Impaired peripheral endothelial function in severe idiopathic pulmonary hypertension correlates with the pulmonary vascular response to inhaled iloprost

Pulmonary hypertension impairs vasomotor function in rat diaphragm arterioles

Pulmonary hypertension (PH) is a chronic, progressive condition in which respiratory muscle dysfunction is a primary contributor to exercise intolerance and dyspnea in patients. Contractile function, blood flow distribution, and the hyperemic response are altered in the diaphragm with PH, and we sought to determine whether this may be attributed, in part, to impaired vasoreactivity of the resistance vasculature. We hypothesized that there would be blunted endothelium-dependent vasodilation and impaired myogenic responsiveness in arterioles from the diaphragm of PH rats. Female Sprague-Dawley rats were randomized into healthy control (HC, n = 9) and monocrotaline-induced PH rats (MCT, n = 9). Endothelium-dependent and -independent vasodilation and myogenic responses were assessed in first-order arterioles (1As) from the medial costal diaphragm in vitro. There was a significant reduction in endothelium-dependent (via acetylcholine; HC, 78 ± 15% vs. MCT, 47 ± 17%; P < 0.05) and -independent (via sodium nitroprusside; HC, 89 ± 10% vs. MCT, 66 ± 10%; P < 0.05) vasodilation in 1As from MCT rats. MCT-induced PH also diminished myogenic constriction (P < 0.05) but did not alter passive pressure responses. The diaphragmatic weakness, impaired hyperemia, and blood flow redistribution associated with PH may be due, in part, to diaphragm vascular dysfunction and thus compromised oxygen delivery which occurs through both endothelium-dependent and -independent mechanisms.

Endothelial Function Correlates With Pulmonary Pressures in Subjects With Clinically Suspected Pulmonary Hypertension

Impaired pulmonary circulation hemodynamics are characteristic of pulmonary hypertension (PH). We therefore sought to evaluate possible correlations between endothelial function noninvasively assessed by brachial artery flow-mediated dilation (FMD) and hemodynamic parameters at right-sided cardiac catheterization in patients with clinically suspected PH. Consecutive outpatients with suspected PH were enrolled in the study. In all patients, endothelial function was assessed by FMD and hemodynamic parameters (pulmonary artery pressure [PAP]); pulmonary vascular resistances [PVR]) were derived by right-sided cardiac catheterization. For this study, 95 consecutive patients with suspected PH were enrolled (mean age 63 ± 13 years, 58% male) and included in the analysis. FMD values were significantly correlated with systolic (s)PAP levels (r = -0.29, p = 0.016); correlation with PVR was of borderline significance (r = -0.21, p = 0.78). After multivariable regression analysis including age, gender, tricuspid annular plane systolic excursion and peak tricuspid regurgitation velocity (peak TRV), and FMD, the latter remained significantly correlated with systolic pulmonary artery pressure (sPAP) values (B = -47, p = 0.02). After classifying patients according to median levels of peak TRV and FMD into 3 groups (neither, either, or both impaired), progressively increased levels of sPAP, mean PAP, and PVR were found (p for trend <0.001 in all cases). FMD values were inversely related to sPAP levels in a small population of patients with clinically suspected PH. In combination with peak TRV levels, FMD values noninvasively assessed were predictive of increased sPAP, mean PAP, and PVR.

Association between preoperative albumin and length of hospital stay in non-cardiac surgery patients with pulmonary hypertension: A secondary retrospective analysis

To explore the risk factors affecting the length of hospital stay (LOS) as well as to examine the relationship between preoperative serum albumin levels and LOS following non-cardiac, non-obstetric surgery in patients with pulmonary hypertension (PHTN). This study represents a secondary retrospective analysis based on 287 non-cardiac, non-obstetric procedures performed on 195 PTHN patients at a single institution in the USA between 2007 and 2013. The primary outcome was the LOS. We conducted a multiple logistic regression analysis to compare the LOS between the 2 groups, divided at a serum albumin level of 3.5 g/dL. After adjusting for multiple covariates, the ORs for the long length of stay (LOS > 7 days) for the high group(albumin > 3.5 g/dL) compared with the low group (albumin ≤ 3.5 g/dL) were 0.35 (95%CI: 0.21~0.6), 0.41 (95%CI: 0.22 ~0.76), 0.41 (95%CI: 0.18~0.94) from model 2 to model 4. The stratified analysis results indicate that these findings are stable (p for trend > 0.05). In this study, it was observed that low levels of preoperative albumin were associated with an increased risk of prolonged hospital stay after non-cardiac, non-obstetric surgery in patients with PHTN. This implies that optimizing preoperative nutrition could potentially reduce the LOS for non-cardiac, non-obstetric surgery in patients with PHTN.

Endothelial Function in Pulmonary Arterial Hypertension: From Bench to Bedside

Pulmonary arterial hypertension is a complex pathology whose etiology is still not completely well clarified. The pathogenesis of pulmonary arterial hypertension involves different molecular mechanisms, with endothelial dysfunction playing a central role in disease progression. Both individual genetic predispositions and environmental factors seem to contribute to its onset. To further understand the complex relationship between endothelial and pulmonary hypertension and try to contribute to the development of future therapies, we report a comprehensive and updated review on endothelial function in pulmonary arterial hypertension.

Identification of potential biomarkers for idiopathic pulmonary arterial hypertension using single-cell and bulk RNA sequencing analysis

Idiopathic pulmonary arterial hypertension (IPAH) is a rare and severe cardiopulmonary disease with a challenging prognosis, and its underlying pathogenesis remains elusive. A comprehensive understanding of IPAH is crucial to unveil potential diagnostic markers and therapeutic targets. In this study, we investigated cellular heterogeneity and molecular pathology in IPAH using single-cell RNA sequencing (scRNA-seq) analysis. Our scRNA-seq results revealed significant alterations in three crucial signaling pathways in IPAH: the hypoxia pathway, TGF β pathway, and ROS pathway, primarily attributed to changes in gene expression within arterial endothelial cells. Moreover, through bulk RNA sequencing analysis, we identified differentially expressed genes (DEGs) enriched in GO and KEGG pathways, implicated in regulating cell adhesion and oxidative phosphorylation in IPAH lungs. Similarly, DEGs-enriched pathways in IPAH arterial endothelial cells were also identified. By integrating DEGs from three IPAH datasets and applying protein-protein interaction (PPI) analysis, we identified 12 candidate biomarkers. Subsequent validation in two additional PAH datasets led us to highlight five potential biomarkers (CTNNB1, MAPK3, ITGB1, HSP90AA1, and DDX5) with promising diagnostic significance for IPAH. Furthermore, real-time quantitative polymerase chain reaction (RT-qPCR) confirmed significant differences in the expression of these five genes in pulmonary arterial endothelial cells from PAH mice. In conclusion, our findings shed light on the pivotal role of arterial endothelial cells in the development of IPAH. Furthermore, the integration of single-cell and bulk RNA sequencing datasets allowed us to pinpoint novel candidate biomarkers for the diagnosis of IPAH. This work opens up new avenues for research and potential therapeutic interventions in IPAH management.

