Exercise capacity and haemodynamics in patients with sickle cell disease with pulmonary hypertension treated with bosentan: results of the ASSET studies

Macitentan Administration for Pulmonary Hypertension Due to β-thalassemia with Multiple Organ Failure

A 51-year-old Thai woman diagnosed with β-thalassemia underwent regular blood transfusion and iron-chelating therapy. However, after voluntarily discontinuing treatment, the patient developed progressive dyspnea and was diagnosed with pulmonary hypertension following right heart catheterization. Despite resuming blood transfusions, her condition did not improve. Because the patient had a history of multiple organ failure, curative treatment for β-thalassemia was not feasible, and macitentan was administered. Despite experiencing hypotension as an adverse event, her condition remained stable during macitentan treatment. Thus, macitentan may be well tolerated in patients with pulmonary hypertension caused by β-thalassemia with multiple organ dysfunction.

Pulmonary Hypertension in Sickle Cell Disease: Novel Findings of Gene Polymorphisms Related to Pathophysiology

Pulmonary hypertension (PH) is a progressive and potentially fatal complication of sickle cell disease (SCD), affecting 6-10% of adult SCD patients. Various mechanisms and theories have been evaluated to explain the pathophysiology of this disease. However, questions remain, particularly regarding the clinical heterogeneity of the disease in terms of symptoms, complications, and survival. Beyond the classical mechanisms that have been thoroughly investigated and include hemolysis, nitric oxide availability, endothelial disorders, thrombosis, and left heart failure, attention is currently focused on the potential role of genes involved in such processes. Potential candidate genes are investigated through next-generation sequencing, with the transforming growth factor-beta (TGF-β) pathway being the initial target. This field of research may also provide novel targets for pharmacologic agents in the future, as is already the case with idiopathic PH. The collection and processing of data and samples from multiple centers can yield reliable results that will allow a better understanding of SCD-related PH as a part of the disease's clinical spectrum. This review attempts to capture the most recent findings of studies on gene polymorphisms that have been associated with PH in SCD patients.

Cardiovascular complications of sickle cell disease: A primer for the general clinician

Sickle cell disease (SCD) is the most common hereditary hemoglobinopathy and mainly affects individuals of African ancestry. As survival has improved especially in high-income countries, increased rates of cardiopulmonary complications such as pulmonary hypertension, heart failure with diastolic dysfunction, and sudden death are encountered in clinical practice. These complications are the leading causes of morbidity and mortality as these individuals survive into adulthood. Understanding the need for, early identification, timely intervention, and implementation of preventive strategies are critical in reversing this trend and improving quality of life and survival rates. This manuscript aims to provide a comprehensive review of the pathogenesis of cardiovascular complications associated with sickle cell disease and equip the clinician with tools to facilitate the early diagnosis and management of patients with SCD as increasing numbers survive into adulthood.

Pulmonary hypertension in sickle cell disease

Sickle cell disease (SCD) is a complex genetic disorder that has long challenged both patients and healthcare professionals. One of its chronic and debilitating complications is pulmonary hypertension (PH). SCD-associated PH is often post-capillary, secondary to left heart disease. It can also sometimes be pre-capillary with multiple and often interrelated mechanisms including obstructive remodeling of the pulmonary vascular bed secondary to hemolysis, endothelial dysfunction, thrombosis, hypoxia, or associated risk factors like portal hypertension. Screening symptomatic patients with echocardiographic signs of PH is crucial to determine those who should undergo right heart catheterization, the cornerstone exam to diagnose and categorize patients with PH. The workup following the diagnosis relies on identifying the cause of PH to personalize treatment. Ongoing efforts are made to treat this complex condition, starting with treating the underlying disease with hydroxyurea or chronic blood exchange transfusion. Robust data on the efficacy of PAH-specific therapies are lacking in this specific population. Initiation of such therapies must be made by an expert center after a case-by-case assessment of the benefit-risk ratio according to the phenotype and the mechanisms involved in the development of PH. Efforts are also poured into studying the interventional and medical therapies used on chronic thromboembolic PH for patients presenting with a thrombotic form. The management of those patients requires a multidisciplinary approach, with conjoint efforts from PH and SCD specialists.

Bosentan attenuates sickle cell disease erythrocyte HbS polymerization and impaired deformability induced by endothelin-1

The effects of endothelin-1 (ET-1) on erythrocytes from sickle cell disease (SCD) patients have been described, but mechanisms of ET-1 regarding primary erythrocyte functions remain unknown. ET-1 is a vasoconstrictor peptide produced by endothelial cells, and the expression of ET-1 is increased in SCD. The present study used ex vivo experiments with sickle cell erythrocytes, ET-1, and bosentan, a dual antagonist of ETA and ETB receptors. We performed a hemoglobin S (HbS) polymerization assay with three concentrations of ET-1 (1, 20, and 50 pg/mL) and bosentan (100 nmol/L). ET-1 increased HbS polymerization at all concentrations, and this effect was suppressed by bosentan. For the deformability assay, red blood cells (RBCs) were incubated on a Sephacryl column with the same concentrations of ET-1 and bosentan. ET-1 decreased deformability, and this effect was reversed by bosentan. To observe erythrocyte adhesion, ET-1 and bosentan were incubated with RBCs in thrombospondin-coated 96-well plate, which demonstrated that ET-1 decreased adhesion but that bosentan enhanced adhesion. We also assessed erythrocyte apoptosis and observed decreased eryptosis induced by ET-1, and these effects were inhibited bosentan. Thus, these findings demonstrated that ET-1 modulates HbS polymerization, erythrocyte deformability, adhesion to thrombospondin, and eryptosis, and these effects were suppressed or enhanced by bosentan.

Blockade of the mineralocorticoid receptor improves markers of human endothelial cell dysfunction and hematological indices in a mouse model of sickle cell disease

Increased endothelin-1 (ET-1) levels in patients with sickle cell disease (SCD) and transgenic mouse models of SCD contribute to disordered hematological, vascular, and inflammatory responses. Mineralocorticoid receptor (MR) activation by aldosterone, a critical component of the Renin-Angiotensin-Aldosterone-System, modulates inflammation and vascular reactivity, partly through increased ET-1 expression. However, the role of MR in SCD remains unclear. We hypothesized that MR blockade in transgenic SCD mice would reduce ET-1 levels, improve hematological parameters, and reduce inflammation. Berkeley SCD (BERK) mice, a model of severe SCD, were randomized to either sickle standard chow or chow containing the MR antagonist (MRA), eplerenone (156 mg/Kg), for 14 days. We found that MRA treatment reduced ET-1 plasma levels (p = .04), improved red cell density gradient profile (D50 ; p < .002), and increased mean corpuscular volume in both erythrocytes (p < .02) and reticulocytes (p < .024). MRA treatment also reduced the activity of the erythroid intermediate-conductance Ca2+ -activated K+ channel - KCa 3.1 (Gardos channel, KCNN4), reduced cardiac levels of mRNAs encoding ET-1, Tumor Necrosis Factor Receptor-1, and protein disulfide isomerase (PDI) (p < .01), and decreased plasma PDI and myeloperoxidase activity. Aldosterone (10-8  M for 24 h in vitro) also increased PDI mRNA levels (p < .01) and activity (p < .003) in EA.hy926 human endothelial cells, in a manner blocked by pre-incubation with the MRA canrenoic acid (1 μM; p < .001). Our results suggest a novel role for MR activation in SCD that may exacerbate SCD pathophysiology and clinical complications.

