The diverging roles of insulin-like growth factor binding proteins in pulmonary arterial hypertension.

Pulmonary hypertension (PH) is a progressive, severe and to date not curable disease of the pulmonary vasculature. Alterations of the insulin-like growth factor 1 (IGF-1) system are known to play a role in vascular pathologies and IGF-binding proteins (IGFBPs) are important regulators of the bioavailability and function of IGFs. In this study, we show that circulating plasma levels of IGFBP-1, IGFBP-2 and IGFBP-3 are increased in idiopathic pulmonary arterial hypertension (IPAH) patients compared to healthy individuals. These binding proteins inhibit the IGF-1 induced IGF-1 receptor (IGF1R) phosphorylation and exhibit diverging effects on the IGF-1 induced signaling pathways in human pulmonary arterial cells (i.e. healthy as well as IPAH-hPASMCs, and healthy hPAECs). Furthermore, IGFBPs are differentially expressed in an experimental mouse model of PH. In hypoxic mouse lungs, IGFBP-1 mRNA expression is decreased whereas the mRNA for IGFBP-2 is increased. In contrast to IGFBP-1, IGFBP-2 shows vaso-constrictive properties in the murine pulmonary vasculature. Our analyses show that IGFBP-1 and IGFBP-2 exhibit diverging effects on IGF-1 signaling and display a unique IGF1R-independent kinase activation pattern in human pulmonary arterial smooth muscle cells (hPASMCs), which represent a major contributor of PAH pathobiology. Furthermore, we could show that IGFBP-2, in contrast to IGFBP-1, induces epidermal growth factor receptor (EGFR) signaling, Stat-3 activation and expression of Stat-3 target genes. Based on our results, we conclude that the IGFBP family, especially IGFBP-1, IGFBP-2 and IGFBP-3, are deregulated in PAH, that they affect IGF signaling and thereby regulate the cellular phenotype in PH.

Right heart catheterization in idiopathic pulmonary hypertension: An all-inclusive necessity.

The gold standard for diagnosis of pulmonary hypertension is right heart catheterization. This procedure requires considerable expertise and has its own procedure related complications. If not done properly, it can lead to misinterpretations of its findings. We have highlighted the procedural technique and major pitfalls in the diagnosis of pulmonary hypertension.

[Heritable pulmonary arterial hypertension]. / Hereditäre pulmonal-arterielle Hypertonie.

Heritable pulmonary arterial hypertension (PAH) can be triggered by at least 18 genes. The most frequently altered gene is the bone morphogenetic protein receptor 2 (BMPR2). Further genes from the same pathway are also well known PAH-causing genes. Genetic testing can aid to confirm differential diagnoses such as a pulmonary veno-occlusive disease. It also enables the testing of healthy family members. In addition to the PAH patient population particularly served by genetic testing, this article touches on the mode of inheritance and provides insights into the first treatments soon on the market that rebalance the BMPR2 signaling pathway.

Association of non-insulin-based insulin resistance indices with disease severity and adverse outcome in idiopathic pulmonary arterial hypertension: a multi-center cohort study.