Pulmonary hypertension alters blood flow distribution and impairs the hyperemic response in the rat diaphragm

Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling, respiratory muscle and cardiac impairments, and exercise intolerance. Specifically, impaired gas exchange increases work of the diaphragm; however, compromised contractile function precludes the diaphragm from meeting the increased metabolic demand of chronic hyperventilation in PH. Given that muscle contractile function is in part, dependent upon adequate blood flow (Q ˙ ), diaphragmatic dysfunction may be predicated by an inability to match oxygen delivery with oxygen demand. We hypothesized that PH rats would demonstrate a decreased hyperemic response to contractions compared to healthy controls. Methods: Sprague-Dawley rats were randomized into healthy (HC, n = 7) or PH (n = 7) groups. PH rats were administered monocrotaline (MCT) while HC rats received vehicle. Disease progression was monitored via echocardiography. Regional and total diaphragm blood flow and vascular conductance at baseline and during 3 min of electrically-stimulated contractions were determined using fluorescent microspheres. Results: PH rats displayed morphometric and echocardiographic criteria for disease (i.e., acceleration time/ejection time, right ventricular hypertrophy). In all rats, total costal diaphragm Q ˙ increased during contractions and did not differ between groups. In HC rats, there was a greater increase in medial costal Q ˙ compared to PH rats (55% ± 3% vs. 44% ± 4%, p < 0.05), who demonstrated a redistribution of Q ˙ to the ventral costal region. Conclusion: These findings support a redistribution of regional diaphragm perfusion and an impaired medial costal hyperemic response in PH, suggesting that PH alters diaphragm vascular function and oxygen delivery, providing a potential mechanism for PH-induced diaphragm contractile dysfunction.

Flow-mediated dilation as a marker of endothelial dysfunction in pulmonary diseases: A narrative review

The endothelium is an active and crucial component of vessels and produces several key regulatory factors for the homeostasis of the entire organism. Endothelial function can be investigated invasively or non-invasively, both in the coronary and peripheral circulation. A widely accepted method for the assessment of endothelial function is measurement of flow-mediated dilation (FMD), which evaluates the vascular response to changes in blood flow. In this current review, we describe FMD applications in the clinical setting of different respiratory diseases: acute SARS-COV2 infection, pulmonary embolism; post-acute SARS-COV2 infection, Chronic Obstructive Pulmonary Disease, Obstructive Sleep Apneas Syndrome, Pulmonary Hypertension, Interstitial Lung Diseases. Emerging evidence shows that FMD might be an effective tool to assess the cardiovascular risk in patients suffering from the undermentioned respiratory diseases as well as an independent predictive factor of disease severity and/or recovery.

Correlation between Pulmonary Artery Pressure and Vortex Duration Determined by 4D Flow MRI in Main Pulmonary Artery in Patients with Suspicion of Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

Chronic thromboembolic pulmonary hypertension (CTEPH) is one of the causes of pulmonary hypertension (PH) and requires invasive measurement of the mean pulmonary artery pressure (mPAP) during right heart catheterisation (RHC) for the diagnosis. 4D flow MRI could provide non-invasive parameters to estimate the mPAP. Twenty-five patients with suspected CTEPH underwent cardiac MRI. Mean vortex duration (%), pulmonary distensibility, right ventricular volumes and function were measured using 4D flow MRI and cine sequences, and compared with the mPAP measured by RHC. The mPAP measured during RHC was 33 ± 16 mmHg (10−66 mmHg). PH (defined as mPAP > 20 mmHg) was present in 19 of 25 patients (76%). A vortical flow was observed in all but two patients (92%) on 4D flow images, and vortex duration showed good correlation with the mPAP (r = 0.805; p < 0.0001). Youden index analysis showed that a vortex duration of 8.6% of the cardiac cycle provided a 95% sensitivity and an 83% specificity to detect PH. Reliability for the measurement of vortex duration was excellent for both intra-observer ICC = 0.823 and inter-observer ICC = 0.788. Vortex duration could be a useful parameter to non-invasively estimate mPAP in patients with suspected CTEPH.

Effects of pulmonary hypertension on microcirculatory hemodynamics in rat skeletal muscle

Pulmonary hypertension (PH) has previously been characterized as a disease of the pulmonary vasculature that subsequently results in myocardial dysfunction. Heart failure compromises skeletal muscle microvascular function, which contributes to exercise intolerance. Therefore, we tested the hypothesis that such changes might be present in PH. Thus, we investigated skeletal muscle oxygen (O₂) transport in the rat model of PH to determine if O₂ delivery (Q̇O₂) is impaired at the level of the microcirculation as evidenced via reduced red blood cell (RBC) flux, velocity, hematocrit, and percentage of capillaries flowing in quiescent muscle. Adult male Sprague-Dawley rats were randomized into healthy (n = 9) and PH groups (n = 9). Progressive PH was induced via a one-time intraperitoneal injection of monocrotaline (MCT; 50 mg/kg) and rats were monitored weekly via echocardiography. Intravital microscopy in the spinotrapezius muscle was performed when echocardiograms confirmed moderate PH (preceding right ventricular (RV) failure). At 25 ± 9 days post-MCT, PH rats displayed RV hypertrophy (RV/(Left ventricle + Septum): 0.28 ± 0.05 vs. 0.44 ± 0.11), pulmonary congestion, and increased right ventricular systolic pressure (21 ± 8 vs. 55 ± 14 mm Hg) compared to healthy rats (all P < 0.05). Reduced capillary RBC velocity (403 ± 140 vs. 227 ± 84 μm/s; P = 0.01), RBC flux (33 ± 12 vs. 23 ± 5 RBCs/s; P = 0.04) and % of capillaries supporting continuous RBC flux at rest (79 ± 8 vs. 56 ± 13%; P = 0.01) were evident in PH rats compared to healthy rats. When Q̇O₂ within a given field of view was quantified (RBC flux x % of capillaries supporting continuous RBC flux), PH rats demonstrated lower overall Q̇O₂ (↓ 50%; P = 0.002). These data support that microcirculatory hemodynamic impairments (↓ Q̇O₂ and therefore altered Q̇O₂-to-V̇O₂ matching) may compromise blood-myocyte O₂ transport in PH. The mechanistic bases for decreased capillary RBC flux, velocity, and percentage of capillaries supporting RBC flow remains an important topic.

Impaired endothelium-dependent and endothelium-independent systemic vasodilatory reserve in pulmonary hypertension regardless the clinical group: A generalized dysfunction beyond the pulmonary arteries?

OBJECTIVE

Endothelium-dependent (ED) and endothelium-independent (EI) flow-mediated vasodilatation (FMD) have been used as measures of systemic arterial vasodilatory reserve. In this study, we aimed to assess both ED-FMD and EI-FMD in different groups with pulmonary hypertension (PH), and to investigate the relationship of these measures with clinical, echocardiographic, and invasive parameters of diseases severity and targeted treatment status.

METHODS

Our study population comprised 41 patients with PH [28 (68.2%) women, age 46.3±19.6 years] including idiopathic pulmonary arterial hypertension, Eisenmenger syndrome, and chronic thromboembolic PH in whom diagnosis were confirmed in accordance with current guidelines and 17 age and sex-matched healthy controls. The brachial artery (BA) was used for assessment of FMD with Duplex ultrasound, and serial changes in diameter were recorded at baseline, 1, and 3 minutes after termination of 2-minute external occlusive compression for ED-FMD, and after sublingual intake of glycerol trinitrate for EI-FMD, respectively.

RESULTS

Compared with controls, overall the PH group showed significantly lower ED-FMD (0.65±0.21 vs. 0.30±0.23 and 0.65±0.18 vs. 0.24±0.21) and EI-FMD (0.67±0.15 vs. 0.37±0.25 and 0.75±0.20 vs. 0.32±0.24) responses at 1st and 3rd min (p<0.001 for all). All these changes in the values of ED-FMD and EI-FMD were comparable among the PH subgroups. Neither ED-FMD nor EI-FMD were correlated with measures of PH severity and targeted therapy (TT) status (p>0.05).

