Pulmonary hypertension in patients with sickle cell disease: a longitudinal study

Prediction of obstetric outcomes in sickle cell patients based on tricuspid regurgitant velocity

Background

Transthoracic echocardiography, a validated tool for risk assessment in non-pregnant population with sickle cell disease (SCD), uses tricuspid regurgitant velocity (TRV) over 2.5 m/s is an independent mortality risk factor. Its applicability in obstetrics lacks sufficient evidence.

Methods

In this multicenter retrospective cohort study across five tertiary centers, we aimed to validate TRV as a determinant of increased maternal and fetal risk. Data was collected on 93 women and included 21 patients with TRV of at least 2.5 m/s. The maternal primary composite outcome included occurrence of vaso-occlusive crisis, acute chest syndrome, gestational hypertension, preeclampsia, and mortality. The fetal primary composite outcome comprised perinatal mortality, premature delivery, reduced birth weight, and fetal distress.

Results

Adverse maternal and fetal events arose in both groups with no statistical difference.

Conclusion

This study cannot support TRV of 2.5 m/s or more as an independent predictor of adverse obstetric outcomes among women with SCD.

Prevalence of Pulmonary Hypertension among Sudanese Patients with Sickle Cell Disease

Background

Sickle Cell Disease (SCD) is a hereditary condition characterized by aberrant red blood cell morphology, leading to persistent hemolytic anemia. The consequential impact of SCD on the pulmonary vasculature can result in pulmonary hypertension (PHT), a severe complication that detrimentally affects the well-being and survival of individuals with SCD. The prevalence and risk determinants of PHT in SCD patients exhibit variations across diverse geographical regions and populations. This study aims to ascertain the prevalence of PHT among Sudanese SCD patients and identify associated factors.

Methods

A cohort of thirty-one adult sickle cell disease (SCD) patients, as confirmed by hemoglobin electrophoresis, were recruited for participation in this cross-sectional study. Comprehensive data encompassing demographic, clinical, and laboratory parameters were collected. Doppler echocardiography was employed to quantify pulmonary arterial systolic pressure (PASP) and evaluate right ventricular size and function.

Results

Within our cohort, the prevalence of PHT was 29%. Active cigarette smoking demonstrated a significant association with PHT (P=0.042), while hydroxyurea therapy exhibited no noticeable impact on PHT (P=0.612).

Conclusion

Our investigation revealed a PHT prevalence of less than one-third in our SCD patient population, aligning with prior studies. Notably, independent of other factors, cigarette smoking emerged as a distinct risk factor for PHT in SCD patients. This highlights the potential utility of smoking cessation as an intervention to delay the onset of this condition. However, further research is imperative to elucidate the mechanisms through which smoking contributes to PHT development in individuals with SCD.

Nontargeted Plasma Proteomic Analysis of Renal Disease and Pulmonary Hypertension in Patients with Sickle Cell Disease

Sickle cell disease (SCD) is characterized by red blood cell sickling, vaso-occlusion, hemolytic anemia, damage to multiple organ systems, and, as a result, shortened life expectancy. Sickle cell disease nephropathy (SCDN) and pulmonary hypertension (pHTN) are common and frequently co-occurring complications of SCD; both are associated with markedly accelerated mortality. To identify candidate circulating biomarkers of SCDN and pHTN, we used mass spectrometry to quantify the relative abundance of >1000 proteins in plasma samples from 189 adults with SCD from the Outcome Modifying Genes in SCD (OMG-SCD) cohort (ProteomeXchange identifier PXD048716). Forty-four proteins were differentially abundant in SCDN, most significantly cystatin-C and collagen α-1(XVIII) chain (COIA1), and 55 proteins were dysregulated in patients with SCDN and pHTN, most significantly insulin-like growth factor-binding protein 6 (IBP6). Network analysis identified a module of 133 coregulated proteins significantly associated with SCDN, that was enriched for extracellular matrix proteins, insulin-like growth factor binding proteins, cell adhesion proteins, EGF-like calcium binding proteins, and several cadherin family members. Collectively, these data provide a comprehensive understanding of plasma protein changes in SCDN and pHTN which validate numerous studies of chronic kidney disease and suggest shared profiles of protein disruption in kidney dysfunction and pHTN among SCD patients.

