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.

Application of a modified clinical classification for pulmonary arterial hypertension associated with congenital heart disease in children: emphasis on atrial septal defects and transposition of the great arteries. An analysis from the TOPP registry.

Aims: A proportion of patients with pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD) do not fit in the current classification. We aimed to analyse the applicability of an adapted clinical classification of PAH-CHD to pediatric patients using the TOPP-1 registry (Tracking Outcomes and Practice in Pediatric Pulmonary Hypertension) and focus on atrial septal defects (ASD) and transposition of the great arteries (TGA). Methods and results: Hemodynamic and clinical data of all patients with PAH-CHD in the TOPP cohort were reviewed. Patients were classified according to predefined ABCDE categories (A: Eisenmenger syndrome, B: left-to-right shunt, C: coincidental defects, including all ASDs, D: corrected CHD, E: TGA), or as complex CHD (group 5), by 2 independent investigators. In case of disagreement, a third reviewer could either settle a final decision, or the patient was deemed not classifiable. Survival curves were calculated for each group and compared to idiopathic PAH patients of the registry. A total of 223 out of 531 patients in the registry had PAH-CHD, and 193 were categorized to the following groups: A 39(20%), B 27(14%), C 62(32%) including 43 ASDs, D 58(30%), E 7(4%), whereas 6 patients were categorized as group 5, and 10 patients were unable to be classified. No survival difference could be demonstrated between the groups. Conclusions: This modified classification seems to be more applicable to pediatric PAH-CHD patients than the previous classification, but some patients with PAH-CHD who never had a shunt remain unclassifiable. The role of ASD in pediatric PH should be reconsidered.

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.

Kids Mod PAH trial: A multicenter trial comparing mono- versus duo-therapy for initial treatment of pediatric pulmonary hypertension.

Pulmonary hypertension (PH) is a significant health problem that contributes to high morbidity and mortality in diverse cardiac, pulmonary, and systemic diseases in children. Evidence-based advances in PH care have been challenged by a paucity of quality endpoints for assessing clinical course and the lack of robust clinical trial data to guide pharmacologic therapies in children. While the landmark adult AMBITION trial demonstrated the benefit of up-front combination PH therapy with ambrisentan and tadalafil, it remains unknown whether upfront combination therapy leads to more rapid and sustained clinical benefits in children with various categories of PH. In this article, we describe the inception of the Kids Mod PAH Trial, a multicenter Phase III trial, to address whether upfront combination therapy (sildenafil and bosentan vs. sildenafil alone) improves PH outcomes in children, recognizing that marked differences between the etiology and therapeutic response between adults and children exist. The primary endpoint of this study is WHO functional class (FC) 12 months after initiation of study drug therapy. In addition to the primary outcome, secondary endpoints are being assessed, including a composite measure of time to clinical worsening, WHO FC at 24 months, echocardiographic assessment of PH and quantitative assessment of right ventricular function, 6-min walk distance, and NT-proBNP levels. Exploratory endpoints include selected biomarkers, actigraphy, and assessments of quality of life. This study is designed to pave the way for additional clinical trials by establishing a robust infrastructure through the development of a PPHNet Clinical Trials Network.

Computational platform for doctor-artificial intelligence cooperation in pulmonary arterial hypertension prognostication: a pilot study.

Background: Pulmonary arterial hypertension (PAH) is a heterogeneous and complex pulmonary vascular disease associated with substantial morbidity. Machine-learning algorithms (used in many PAH risk calculators) can combine established parameters with thousands of circulating biomarkers to optimise PAH prognostication, but these approaches do not offer the clinician insight into what parameters drove the prognosis. The approach proposed in this study diverges from other contemporary phenotyping methods by identifying patient-specific parameters driving clinical risk. Methods: We trained a random forest algorithm to predict 4-year survival risk in a cohort of 167 adult PAH patients evaluated at Stanford University, with 20% withheld for (internal) validation. Another cohort of 38 patients from Sheffield University were used as a secondary (external) validation. Shapley values, borrowed from game theory, were computed to rank the input parameters based on their importance to the predicted risk score for the entire trained random forest model (global importance) and for an individual patient (local importance). Results: Between the internal and external validation cohorts, the random forest model predicted 4-year risk of death/transplant with sensitivity and specificity of 71.0-100% and 81.0-89.0%, respectively. The model reinforced the importance of established prognostic markers, but also identified novel inflammatory biomarkers that predict risk in some PAH patients. Conclusion: These results stress the need for advancing individualised phenotyping strategies that integrate clinical and biochemical data with outcome. The computational platform presented in this study offers a critical step towards personalised medicine in which a clinician can interpret an algorithm's assessment of an individual patient.

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.

High altitude pulmonary edema in children: A systematic review.