CONCLUSION

Our results suggest an impaired BA vasodilatory reserve in patients with PH regardless of the clinical subgroup. Although these findings seem to be consistent with systemic dysfunction, acute FMD may not reflect the severity of PH and cannot be used as a potential surrogate for outcome in this setting.

Impaired endothelium-dependent and endothelium-independent systemic vasodilatory reserve in pulmonary hypertension regardless the clinical group: A generalized dysfunction beyond the pulmonary arteries?

OBJECTIVE

Endothelium-dependent (ED) and endothelium-independent (EI) flow-mediated vasodilatation (FMD) have been used as measures of systemic arterial vasodilatory reserve. In this study, we aimed to assess both ED-FMD and EI-FMD in different groups with pulmonary hypertension (PH), and to investigate the relationship of these measures with clinical, echocardiographic, and invasive parameters of diseases severity and targeted treatment status.

METHODS

Our study population comprised 41 patients with PH [28 (68.2%) women, age 46.3±19.6 years] including idiopathic pulmonary arterial hypertension, Eisenmenger syndrome, and chronic thromboembolic PH in whom diagnosis were confirmed in accordance with current guidelines and 17 age and sex-matched healthy controls. The brachial artery (BA) was used for assessment of FMD with Duplex ultrasound, and serial changes in diameter were recorded at baseline, 1, and 3 minutes after termination of 2-minute external occlusive compression for ED-FMD, and after sublingual intake of glycerol trinitrate for EI-FMD, respectively.

RESULTS

Compared with controls, overall the PH group showed significantly lower ED-FMD (0.65±0.21 vs. 0.30±0.23 and 0.65±0.18 vs. 0.24±0.21) and EI-FMD (0.67±0.15 vs. 0.37±0.25 and 0.75±0.20 vs. 0.32±0.24) responses at 1st and 3rd min (p<0.001 for all). All these changes in the values of ED-FMD and EI-FMD were comparable among the PH subgroups. Neither ED-FMD nor EI-FMD were correlated with measures of PH severity and targeted therapy (TT) status (p>0.05).

CONCLUSION

Our results suggest an impaired BA vasodilatory reserve in patients with PH regardless of the clinical subgroup. Although these findings seem to be consistent with systemic dysfunction, acute FMD may not reflect the severity of PH and cannot be used as a potential surrogate for outcome in this setting.

The effects of pulmonary hypertension on skeletal muscle oxygen pressures in contracting rat spinotrapezius muscle

NEW FINDINGS

What is the central question of this study? Does impairment in the dynamics of O₂ transport in skeletal muscle during a series of contractions constitute a potential mechanism underlying reduced exercise capacity in pulmonary hypertension? What is the main finding and its importance? Pulmonary hypertension compromises the dynamic matching of skeletal muscle O₂ delivery-to-utilization following contraction onset in the rat spinotrapezius muscle. These results implicate a role for vascular dysfunction in the slow V ̇ O 2 kinetics and exercise intolerance present in pulmonary hypertension.

ABSTRACT

Pulmonary hypertension (PH) is characterized by pulmonary vascular dysfunction and exercise intolerance due, in part, to compromised pulmonary and cardiac function. We tested the hypothesis that there are peripheral (i.e., skeletal muscle) aberrations in O₂ delivery ( Q ̇ O 2 )-to-O₂ utilization ( V ̇ O 2 ) matching and vascular control that might help to explain poor exercise tolerance in PH. Furthermore, we investigated the peripheral effects of nitric oxide (NO) in attenuating these decrements. Male Sprague-Dawley rats (n = 21) were administered monocrotaline (MCT; 50 mg/kg, i.p.) to induce PH. Disease progression was monitored via echocardiography. Phosphorescence quenching determined the O₂ partial pressure in the interstitial space ( P O 2 is ) in the spinotrapezius muscle at rest and during contractions under control (SNP-) and NO-donor (sodium nitroprusside, SNP+) conditions. MCT rats displayed right ventricular (RV) hypertrophy (right ventricle/(left ventricle + septum): 0.44 (0.13) vs. 0.28 (0.05)), pulmonary congestion, increased RV systolic pressure (48 (18) vs. 20 (8) mmHg) and arterial hypoxaemia ( P a O 2 : 64 (9) vs. 82 (9) mmHg) compared to healthy controls (HC) (P < 0.05). P O 2 is was significantly lower in MCT rats during the first 30 s of SNP- contractions. SNP superfusion elevated P O 2 is in both groups; however, MCT rats demonstrated a lower P O 2 is throughout SNP+ contractions versus HC (P < 0.05). Thus, for small muscle mass exercise in MCT rats, muscle oxygenation is impaired across the rest-to-contractions transition and exogenous NO does not raise the Q ̇ O 2 -to- V ̇ O 2 ratio in contracting muscle to the same levels as HC. These data support muscle Q ̇ O 2 -to- V ̇ O 2 mismatch as a potential contributor to slow V ̇ O 2 kinetics and therefore exercise intolerance in PH and suggest peripheral vascular dysfunction or remodelling as a possible mechanism.

Endothelial cells in the pathogenesis of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a devastating disease that involves pulmonary vasoconstriction, small vessel obliteration, large vessel thickening and obstruction, and development of plexiform lesions. PAH vasculopathy leads to progressive increases in pulmonary vascular resistance, right heart failure and, ultimately, premature death. Besides other cell types that are known to be involved in PAH pathogenesis (e.g. smooth muscle cells, fibroblasts and leukocytes), recent studies have demonstrated that endothelial cells (ECs) have a crucial role in the initiation and progression of PAH. The EC-specific role in PAH is multi-faceted and affects numerous pathophysiological processes, including vasoconstriction, inflammation, coagulation, metabolism and oxidative/nitrative stress, as well as cell viability, growth and differentiation. In this review, we describe how EC dysfunction and cell signalling regulate the pathogenesis of PAH. We also highlight areas of research that warrant attention in future studies, and discuss potential molecular signalling pathways in ECs that could be targeted therapeutically in the prevention and treatment of PAH.

Non-Invasive Assessment of Endothelial Dysfunction in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterised by an increased pressure in the pulmonary arterial circulation, resulting in the elevation of pulmonary vascular resistance. Pulmonary endothelial dysfunction and inflammation, triggered by shear stress and hypoxia, constitute the hallmarks of pulmonary vasculopathy by promoting endothelial and smooth muscle cells proliferation, vasoconstriction, and thrombosis. While research was predominantly focused on pulmonary vasculature, the investigation of peripheral endothelial damage in different vascular beds has attracted the interest over the last years. As a result, effective non-invasive methods that can assess the endothelial function and the architectural integrity have been utilized for the evaluation of pulmonary and peripheral vasculature. Non-invasive plethysmography, pulmonary flow reserve, nailfold videocapillaroscopy, near-infrared spectroscopy, and imaging techniques such as magnetic resonance angiography and perfusion imaging coupled by a number of biomarkers can be used for the assessment of peripheral vascular function in PAH individuals. In this review, we summarise and critically approach the current evidence of more systemic derangement of vascular function in PAH defined by novel, non-invasive methods employed for functional and morphological assessment of endothelium and microcirculation.