The Cardiopulmonary Complications of Sickle Cell Disease

Sickle cell disease (SCD) is a genetic hemoglobinopathy associated with extensive morbidity and early mortality. While there have been recent improvements in available disease-modifying therapies for SCD, cardiopulmonary complications remain a major risk factor for death in this population. We provide an overview of current knowledge regarding several of the major acute and chronic cardiopulmonary complications in SCD, including: acute chest syndrome, airway disease, lung function abnormalities, nocturnal hypoxemia and sleep disordered breathing, pulmonary vascular disease, and sickle cell cardiomyopathy.

Advances in the diagnosis and treatment of sickle cell disease

Sickle cell disease (SCD), which affects approximately 100,000 individuals in the USA and more than 3 million worldwide, is caused by mutations in the βb globin gene that result in sickle hemoglobin production. Sickle hemoglobin polymerization leads to red blood cell sickling, chronic hemolysis and vaso-occlusion. Acute and chronic pain as well as end-organ damage occur throughout the lifespan of individuals living with SCD resulting in significant disease morbidity and a median life expectancy of 43 years in the USA. In this review, we discuss advances in the diagnosis and management of four major complications: acute and chronic pain, cardiopulmonary disease, central nervous system disease and kidney disease. We also discuss advances in disease-modifying and curative therapeutic options for SCD. The recent availability of L-glutamine, crizanlizumab and voxelotor provides an alternative or supplement to hydroxyurea, which remains the mainstay for disease-modifying therapy. Five-year event-free and overall survival rates remain high for individuals with SCD undergoing allogeneic hematopoietic stem cell transplant using matched sibling donors. However, newer approaches to graft-versus-host (GVHD) prophylaxis and the incorporation of post-transplant cyclophosphamide have improved engraftment rates, reduced GVHD and have allowed for alternative donors for individuals without an HLA-matched sibling. Despite progress in the field, additional longitudinal studies, clinical trials as well as dissemination and implementation studies are needed to optimize outcomes in SCD.

Treatment dilemmas: strategies for priapism, chronic leg ulcer disease, and pulmonary hypertension in sickle cell disease

Sickle cell disease is a disorder characterized by chronic hemolytic anemia and multiorgan disease complications. Although vaso-occlusive episodes, acute chest syndrome, and neurovascular disease frequently result in complication and have well-documented guidelines for management, the management of chronic hemolytic and vascular-related complications, such as priapism, leg ulcers, and pulmonary hypertension, is not as well recognized despite their increasing reported prevalence and association with morbidity and mortality. This chapter therefore reviews the current updates on diagnosis and management of priapism, leg ulcers, and pulmonary hypertension.

The different facets of sickle cell disease-related pulmonary hypertension

PURPOSE OF REVIEW

Sickle cell disease (SCD), one of the most common genetic diseases in the world, is characterized by repeated episodes of hemolysis and vaso-occlusion. Hemolytic anemia is a risk factor for the development of pulmonary hypertension, and currently SCD-related pulmonary hypertension is classified as World Health Organization group 5 pulmonary hypertension. Patients with SCD-related pulmonary hypertension have unique hemodynamics, multiple comorbidities, and distinct phenotypes that may contribute to the development of pulmonary hypertension.

RECENT FINDINGS

SCD-related pulmonary hypertension is defined as a mean pulmonary artery pressure >20 mmHg, a pulmonary artery occlusion pressure ≤15 mmHg and relatively low pulmonary vascular resistance (>2 Wood units) rather than the traditional definition of ≥3 Wood units, an important distinction due to a baseline high-cardiac output state in the setting of chronic anemia and low vascular resistance. Diastolic dysfunction is frequently identified in this patient population and right heart catheterization is essential to determine if combined pre- and postcapillary pulmonary hypertension is present. Thromboembolism is common among patients with SCD, and screening for chronic thromboembolic pulmonary hypertension is essential. Data regarding advanced therapies are limited. Primary treatment options include targeting correction of their primary hemoglobinopathy as well as aggressive management of underlying comorbid conditions.

SUMMARY

SCD-related pulmonary hypertension is common among patients with SCD and is associated with increased mortality. A high index of suspicion is warranted during evaluation to identify all potential factors that may be contributing to disease.

Comparative assessment of efficacy and safety of ambrisentan and bosentan in patients with pulmonary arterial hypertension: A meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Two endothelin receptor antagonists, ambrisentan and bosentan, have been demonstrated to be effective individually compared with placebo in the treatment of patients with pulmonary arterial hypertension (PAH). This network meta-analysis compared the efficacy and safety of ambrisentan and bosentan in patients with PAH.

METHODS

Clinical trials were identified from the Cochrane Central Register of Controlled Trials (CENTRAL/CCTR), EMBASE and PubMed databases. Weighted mean differences (MD) with 95% confidence intervals (CI) were calculated for continuous outcomes (6-min walk distance [6MWD] and Borg dyspnoea index [BDI]). Hazard ratio (HR) was calculated for binary outcomes, including clinical worsening, discontinuation due to adverse events (AEs) and liver dysfunction. Surface under cumulative ranking curve (SUCRA) was used to rank the treatments in each index.

RESULTS

Five clinical trials from four published studies (total patients: n = 920) were included. Ambrisentan and bosentan showed no significant difference in 6MWD (MD: -1.32; 95% CI: -27.87, 25.31, SUCRA score: ambrisentan 0.73, bosentan 0.77), BDI (MD: -0.16; 95% CI: -0.98, 0.65, SUCRA score: ambrisentan 0.83, bosentan 0.66), clinical worsening (HR: 0.99; 95% CI: 0.33, 2.94, SUCRA score: ambrisentan 0.75, bosentan 0.74) and discontinuation due to AEs (HR: 0.84; 95% CI: 0.11, 5.86, SUCRA score: ambrisentan 0.47, bosentan 0.57). However, ambrisentan was significantly better than bosentan with respect to abnormal liver function (HR: 23.18; 95% CI: 2.24, 377.20, SUCRA score: ambrisentan 0.99, bosentan 0.02).

WHAT IS NEW AND CONCLUSION

The results of this network meta-analysis suggest that ambrisentan was similar to bosentan in efficacy, while it exhibited better tolerability with respect to abnormal liver function in comparison with bosentan, in patients with PAH.

Long-term tolerability of phosphodiesterase-5 inhibitors in pulmonary hypertension of sickle cell disease

OBJECTIVES

Sickle cell disease-related pulmonary hypertension (SCD-PH) is a complex disorder with multifactorial contributory mechanisms. Previous trials have evaluated the efficacy of pulmonary arterial hypertension (PAH) therapies in SCD-PH with mixed results. We hypothesized that a subset of patients with right heart catheterization (RHC) confirmed disease may benefit from PAH therapy.

METHODS

We performed a retrospective chart review of patients with SCD-PH diagnosed by RHC who were treated with phosphodiesterase 5 inhibitor (PDE5-I) therapy for ≥4 months between 2008 and 2019 at two institutions.

RESULTS

Thirty-six patients were included in the analysis. The median age (IQR) upon PDE5-I initiation was 47.5 years (35-51.5 years); 58% were female and twenty-nine (81%) had HbSS disease. Of these, 53% of patients had a history of acute chest syndrome, 42% had a history of venous thromboembolism, and 38% had imaging consistent with chronic thromboembolic PH. Patients were treated for a median duration of 25 months (IQR 13-60 months). Use of PDE5-I was associated with a significant improvement in symptoms as assessed by NYHA Class (P = .002).

CONCLUSIONS

In SCD patients with PH defined by RHC, PDE5-I therapy was tolerated long-term and may improve physical activity.