BACKGROUND: Insulin resistance (IR) plays an important role in the pathophysiology of cardiovascular disease. Recent studies have shown that diabetes mellitus and impaired lipid metabolism are associated with the severity and prognosis of idiopathic pulmonary arterial hypertension (IPAH). However, the relationship between IR and pulmonary hypertension is poorly understood. This study explored the association between four IR indices and IPAH using data from a multicenter cohort. METHODS: A total of 602 consecutive participants with IPAH were included in this study between January 2015 and December 2022. The metabolic score for IR (METS-IR), triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio, triglyceride and glucose (TyG) index, and triglyceride-glucose-body mass index (TyG-BMI) were used to quantify IR levels in patients with IPAH. The correlation between non-insulin-based IR indices and long-term adverse outcomes was determined using multivariate Cox regression models and restricted cubic splines. RESULTS: During a mean of 3.6 years' follow-up, 214 participants experienced all-cause death or worsening condition. Compared with in low to intermediate-low risk patients, the TG/HDL-C ratio (2.9 ± 1.7 vs. 3.3 ± 2.1, P = 0.003) and METS-IR (34.5 ± 6.7 vs. 36.4 ± 7.5, P < 0.001) were significantly increased in high to intermediate-high risk patients. IR indices correlated with well-validated variables that reflected the severity of IPAH, such as the cardiac index and stroke volume index. Multivariate Cox regression analyses indicated that the TyG-BMI index (hazard ratio [HR] 1.179, 95% confidence interval [CI] 1.020, 1.363 per 1.0-standard deviation [SD] increment, P = 0.026) and METS-IR (HR 1.169, 95% CI 1.016, 1.345 per 1.0-SD increment, P = 0.030) independently predicted adverse outcomes. Addition of the TG/HDL-C ratio and METS-IR significantly improved the reclassification and discrimination ability beyond the European Society of Cardiology (ESC) risk score. CONCLUSIONS: IR is associated with the severity and long-term prognosis of IPAH. TyG-BMI and METS-IR can independently predict clinical worsening events, while METS-IR also provide incremental predictive performance beyond the ESC risk stratification.

Fractional exhaled nitric oxide in idiopathic pulmonary arterial hypertension and mixed connective tissue disease complicating pulmonary hypertension.

BACKGROUND: Fractional exhaled nitric oxide (FeNO) has been extensively studied in various causes of pulmonary hypertension (PH), but its utility as a noninvasive marker remains highly debated. The objective of our study was to assess FeNO levels in patients with idiopathic pulmonary arterial hypertension (IPAH) and mixed connective tissue disease complicating pulmonary hypertension (MCTD-PH), and to correlate them with respiratory functional data, disease severity, and cardiopulmonary function. METHODS: We collected data from 54 patients diagnosed with IPAH and 78 patients diagnosed with MCTD-PH at the Shanghai Pulmonary Hospital Affiliated to Tongji University. Our data collection included measurements of brain natriuretic peptide (pro-BNP), cardiopulmonary exercise test (CPET), pulmonary function test (PFT), impulse oscillometry (IOS), and FeNO levels. Additionally, we assessed World Health Organization functional class (WHO-FC) of each patient. RESULTS: (1) The fractional exhaled concentration of nitric oxide was notably higher in patients with IPAH compared to those with MCTD-PH. Furthermore, within the IPAH group, FeNO levels were found to be lower in cases of severe IPAH compared to mild IPAH (P = 0.024); (2) In severe pulmonary hypertension as per the WHO-FC classification, FeNO levels in IPAH exhibited negative correlations with FEV1/FVC (Forced Expiratory Velocity at one second /Forced Vital Capacity), MEF50% (Maximum Expiratory Flow at 50%), MEF25%, and MMEF75/25% (Maximum Mid-expiratory Flow between 75% and 25%), while in severe MCTD-PH, FeNO levels were negatively correlated with R20% (Resistance at 20 Hz); (3) ROC (Receiving operator characteristic curve) analysis indicated that the optimal cutoff value of FeNO for diagnosing severe IPAH was 23ppb; (4) While FeNO levels tend to be negatively correlated with peakPETO2(peak end-tidal partial pressure for oxygen) in severe IPAH, in mild IPAH they had a positive correlation to peakO2/Heart rate (HR). An interesting find was observed in cases of severe MCTD-PH, where FeNO levels were negatively correlated with HR and respiratory exchange ratio (RER), while positively correlated with O2/HR throughout the cardiopulmonary exercise test. CONCLUSION: FeNO levels serve as a non-invasive measure of IPAH severity. Although FeNO levels may not assess the severity of MCTD-PH, their significant makes them a valuable tool when assessing severe MCTD-PH.