Parasympathetic modulation withdrawal improves functional capacity in pulmonary arterial hypertension

In 15 pulmonary arterial hypertension patients, the relation of functional capacity to their peripheral endothelial function and sympathaovagal modulation was studied by carrying out brachial artery ultrasound and electrocardiogram spectral analysis, respectively. The functional capacity was assessed by cardiopulmonary exercise testing and six-minute walking test. The sympathovagal modulation was correlated with the predicted peak oxygen consumption (peak VO₂ %; r = 0.692, P < 0.05), peak O₂ pulse (mL/beat; r = 0.661, P < 0.05), VE, minute ventilation, VCO₂ carbon dioxide production (VE/VCO₂ slope; r=-0.806, P < 0.01) and distance walked predicted (%6MWT; r = 0.694, P < 0.05). Moreover, there were negative correlations between parasympathetic modulation with peak VO₂ (r = 0.755, P < 0.01), peak VO₂% (r=-0.727, P < 0.01) and peak O₂ pulse (r = 0.615, P < 0.05), %6MWT (r=-0.834, P < 0.01). Collectively these correlations indicate that parasympathetic withdrawal is crucial for improving functional capacity. This conclusion is supported by both positive and negative correlations of parasympathetic modulation with the functional capacity parameters. The sympathetic modulation predominance, although increases the cardiovascular risk, is probably crucial to facilitate the bronchodilation and the oxygen uptake.

Nailfold videocapillaroscopy: a novel possible surrogate marker for the evaluation of peripheral microangiopathy in pulmonary arterial hypertension

Nailfold videocapillaroscopy (NVC) changes in systemic sclerosis (SSc) are correlated with vascular complications, such as pulmonary arterial hypertension (PAH), supporting a potential link between peripheral and internal organ vasculopathy. The current stage of knowledge regarding NVC and PAH is discussed, focusing on the assessment of peripheral microangiopathy and a potential relationship with functional, echocardiographic, and haemodynamic markers of cardiac dysfunction. A comprehensive literature search was carried out to identify all studies focusing on NVC findings in patients with PAH, diagnosed with right heart catheterization. The majority of the studies examined NVC findings in patients with SSc-PAH, while three studies reported NVC abnormalities in patients with idiopathic PAH. Besides the pulmonary vasculature, a systemic component of microangiopathy seems to be involved in PAH. Well-designed prospective trials are warranted to validate NVC as a biomarker, with clinical implications in the diagnostic evaluation, risk stratification, and overall management of PAH in the daily clinical setting.

Peripheral Microangiopathy in Patients with Precapillary Pulmonary Hypertension: Correlation with Cardiac Function and Patients' Functional Capacity. Study Design and Rationale

Pulmonary hypertension (PH) is a rare, heterogenous clinical entity characterised by a progressive remodelling of pulmonary arterioles, which leads to obstructive pulmonary arteriopathy, increased pulmonary vascular resistance, and eventually, right heart failure. Inflammation, endothelial dysfunction, and microvascular changes of the pulmonary vasculature constitute the hallmarks of pulmonary arterial hypertension (PAH), explaining much of the pathophysiology and clinical manifestations of the disease. Besides pulmonary vasculature, a systemic component of endothelial dysfunction and microcirculation may be involved in PAH, affecting different vascular beds. Nailfold videocapillaroscopy (NVC) is an established method for the assessment of the microvasculature with clinical implications in the diagnostic assessment of individuals with Raynaud syndrome and systemic sclerosis (SSc). Nowadays, growing amounts of evidence suggest that NVC changes in SSc are correlated with other vascular complications such as PAH, supporting a potential link between peripheral and internal organ vasculopathy. The purpose of the current prospective observational study is to explore: 1. the presence of peripheral microangiopathy in precapillary PH using NVC, 2. possible NVC differences among PH subgroups, 3. a potential relationship between NVC morphological abnormalities and clinical, functional, biochemical, echocardiographic and hemodynamic markers of cardiac dysfunction in precapillary PH.

Beyond the Lungs: Systemic Manifestations of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a disease characterized by progressive loss and remodeling of the pulmonary arteries, resulting in right heart failure and death. Until recently, PAH was seen as a disease restricted to the pulmonary circulation. However, there is growing evidence that patients with PAH also exhibit systemic vascular dysfunction, as evidenced by impaired brachial artery flow-mediated dilation, abnormal cerebral blood flow, skeletal myopathy, and intrinsic kidney disease. Although some of these anomalies are partially due to right ventricular insufficiency, recent data support a mechanistic link to the genetic and molecular events behind PAH pathogenesis. This review serves as an introduction to the major systemic findings in PAH and the evidence that supports a common mechanistic link with PAH pathophysiology. In addition, it discusses recent studies describing morphological changes in systemic vessels and the possible role of bronchopulmonary anastomoses in the development of plexogenic arteriopathy. On the basis of available evidence, we propose a paradigm in which metabolic abnormalities, genetic injury, and systemic vascular dysfunction contribute to systemic manifestations in PAH. This concept not only opens exciting research possibilities but also encourages clinicians to consider extrapulmonary manifestations in their management of patients with PAH.

Endothelial Cell Mechano-Metabolomic Coupling to Disease States in the Lung Microvasculature

Lungs are the most vascular part of humans, accepting the totality of cardiac output in a volume much smaller than the body itself. Due to this cardiac output, the lung microvasculature is subject to mechanical forces including shear stress and cyclic stretch that vary with the cardiac and breathing cycle. Vessels are surrounded by extracellular matrix which dictates the stiffness which endothelial cells also sense and respond to. Shear stress, stiffness, and cyclic stretch are known to influence endothelial cell state. At high shear stress, endothelial cells exhibit cell quiescence marked by low inflammatory markers and high nitric oxide synthesis, whereas at low shear stress, endothelial cells are thought to "activate" into a pro-inflammatory state and have low nitric oxide. Shear stress' profound effect on vascular phenotype is most apparent in the arterial vasculature and in the pathophysiology of vascular inflammation. To conduct the flow of blood from the right heart, the lung microvasculature must be rigid yet compliant. It turns out that excessive substrate rigidity or stiffness is important in the development of pulmonary hypertension and chronic fibrosing lung diseases via excessive cell proliferation or the endothelial-mesenchymal transition. Recently, a new body of literature has evolved that couples mechanical sensing to endothelial phenotypic changes through metabolic signaling in clinically relevant contexts such as pulmonary hypertension, lung injury syndromes, as well as fibrosis, which is the focus of this review. Stretch, like flow, has profound effect on endothelial phenotype; metabolism studies due to stretch are in their infancy.

The ADAMTS13-VWF axis is dysregulated in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is an important consequence of pulmonary embolism that is associated with abnormalities in haemostasis. We investigated the ADAMTS13–von Willebrand factor (VWF) axis in CTEPH, including its relationship with disease severity, inflammation, ABO groups and ADAMTS13 genetic variants.

ADAMTS13 and VWF plasma antigen levels were measured in patients with CTEPH (n=208), chronic thromboembolic disease without pulmonary hypertension (CTED) (n=35), resolved pulmonary embolism (n=28), idiopathic pulmonary arterial hypertension (n=30) and healthy controls (n=68). CTEPH genetic ABO associations and protein quantitative trait loci were investigated. ADAMTS13–VWF axis abnormalities were assessed in CTEPH and healthy control subsets by measuring ADAMTS13 activity, D-dimers and VWF multimeric size.

Patients with CTEPH had decreased ADAMTS13 (adjusted β −23.4%, 95% CI −30.9– −15.1%, p<0.001) and increased VWF levels (β +75.5%, 95% CI 44.8–113%, p<0.001) compared to healthy controls. ADAMTS13 levels remained low after reversal of pulmonary hypertension by pulmonary endarterectomy surgery and were equally reduced in CTED. We identified a genetic variant near the ADAMTS13 gene associated with ADAMTS13 protein that accounted for ∼8% of the variation in levels.