Sickle cell disease related chronic thromboembolic pulmonary hypertension: challenging clinical scenario

Sickle cell disease (SCD), a haemoglobinopathy characterized by chronic haemolysis with acute exacerbations and vascular occlusion episodes, may be complicated by pulmonary hypertension. The latter may be caused by chronic thromboembolic disease of pulmonary artery branches and its management is not well-defined. Herein, we present a case of SCD complicated by chronic thromboembolic pulmonary hypertension of subsegmental pulmonary artery branches successfully treated with endothelin receptor antagonists, orally administered prostacyclin analogs and balloon pulmonary angioplasty. This challenging case highlights the need for clinical awareness of chronic thromboembolic pulmonary hypertension as a specific and potentially curable form of pulmonary hypertension complicating SCD course that may necessitate combined pharmacologic and interventional management.

Is Skeletal Muscle Dysfunction a Limiting Factor of Exercise Functional Capacity in Patients with Sickle Cell Disease?

Patients with sickle cell disease (SCD) have reduced functional capacity due to anemia and cardio-respiratory abnormalities. Recent studies also suggest the presence of muscle dysfunction. However, the interaction between exercise capacity and muscle function is currently unknown in SCD. The aim of this study was to explore how muscle dysfunction may explain the reduced functional capacity. Nineteen African healthy subjects (AA), and 24 sickle cell anemia (SS) and 18 sickle cell hemoglobin C (SC) patients were recruited. Maximal isometric torque (Tmax) was measured before and after a self-paced 6-min walk test (6-MWT). Electromyographic activity of the Vastus Lateralis was recorded. The 6-MWT distance was reduced in SS (p < 0.05) and SC (p < 0.01) patients compared to AA subjects. However, Tmax and root mean square value were not modified by the 6-MWT, showing no skeletal muscle fatigue in all groups. In a multiple linear regression model, genotype, step frequency and hematocrit were independent predictors of the 6-MWT distance in SCD patients. Our results suggest that the 6-MWT performance might be primarily explained by anemia and the self-paced step frequency in SCD patients attempting to limit metabolic cost and fatigue, which could explain the absence of muscle fatigue.

Endothelin receptor antagonists for pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension is a devastating disease that leads to right heart failure and premature death. Endothelin receptor antagonists have shown efficacy in the treatment of pulmonary arterial hypertension.

OBJECTIVES

To evaluate the efficacy of endothelin receptor antagonists (ERAs) in pulmonary arterial hypertension.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and the reference sections of retrieved articles. The searches are current as of 4 November 2020.

SELECTION CRITERIA

We included randomised trials and quasi-randomised trials involving participants with pulmonary arterial hypertension.

DATA COLLECTION AND ANALYSIS

Two of five review authors selected studies, extracted data and assessed study quality according to established criteria. We used standard methods expected by Cochrane. The primary outcomes were exercise capacity (six-minute walk distance, 6MWD), World Health Organization (WHO) or New York Heart Association (NYHA) functional class, Borg dyspnoea scores and dyspnoea-fatigue ratings, and mortality.

MAIN RESULTS

We included 17 randomised controlled trials involving a total of 3322 participants. Most trials were of relatively short duration (12 weeks to six months). Sixteen trials were placebo-controlled, and of these nine investigated a non-selective ERA and seven a selective ERA.   We evaluated two comparisons in the review: ERA versus placebo and ERA versus phosphodiesterase type 5 (PDE5) inhibitor. The abstract focuses on the placebo-controlled trials only and presents the pooled results of selective and non-selective ERAs. After treatment, participants receiving ERAs could probably walk on average 25.06 m (95% confidence interval (CI) 17.13 to 32.99 m; 2739 participants; 14 studies; I² = 34%, moderate-certainty evidence) further than those receiving placebo in a 6MWD. Endothelin receptor antagonists probably improved more participants' WHO functional class (odds ratio (OR) 1.41, 95% CI 1.16 to 1.70; participants = 3060; studies = 15; I² = 5%, moderate-certainty evidence) and probably lowered the odds of functional class deterioration (OR 0.43, 95% CI 0.26 to 0.72; participants = 2347; studies = 13; I² = 40%, moderate-certainty evidence) compared with placebo. There may be a reduction in mortality with ERAs (OR 0.78, 95% CI 0.58, 1.07; 2889 participants; 12 studies; I² = 0%, low-certainty evidence), and pooled data suggest that ERAs probably improve cardiopulmonary haemodynamics and may reduce Borg dyspnoea score in symptomatic patients. Hepatic toxicity was not common, but may be increased by ERA treatment from 37 to 67 (95% CI 34 to 130) per 1000 over 25 weeks of treatment (OR 1.88, 95% CI 0.91 to 3.90; moderate-certainty evidence). Although ERAs were well tolerated in this population, several cases of irreversible liver failure caused by sitaxsentan have been reported, which led the licence holder for sitaxsentan to withdraw the product from all markets worldwide.  As planned, we performed subgroup analyses comparing selective and non-selective ERAs, and with the exception of mean pulmonary artery pressure, did not detect any clear subgroup differences for any outcome.

AUTHORS' CONCLUSIONS

For people with pulmonary arterial hypertension with WHO functional class II and III, endothelin receptor antagonists probably increase exercise capacity, improve WHO functional class, prevent WHO functional class deterioration, result in favourable changes in cardiopulmonary haemodynamic variables compared with placebo. However, they are less effective in reducing dyspnoea and mortality. The efficacy data were strongest in those with idiopathic pulmonary hypertension. The irreversible liver failure caused by sitaxsentan and its withdrawal from global markets emphasise the importance of hepatic monitoring in people treated with ERAs. The question of the effects of ERAs on pulmonary arterial hypertension has now likely been answered.. The combined use of ERAs and phosphodiesterase inhibitors may provide more benefit in pulmonary arterial hypertension; however, this needs to be confirmed in future studies.

Epidemiology, Pathogenesis, and Clinical Approach in Group 5 Pulmonary Hypertension

Pulmonary hypertension (PH) is recognized to be associated with a number of comorbid conditions. Based on these associations, PH is classified into 5 groups, considering common pathophysiologic drivers of disease, histopathologic features, clinical manifestations and course, and response to PH therapy. However, in some of these associated conditions, these characteristics are less well-understood. These include, among others, conditions commonly encountered in clinical practice such as sarcoidosis, sickle cell disease, myeloproliferative disorders, and chronic kidney disease/end stage renal disease. PH in these contexts presents a significant challenge to clinicians with respect to disease management. The most recent updated clinical classification schemata from the 6th World Symposium on PH classifies such entities in Group 5, highlighting the often unclear and/or multifactorial nature of PH. An in-depth review of the state of the science of Group 5 PH with respect to epidemiology, pathogenesis, and management is provided. Where applicable, future directions with respect to research needed to enhance understanding of the clinical course of these entities is also discussed.

