterial pressure ⩾25 mmHg, pulmonary vascular resistance index ⩾3 Wood units×m2, and mean pulmonary capillary wedge pressure ⩽12 mmHg). At diagnostic catheterisation, 217/244 patients (88.9%) were treatment naïve for pulmonary hypertension-targeted therapy. Targeted therapy was initiated after catheterisation in 170 (78.3%) treatment-naïve patients. A total of 19 patients received supportive therapy, 28 patients were not started on therapy, and 26 patients (10.7%) were on targeted treatment before catheterisation. Among treatment-naïve subjects, treatment was initiated with one targeted drug (n=112, 51.6%), dual therapy (n=39, 18%) or triple-therapy (n=5, 2.3%), and calcium channel blockers with one targeted medication in one patient (0.5%). Phosphodiesterase inhibitors type 5 were used frequently; some patients with pulmonary hypertension related to lung disease received targeted therapy. There is a diverse therapeutic approach for children with pulmonary hypertension with a need of better-defined treatment algorithms based on paediatric consensus for different aetiologies including the best possible diagnostic workup.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Pulmonary Hypertension.

OBJECTIVE: To review the pharmacologic treatment options for pulmonary arterial hypertension in the cardiac intensive care setting and summarize the most-recent literature supporting these therapies. DATA SOURCES AND STUDY SELECTION: Literature search for prospective studies, retrospective analyses, and case reports evaluating the safety and efficacy of pulmonary arterial hypertension therapies. DATA EXTRACTION: Mechanisms of action and pharmacokinetics, treatment recommendations, safety considerations, and outcomes for specific medical therapies. DATA SYNTHESIS: Specific targeted therapies developed for the treatment of adult patients with pulmonary arterial hypertension have been applied for the benefit of children with pulmonary arterial hypertension. With the exception of inhaled nitric oxide, there are no pulmonary arterial hypertension medications approved for children in the United States by the Food and Drug Administration. Unfortunately, data on treatment strategies in children with pulmonary arterial hypertension are limited by the small number of randomized controlled clinical trials evaluating the safety and efficacy of specific treatments. The treatment options for pulmonary arterial hypertension in children focus on endothelial-based pathways. Calcium channel blockers are recommended for use in a very small, select group of children who are responsive to vasoreactivity testing at cardiac catheterization. Phosphodiesterase type 5 inhibitor therapy is the most-commonly recommended oral treatment option in children with pulmonary arterial hypertension. Prostacyclins provide adjunctive therapy for the treatment of pulmonary arterial hypertension as infusions (IV and subcutaneous) and inhalation agents. Inhaled nitric oxide is the first-line vasodilator therapy in persistent pulmonary hypertension of the newborn and is commonly used in the treatment of pulmonary arterial hypertension in the ICU. Endothelin receptor antagonists have been shown to improve exercise tolerance and survival in adult patients with pulmonary arterial hypertension. Soluble guanylate cyclase stimulators are the first drug class to be Food and Drug Administration approved for the treatment of chronic thromboembolic pulmonary hypertension. CONCLUSIONS: Literature and data supporting the safe and effective use of pulmonary arterial hypertension therapies in children in the cardiac intensive care are limited. Extrapolation of adult data has afforded safe medical treatment of pulmonary hypertension in children. Large multicenter trials are needed in the search for safe and effective therapy of pulmonary hypertension in children.

A Zero-Dimensional Model and Protocol for Simulating Patient-Specific Pulmonary Hemodynamics From Limited Clinical Data.

In pulmonary hypertension (PH) diagnosis and management, many useful functional markers have been proposed that are unfeasible for clinical implementation. For example, assessing right ventricular (RV) contractile response to a gradual increase in pulmonary arterial (PA) impedance requires simultaneously recording RV pressure and volume, and under different afterload/preload conditions. In addition to clinical applications, many research projects are hampered by limited retrospective clinical data and could greatly benefit from simulations that extrapolate unavailable hemodynamics. The objective of this study was to develop and validate a 0D computational model, along with a numerical implementation protocol, of the RV-PA axis. Model results are qualitatively compared with published clinical data and quantitatively validated against right heart catheterization (RHC) for 115 pediatric PH patients. The RV-PA circuit is represented using a general elastance function for the RV and a three-element Windkessel initial value problem for the PA. The circuit mathematically sits between two reservoirs of constant pressure, which represent the right and left atriums. We compared Pmax, Pmin, mPAP, cardiac output (CO), and stroke volume (SV) between the model and RHC. The model predicted between 96% and 98% of the variability in pressure and 98-99% in volumetric characteristics (CO and SV). However, Bland Altman plots showed the model to have a consistent bias for most pressure and volumetric parameters, and differences between model and RHC to have considerable error. Future studies will address this issue and compare specific waveforms, but these initial results are extremely promising as preliminary proof of concept of the modeling approach.