The ADAMTS13–VWF axis is dysregulated in CTEPH. This is unrelated to pulmonary hypertension, disease severity or markers of systemic inflammation and implicates the ADAMTS13–VWF axis in CTEPH pathobiology.

The ADAMTS-13–VWF axis is dysregulated in chronic thromboembolism with and without pulmonary hypertension and is implicated in the pathogenesishttp://ow.ly/J9SC30nh5T0

Prognostic Significance of Biomarkers in Pulmonary Arterial Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a rare progressive disease of the pulmonary vasculature that is characterized by endothelial dysfunction, inflammation, and right ventricular dysfunction.

OBJECTIVES

The main objective was to determine whether endothelial, inflammatory, and cardiac biomarkers would be associated with the World Health Organization functional assessment and survival in patients with PAH.

METHODS

We performed a retrospective cohort study of patients with PAH enrolled in the Randomized Clinical Trial of Aspirin and Simvastatin for Pulmonary Arterial Hypertension (ASA-STAT). Biomarkers (N-terminal fragment of pro-BNP [NT-pro-BNP], von Willebrand factor [vWF], soluble P selectin, C-reactive protein, total and high-density lipoprotein cholesterol, triglycerides, tumor necrosis factor, IL-6, β-thromboglobulin, and thromboxane B2) were measured at baseline. Patients from the study were followed until lung transplantation, death, or August 1, 2013. Ordinal logistic regression and Cox regression analyses were performed.

MEASUREMENTS AND MAIN RESULTS

Sixty-five patients with PAH were enrolled. The mean age was 51 years, and 86% were women. Higher vWF activity, lower high-density lipoprotein cholesterol, and higher thromboxane B2 levels were associated with worse World Health Organization functional class after adjustment for age, sex, and etiology of PAH. Higher NT-pro-BNP levels, lower vWF activity, and lower total cholesterol were associated with an increased risk of death or lung transplant after adjustment for age, sex, etiology of PAH, and 6-minute-walk distance.

CONCLUSIONS

In patients with PAH, lower vWF activity and cholesterol levels and higher NT-pro-BNP levels at baseline were associated with an increased risk of death or transplantation. Clinical trial registered with www.clinicaltrials.gov (NCT00384865).

Non-invasive evaluation of pulmonary arterial blood flow and wall shear stress in pulmonary arterial hypertension with 3D phase contrast magnetic resonance imaging

Background

Recently, time-resolved 3D phase contrast magnetic resonance imaging (4D-flow) allows flow dynamics in patients with pulmonary arterial hypertension to be measured. Abnormal flow dynamics, such as vortex blood flow pattern in the pulmonary artery (PA), may reflect progression of pulmonary arterial hypertension (PAH). Some reports suggested that abnormal blood flow parameters including wall shear stress (WSS) could be markers of PAH. However, it was not fully assessed clinical usefulness of these variables. We aimed to assess whether these flow dynamic parameters, such as vortex formation time (VFT) and WSS, were associated with right ventricular (RV) function.

Results

Fifteen subjects, nine with PAH and six healthy volunteers, underwent 4D-flow. Differences of Blood flow patterns, blood flow velocities and WSS between PAH patients and healthy volunteers were evaluated. We also assessed the association between VFT, WSS and RV function in PAH patients. Both vortex blood flow patterns and early systolic retrograde flow in the main PA were observed in all patients with PAH. The PA flow velocities and WSS in patients with PAH were lower than those in healthy volunteers, but that blood flow volumes in the MPA, RPA and LPA and SV in the MPA were broadly comparable between the groups. The mean VFT was 35.0 ± 16.6 % of the cardiac cycle. The VFT significantly correlated with RV ejection fraction, RV end systolic volume, and RV end systolic volume index (RVEF = 75.1 + (−85.7)·VFT, p = 0.003, RVESV = 12.4 + 181.8·VFT, p = 0.037 and RVESVI = 10.6 + 114.8·VFT, p = 0.038, respectively) in PAH patients, whereas WSS did not correlate with RV function.

Conclusions

We confirmed that abnormal blood flow dynamics, including the vortex formation and the early onset of retrograde flow, low WSS in the PA were characteristics of PAH. The VFT may be associated with right ventricular dysfunction, whereas WSS was not. Our results suggest that 4D-flow is an effective means of detecting right heart failure as well as diagnosing PAH.

Clinical trial registration URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi. Unique identifier: UMIN000011128

Electronic supplementary material

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Effects of bosentan on peripheral endothelial function in patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension

Endothelin receptor antagonists (ERAs) have been shown to improve the prognosis of patients with pulmonary arterial hypertension (PAH). However, the effect of the oral dual ERA bosentan on peripheral endothelial dysfunction (PED), as assessed by flow-mediated vasodilation (FMD), in patients with pulmonary hypertension is not well characterized. We investigated the effect of bosentan on PED in patients with PAH or inoperable chronic thromboembolic pulmonary hypertension (CTEPH). A total of 18 patients with PAH and 8 with CTEPH were treated with bosentan. All patients underwent FMD assessment before and after 3 months of bosentan treatment. Whereas FMD increased from 6.01% ± 2.42% at baseline to 8.07% ± 3.18% after 3 months (P < 0.0001) in patients with PAH, those with CTEPH showed no change in FMD after bosentan therapy. In addition, FMD at baseline showed no correlation with pulmonary vascular resistance (r = 0.09) or plasma brain natriuretic peptide levels (r = -0.23) in patients with PAH. Bosentan treatment ameliorated PED in patients with PAH but not in those with inoperable CTEPH. In addition, FMD did not correlate with PAH severity.

Respiratory and limb muscle dysfunction in pulmonary arterial hypertension: a role for exercise training?

Respiratory and limb muscle dysfunction is emerging as an important pathophysiological abnormality in pulmonary arterial hypertension (PAH). Muscle abnormalities appear to occur frequently and promote dyspnea, fatigue, and exercise limitation in patients with PAH. Preliminary data suggest that targeted muscle training may be of benefit, although further evidence is required to consolidate these findings into specific recommendations for exercise training in patients with PAH. This article reviews the current evidence on prevalence, risk factors, and implications of respiratory and limb muscle dysfunction in patients with PAH. It also reviews the impact of exercise rehabilitation on morphologic, metabolic, and functional muscle profile and outcomes in PAH. Future research priorities are highlighted.

Widespread endotheliopathy in adults with cyanotic congenital heart disease

INTRODUCTION

Cyanotic congenital heart disease is associated with functional limitation and vascular events. The nature and extent of endothelial dysfunction in cyanotic adults is poorly understood. We sought to characterise endothelial function in this setting.

METHODS

A total of fourteen adults with cyanotic congenital heart disease (40±3 years) together with age- and sex-matched healthy controls underwent assessment of nitric oxide-dependent vascular responses, including flow-mediated dilatation of the brachial artery and dynamic vessel analysis of the retina in response to flickering light. Plasma levels of the endothelium-derived vasoconstrictor endothelin-1 and the nitric oxide antagonist, asymmetric dimethylarginine, were measured. Circulating endothelial progenitor cells were assessed by flow cytometry.