Bosentan-induced immune hemolytic anemia in 17 years old man. A case report

Hemolytic anemia is a very important immune-mediated reaction, which its late diagnosis can be fatal. Medications along with other causes can induce hemolytic anemia. Drug induced immune hemolytic anemia (DIIHA) is caused by the development of autoantibodies. Accordingly, DIIHA is rare and there is not enough data for its prevalence. Number of drugs that can cause DIIHA have increased in recent decades. A 17-year-old man who had congenital single ventricle heart (CHB) and pulmonary artery hypertension (PAH) was admitted at Imam Khomeini hospital complex affiliated to Tehran University of Medical Sciences, with chief complaint of jaundice and icter. Bosentan and Tadalafil were in the list of the drugs used by this patient. Although both drugs were recommended to be discontinued in the patient, in the course of hospitalization, the patient accidentally continued to take his Tadalafil. However, the patient's recovery continued. Given that the patient's Coombs test was positive, his hemolytic anemia mechanism was drug-induced immune-mediated hemolytic anemia. As a result, according to Naranjo score = 6, Bosentan was considered as the main possible culprit to induce DIIHA in this patient. Following the discontinuation of Bosentan and receiving Prednisolone, the patient's clinical symptoms and laboratory parameters resolved and the patient was then discharged.

The Sickle Cell Pro-Inflammatory Response to Interval Testing Study (SPRINTS) in children and young adults with sickle cell anemia - Study design and methodological strategies

The impact of sickle cell anemia (SCA) and its complications on physical functioning and cardiopulmonary/aerobic fitness in affected individuals is significant. Although limited data support the safety of maximal cardiopulmonary exercise testing (CPET) for children and adults with SCA, the safety of submaximal moderate and high intensity, and longer duration, exercise in this population is not clear. The Sickle Cell Pro-Inflammatory Response to Interval Testing Study (SPRINTS) is a multicenter, randomized, prospective trial. SPRINTS leverages unique collaborations between investigators in pediatric hematology and exercise science to evaluate the impact of exercise intensity on the acute phase inflammatory response to exercise and changes in airway dynamics in children and young adults with SCA. Here we describe the study design and methodological strategies employed in SPRINTS, including an exercise challenge that mimics real-life patterns of childhood physical activity, characterized by multiple moderate and high intensity brief bouts of exercise interspersed with rest periods. Primary outcomes comprise pre- and post-exercise biomarkers of inflammation and endothelial dysfunction and spirometry. Secondary outcomes include assessment of physical activity and functioning, genomic studies and near-infrared spectroscopy measurements to assess tissue oxygenation status during exercise. SPRINTS aims to enroll 70 subjects with SCA and 70 matched, healthy controls. We anticipate that data from SPRINTS will address gaps in our understanding of exercise responses and safety in SCA and support the future development of evidence-based, exercise prescription guidelines in this population.

Focused Update on Pulmonary Hypertension in Children-Selected Topics of Interest for the Adult Cardiologist

Pulmonary hypertensive vascular disease (PHVD), and pulmonary hypertension (PH), which is a broader term, are severe conditions associated with high morbidity and mortality at all ages. Treatment guidelines in childhood are widely adopted from adult data and experience, though big differences may exist regarding aetiology, concomitant conditions and presentation. Over the past few years, paediatric aspects have been incorporated into the common guidelines, which currently address both children and adults with pulmonary hypertension (PH). There are multiple facets of PH in the context of cardiac conditions in childhood. Apart from Eisenmenger syndrome (ES), the broad spectrum of congenital heart disease (CHD) comprises PH in failing Fontan physiology, as well as segmental PH. In this review we provide current data and novel aspects on the pathophysiological background and individual management concepts of these conditions. Moreover, we focus on paediatric left heart failure with PH and its challenging issues, including end stage treatment options, such as mechanical support and paediatric transplantation. PH in the context of rare congenital disorders, such as Scimitar Syndrome and sickle cell disease is discussed. Based on current data, we provide an overview on multiple underlying mechanisms of PH involved in these conditions, and different management strategies in children and adulthood. In addition, we summarize the paediatric aspects and the pros and cons of the recently updated definitions of PH. This review provides deeper insights into some challenging conditions of paediatric PH in order to improve current knowledge and care for children and young adults.

Combined Methods (Formal Adjusted Indirect Comparison, Meta-Analysis and Principal Component Analysis) Comparisons of the Safety and Efficacy of Ambrisentan, Bosentan, and Sildenafil in the Patients With Pulmonary Arterial Hypertension

BACKGROUND

Three oral drugs (ambrisentan, bosentan, and sildenafil) have been widely used to treat patients with pulmonary arterial hypertension (PAH). 1) There are no studies that directly compare the safety and efficacy of these three drugs. Existing studies could not meet the physician's need to select the most beneficial drugs for patients. 2) Principal component analysis is mainly used for scale analysis and has not been reported in clinical field. 3) When the results of the indirect meta-analysis were not satisfactory, no new solutions have been proposed in existing meta-analysis studies.

METHODS

The overall process of this study is divided into 4 steps 1) literature search and data extraction; 2) principal component analysis; 3) common reference-based indirect comparison meta-analysis; 4) formal adjusted indirect comparison.

RESULTS

Nine randomized controlled trials (RCTs) experiments and eight long-term experiments were selected. The main influencing factors are mortality, 6-min walk distance (6MW), mean pulmonary arterial pressure (PAP), cardiac index (CI) by principal component analysis. There was no significant heterogeneity among the indirect meta-analysis of three drugs. But in the formal adjusted indirect comparison 1) the level of PAP of sildenafil group (60.5 ± 22.35, 220) was higher than that of the other three groups, placebo (53.5 ± 17.63, 507) (p < 0.001), ambrisentan (49.5 ± 15.08, 130) (p < 0.001), and bosentan (54.6 ± 118.41, 311) (p < 0.001); 2) the level of CI of sildenafil group (54 ± 18, 311) was higher than that of the other three groups, placebo (2.7 ± 1.09, 518) (p < 0.001), ambrisentan (2.5 ± 0.75, 130) (p < 0.001), and bosentan (2.5 ± 1.06, 333) (p < 0.001). In addition, sildenafil significantly improved the survival rate comparing with ambrisentan and bosentan.

CONCLUSIONS

The results of this study suggest that sildenafil might be more suitable for long-term treatment of PAH patients than ambrisentan and bosentan. In order to enable clinicians to draw conclusions more quickly and directly in the data-rich literature, we suggest the use of principal component analysis combined with formal adjusted indirect comparison to compare the efficacy and safety of drugs.

Ischemia-Reperfusion Injury in Sickle Cell Disease: From Basics to Therapeutics

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide, affecting almost 400,000 newborns globally each year. It is characterized by chronic hemolytic anemia and endothelial dysfunction, resulting in a constant state of disruption of the vascular system and leading to recurrent episodes of ischemia-reperfusion injury (I/RI) to multiple organ systems. I/RI is a fundamental vascular pathobiological paradigm and contributes to morbidity and mortality in a wide range of conditions, including myocardial infarction, stroke, acute kidney injury, and transplantation. I/RI is characterized by an initial restriction of blood supply to an organ, which can lead to ischemia, followed by the subsequent restoration of perfusion and concomitant reoxygenation. Recent advances in the pathophysiology of SCD have led to an understanding that many of the consequences of this disease can be explained by mechanisms associated with I/RI. The following review focuses on the evolving pathobiology of SCD, how various complications of SCD can be attributed to I/RI, and the role of timely therapeutic intervention(s) based on targeting mediators or pathways that influence I/R insult.

American Society of Hematology 2019 guidelines for sickle cell disease: cardiopulmonary and kidney disease

BACKGROUND

Prevention and management of end-organ disease represent major challenges facing providers of children and adults with sickle cell disease (SCD). Uncertainty and variability in the screening, diagnosis, and management of cardiopulmonary and renal complications in SCD lead to varying outcomes for affected individuals.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in their decisions about screening, diagnosis, and management of cardiopulmonary and renal complications of SCD.