Blood urea nitrogen to serum albumin ratio as a new indicator of disease severity and prognosis in idiopathic pulmonary artery hypertension.

BACKGROUND: Emerging evidence has shown that the blood urea nitrogen to serum albumin ratio (BAR) is associated with the severity and prognosis of heart failure. However, its role in idiopathic pulmonary arterial hypertension (IPAH) remains unclear. This study investigated the associations between BAR and functional status, echocardiographic findings, hemodynamics, and long-term outcomes among patients with IPAH. METHODS: This study included consecutive patients who underwent right heart catheterization (RHC) and were diagnosed with IPAH between January 2013 and January 2018 at Fuwai Hospital. The primary outcome was the worsening of clinical symptoms. Spearman correlation coefficients were used to evaluate the association between the BAR and established markers of IPAH severity. Receiver operating characteristic (ROC) curve analysis was used to determine BAR's optimal cut-off and predictive performance. Kaplan-Meier analysis and Cox proportional hazard models assessed the relationship between BAR and clinical worsening. RESULTS: A total of 340 patients with IPAH were included in this study. BAR correlated with well-validated variables that reflected the severity of IPAH, such as World Health Organization functional class, 6-min walk distance, N-terminal pro-brain natriuretic peptide (NT-proBNP) level, mixed venous oxygen saturation, and cardiac index. Kaplan-Meier curves indicated that patients with BAR＞3.80 had a significantly higher clinical worsening rate (log-rank test, P < 0.001) than those with BAR≤3.80. Multivariate Cox analysis showed that BAR could independently predict clinical worsening [hazard ratio(HR):2.642, 95 % confidence interval (CI):1.659-4.208, P < 0.001]. In addition, BAR provided additional predictive value for the European Society of Cardiology (ESC)/European Respiratory Society (ERS) risk assessment score. CONCLUSIONS: BAR reflects disease severity and is independently associated with the prognosis of patients with IPAH.

Clinical Correlates of a Nonplexiform Vasculopathy in Patients With a Diagnosis of Idiopathic Pulmonary Arterial Hypertension.

BACKGROUND: The clinical phenotype of patients with idiopathic pulmonary arterial hypertension (IPAH) has changed. Whether subgroups of patients with IPAH have different vascular phenotypes is a subject of debate. RESEARCH QUESTION: What are the histologic patterns and their clinical correlates in patients with a diagnosis of IPAH or hereditary pulmonary arterial hypertension? STUDY DESIGN AND METHODS: In this this cross-sectional registry study, lung histology of 50 patients with IPAH was assessed qualitatively by two experienced pathologists. In addition, quantitative analysis by means of histopathologic morphometry using immunohistochemistry was performed. Histopathologic characteristics were correlated with clinical and hemodynamic parameters. RESULTS: In this cohort of 50 patients with IPAH, a plexiform vasculopathy was observed in 26 of 50 patients (52%), whereas 24 of 50 patients (48%) showed a nonplexiform vasculopathy. The nonplexiform vasculopathy was characterized by prominent pulmonary microvascular (arterioles and venules) remodeling and vascular rarefaction. Although hemodynamic parameters were comparable in plexiform vs nonplexiform vasculopathy, patients with nonplexiform vasculopathy were older, more often were male, more often had a history of cigarette smoking, and had lower diffusing capacity of the lungs for carbon monoxide at diagnosis. No mutations in established pulmonary arterial hypertension genes were found in the nonplexiform group. INTERPRETATION: This study revealed different vascular phenotypes within the current spectrum of patients with a diagnosis of IPAH, separated by clinical characteristics (age, sex, history of cigarette smoking, and diffusing capacity of the lungs for carbon monoxide at diagnosis). Potential differences in underlying pathobiological mechanisms between patients with plexiform and nonplexiform microvascular disease should be taken into account in future research strategies unravelling the pathophysiologic features of pulmonary hypertension and developing biology-targeted treatment approaches.