RESULTS

Flow-mediated dilatation was significantly lower in cyanosed adults than controls (4.0±0.8 versus 7.2±1.0%, p=0.019, n=11 per group). Retinal arterial and venous dilatory responses were also impaired (2.9±0.8 versus 5.0±0.6%, p=0.05 and 3.4±0.3 versus 5.2±0.7%, p=0.04, n=13). Serum levels of endothelin-1 and asymmetric dimethylarginine were higher in cyanosed adults (3.0±0.6 versus 1.1±0.1 pg/ml, p=0.004 and 0.68±0.05 versus 0.52±0.02 μmol/L, p=0.03, n=11). Endothelial progenitor cells (CD34+CD45dimCD133+KDR+) were reduced in those with chronic cyanosis (17±4 versus 40±6 per million white blood cells, p=0.005, n=11).

CONCLUSIONS

Endothelial function is impaired in the systemic arteries and retinal vessels in adults with cyanotic congenital heart disease, suggesting a widespread endotheliopathy. Diminished numbers of endothelial progenitor cells might potentially contribute to these observations.

Sublingual microcirculation in pulmonary arterial hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a pulmonary vasculopathy that leads to failure of the right ventricle and premature death.

OBJECTIVES

To determine whether the sublingual microcirculation is affected in patients with PAH compared with healthy age- and sex-matched control subjects.

METHODS

Using the CapiScope Handheld Video Capillaroscope we measured the sublingual microvasculature density, flow index, tortuosity, and curvature. Videos were acquired immediately after right heart catheterization, and determinations were made off-line by investigators blinded to the group assignment or hemodynamics.

MEASUREMENTS AND MAIN RESULTS

In this cross-sectional pilot study, we included 26 patients with PAH (age, mean ± SD, 56.7 ± 10 yr; 77% women) and 14 healthy control subjects (age, 53.1 ± 12 yr; 71% women). Sublingual microvasculature flow index was lower (2 ± 0.66 vs. 2.7 ± 0.37, P < 0.001) with higher heterogeneity index (0.63 ± 0.63 vs. 0.25 ± 0.25, P = 0.04) in patients with PAH than control subjects. Microvasculature density was similar between the groups, but tortuosity was more pronounced in patients than control subjects (tort 0: 45 ± 19 vs. 23.6 ± 12, P = 0.001 and tort 1: 0.2 ± 0.16 vs. 0.06 ± 0.04, P < 0.001).

CONCLUSIONS

Patients with PAH showed lower sublingual microvasculature flow index and higher tortuosity compared with healthy age- and sex-matched control subjects. Further investigations are needed to assess whether this methodology can provide information on disease prognosis and/or response to therapy in this condition.

Oxidative-stress biomarkers in patients with pulmonary hypertension

This controlled, prospective, nonrandomized clinical investigation has as its chief strength the fact that it was done in humans with active disease and apparently on fairly modest therapeutic regimens. The aim was to present the results of oxidative-stress biomarkers in humans suffering from pulmonary artery hypertension (PAH). Inflammation and oxidative stress are essential in PAH with increased lipid peroxidation and reduced antioxidant defenses. Twenty-four adult patients of both sexes, with a mean age of 21 years, were subdivided into 2 groups: a control group of 12 healthy, nonsmoking volunteers and a PAH group (PAHG) of 12 volunteers with PAH receiving outpatient treatment. Oxidative stress was evaluated by plasma activity of reduced glutathione (GSH); lipid peroxidation was expressed by malondialdehyde (MDA) and lipid hydroperoxide (ferrous oxidation of xylenol orange [FOX] assay); vitamin E was measured by high-performance liquid chromatography and tumor necrosis factor-α (TNF-α) by enzyme-linked immunosorbent assay. Statistical analyses showed significant differences for (1) the TNF-α measure, with highest values in PAHG patients; (2) the plasma GSH, with lowest values in PAHG patients; (3) vitamin E, with the lowest concentrations in PAHG patients; (4) MDA measure, with highest values in PAHG patients; and (5) the lipid hydroperoxide FOX measure, with highest values in PAHG patients. In conclusion, inflammation and oxidative stress are present in patients with PAH, as confirmed by increased lipid peroxidation, reduced GSH, and low concentrations of vitamin E.

Systemic arterial endothelial function in children and young adults with idiopathic pulmonary arterial hypertension: is there a relation to pulmonary endothelium-dependent relaxation?

Pulmonary arterial endothelial function is known to be affected in patients with idiopathic pulmonary arterial hypertension (IPAH). Current reports also detected peripheral systemic arterial dysfunction in IPAH patients. The purpose of this study was to assess whether there is a relation between pulmonary arterial and systemic arterial endothelial function. Pulmonary arterial endothelium-dependent relaxation was assessed by changes in pulmonary blood flow in response to acetylcholine which were determined using intravascular Doppler flow measurements. Pulmonary flow reserve (PFR) was calculated as the ratio of pulmonary blood flow velocity in response to acetylcholine relative to baseline values. Systemic arterial endothelial function was assessed by the vascular response to reactive hyperemia, and was recorded non-invasively by peripheral arterial finger tonometry under standardized conditions. Thirteen children and young adults [mean age 16.7 (±5.6) years] with IPAH and 13 age-/gender-matched controls were included in the study. Digital reactive hyperemic index (RHI) of the IPAH patients was 1.54 (±0.69), and of the controls was 1.67 (±0.66) [p = 0.64]. The mean baseline flow velocity in the segmental pulmonary artery of all patients was 18.5 (±5.5) cm/s, increasing to 27.4 (±12.3) cm/s (p = 0.003) during acetylcholine infusion. The calculated mean PFR was 1.48 (±0.4). There was no significant correlation between the PFR and RHI (r = 0.19; p = 0.54). According to our results, systemic arterial endothelial function assessed by peripheral arterial finger tonometry was not significantly impaired in children and young adults with IPAH compared with age-/gender-matched controls. There was no correlation between systemic arterial and pulmonary arterial endothelial function, suggesting that different mechanisms may contribute to their pathogenesis and progression.

Brachial artery diameter and the right ventricle: the Multi-Ethnic Study of Atherosclerosis-right ventricle study

BACKGROUND

Endothelial dysfunction is associated with left ventricular morphology and long-term cardiovascular outcomes. The purpose of this study was to assess the relationship between both baseline brachial artery diameter and peripheral endothelial function (assessed by brachial artery ultrasonography) and right ventricular (RV) mass, RV end-diastolic volume (RVEDV), and RV ejection fraction (RVEF).

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) performed cardiac MRI and brachial artery ultrasonography on participants without clinical cardiovascular disease. Baseline brachial artery diameter and flow-mediated dilation were assessed.

RESULTS

The mean age was 60.9 years, and 49.4% of subjects were men (n = 2,425). In adjusted models, larger brachial artery diameter was strongly associated with greater RV mass (β = 0.55 g, P &lt; .001), larger RVEDV (β = 3.99 mL, P &lt; .001), and decreased RVEF (β = -0.46%, P = .03). These relationships persisted after further adjustment for the respective left ventricular parameters. Flow-mediated dilation was not associated with RV mass or RVEF and was only weakly associated with RVEDV.

CONCLUSIONS

Brachial artery diameter is associated with greater RV mass and RVEDV, as well as lower RVEF. Changes in the systemic arterial circulation may have pathophysiologic links to pulmonary vascular dysfunction or abnormalities in RV perfusion.