METHODS

ASH formed a multidisciplinary guideline panel that included 2 patient representatives and was balanced to minimize potential bias from conflicts of interest. The Mayo Evidence-Based Practice Research Program supported the guideline development process, including performing systematic evidence reviews up to September 2017. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including GRADE evidence-to-decision frameworks, to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 10 recommendations for screening, diagnosis, and management of cardiopulmonary and renal complications of SCD. Recommendations related to anticoagulation duration for adults with SCD and venous thromboembolism were also developed.

CONCLUSIONS

Most recommendations were conditional due to a paucity of direct, high-quality evidence for outcomes of interest. Future research was identified, including the need for prospective studies to better understand the natural history of cardiopulmonary and renal disease, their relationship to patient-important outcomes, and optimal management.

Regular long-term red blood cell transfusions for managing chronic chest complications in sickle cell disease

BACKGROUND

Sickle cell disease is a genetic haemoglobin disorder, which can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Sickle cell disease is one of the most common severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. The two most common chronic chest complications due to sickle cell disease are pulmonary hypertension and chronic sickle lung disease. These complications can lead to morbidity (such as reduced exercise tolerance) and increased mortality. This is an update of a Cochrane Review first published in 2011 and updated in 2014 and 2016.

OBJECTIVES

We wanted to determine whether trials involving people with sickle cell disease that compare regular long-term blood transfusion regimens with standard care, hydroxycarbamide (hydroxyurea) any other drug treatment show differences in the following: mortality associated with chronic chest complications; severity of established chronic chest complications; development and progression of chronic chest complications; serious adverse events.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register. Date of the last search: 19 September 2019. We also searched for randomised controlled trials in the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library, Issue 10, 14 November 2018), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950), and ongoing trial databases to 14 November 2018.

SELECTION CRITERIA

We included randomised controlled trials of people of any age with one of four common sickle cell disease genotypes, i.e. Hb SS, Sβº, SC, or Sβ⁺ that compared regular red blood cell transfusion regimens (either simple or exchange transfusions) to hydroxycarbamide, any other drug treatment, or to standard care that were aimed at reducing the development or progression of chronic chest complications (chronic sickle lung and pulmonary hypertension).

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

No studies matching the selection criteria were found.

AUTHORS' CONCLUSIONS

There is a need for randomised controlled trials looking at the role of long-term transfusion therapy in pulmonary hypertension and chronic sickle lung disease. Due to the chronic nature of the conditions, such trials should aim to use a combination of objective and subjective measures to assess participants repeatedly before and after the intervention.

Sickle cell disease: a review for the internist

Sickle cell disease (SCD) is the most important hemoglobinopathy worldwide in terms of frequency and social impact, recently recognized as a global public health problem by the World Health Organization. It is a monogenic but multisystem disorder with high morbidity and mortality. Vaso-occlusion, hemolytic anemia and vasculopathy are the hallmarks of SCD pathophysiology. This review focuses both on "time-dependent" acute clinical manifestations of SCD and chronic complications commonly described in adults with SCD. The review covers a broad spectrum of topics concerning current management of SCD targeted at the internists and emergency specialists who are increasingly involved in the care of acute and chronic complications of SCD patients.

Identifying Clinical and Research Priorities in Sickle Cell Lung Disease. An Official American Thoracic Society Workshop Report

Background: Pulmonary complications of sickle cell disease (SCD) are diverse and encompass acute and chronic disease. The understanding of the natural history of pulmonary complications of SCD is limited, no specific therapies exist, and these complications are a primary cause of morbidity and mortality.Methods: We gathered a multidisciplinary group of pediatric and adult hematologists, pulmonologists, and emergency medicine physicians with expertise in SCD-related lung disease along with an SCD patient advocate for an American Thoracic Society-sponsored workshop to review the literature and identify key unanswered clinical and research questions. Participants were divided into four subcommittees on the basis of expertise: 1) acute chest syndrome, 2) lower airways disease and pulmonary function, 3) sleep-disordered breathing and hypoxia, and 4) pulmonary vascular complications of SCD. Before the workshop, a comprehensive literature review of each subtopic was conducted. Clinically important questions were developed after literature review and were finalized by group discussion and consensus.Results: Current knowledge is based on small, predominantly observational studies, few multicenter longitudinal studies, and even fewer high-quality interventional trials specifically targeting the pulmonary complications of SCD. Each subcommittee identified the three or four most important unanswered questions in their topic area for researchers to direct the next steps of clinical investigation.Conclusions: Important and clinically relevant questions regarding sickle cell lung disease remain unanswered. High-quality, multicenter, longitudinal studies and randomized clinical trials designed and implemented by teams of multidisciplinary clinician-investigators are needed to improve the care of individuals with SCD.

Successful Use of Pulmonary Vasodilators in Acute Chest Syndrome Complicated by Persistent Right Ventricular Failure

Pulmonary hypertension (PH) is a known consequence of sickle cell disease (SCD) and is associated with increased mortality and more frequent episodes of acute chest syndrome (ACS). Pulmonary pressures are known to increase during ACS, and right ventricular (RV) failure has been described as a significant cause of mortality in this condition. Management of ACS includes exchange transfusion, pain control, and prevention of hypovolemia and hypoxemia. However, in patients with a history of precapillary PH in whom ACS is complicated by persistent RV failure and cardiogenic shock, RV afterload reduction with pulmonary vasodilators may be an effective treatment strategy. Here, we present a case of a young man with SCD-associated PH and ACS who was successfully managed with inhaled and oral pulmonary vasodilators in the setting of persistent elevations in pulmonary vascular resistance leading to acute RV failure and cardiogenic shock.

Therapeutic strategies for sickle cell disease: towards a multi-agent approach

For over 100 years, clinicians and scientists have been unravelling the consequences of the A to T substitution in the β-globin gene that produces haemoglobin S, which leads to the systemic manifestations of sickle cell disease (SCD), including vaso-occlusion, anaemia, haemolysis, organ injury and pain. However, despite growing understanding of the mechanisms of haemoglobin S polymerization and its effects on red blood cells, only two therapies for SCD - hydroxyurea and L-glutamine - are approved by the US Food and Drug Administration. Moreover, these treatment options do not fully address the manifestations of SCD, which arise from a complex network of interdependent pathophysiological processes. In this article, we review efforts to develop new drugs targeting these processes, including agents that reactivate fetal haemoglobin, anti-sickling agents, anti-adhesion agents, modulators of ischaemia-reperfusion and oxidative stress, agents that counteract free haemoglobin and haem, anti-inflammatory agents, anti-thrombotic agents and anti-platelet agents. We also discuss gene therapy, which holds promise of a cure, although its widespread application is currently limited by technical challenges and the expense of treatment. We thus propose that developing systems-oriented multi-agent strategies on the basis of SCD pathophysiology is needed to improve the quality of life and survival of people with SCD.

The improvement of pulmonary artery pressure after bosentan therapy in patients with β-thalassemia and Doppler-defined pulmonary arterial hypertension

Introduction

Pulmonary arterial hypertension (PAH) is relatively prevalent in patients with thalassemia. PAH treatment is necessary as the prevalence of Doppler-estimated PAH and the resultant mortality is high in such patients.

Materials and methods

This study aimed at evaluating the effect of bosentan therapy on patients with thalassemia suspected of PAH. Based on pulsed Doppler echocardiography, all the cases were suspected of severe PAH. Consequently, bosentan was initiated at a dose of 62.5 mg twice a day for 4 weeks, which was increased to 62.5–125 mg twice a day, if no adverse side effects were observed.