Idiopathic and connective tissue disease-associated pulmonary arterial hypertension (PAH): Similarities, differences and the role of autoimmunity.

Pre-capillary pulmonary arterial hypertension (PAH) is hemodynamically characterized by a mean pulmonary arterial pressure (mPAP) ≥ 20 mmHg, pulmonary capillary wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) > 2. PAH is classified in six clinical subgroups, including idiopathic PAH (IPAH) and PAH associated to connective tissue diseases (CTD-PAH), that will be the main object of this review. The aim is to compare these two PAH subgroups in terms of epidemiology, histological and pathogenic findings in an attempt to define disease-specific features, including autoimmunity, that may explain the heterogeneity of response to therapy between IPAH and CTD-PAH.

Prognostic impact of follow-up pulmonary vascular resistance in pulmonary arterial hypertension.

OBJECTIVE: Pulmonary arterial hypertension (PAH), caused by pulmonary artery remodelling and increased pulmonary vascular resistance (PVR) due to an unknown mechanism, is an intractable disease with a poor prognosis. The recent development of PAH-specific treatment medications may allow for higher PVR reduction than previously achieved. This study aimed to identify the prognostic significance of follow-up PVR levels achieved shortly after the initiation of targeted treatment in patients with idiopathic/heritable pulmonary arterial hypertension (I/H-PAH). METHODS: We analysed the data of all patients with I/H-PAH admitted to our hospital between 1998 and 2019. We collected data at baseline and during the first invasive haemodynamic evaluation. The primary outcome was death or lung transplantation. RESULTS: Of the 133 treatment-naïve patients enrolled in this study, 47 experienced adverse events during a median follow-up period of 6.4 (IQR 3.5-11.5) years. The median time interval to first follow-up from diagnosis was 162 (IQR 117-253) days. Incidence of the primary outcome was significantly lower in patients who achieved low PVR at follow-up. Of risk factors evaluated at follow-up, the multivariate Cox regression analysis revealed PVR as an independent predictor of the primary outcome (HR 1.103, 95% CI 1.029 to 1.183; p=0.006). The results were consistent across risk profiles according to the simplified risk stratification recommended by the European Society of Cardiology and European Respiratory Society guidelines. CONCLUSION: Follow-up PVR was an independent predictor of transplant-free survival in patients with I/H-PAH. Evaluation of haemodynamic status shortly after initiating treatment may help predict long-term prognosis.

Early implementation of renal replacement therapy after lung transplantation does not impair long-term kidney function in patients with idiopathic pulmonary arterial hypertension.

OBJECTIVES: In patients with idiopathic pulmonary arterial hypertension, cardiac function can be impaired in the early postoperative phase after lung transplantation because the chronically untrained left ventricle is prone to fail. Thus, restrictive fluid management is pivotal to unload the left heart. In our institution, continuous renal replacement therapy is implemented liberally whenever a patient cannot be balanced negatively. It remains unclear whether such strategy impairs long-term kidney function. METHODS: We retrospectively reviewed our institutional database for patients with idiopathic pulmonary arterial hypertension who underwent transplantation between 2000 and 2018. The impact of postoperative continuous renal replacement therapy on long-term outcomes was investigated using a linear mixed model and multivariable Cox regression. RESULTS: A total of 87 idiopathic pulmonary arterial hypertension lung transplant recipients were included in this analysis. In 38 patients (43%), continuous renal replacement therapy was started in the early postoperative period for a median of 16 days (10-22). In this group, urine production significantly decreased and patients began to acquire a positive fluid balance; however, homeostatic functions of the kidney were still preserved at the time of continuous renal replacement therapy initiation. All patients were successfully weaned from continuous renal replacement therapy and fully recovered their kidney function at the time of hospital discharge. No difference in kidney function was found between continuous renal replacement therapy and noncontinuous renal replacement therapy in patients within 5 years. CONCLUSIONS: Early implementation of continuous renal replacement therapy for perioperative volume management does not impair long-term kidney function in idiopathic pulmonary arterial hypertension lung transplant recipients. Our data suggest that such a strategy leads to excellent long-term outcomes.