INTRODUCTION: High altitude pulmonary edema (HAPE) is a form of acute noncardiogenic pulmonary edema caused by altitude-related hypoxia seen in children as well as in adults. In this systematic review we focus in HAPE occurring in children and adolescents. METHODS: A systematic review was conducted including publications in children 0-18 years of age from three databases up to June 2022. RESULTS: Thirty-five studies representing 210 cases were found. The mean age was 9.8 ± 3.6 years with a male/female ratio of 2.6. The peak age incidence was seen in children between 6 and 10 years old. Only two children (0.9%) were ≤2 years old. The mean altitude in 166 cases was 2861 masl. Only 17 cases (8.1%) occurred at altitudes below 2500 masl. Regarding the different HAPE subtypes there was a predominance of re-entry HAPE (R-HAPE) with 58%, followed by classic HAPE (C-HAPE) with 37.6%. The mean time between arrival and onset of symptoms was 16.5 h. The mortality rate was 1.4%. In 10/28 (36%) of C-HAPE cases there was a structural cardiac/pulmonary anomaly compared to 1/19 (5%) in R-HAPE (p < 0.01). HAPE recurrence was found in 46 cases (21.9%). The involvement in the chest X-rays was seen predominantly in the apices and in the right lung. CONCLUSIONS: R-HAPE was the most common HAPE subtype; HAPE peak age was found between 6 and 10 years of age; HAPE was more frequent in males and was rare in children under 2 years old; associated HAPE structural abnormalities were more common in C-HAPE than in R-HAPE.

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.

Proteomics discovery of pulmonary hypertension biomarkers: Insulin-like growth factor binding proteins are associated with disease severity.

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by sustained elevations of pulmonary artery pressure. To date, we lack circulating, diagnostic, and prognostic markers that correlate to clinical and functional parameters. In this study, we performed mass spectrometry-based proteomics analysis to identify circulating biomarkers of PAH. Plasma samples from patients with idiopathic pulmonary arterial hypertension (IPAH, N = 9) and matched normal controls (N = 9) were digested with trypsin and analyzed using data-dependent acquisition on an Orbitrap mass spectrometer. A total of 826 (false discovery rate [FDR] 0.047) and 461 (FDR 0.087) proteins were identified across all plasma samples obtained from IPAH and control subjects, respectively. Of these, 153 proteins showed >2 folds change (p < 0.05) between groups. Circulating levels of carbonic anhydrase 2 (CA2), plasma kallikrein (KLKB1), and the insulin-like growth factor binding proteins (IGFBP1-7) were quantified by immunoassay in an independent verification cohort (N = 36 PAH and N = 35 controls). CA2 and KLKB1 were significantly different in PAH versus control but were not associated with any functional or hemodynamic measurements. Whereas, IGFBP1 and 2 were associated with higher pulmonary vascular resistance, IGFBP2, 4, and 7 with decreased 6-min walk distance (6MWD), and IGFBP1, 2, 4, and 7 with worse survival. This plasma proteomic discovery analysis suggests the IGF axis may serve as important new biomarkers for PAH and play an important role in PAH pathogenesis.

Hepatoma-derived growth factor is associated with pulmonary vascular remodeling and PAH disease severity and survival.

Hepatoma-derived growth factor (HDGF) was previously shown to be associated with increased mortality in a small study of idiopathic and connective tissue disease-associated pulmonary arterial hypertension (PAH). In this study, we measured serum HDGF levels in a large multicenter cohort (total 2017 adult PAH-Biobank enrollees), we analyzed the associations between HDGF levels and various clinical measures using linear or logistic regression models. Higher HDGF levels were found to be significantly associated with worse pulmonary hemodynamics, prostacyclin treatment; among PAH subtypes, higher HDGF levels were most associated with portopulmonary hypertension (beta = 0.469, p < 0.0001). Both Kaplan-Meier curve and Cox proportional hazard regression demonstrated that higher HDGF levels are associated with a higher risk of mortality (COX hazard ratio 1.31, p < 0.0001). Further, in the Sugen hypoxia (SuHx) rat model, the highest HDGF levels were post-pulmonary circulation, and HDGF levels significantly increased with the development of PAH. In pulmonary arteries, immunohistochemistry staining showed that HDGF was highly expressed in pulmonary smooth muscle cells in both PAH patients and SuHx rats. In conclusion, we found that higher serum HDGF was linked with increased mortality, and associated with disease severity in a large multi-center adult PAH cohort (n = 2017). In the SuHX PAH models, circulating HDGF levels are pulmonary in origin and increase with PAH progression. HDGF may be actively involved in vascular remodeling in PAH.

High-Altitude Pulmonary Edema in Colorado Children: A Cross-Sectional Survey and Retrospective Review.