Results

The results of this study showed that pulmonary artery pressure (PAP) decreased after the administration of bosentan in three cases, from 160 to 120, 110 to 65, and 60 to 25 mmHg; in other words, the PAP reduced in the mentioned cases by 25%, 36.4%, and 58.4%, respectively.

Conclusion

In this study, PAP improved after bosentan therapy in patients with β-thalassemia suspected of PAH; however, further studies are required to confirm the findings.

Balancing exercise risk and benefits: lessons learned from sickle cell trait and sickle cell anemia

Development of exercise guidelines for individuals with sickle cell trait (SCT) and sickle cell anemia (SCA) is hampered by the need to weigh the benefits against risks of exercise in these populations. In SCT, concern for exercise collapse associated with sickle cell trait has resulted in controversial screening of student athletes for SCT. In SCA, there exists unsubstantiated concerns that high-intensity exercise may result in pain and other complications. In both, finding the "right dose" of exercise remains a challenge for patients and their providers. Despite assumptions that factors predisposing to adverse events from high-intensity exercise overlap in SCT and SCA, the issues that frame our understanding of exercise-related harms in both are distinct. This review will compare issues that affect the risk-benefit balance of exercise in SCT and SCA through these key questions: (1) What is the evidence that high-intensity exercise is associated with harm? (2) What are the pathophysiologic mechanisms that could predispose to harm? (3) What are the preventive strategies that may reduce risk? and (4) Why do we need to consider the benefits of exercise in this debate? Addressing these knowledge gaps is essential for developing an evidence-based exercise prescription for these patient populations.

Chronic blood exchange transfusions in the management of pre-capillary pulmonary hypertension complicating sickle cell disease

The long-term effects of chronic blood exchange transfusions (BETs) on pre-capillary pulmonary hypertension complicating sickle cell disease (SCD) are unknown.13 homozygous SS SCD patients suffering from pre-capillary pulmonary hypertension and treated by chronic BETs were evaluated retrospectively. Assessments included haemodynamics, New York Heart Association Functional Class (NYHA FC), 6-min walk distance (6MWD) and blood tests.Before initiating BETs, all patients were NYHA FC III or IV, median (range) 6MWD was 223 (0-501) m and median (range) pulmonary vascular resistance (PVR) was 3.7 (2-12.5) Wood Units. After a median number of 4 BET sessions, all patients had improved to NYHA FC II or III. Significant improvements in haemodynamics were observed, including a decrease in PVR (p=0.01). There was a trend to higher 6MWD (p=0.09). Median (range) follow-up time after initiation of BETs was 25 (6-53) months. During this period, two patients decided to stop BETs. One of them died from acute right heart failure and the other experienced worsening pulmonary hypertension. Two other patients died during follow-up at 25 and 54 months after BET initiation.Chronic BETs may be a potential therapeutic option in pre-capillary pulmonary hypertension complicating SCD, leading to significant clinical and haemodynamic improvements. These data must be confirmed in a prospective study.

How I treat the older adult with sickle cell disease

With increasing survival, cumulative complications of sickle cell disease (SCD), which develop insidiously over time, are becoming more apparent and common in older patients, particularly those in their fifth decade and beyond. The older patient is also more likely to develop other age-related nonsickle conditions that interact and add to the disease morbidity. A common misconception is that any symptom in a SCD patient is attributable to their SCD and this may lead to delays in diagnosis and appropriate intervention. We recommend regular comprehensive reviews and monitoring for early signs of organ damage and a low threshold for the use of hydroxyurea and blood transfusions as preventative measures for end-organ disease. Treatable comorbidities and acute deterioration should be managed aggressively. Although the primary goal in management of the older adult with SCD is improving anemia and minimizing organ damage, the time has come for us to be more proactive in considering curative therapies previously offered to the younger patient. Curative or experimental interventions should be discussed early, before complications render the patients ineligible for these treatments.

Effects of living at moderate altitude on pulmonary vascular function and exercise capacity in mice with sickle cell anaemia

KEY POINTS

Sickle cell disease (SCD) results in cardiopulmonary dysfunction, which may be exacerbated by prolonged exposure to environmental hypoxia. It is currently unknown whether exposure to mild and moderate altitude exacerbates SCD associated cardiopulmonary and systemic complications. Three months of exposure to mild (1609 m) and moderate (2438 m) altitude increased rates of haemolysis and right ventricular systolic pressures in mice with SCD compared to healthy wild-type cohorts and SCD mice at sea level. The haemodynamic changes in SCD mice that had lived at mild and moderate altitude were accompanied by changes in the balance between pulmonary vascular endothelial nitric oxide synthase and endothelin receptor expression and impaired exercise tolerance. These data demonstrate that chronic altitude exposure exacerbates the complications associated with SCD and provides pertinent information for the clinical counselling of SCD patients.

ABSTRACT

Exposure to high altitude worsens symptoms and crises in patients with sickle cell disease (SCD). However, it remains unclear whether prolonged exposure to low barometric pressures exacerbates SCD aetiologies or impairs quality of life. We tested the hypothesis that, relative to wild-type (WT) mice, Berkley sickle cell mice (BERK-SS) residing at sea level, mild (1609 m) and moderate (2438 m) altitude would have a higher rate of haemolysis, impaired cardiac function and reduced exercise tolerance, and that the level of altitude would worsen these decrements. Following 3 months of altitude exposure, right ventricular systolic pressure was measured (solid-state transducer). In addition, the adaptive balance between pulmonary vascular endothelial nitric oxide synthase and endothelin was assessed in lung tissue to determine differences in pulmonary vascular adaptation and the speed/duration relationship (critical speed) was used to evaluate treadmill exercise tolerance. At all altitudes, BERK-SS mice had a significantly lower percentage haemocrit and higher total bilirubin and free haemoglobin concentration (P < 0.05 for all). right ventricular systolic pressures in BERK-SS were higher than WT at moderate altitude and also compared to BERK-SS at sea level (P < 0.05, for both). Critical speed was significantly lower in BERK-SS at mild and moderate altitude (P < 0.05). BERK-SS demonstrated exacerbated SCD complications and reduced exercise capacity associated with an increase in altitude. These results suggest that exposure to mild and moderate altitude enhances the progression of SCD in BERK-SS mice compared to healthy WT cohorts and BERK-SS mice at sea level and provides crucial information for the clinical counselling of SCD patients.

Riociguat use in sickle cell related chronic thromboembolic pulmonary hypertension: A case series

Adults with sickle cell disease can develop pulmonary hypertension from a multitude of etiologies. Classified as WHO Group 5, there are no therapies approved for the treatment of sickle cell disease-pulmonary hypertension. Thromboembolic disease is prevalent in sickle cell disease and can lead to pulmonary hypertension. The only approved medical therapy for chronic thromboembolic pulmonary hypertension is riociguat. We report the experience, safety and tolerability of riociguat use in a series of sickle cell disease patients with chronic thromboembolic pulmonary hypertension.

Successful pulmonary thromboendarterectomy in a patient with sickle cell disease and associated resolution of a leg ulcer

Pulmonary hypertension (PH) is a relatively frequent and severe complication of sickle cell disease (SCD). PH associated with SCD is classified as Group 5 PH. The exact pathogenesis of PH in SCD in not known. There are also very limited treatment options available at this time for such patients with Group 5 PH. Patients with SCD are predisposed to a hypercoagulable state and thus can also suffer from chronic thromboembolism. These patients can have associated chronic thromboembolic pulmonary hypertension (CTEPH), thus being classified as Group 4 PH. We present such a case of a patient with SCD diagnosed with severe PH who was found to have CTEPH and successfully underwent a thromboendarterectomy with resolution of his symptoms such as reduction of his oxygen requirements and healing of chronic leg ulcer. This case illustrates the importance of screening patients with SCD and elevated pulmonary artery pressures for CTEPH as this would offer possible treatment options such as pulmonary thromboendarterectomy and/or riociguat in this subset of patients.