Systemic endothelial dysfunction in children with idiopathic pulmonary arterial hypertension correlates with disease severity

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is a life-threatening disease manifested by progressive pulmonary vascular remodeling, compromised pulmonary blood flow and right heart failure. Most studies have explored how pulmonary endothelial function modulates disease pathogenesis. We hypothesize that IPAH is a progressive panvasculopathy, affecting both pulmonary and systemic vascular beds, and that systemic endothelial dysfunction correlates with disease severity. Recent studies have demonstrated systemic endothelial dysfunction in adults with pulmonary hypertension; however, adults often have additional comorbidities affecting endothelial function. Systemic endothelial function has not been explored in children with IPAH.

METHODS

In this single-center, prospective, cross-sectional study we examined brachial artery flow-mediated dilation (FMD), a nitric oxide-mediated, endothelial-dependent response, in children with IPAH and matched controls. FMD measurements were compared with clinical and echocardiographic measures of IPAH severity.

RESULTS

Thirteen patients and 13 controls were studied, ranging in age from 6 to 20 years. FMD was decreased in IPAH subjects compared with controls (5.1 ± 2.1% vs 9.7 ± 2.0%; p < 0.0001). In IPAH subjects, FMD correlated directly with cardiac index (R(2) = 0.34, p = 0.035), and inversely with tricuspid regurgitation velocity (R(2) = 0.57, p = 0.019) and right ventricular myocardial performance index (R(2) = 0.44, p = 0.028).

CONCLUSIONS

The presence of systemic endothelial dysfunction in children with IPAH and its strong association with IPAH severity demonstrate that IPAH is a global vasculopathy. Although morbidity in IPAH is typically associated with pulmonary vascular disease, systemic vascular changes may also relate to disease pathogenesis and progression. Further study into shared mechanisms of systemic and pulmonary endothelial dysfunction may contribute to future therapies for IPAH.

Peripheral endothelial dysfunction is associated with gas exchange inefficiency in smokers

Aims

To assess the cross-sectional association between exercise capacity, gas exchange efficiency and endothelial function, as measured by flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD) of the brachial artery, in a large-scale population-based survey.

Methods

The study population was comprised of 1416 volunteers 25 to 85 years old. Oxygen uptake at anaerobic threshold (VO₂@AT), peak exercise (peakVO₂) and ventilatory efficiency (VE vs. VCO₂ slope and VE/VCO₂@AT) were assessed on a breath-by-breath basis during incremental symptom-limited cardiopulmonary exercise. FMD and NMD measurements at rest were performed using standardised ultrasound techniques.

Results

Multivariable logistic regression analyses revealed a significant association between FMD and ventilatory efficiency in current smokers but not in ex-smokers or non-smokers. There was no association between FMD and VO₂@AT or peak VO₂. In current smokers, for each one millimetre decrement in FMD, VE/VCO₂@AT improved by -3.6 (95% CI -6.8, -0.4) in the overall population [VE vs. VCO₂ slope -3.9 (-7.1, -0.6)]. These results remained robust after adjusting for all major influencing factors. Neither exercise capacity nor ventilatory efficiency was significantly associated with NMD.

Conclusion

In current smokers, FMD is significantly associated with ventilatory efficiency. This result may be interpreted as a potential clinical link between smoking and early pulmonary vasculopathy due to smoking.

Right and left ventricular myocardial perfusion reserves correlate with right ventricular function and pulmonary hemodynamics in patients with pulmonary arterial hypertension

PURPOSE

To evaluate the relationships of right ventricular (RV) and left ventricular (LV) myocardial perfusion reserves with ventricular function and pulmonary hemodynamics in patients with pulmonary arterial hypertension (PAH) by using adenosine stress perfusion cardiac magnetic resonance (MR) imaging.

MATERIALS AND METHODS

This HIPAA-compliant study was institutional review board approved. Twenty-five patients known or suspected to have PAH underwent right heart catheterization and adenosine stress MR imaging on the same day. Sixteen matched healthy control subjects underwent cardiac MR imaging only. RV and LV perfusion values at rest and at adenosine-induced stress were calculated by using the Fermi function model. The MR imaging-derived RV and LV functional data were calculated by using dedicated software. Statistical testing included Kruskal-Wallis tests for continuous data, Spearman rank correlation tests, and multiple linear regression analyses.

RESULTS

Seventeen of the 25 patients had PAH: 11 with scleroderma-associated PAH, and six with idiopathic PAH. The remaining eight patients had scleroderma without PAH. The myocardial perfusion reserve indexes (MPRIs) in the PAH group (median RV MPRI, 1.7 [25th-75th percentile range, 1.3-2.0]; median LV MPRI, 1.8 [25th-75th percentile range, 1.6-2.1]) were significantly lower than those in the scleroderma non-PAH (median RV MPRI, 2.5 [25th-75th percentile range, 1.8-3.9] [P = .03]; median LV MPRI, 4.1 [25th-75th percentile range, 2.6-4.8] [P = .0003]) and control (median RV MPRI, 2.9 [25th-75th percentile range, 2.6-3.6] [P < .01]; median LV MPRI, 3.6 [25th-75th percentile range, 2.7-4.1] [P < .01]) groups. There were significant correlations between biventricular MPRI and both mean pulmonary arterial pressure (mPAP) (RV MPRI: ρ = -0.59, Bonferroni P = .036; LV MPRI: ρ = -0.79, Bonferroni P < .002) and RV stroke work index (RV MPRI: ρ = -0.63, Bonferroni P = .01; LV MPRI: ρ = -0.75, Bonferroni P < .002). In linear regression analysis, mPAP and RV ejection fraction were independent predictors of RV MPRI. mPAP was an independent predictor of LV MPRI.

CONCLUSION

Biventricular vasoreactivity is significantly reduced with PAH and inversely correlated with RV workload and ejection fraction, suggesting that reduced myocardial perfusion reserve may contribute to RV dysfunction in patients with PAH.

Chronic cyanosis and vascular function: implications for patients with cyanotic congenital heart disease

In patients with cyanotic congenital heart disease, chronic hypoxaemia leads to important changes in blood vessel function and structure. Some of these alterations are maladaptive and probably contribute to impaired cardiopulmonary performance and an increased incidence of thrombotic and embolic events. Recent evidence suggests that deranged endothelial function, a sequel of chronic cyanosis, could be an important factor in the pathogenesis of cyanosis-associated cardiovascular risk. In this article, we discuss the physiological and mechanical consequences of compensatory erythrocytosis and possible pathophysiological mechanisms of vascular dysfunction in chronic cyanosis.

Mild renal dysfunction as a non-traditional cardiovascular risk factor?-Association of cystatin C-based glomerular filtration rate with flow-mediated vasodilation

OBJECTIVE

Chronic kidney disease, at least in its advanced stages, can be regarded as a non-traditional cardiovascular risk factor. The purpose of this study was to evaluate whether early stages of renal dysfunction are associated with flow-mediated vasodilatation, as an early marker of the atherosclerotic disease process.

METHODS

In 1515 subjects (753 females) from the population-based Study of Health in Pomerania, the relationship between flow-mediated vasodilatation of the brachial artery (cuff occlusion of the forearm for 5 min) and glomerular filtration rate, estimated on the basis of serum cystatin C levels, was analyzed under consideration of various cardiovascular risk factors.