Predictive value of chest HRCT for survival in idiopathic pulmonary arterial hypertension.

BACKGROUND: Little attention has been paid to chest high resolution computed tomography (HRCT) findings in idiopathic pulmonary arterial hypertension (IPAH) patients so far, while a couple of small studies suggested that presence of centrilobular ground-glass opacifications (GGO) on lung scans could have a significant negative prognostic value. Therefore, the aims of the present study were: to assess frequency and clinical significance of GGO in IPAH, and to verify if it carries an add-on prognostic value in reference to multidimensional risk assessment tool recommended by the 2015 European pulmonary hypertension guidelines. METHODS: Chest HRCT scans of 110 IPAH patients were retrospectively analysed. Patients were divided into three groups: with panlobular (p)GGO, centrilobular (c)GGO, and normal lung pattern. Association of different GGO patterns with demographic, functional, haemodynamic, and biochemical parameters was tested. Survival analysis was also performed. RESULTS: GGO were found in 46% of the IPAH patients: pGGO in 24% and cGGO in 22%. Independent predictors of pGGO were: positive history of haemoptysis, higher number of low-risk factors, and lower cardiac output. Independent predictors of cGGO were: positive history of haemoptysis, younger age, higher right atrial pressure, and higher mixed venous blood oxygen saturation. CGGO had a negative prognostic value for outcome in a 2-year perspective. This effect was not seen in the longer term, probably due to short survival of cGGO patients. CONCLUSIONS: Lung HRCT carries a significant independent prognostic information in IPAH, and in patients with cGGO present on the scans an early referral to lung transplantation centres should be considered.

Iron Metabolism and Idiopathic Pulmonary Arterial Hypertension: New Insights from Bioinformatic Analysis.

Idiopathic pulmonary arterial hypertension (IPAH) is a rare vascular disease with a poor prognosis, and the mechanism of its development remains unclear. Further molecular pathology studies may contribute to a comprehensive understanding of IPAH and provide new insights into diagnostic markers and potential therapeutic targets. Iron deficiency has been reported in 43-63% of patients with IPAH and is associated with reduced exercise capacity and higher mortality, suggesting that dysregulated iron metabolism may play an unrecognized role in influencing the development of IPAH. In this study, we explored the regulatory mechanisms of iron metabolism in IPAH by bioinformatic analysis. The molecular function of iron metabolism-related genes (IMRGs) is mainly enriched in active transmembrane transporter activity, and they mainly affect the biological process of response to oxidative stress. Ferroptosis and fluid shear stress and atherosclerosis pathways may be the critical pathways regulating iron metabolism in IPAH. We further identified 7 key genes (BCL2, GCLM, MSMO1, SLC7A11, SRXN1, TSPAN5, and TXNRD1) and 5 of the key genes (BCL2, MSMO1, SLC7A11, TSPAN5, and TXNRD1) as target genes may be regulated by 6 dysregulated miRNAs (miR-483-5p, miR-27a-3p, miR-27b-3p, miR-26b-5p, miR-199a-5p, and miR-23b-3p) in IPAH. In addition, we predicted potential IPAH drugs-celastrol and cinnamaldehyde-that target iron metabolism based on our results. These results provide insights for further definition of the role of dysregulated iron metabolism in IPAH and contribute to a deeper understanding of the molecular mechanisms and potential therapeutic targets of IPAH.

Myocardial adaptation and exercise performance in patients with pulmonary arterial hypertension assessed with patient-specific computer simulations.