A reappraisal of the mechanisms underlying the cardiac complications of sickle cell anemia

Anemia, hemolysis-driven vasculopathy, and intrinsic myocardial injury have been proposed as predisposing factors to cardiac disease in sickle cell anemia (SCA). The individual impact of these mechanisms on the cardiac features of SCA and the way they influence complications such as sudden death and dysrhythmias have been unclear. Recent findings of an acquired restrictive SCA-related cardiomyopathy, driven by myocardial fibrosis, may explain some of these cardiac features. Given the complexity of cardiac pathology in SCA, using additional parameters to tricuspid regurgitant jet velocity (left atrial volume, diastolic parameters, NT-proBNP) may improve the accuracy of noninvasive screening for cardiopulmonary complications in SCA.

Medical Management of Pulmonary Hypertension with Unclear and/or Multifactorial Mechanisms (Group 5): Is There a Role for Pulmonary Arterial Hypertension Medications?

PURPOSE OF REVIEW

The purpose of this review was to outline the mechanisms and to review recent literature on pulmonary arterial hypertension (PAH) medications in group 5 pulmonary hypertension (PH).

RECENT FINDINGS

The first steps in management are to understand the mechanisms and hemodynamic profile and to exclude chronic thromboembolic disease. Recent studies in the past 5 years have found that PAH medications may improve hemodynamics in patients with pre-capillary pulmonary hypertension due to sarcoidosis, pulmonary Langerhans cell histiocytosis, lymphangioleiomyomatosis, and myeloproliferative disorders with dasatinib-induced PH. Improvements in exercise capacity are uncommon, and no survival benefit has been demonstrated. There is a risk of pulmonary edema in patients with pulmonary venous involvement or fibrosing mediastinitis when treated with PAH therapies. There is limited evidence supporting the use of PAH medications in group 5 patients, and they may be harmful in certain cases. In most patients with group 5 PH, treatment should be directed to the underlying disease with PAH therapies reserved for patients with severe pre-capillary PH.

Pathways to pulmonary hypertension in sickle cell disease: the search for prevention and early intervention

INTRODUCTION

Pulmonary hypertension (PH) develops in a significant number of patients with sickle cell disease (SCD), resulting in increased morbidity and mortality. This review focuses on PH pathophysiology, risk stratification, and new recommendations for screening and treatment for patients with SCD. Areas covered: An extensive PubMed literature search was performed. While the pathophysiology of PH in SCD is yet to be fully deciphered, it is known that the etiology is multifactorial; hemolysis, hypercoagulability, hypoxemia, ischemic-reperfusion injury, oxidative stress, and genetic susceptibility all contribute in varying degrees to endothelial dysfunction. Hemolysis, in particular, seems to play a key role by inciting an imbalance in the regulatory axis of nitric oxide and arginine metabolism. Systematic risk stratification starting in childhood based on clinical features and biomarkers that enable early detection is necessary. Multi-faceted, targeted interventions, before irreversible vasculopathy develops, will allow for improved patient outcomes and life expectancy. Expert commentary: Despite progress in our understanding of PH in SCD, clinically proven therapies remain elusive and additional controlled clinical trials are needed. Prevention of disease starts in childhood, a critical window for intervention. Given the complex and multifactorial nature of SCD, patients will ultimately benefit from combination therapies that simultaneously targets multiple mechanisms.

Peroxisome Proliferator-Activated Receptor γ Regulates the V-Ets Avian Erythroblastosis Virus E26 Oncogene Homolog 1/microRNA-27a Axis to Reduce Endothelin-1 and Endothelial Dysfunction in the Sickle Cell Mouse Lung

Pulmonary hypertension (PH), a serious complication of sickle cell disease (SCD), causes significant morbidity and mortality. Although a recent study determined that hemin release during hemolysis triggers endothelial dysfunction in SCD, the pathogenesis of SCD-PH remains incompletely defined. This study examines peroxisome proliferator-activated receptor γ (PPARγ) regulation in SCD-PH and endothelial dysfunction. PH and right ventricular hypertrophy were studied in Townes humanized sickle cell (SS) and littermate control (AA) mice. In parallel studies, SS or AA mice were gavaged with the PPARγ agonist, rosiglitazone (RSG), 10 mg/kg/day, or vehicle for 10 days. In vitro, human pulmonary artery endothelial cells (HPAECs) were treated with vehicle or hemin for 72 hours, and selected HPAECs were treated with RSG. SS mice developed PH and right ventricular hypertrophy associated with reduced lung levels of PPARγ and increased levels of microRNA-27a (miR-27a), v-ets avian erythroblastosis virus E26 oncogene homolog 1 (ETS1), endothelin-1 (ET-1), and markers of endothelial dysfunction (platelet/endothelial cell adhesion molecule 1 and E selectin). HPAECs treated with hemin had increased ETS1, miR-27a, ET-1, and endothelial dysfunction and decreased PPARγ levels. These derangements were attenuated by ETS1 knockdown, inhibition of miR-27a, or PPARγ overexpression. In SS mouse lung or in hemin-treated HPAECs, activation of PPARγ with RSG attenuated reductions in PPARγ and increases in miR-27a, ET-1, and markers of endothelial dysfunction. In SCD-PH pathogenesis, ETS1 stimulates increases in miR-27a levels that reduce PPARγ and increase ET-1 and endothelial dysfunction. PPARγ activation attenuated SCD-associated signaling derangements, suggesting a novel therapeutic approach to attenuate SCD-PH pathogenesis.

Comparative efficacy and acceptability of endothelin receptor antagonists for pulmonary arterial hypertension: A network meta-analysis

BACKGROUND

Endothelin receptor antagonists (ERAs) such as ambrisentan, sitaxsentan, bosentan and macitentan are primary drug therapies for pulmonary arterial hypertension (PAH) patients. However, the optimal drugs for PAH remained controversial due to heterogeneous nature of randomized control trials (RCTs).

METHODS

Apart from traditional meta-analysis, network meta-analysis (NMA) was performed in this study for multiple comparisons among PAH therapies. The 6 minute walking distance (6MWD) and clinical worsening were efficacy outcomes whereas serious adverse effects (SAE) and all-cause discontinuation were acceptability outcomes. The weighted mean difference (WMD) and odds ratio (OR) along with their 95% confidence interval (95% CI) or 95% credible interval (95% CrI) were used to evaluate the positive and negative effects of these therapies on PAH patients.

RESULTS

By synthesizing direct evidence from 10 studies with a total number of 2172 patients, we discovered that all of the four PAH therapies significantly increased the average 6MWD in comparison to the placebo (P-value<0.05). Moreover, bosentan and ambrisentan both showed significant association with a decrease in the risk of clinical worsening compared to placebo. Regarding of all-cause discontinuation, ambrisentan is the only therapy which was significantly associated with a risk decrease compared to placebo. However, there was no sufficient evidence suggesting significant difference in any efficacy or acceptability outcomes between any two of the PAH therapies (P-value>0.05).

CONCLUSION

Ambrisentan could be considered as the most appropriate therapy among the four ERAs for PAH patients. Bosentan also behaved well, but it is not as safe as ambrisentan.