RESULTS

Flow-mediated vasodilatation was 5.75 + or - 0.16% in women and 4.29+/-0.12% in men (mean + or - SEM). Glomerular filtration rate amounted to 94.2 + or - 0.7 ml/min/1.73 m(2), with 8.1% subjects with glomerular filtration rate < or = 60 ml/min/1.73 m(2). Flow-mediated vasodilatation significantly correlated with glomerular filtration rate in the entire population (r=0.237, p<0.001), in women (r=0.224, p<0.001) and in men (r=0.168, p<0.001). Adjusting for age and multiple cardiovascular risk factors and also for high-sensitive C-reactive protein levels revealed a significant association of flow-mediated vasodilatation and glomerular filtration rate in women (p=0.01), but not in men, with similar results when the analyses were restricted to individuals with glomerular filtration rate >60 ml/min/1.73 m(2).

CONCLUSION

Mild reduction in renal function is associated with alterations in endothelial function in females. Hence, very mild alterations in kidney function may also be regarded as a cardiovascular risk factor at least in women.

Proteomic Analysis of Vascular Endothelial Cells-Effects of Laminar Shear Stress and High Glucose

This study directly measured the relative protein levels in bovine aortic endothelial cells (BAEC) that were cultured for two weeks in normal (5 mM, NG) or high (22 mM, HG) glucose and then were subjected to laminar shear stress at 0 or 15 dynes/cm(2). Membrane preparations were labeled with one of the four isobaric tagging reagents (iTRAQ), followed by LC-MS/MS analysis. The results showed that HG and/or shear stress induced alterations in various membrane associated proteins involving many signaling pathways. While shear stress induced an increase in heat shock proteins and protein ubiquitination, which remained enhanced in HG, the effects of shear stress on the mechanosensing and protein phosphorylation pathways were altered by HG. These results were validated by Western blot analysis, suggesting that HG importantly modulates shear stress-mediated endothelial function.

Impaired endothelial function in hypertensive patients with target organ damage

To evaluate the correlation between endothelial dysfunction and multiple target organ damage (TOD), we measured endothelial function using high-resolution ultrasonography in hypertensive patients with or without TOD. Two hundred and eighty patients with hypertension were divided into four groups as follows: no TOD (Group I, n=61); 1 TOD (Group II, n=113); 2 TOD (Group III, n=59); and >or=3 TOD (Group IV, n=47). Endothelial function was assessed by endothelium-dependent flow-mediated dilatation (FMD) and -independent vasodilation (after sublingual administration of nitroglycerin) of the brachial artery using high-resolution vascular ultrasound. We also assessed the intima-media thickness (IMT) of the common carotid, carotid to femoral pulse wave velocity (cf-PWV) and left ventricular mass index (LVMI). FMD was inversely associated with the number of affected organs. FMD was lower in the patient groups with >or=3 TOD (Group IV: 6.85+/-4.70% vs Group II: 10.00+/-6.15%, P<0.01), 2 TOD (Group III: 7.37+/-5.02% vs Group II, P<0.01) and 1 TOD as compared with patients with no TOD (Group I: 11.88+/-7.11% vs Group II, P<0.05). In univariate correlation analysis, there was a significant relationship between FMD and IMT, serum creatinine, LVMI and cf-PWV. In stepwise multivariate regression analysis, FMD still correlated with waist size (beta=-0.283, P<0.01), age (beta=-0.231, P<0.05) and IMT (beta=-0.197, P=0.05). These findings suggested that reduced FMD was associated with the number of TOD and may be considered an indicator for evaluating TOD.

Molecular mechanisms of pulmonary hypertension

The pathogenesis of pulmonary arterial hypertension (PAH) is complex, involving multiple modulating genes and environmental factors. Multifactorial impairment of the physiologic balance can lead to vasoconstriction, vascular smooth muscle cell and endothelial cell proliferation/fibrosis, inflammation, remodeling and in-situ thrombosis. These are the likely mechanisms that lead to narrowing of the vessel followed by progressive increase in pulmonary vascular resistance and the clinical manifestations of pulmonary hypertension. Subsequently, major goal of the therapy is to avoid acute pulmonary vasoconstriction, halt the progression of vascular remodeling, and reverse the early vascular remodeling if possible. Recently published data addressing certain molecular mechanisms for pathogenesis of PAH have led to the successful therapeutic interventions. This review will focus on the common and critical molecular pathways including genetic basis of the development of PAH that on the whole may be new targets for therapeutic interventions.

Peripheral endothelial dysfunction in patients with pulmonary arterial hypertension

BACKGROUND

Pulmonary endothelium plays an important role in the mechanism of pulmonary arterial hypertension (PAH). However, there is only a few data regarding the systemic endothelium in this syndrome. This study focused on the systemic endothelial involvement in PAH.

METHODS

Endothelial function was evaluated in 54 patients with idiopathic (n=28), scleroderma-associated (n=10), chronic thromboembolic (n=7), or Eisenmenger (n=9) PAH and 21 controls (13 healthy; eight scleroderma and normal pulmonary pressure). All underwent clinical evaluation, pulmonary assessment, echocardiography, and pulmonary cardiac stress test. Endothelial function was evaluated by measuring the forearm blood flow dilatation response to brachial arterial occlusion by a non-invasive plethysmograph, yielding a peripheral arterial tone (PAT) ratio.

RESULTS

The PAT ratio was significantly lower (p<0.05) than healthy controls in all patients except the Eisenmenger group (control: 2.20+/-0.25; idiopathic 1.84+/-0.51; scleroderma 1.66+/-0.66; thromboembolic 1.89+/-0.32; Eisenmenger 2.17+/-0.62). The impaired hyperemic response significantly correlated with disease severity, as measured by NYHA classification (r=-0.210, p=0.035), pulmonary pressure (r=-0.228, p=0.035), 6 min walking distance (r=0.215, p=0.047), and oxygen desaturation on effort (r=0.207, p=0.038). Mean systolic pulmonary pressure among patients was 54-99 mmHg.

CONCLUSION

A systemic component of endothelial dysfunction might be involved in idiopathic, scleroderma-associated and chronic thromboembolic PAH that is correlated with disease severity.

Vasorelaxation induced by prostaglandin E2 in human pulmonary vein: role of the EP4 receptor subtype

BACKGROUND AND PURPOSE

PGE2 has been shown to induce relaxations in precontracted human pulmonary venous preparations, while in pulmonary arteries this response was not observed. We investigated and characterized the prostanoid receptors which are activated by PGE2 in the human pulmonary veins.

EXPERIMENTAL APPROACH

Human pulmonary arteries and veins were cut as rings and set up in organ baths in presence of a TP antagonist. A pharmacological study was performed using selective EP1-4 ligands. The cellular localization of the EP4 receptors by immunohistochemistry and their corresponding transcripts were also investigated in these vessels.

KEY RESULTS

PGE2 and the EP4 agonists (L-902688, ONO-AE1-329) induced potent vasodilatation of the human pulmonary vein, pEC50 values: <7.22+/-0.20, 8.06+/-0.12 and 7.80+/-0.09, respectively. These relaxations were inhibited by the EP(4) antagonist GW627368X and not modified in presence of the DP antagonist L-877499. Higher concentrations (>or=1 microM) of the EP2 agonist ONO-AE1-259 induced relaxations of the veins. The EP4 agonists had no effect on the precontracted arteries. Finally, the EP(1) antagonists ONO-8713 and SC-51322 potentiated the relaxation of the veins induced by PGE2. EP4 and EP1 receptors were detected by immunohistochemistry in the veins but not in the arteries. EP4 mRNA accumulation was also greater in the veins when compared with the arterial preparations.

CONCLUSIONS AND IMPLICATIONS

Of the 4 EP receptor subtypes, smooth muscle cells in the human pulmonary vein express the EP4 and EP1 receptor subtypes. The relaxations induced by PGE2 in this vessel result from the activation of the EP4 receptor.