Myocardial function and exercise reserve are important determinants of outcome in pulmonary arterial hypertension (PAH) but are incompletely understood. For this study, we performed subject-specific computer simulations, based on invasive measurements and cardiac magnetic resonance imaging (CMR), to investigate whole circulation properties in PAH at rest and exercise and determinants of exercise reserve. CMR and right heart catheterization were performed in nine patients with idiopathic PAH, and CMR in 10 healthy controls. CMR during exercise was performed in seven patients with PAH. A full-circulation computer model was developed, and model parameters were optimized at the individual level. Patient-specific simulations were used to analyze the effect of right ventricular (RV) inotropic reserve on exercise performance. Simulations achieved a high consistency with observed data. RV contractile force was increased in patients with PAH (127.1 ± 28.7 kPa vs. 70.5 ± 14.5 kPa, P < 0.001), whereas left ventricular contractile force was reduced (107.5 ± 17.5 kPa vs. 133.9 ± 10.3 kPa, P = 0.002). During exercise, RV contractile force increased by 1.56 ± 0.17, P = 0.001. In silico experiments confirmed RV inotropic reserve as the important limiting factor for cardiac output. Subject-specific computer simulation of myocardial mechanics in PAH is feasible and can be used to evaluate myocardial performance. With this method, we demonstrate marked functional myocardial adaptation to PAH in the resting state, primarily composed of increased contractile force development by RV myofibers, and we show the negative impact of reduced RV inotropic reserve on cardiac output during exercise.NEW & NOTEWORTHY Computer simulations of the myocardial mechanics and hemodynamics of rest and exercise were performed in nine patients with pulmonary arterial hypertension and 10 control subjects, with the use of data from invasive catheterization and from cardiac magnetic resonance. This approach allowed a detailed analysis of myocardial adaptation to pulmonary arterial hypertension and showed how reduction in right ventricular inotropic reserve is the important limiting factor for an increase in cardiac output during exercise.

Prognostic Significance of Systemic Arterial Stiffness Evaluated by Cardio-Ankle Vascular Index in Patients with Idiopathic Pulmonary Hypertension.

BACKGROUND: In a previous study, the cardio-ankle vascular index (CAVI) was increased significantly in idiopathic pulmonary arterial hypertension (IPAH) patients compared to the healthy group and did not much differ from one in systemic hypertensives. In this study the relations between survival and CAVI was evaluated in patients with IPAH. PATIENTS AND METHODS: We included 89 patients with new-diagnosed IPAH without concomitant diseases. Standard examinations, including right heart catheterization (RHC) and systemic arterial stiffness evaluation, were performed. All patients were divided according to CAVI value: the group with CAVI ≥ 8 (n = 18) and the group with CAVI < 8 (n = 71). The mean follow-up was 33.8 ± 23.7 months. Kaplan-Meier and Cox regression analysis were performed for the evaluation of our cohort survival and the predictors of death. RESULTS: The group with CAVI≥8 was older and more severe compared to the group with CAVI< 8. Patients with CAVI≥8 had significantly reduced end-diastolic (73.79±18.94 vs 87.35±16.69 mL, P<0.009) and end-systolic (25.71±9.56 vs 33.55±10.33 mL, P<0.01) volumes of the left ventricle, the higher right ventricle thickness (0.77±0.12 vs 0.62±0.20 mm, P < 0.006), and the lower TAPSE (13.38±2.15 vs 15.98±4.4 mm, P<0.018). RHC data did not differ significantly between groups, except the higher level of the right atrial pressure in patients with CAVI≥ 8-11.38±7.1 vs 8.76±4.7 mmHg, P<0.08. The estimated overall survival rate was 61.2%. The CAVI≥8 increased the risk of mortality 2.34 times (CI 1.04-5.28, P = 0.041). The estimated Kaplan-Meier survival in the patients with CAVI ≥ 8 was only 46.7 ± 7.18% compared to patients with CAVI < 8 - 65.6 ± 4.2%, P = 0.035. At multifactorial regression analysis, the CAVI reduced but saved its relevance as death predictor - OR = 1.13, CI 1.001-1.871. SUMMARY: We suggested the CAVI could be a new independent predictor of death in the IPAH population and could be used to better risk stratify this patient population if CAVI is validated as a marker in a larger multicenter trial.

