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Background: Risk assessment in pulmonary arterial hypertension (PAH) is fundamental to guiding treatment and improved outcomes. Clinical models are excellent at identifying high-risk patients, but leave uncertainty amongst moderate-risk patients., Research Question: Can a multiple blood biomarker model of PAH, using previously described biomarkers, improve risk discrimination over current models?, Study Design and Methods: Using a multiplex enzyme-linked immunosorbent assay, we measured N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP), soluble suppressor of tumorigenicity, IL-6, endostatin, galectin 3, HDGF, and insulin-like growth factor binding proteins (IGFBP1-7) in training (n = 1,623), test (n = 696), and validation (n = 237) cohorts. Clinical variables and biomarkers were evaluated by principal component analysis. NT-proBNP was not included to develop a model independent of NT-proBNP. Unsupervised k-means clustering classified participants into clusters. Transplant-free survival by cluster was examined using Kaplan-Meier and Cox proportional hazard regressions. Hazard by cluster was compared with NT-proBNP, Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL), and European Society of Cardiology (ESC) and European Respiratory Society (ERS) risk models alone and combined clinical and biomarker models., Results: The algorithm generated 5 clusters with good risk discrimination using 6 biomarkers, weight, height, and age at PAH diagnosis. In the test and validation cohorts, the biomarker model alone performed equivalent to REVEAL (area under the receiver operating characteristic curve, 0.74). Adding the biomarker model to the ESC and ERS score and REVEAL score improved the ESC and ERS score and REVEAL score. The best overall model was the biomarker model adjusted for NT-proBNP with the best C statistic, Akaike information criterion, and calibration for the adjusted model compared with either the biomarker or NT-proBNP model alone., Interpretation: A multibiomarker model alone was equivalent to current PAH clinical mortality risk prediction models and improved performance when combined and added to NT-proBNP. Clinical risk scores offer excellent predictive models, but require multiple tests; adding blood biomarkers to models can improve prediction or can enable more frequent, noninvasive monitoring of risk in PAH to support therapeutic decision-making., Competing Interests: Financial/Nonfinancial Disclosures None declared., (Copyright © 2024 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Background: The prognosis and therapeutic responses are worse for pulmonary arterial hypertension associated with systemic sclerosis (SSc-PAH) compared with idiopathic pulmonary arterial hypertension (IPAH). This discrepancy could be driven by divergence in underlying metabolic determinants of disease., Research Question: Are circulating bioactive metabolites differentially altered in SSc-PAH vs IPAH, and can this alteration explain clinical disparity between these PAH subgroups?, Study Design and Methods: Plasma biosamples from 400 patients with SSc-PAH and 1,082 patients with IPAH were included in the study. Another cohort of 100 patients with scleroderma with no PH and 44 patients with scleroderma with PH was included for external validation. More than 700 bioactive lipid metabolites, representing a range of vasoactive and immune-inflammatory pathways, were assayed in plasma samples from independent discovery and validation cohorts using liquid chromatography/high-resolution mass spectrometry-based approaches. Regression analyses were used to identify metabolites that exhibited differential levels between SSc-PAH and IPAH and associated with disease severity., Results: From hundreds of circulating bioactive lipid molecules, five metabolites were found to distinguish between SSc-PAH and IPAH, as well as associate with markers of disease severity. Relative to IPAH, patients with SSc-PAH carried increased levels of fatty acid metabolites, including lignoceric acid and nervonic acid, as well as eicosanoids/oxylipins and sex hormone metabolites., Interpretation: Patients with SSc-PAH are characterized by an unfavorable bioactive metabolic profile that may explain the poor and limited response to therapy. These data provide important metabolic insights into the molecular heterogeneity underlying differences between subgroups of PAH., (Copyright © 2022 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Background: Pediatric pulmonary hypertension is a severe disease defined by sustained elevation of pulmonary artery pressures and pulmonary vascular resistance (PVR). Noninvasive diagnostic and prognostic markers that are more pulmonary vascular specific have been elusive because of disease heterogeneity and patient growth., Research Question: Is soluble suppressor of tumorigenicity (ST2) associated with pulmonary hemodynamic and functional changes in pediatric pulmonary hypertension? Does ST2 improve mortality risk models in pediatric pulmonary hypertension?, Study Design and Methods: Two pediatric cohorts (age < 21 years) were assayed for ST2 and N-terminal prohormone B-natriuretic peptide: a cross-sectional cohort from the National Heart Lung and Blood Institute-funded National Biological Sample and Data Repository for PAH (PAHB) (N = 182), and a second longitudinal cohort from Children's Hospital of Colorado (N = 61). Adjusted linear regression was used for association with clinical variables. Clinical mortality models (the Registry to Evaluate Early and Long-Term PAH Disease Management [REVEAL] score) with and without ST2 were used to predict worsening outcomes and compared. Pulmonary artery endothelial and smooth muscle cell ST2 expression and secretion were assayed in vitro., Results: In an adjusted (age and sex) analysis in the PAHB, ST2 was significantly associated with shorter 6-min walk distance (P = .03) and increased PVR index (P = .02). In adjusted longitudinal regression in the Children's Hospital of Colorado cohort, ST2 was significantly associated with higher PVR index (P < .001), shorter 6-min walk distance (P = .01), and higher mean pulmonary artery pressure (P < .001). Although the REVEAL Risk Score Calculator 2.0 was predictive of clinical worsening in the PAHB (hazard ratio, 1.88), addition of ST2 significantly improved the model (hazard ratio, 2.05). In cell culture, ST2 was produced and secreted predominately by endothelial cells as opposed to