Kelly, Timothy D., Maxene Meier, Jason P. Weinman, Dunbar Ivy, John T. Brinton, and Deborah R. Liptzin. High-altitude pulmonary edema in Colorado children: a cross-sectional survey and retrospective review. High Alt Med Biol. 23:119-124, 2022. Introduction: Few studies of high-altitude pulmonary edema (HAPE) are specific to the pediatric population. The purpose of this investigation was to further characterize the radiographic patterns of pediatric HAPE, and to better understand ongoing risk following an initial pediatric HAPE episode. Methods: This study uses both a retrospective chart review and cross-sectional survey. Pediatric patients with HAPE at a single quaternary referral center in the Rocky Mountain Region were identified between the years 2013 and 2020. Patients were eligible if they presented with a clinical diagnosis of HAPE and had a viewable chest radiograph (CXR). Surveys were sent to eligible patients/families to gather additional information relating to family history, puberty, and HAPE recurrence. Results: Forty-two individuals met criteria for clinical diagnosis of HAPE with a viewable CXR. A majority of CXRs (24/42, 57.1%) demonstrated predominant right-sided involvement. Similarly, 24 CXRs (24/42, 57.1%) demonstrated predominant upper lobe involvement. Twenty-one (21/42, 50%) surveys were completed. A minority of individuals went on to experience at least one other HAPE episode (8/19, 42.1%). Conclusion: The most common radiographic pattern seen in pediatric HAPE is pulmonary edema that favors the right lung and upper lobes. After an initial HAPE presentation, some children will experience additional HAPE episodes.

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.

An Acute Hyperoxia Test Predicts Survival in Children with Pulmonary Hypertension Living at High Altitude.

Diaz, Gabriel F., Alicia Marquez, Ariel Ruiz-Parra, Maurice Beghetti, and Dunbar Ivy. An acute hyperoxia test predicts survival in children with pulmonary hypertension living at high altitude. High Alt Med Biol. 22:395-405, 2021. Background: Pulmonary hypertension (PH) causes significant morbidity and mortality in children at altitude. Materials and Methods: Fifty-two children living at 2,640 m were included. During hyperoxia test (O2Test), patients received high oxygen concentrations (FiO2 >80, through Mask, using Venturi or nonrebreathing mask); echocardiography was used to evaluate pulmonary vasculature reactivity. A decrease >20% from the basal pulmonary artery systolic pressure was considered a positive response. Results: Most of the patients had severe PH. The median age at diagnosis was 4.5 years; 34 were female (65.4%). Idiopathic PH was present in 44 patients (84.6%). Six developed severe PH after ductus closure. They were classified in responders (n = 25), and nonresponders (n = 26). Responders were younger (3 years vs. 7 years, p = 0.02), and 22 (88%), had better functional class (FC) 1-2, than nonresponders: 18 (69.23%) of them had worse FC: 3-4 (p = 0.000). In responders, 10/12 who went to live at low altitude became asymptomatic, compared with 7/13 who remained at high altitude. FC 1-2 was achieved by 70% of the patients with idiopathic PH who went to a low altitude, compared with 30% who continued at high altitude (p = 0.03). In nonresponders, 10/26 patients moved to a low altitude: four improved, one worsened, and five died; of the 16/26 patients living at high altitude, four are stable, eight worsened, and four died. Four patients (30.76%) in responder group and nine (69.24%) in the nonresponder group died (p = 0.03). There were differences between both groups in systolic (88 mm Hg vs. 110 mm Hg; p = 0.037), diastolic (37 mm Hg vs. 56 mm Hg; p = 0.035), and mean pulmonary artery pressures (57 mm Hg vs. 88 mm Hg; p = 0.038). Conclusions: This specific hyperoxia test applied until 24 hours (not published before) helps to predict survival and prognosis of children with PH. Children with PH at a high altitude improve at low altitude.

Ventricular-vascular coupling is predictive of adverse clinical outcome in paediatric pulmonary arterial hypertension.