Disease-specific platelet signaling defects in idiopathic pulmonary arterial hypertension.

Idiopathic pulmonary arterial hypertension (IPAH) is a rapidly progressive disease with several treatment options. Long-term mortality remains high with great heterogeneity in treatment response. Even though most of the pathology of IPAH is observed in the lung, there is systemic involvement. Platelets from patients with IPAH have characteristic metabolic shifts and defects in activation; therefore, we investigated whether they could be used to identify other disease-specific abnormalities. We used proteomics to investigate protein expression changes in platelets from patients with IPAH compared with healthy controls. Key abnormalities of nitric oxide pathway were tested in platelets from a larger cohort of unique patients with IPAH. Platelets showed abnormalities in the prostacyclin and nitric oxide pathways, which are dysregulated in IPAH and hence targets of therapy. We detected reduced expression of G protein αs and increased expression of the regulatory subunits of the cAMP-dependent protein kinase (PKA) type II isoforms, supporting an overall decrease in the activation of the prostacyclin pathway. We noted reduced levels of the soluble guanylate cyclase (sGC) subunits and increased expression of the phosphodiesterase type 5 A (PDE5A), conditions that affect the response to nitric oxide. Ensuing analysis of 38 unique patients with IPAH demonstrated considerable variation in the levels and specific activity of sGC, a finding with novel implications for personalized therapy. Platelets have some of the characteristic vasoactive signal abnormalities seen in IPAH and may provide comprehensive ex vivo mechanistic information to direct therapeutic decisions.

Peripheral microangiopathy in precapillary pulmonary hypertension: a nailfold video capillaroscopy prospective study.

BACKGROUND: Although pulmonary vascular bed has been the main subject of research for many years in pulmonary hypertension (PH), interest has recently started to divert towards the possibility of a co-existing peripheral microangiopathy. The aim of the current study was to investigate the presence of nailfold video-capillaroscopic (NVC) structural changes in patients with precapillary PH and to identify possible associations of NVC measurements with markers of disease severity. METHODS: Α prospective case-control study was performed in 28 consecutive patients with precapillary PH [14 with idiopathic pulmonary arterial hypertension (IPAH) and 14 with chronic thromboembolic pulmonary hypertension (CTEPH)] and 30 healthy controls. NVC quantitative and qualitative parameters were evaluated using Optilia Digital Capillaroscope. To ensure inter-observer repeatability capillaroscopic images were reviewed by two independent investigators. For multiple comparisons among continuous variables, one-way ANOVA or the Kruskal-Wallis test were used. Differences between the groups were tested with post-hoc analysis with adjustment for multiple comparisons (Bonferroni test). RESULTS: Both IPAH (71.4% were women, mean age 53.1 ± 13.4 years) and CTEPH (64.3% women, mean age 60.9 ± 14.4 years) groups presented reduced capillary density compared to healthy controls (8.4 ± 1.2 loops/mm and 8.0 ± 1.2 loops/mm vs. 9.7 ± 0.81 loops/mm, p < 0.001) and increased loop width (15.7 ± 3.9 µm and 15.8 ± 1.9 µm vs. 11.5 ± 2.3 µm, p < 0.001). More than half of patients with IPAH presented microhaemorrhages on capillary nailfold, while increased shape abnormalities in capillary morphology and more capillary thrombi per linear mm were detected in patients with CTEPH compared to patients with IPAH and healthy controls. All PH patients presented a non-specific NVC pattern compared to controls (p < 0.001). CONCLUSION: The findings of the study reveal a degree of significant peripheral microvascular alterations in patients with IPAH and CTEPH, suggesting a generalized impairment of peripheral microvasculature in pulmonary vascular disease.