smooth muscle cells (P < .0001)., Interpretation: In two pediatric PAH cohorts, elevated ST2 was associated with unfavorable pulmonary hemodynamics and functional measures, clinical worsening, and significantly improved prediction of clinical worsening. Pulmonary artery endothelial cellular expression of ST2 suggests that ST2 is a more pulmonary vascular-specific marker for pulmonary hypertension., (Copyright © 2021 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Background: The treatment, genotyping, and phenotyping of patients with World Health Organization Group 1 pulmonary arterial hypertension (PAH) have evolved dramatically in the last decade., Research Question: The United States Pulmonary Hypertension Scientific Registry was established as the first US PAH patient registry to investigate genetic information, reproductive histories, and environmental exposure data in a contemporary patient population., Study Design and Methods: Investigators at 15 US centers enrolled consecutively screened adults diagnosed with Group 1 PAH who had enrolled in the National Biological Sample and Data Repository for PAH (PAH Biobank) within 5 years of a cardiac catheterization demonstrating qualifying hemodynamic criteria. Exposure and reproductive histories were collected by using a structured interview and questionnaire. The biobank provided genetic data., Results: Between 2015 and 2018, a total of 499 of 979 eligible patients with clinical diagnoses of idiopathic PAH (IPAH) or familial PAH (n = 240 [48%]), associated PAH (APAH; n = 256 [51%]), or pulmonary venoocclusive disease/pulmonary capillary hemangiomatosis (n = 3 [1%]) enrolled. The mean age was 55.8 years, average BMI was 29.2 kg/m 2 , and 79% were women. Mean duration between symptom onset and diagnostic catheterization was 1.9 years. Sixty-six percent of patients were treated with more than one PAH medication at enrollment. Past use of prescription weight loss drugs (16%), recreational drugs (27%), and oral contraceptive pills (77%) was common. Women often reported miscarriage (37%), although PAH was rarely diagnosed within 6 months of pregnancy (1.9%). Results of genetic testing identified pathogenic or suspected pathogenic variants in 13% of patients, reclassifying 18% of IPAH patients and 5% of APAH patients to heritable PAH., Interpretation: Patients with Group 1 PAH remain predominately middle-aged women diagnosed with IPAH or APAH. Delays in diagnosis of PAH persist. Treatment with combinations of PAH-targeted medications is more common than in the past. Women often report pregnancy complications, as well as exposure to anorexigens, oral contraceptives, and/or recreational drugs. Results of genetic tests frequently identify unsuspected heritable PAH., (Copyright © 2020 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Background: Three biomarkers, soluble suppression of tumorigenicity 2 (ST2), galectin 3 (Gal3), and N-terminal brain natriuretic peptide prohormone (NT-proBNP), are approved for noninvasive risk assessment in left-sided heart failure, and small observational studies have shown their prognostic usefulness in heterogeneous pulmonary hypertension cohorts. We examined associations between these biomarkers and disease severity and survival in a large cohort of patients with pulmonary arterial hypertension (PAH) (ie, group 1 pulmonary hypertension). We hypothesized that additive use of biomarkers in combination would improve the prognostic value of survival models., Methods: Biomarker measurements and clinical data were obtained from 2,017 adults with group 1 PAH. Associations among biomarker levels and clinical variables, including survival times, were examined with multivariable regression models. Likelihood ratio tests and the Akaike information criterion were used to compare survival models., Results: Higher ST2 and NT-proBNP were associated with higher pulmonary pressures and vascular resistance and lower 6-min walk distance. Higher ST2 and NT-proBNP levels were associated with increased risk of death (hazard ratios: 2.79; 95% CI, 2.21-3.53; P < .001 and 1.84; 95% CI, 1.62-2.10; P < .001, respectively). The addition of ST2 to survival models composed of other predictors of survival, including NT-proBNP, significantly improved model fit and predictive capacity., Conclusions: ST2 and NT-proBNP are strong, noninvasive prognostic biomarkers in PAH. Despite its prognostic value in left-sided heart failure, Gal3 was not predictive in PAH. Adding ST2 to survival models significantly improves model predictive capacity. Future studies are needed to develop multimarker assays that improve noninvasive risk stratification in PAH., (Copyright © 2020 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Background: Neurofibromatosis type 1 (NF1) is a common disorder of dysregulated tissue growth secondary to mutations in the tumor suppressor gene NF1. Pulmonary arterial hypertension (PAH) in patients with NF1 is hypothesized to be secondary to an underlying vasculopathy., Methods: We describe the entity we term NF1-associated PAH (NF1-PAH) in four new patients and update the data on four previously published reports of patients with PAH and NF1. We performed genetic testing of the bone morphogenic protein receptor 2 (BMPR2) gene, which mutated in 70% of patients with familial PAH and approximately 25% of patients with idiopathic PAH. We report, for the first time, pathologic findings in the autopsy-obtained lung of one patient with NF1-PAH., Results: Patients with NF1-PAH have a generally poor long-term prognosis. In four patients, we observed the mosaic pattern of lung attenuation on a CT scan of the chest, a radiographic finding that can be consistent with an underlying vasculopathy. No mutations or rearrangements in the BMPR2 gene were found. We observed complex plexiform lesions in the one available autopsy specimen. Similar lesions are a hallmark of plexogenic pulmonary arteriopathy and are associated with several severe types of PAH. (Plexiform lesions should not be confused with plexiform neurofibromas, which are distinctive tumors seen in NF1.), Conclusions: Our findings suggest that NF1 should be considered as being "associated with PAH as outlined in the Revised Clinical Classification of Pulmonary Hypertension. Understanding the mechanism of PAH in NF1 may inform the pathogenesis of PAH, NF1-PAH itself, and other NF1-associated vasculopathies. The pulmonary vasculature should now be included among the arterial beds affected by NF1 vasculopathy.