AIMS: Ventricular-vascular coupling, the ratio between the right ventricle's contractile state (Ees) and its afterload (Ea), may be a useful metric in the management of paediatric pulmonary arterial hypertension (PAH). In this study we assess the prognostic capacity of the ventricular-vascular coupling ratio (Ees/Ea) derived using right ventricular (RV) pressure alone in children with PAH. METHODS: One hundred and thirty paediatric patients who were diagnosed with PAH via right heart catheterisation were retrospectively reviewed over a 10-year period. Maximum RV isovolumic pressure and end-systolic pressure were estimated using two single-beat methods from Takeuchi et al (Ees/Ea_(Takeuchi)) and from Kind et al (Ees/Ea_(Kind)) and used with an estimate of end-systolic pressure to compute ventricular-vascular coupling from pressure alone. Patients were identified as either idiopathic/hereditary PAH or associated PAH (IPAH/HPAH and APAH, respectively). Haemodynamic data, clinical functional class and clinical worsening outcomes-separated into soft (mild) and hard (severe) event categories-were assessed. Adverse soft events included functional class worsening, syncopal event, hospitalisation due to a proportional hazard-related event and haemoptysis. Hard events included death, transplantation, initiation of prostanoid therapy and hospitalisation for atrial septostomy and Pott's shunt. Cox proportional hazard modelling was used to assess whether Ees/Ea was predictive of time-to-event. RESULTS: In patients with IPAH/HPAH, Ees/Ea_(Kind) and Ees/Ea_(Takeuchi) were both independently associated with time to hard event (p=0.003 and p=0.001, respectively) and when adjusted for indexed pulmonary vascular resistance (p=0.032 and p=0.013, respectively). Neither Ees/Ea_(Kind) nor Ees/Ea_(Takeuchi) were associated with time to soft event. In patients with APAH, neither Ees/Ea_(Kind) nor Ees/Ea_(Takeuchi) were associated with time to hard event or soft event. CONCLUSIONS: Ees/Ea derived from pressure alone is a strong independent predictor of adverse outcome and could be a potential powerful prognostic tool for paediatric PAH.

Efficacy and safety of tadalafil in a pediatric population with pulmonary arterial hypertension: phase 3 randomized, double-blind placebo-controlled study.

This study evaluated the efficacy and safety of tadalafil in pediatric patients with pulmonary arterial hypertension. This phase-3, international, randomized, multicenter (24 weeks double-blind placebo-controlled period; two-year, open-labeled extension period), add-on (patient's current endothelin receptor antagonist therapy) study included pediatric patients aged <18 years with pulmonary arterial hypertension. Patients received tadalafil 20 mg or 40 mg based on their weight (heavy-weight: ≥40 kg; middle-weight: ≥25 to <40 kg) or placebo orally once daily for 24 weeks. Primary endpoint was change from baseline in six-minute walk distance in patients aged ≥6 years at Week 24. Sample size was amended from 134 to ≥34 patients, due to serious recruitment challenges. Therefore, statistical significance testing was not performed between treatment groups. Results showed that patient demographics and baseline characteristics (N = 35; tadalafil = 17; placebo = 18) were comparable between treatment groups; median age was 14.2 years (6.2-17.9 years) and majority (71.4%, n = 25) of patients were in the heavy-weight cohort. Least square mean (standard error) changes from baseline in six-minute walk distance at Week 24 was numerically greater with tadalafil versus placebo (60.48 (20.41) vs 36.60 (20.78) meters; placebo-adjusted mean difference (standard deviation) 23.88 (29.11)). Safety of tadalafil treatment was as expected without any new safety concerns. During study Period 1, two patients (one in each group) discontinued due to investigator's reported clinical worsening, and no deaths were reported. In conclusion, the statistical significance testing was not performed between the treatment groups due to low sample size; however, the study results show positive trend in improvement in non-invasive measurements, commonly utilized by clinicians to evaluate the disease status for children with pulmonary arterial hypertension. Safety of tadalafil treatment was as expected without any new safety signals.

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.

Practice patterns of pulmonary hypertension secondary to left heart disease among pediatric pulmonary hypertension providers.

Development of pulmonary hypertension (PH) in patients with left side heart disease (LHD) is a predictor of poor prognosis. The use of pulmonary vasodilators in PH associated with LHD (PH-LHD) is controversial. In this study, we describe the practice patterns regarding the use of pulmonary vasodilators in PH-LHD among a group of international pediatric PH specialists. A survey was distributed to the members of three pediatric PH networks: PPHNet, PVRI, and REHIPED. The survey queried participants on the rationale, indications, and contraindications of the use of pulmonary vasodilators in children with PH-LHD. Forty-seven PH specialists from 39 PH centers completed the survey. Participants included PH specialists from North America (57%), South America (15%), and Europe (19%). The majority of participants (74%) recommended the use of pulmonary vasodilators only in patients with combined pre-capillary and post-capillary pulmonary hypertension. Participants required the presence of clinical symptoms or signs of heart failure (68%) or right ventricular dysfunction by echocardiography (51%) in order to recommend pulmonary vasodilator therapy. There was no agreement regarding hemodynamic criteria used to recommend pulmonary vasodilators or the etiologies of LHD considered contraindications for using pulmonary vasodilators to manage PH-LHD. Of the available PH-targeted drugs, most participants preferred the use of phosphodiesterase-5-inhibitors for this indication. In conclusion, the practice of recommending pulmonary vasodilators in PH-LHD is highly variable among international pediatric PH specialists. Most specialists of those surveyed (57% in North America) would consider the use of pulmonary vasodilators in PH-LHD only if pre-capillary pulmonary hypertension and right ventricular dysfunction are present.