Clinical Adverse Effects of Endothelin Receptor Antagonists: Insights From the Meta-Analysis of 4894 Patients From 24 Randomized Double-Blind Placebo-Controlled Clinical Trials

BACKGROUND

Evidence of the clinical safety of endothelin receptor antagonists (ERAs) is limited and derived mainly from individual trials; therefore, we conducted a meta-analysis.

METHODS AND RESULTS

After systematic searches of the Medline, Embase, and Cochrane Library databases and the ClinicalTrials.gov website, randomized controlled trials with patients receiving ERAs (bosentan, macitentan, or ambrisentan) in at least 1 treatment group were included. All reported adverse events of ERAs were evaluated. Summary relative risks and 95% CIs were calculated using random- or fixed-effects models according to between-study heterogeneity. In total, 24 randomized trials including 4894 patients met the inclusion criteria. Meta-analysis showed that the incidence of abnormal liver function (7.91% versus 2.84%; risk ratio [RR] 2.38, 95% CI 1.36-4.18), peripheral edema (14.36% versus 9.68%; RR 1.44, 95% CI 1.20-1.74), and anemia (6.23% versus 2.44%; RR 2.69, 95% CI 1.78-4.07) was significantly higher in the ERA group compared with placebo. In comparisons of individual ERAs with placebo, bosentan (RR 3.78, 95% CI 2.42-5.91) but not macitentan (RR 1.17, 95% CI 0.42-3.31) significantly increased the risk of abnormal liver function, whereas ambrisentan (RR 0.06, 95% CI 0.01-0.45) significantly decreased that risk. Bosentan (RR 1.47, 95% CI 1.06-2.03) and ambrisentan (RR 2.02, 95% CI 1.40-2.91) but not macitentan (RR 1.08, 95% CI 0.81-1.46) significantly increased the risk of peripheral edema. Bosentan (RR 3.09, 95% CI 1.52-6.30) and macitentan (RR 2.63, 95% CI 1.54-4.47) but not ambrisentan (RR 1.30, 95% CI 0.20-8.48) significantly increased the risk of anemia. ERAs were not found to increase other reported adverse events compared with placebo.

CONCLUSIONS

The present meta-analysis showed that the main adverse effects of treatment with ERAs were hepatic transaminitis (bosentan), peripheral edema (bosentan and ambrisentan), and anemia (bosentan and macitentan).

Increased Red Blood Cell Stiffness Increases Pulmonary Vascular Resistance and Pulmonary Arterial Pressure

Patients with sickle cell anemia (SCD) and pulmonary hypertension (PH) have a significantly increased risk of sudden death compared to patients with SCD alone. Sickled red blood cells (RBCs) are stiffer, more dense, more frequently undergo hemolysis, and have a sixfold shorter lifespan compared to normal RBCs. Here, we sought to investigate the impact of increased RBC stiffness, independent of other SCD-related biological and mechanical RBC abnormalities, on the hemodynamic changes that ultimately cause PH and increase mortality in SCD. To do so, pulmonary vascular impedance (PVZ) measures were recorded in control C57BL6 mice before and after ∼50 μl of blood (Hct = 45%) was extracted and replaced with an equal volume of blood containing either untreated RBCs or RBCs chemically stiffened with glutaraldehyde (Hct = 45%). Chemically stiffened RBCs increased mean pulmonary artery pressure (mPAP) (13.5 ± 0.6 mmHg at baseline to 23.2 ± 0.7 mmHg after the third injection), pulmonary vascular resistance (PVR) (1.23 ± 0.11 mmHg*min/ml at baseline to 2.24 ± 0.14 mmHg*min/ml after the third injection), and wave reflections (0.31 ± 0.02 at baseline to 0.43 ± 0.03 after the third injection). Chemically stiffened RBCs also decreased cardiac output, but did not change hematocrit, blood viscosity, pulmonary arterial compliance, or heart rate. The main finding of this study is that increased RBC stiffness alone affects pulmonary pulsatile hemodynamics, which suggests that RBC stiffness plays an important role in the development of PH in patients with SCD.

Review: Hemodynamic Characteristics and Outcomes of Sickle Cell Disease Associated Pulmonary Hypertension

Pulmonary hypertension (PH) is a leading cause of morbidity and early mortality in adults with sickle cell disease (SCD). However, the prevalence, hemodynamic profile and prognosis of SCD-PH remain controversial and need frequent updates. Pulmonary hypertension determined by right heart catheterization (RHC) occurs in 6% to 10% of adults with SCD. Hemodynamically, SCD-PH may be pre-capillary or post-capillary in nature. The exact etiology is unknown and often multifactorial; hence a thorough diagnostic evaluation following established PH guidelines is essential to determine disease prevalence, etiology and outcomes. Data on the efficacy and safety of pulmonary arterial hypertension (PAH) therapy are limited in SCD; clinical trials in these patients are urgently needed. This review provides an overview of RHC-determined hemodynamic characteristics, current management modality and outcomes; we also highlight recent advances and unmet research needs in SCD-PH.

Endothelin receptor antagonists in sickle cell disease: A promising new therapeutic approach

Sickle cell disease (SCD) is a genetic hematologic disorder that is characterized by a variety of potentially life threatening acute and chronic complications. Currently, hydroxyurea is the only clinically approved pharmacological therapy for the treatment of SCD, and the continued prevalence of severe disease complications underscores the desperate need for the development of new therapeutic agents. Central features of the sickle cell disease milieu, including hypoxia, oxidative stress, and thrombosis, are established enhancers of endothelin-1 (ET-1) synthesis. This conceptual connection between ET-1 and SCD was confirmed by multiple studies that demonstrated markedly elevated plasma and urinary levels of ET-1 in SCD patients. Direct evidence for the involvement of ET-1 signaling in the development of SCD pathologies has come from studies using endothelin receptor antagonists in SCD mice. This review summarizes recent studies that have implicated ET-1 signaling as a mechanistic contributor to renal, vascular, pulmonary, and nociceptive complications of sickle cell disease and discusses the potential for the use of ET receptor antagonists in the treatment of SCD.

Group 5 Pulmonary Hypertension: The Orphan's Orphan Disease

Pulmonary hypertension is a complex disorder with multiple etiologies; the World Health Organization classification system divides pulmonary hypertension patients into 5 groups based on the underlying cause and mechanism. Group 5 pulmonary hypertension is a heterogeneous group of diseases that encompasses pulmonary hypertension secondary to multifactorial mechanisms. For many of the diseases, the true incidence, etiology, and treatment remain uncertain. This article reviews the epidemiology, pathogenesis, and management of many of the group 5 pulmonary hypertension disease states.

Endothelin-Receptor Antagonists beyond Pulmonary Arterial Hypertension: Cancer and Fibrosis

The endothelin axis and in particular the two endothelin receptors, ETA and ETB, are targets for therapeutic intervention in human diseases. Endothelin-receptor antagonists are in clinical use to treat pulmonary arterial hypertension and have been under clinical investigation for the treatment of several other diseases, such as systemic hypertension, cancer, vasospasm, and fibrogenic diseases. In this Perspective, we review the molecules that have been evaluated in human clinical trials for the treatment of pulmonary arterial hypertension, as well as other cardiovascular diseases, cancer, and fibrosis. We will also discuss the therapeutic consequences of receptor selectivity with regard to ETA-selective, ETB-selective, or dual ETA/ETB antagonists. We will also consider which chemical characteristics are relevant to clinical use and the properties of molecules necessary for efficacy in treating diseases against which known molecules displayed suboptimal efficacy.