Pulmonary hypertension screening in children with sickle cell disease

BACKGROUND

Screening for pulmonary hypertension (PHT) is recommended in children with sickle cell disease (SCD). However, best approaches are poorly described. We examined the utility of PHT symptoms, echocardiogram (ECHO), N-terminal-pro hormone brain natriuretic peptide (NT-proBNP), and BNP to screen for PHT in the SCD pediatric population.

METHODS

Children (8-18 years old) with SCD-HbSS and HbSthal° were prospectively included and underwent PHT screening. The screening consisted of a comprehensive PHT symptoms evaluation, ECHO measurement, and NT-proBNP and BNP levels.

RESULTS

A total of 73 patients were included (mean age 12 ± 5.7 years; >80% on hydroxyurea), of which 37% had a symptom consistent with PHT, including exertional dyspnea (26.5%), fatigue (17.6%), palpitation (14.7%), and chest pain (10.3%). ECHO was obtained in 53 (72.6%) patients, with only ECHO of 48 patients included in the final analysis. Elevated ECHO peak tricuspid regurgitant jet velocity (TRV) >2.5 m/s or indirect findings to suggest PHT were seen in only two of 48 (4.2%). No significant differences were seen between those with and without PHT symptoms when compared for NT-proBNP, BNP, hemoglobin, pulmonary function testing, fractional exhaled nitric oxide, asthma, oxygen saturation, and sleep apnea.

CONCLUSION

PHT symptoms are not consistent with ECHO, NT-proBNP nor BNP findings in children with SCD. PHT prevalence based on TRV was low in children on hydroxyurea, therefore screening may not be warranted for this group.

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.

High risk and low prevalence diseases: Acute chest syndrome in sickle cell disease

INTRODUCTION

Acute chest syndrome (ACS) in sickle cell disease (SCD) is a serious condition that carries with it a high rate of morbidity and mortality.

OBJECTIVE

This review highlights the pearls and pitfalls of ACS in SCD, including diagnosis and management in the emergency department (ED) based on current evidence.

DISCUSSION

ACS is defined by respiratory symptoms and/or fever and a new radiodensity on chest imaging in a patient with SCD. There are a variety of inciting causes, including infectious and non-infectious etiologies. Although ACS is more common in those with homozygous SCD, clinicians should consider ACS in all SCD patients, as ACS is a leading cause of death in SCD. Patients typically present with or develop respiratory symptoms including fever, cough, chest pain, and shortness of breath, which can progress to respiratory failure requiring mechanical ventilation in 20% of adult patients. However, the initial presentation can vary. While the first line imaging modality is classically chest radiograph, lung ultrasound has demonstrated promise. Further imaging to include computed tomography may be necessary. Management focuses on analgesia, oxygen supplementation, incentive spirometry, bronchodilators, rehydration, antibiotics, consideration for transfusion, and specialist consultation. Empiric antibiotics that cover atypical pathogens are necessary along with measures to increase oxygen-carrying capacity in those with hypoxemia such as simple transfusion or exchange transfusion.

CONCLUSIONS

An understanding of ACS can assist emergency clinicians in diagnosing and managing this potentially deadly disease.

Endothelial superoxide dismutase 2 is decreased in sickle cell disease and regulates fibronectin processing

Sickle cell disease (SCD) is a genetic red blood cell disorder characterized by increased reactive oxygen species (ROS) and a concordant reduction in antioxidant capacity in the endothelium. Superoxide dismutase 2 (SOD2) is a mitochondrial-localized enzyme that catalyzes the dismutation of superoxide to hydrogen peroxide. Decreased peripheral blood expression of SOD2 is correlated with increased hemolysis and cardiomyopathy in SCD. Here, we report for the first time that endothelial cells exhibit reduced SOD2 protein expression in the pulmonary endothelium of SCD patients. To investigate the impact of decreased SOD2 expression in the endothelium, SOD2 was knocked down in human pulmonary microvascular endothelial cells (hPMVECs). We found that SOD2 deficiency in hPMVECs results in endothelial cell dysfunction, including reduced cellular adhesion, diminished migration, integrin protein dysregulation, and disruption of permeability. Furthermore, we uncover that SOD2 mediates changes in endothelial cell function via processing of fibronectin through its inability to facilitate dimerization. These results demonstrate that endothelial cells are deficient in SOD2 expression in SCD patients and suggest a novel pathway for SOD2 in regulating fibronectin processing.

Implications for the Metabolic Fate of Oral Glutamine Supplementation within Plasma and Erythrocytes of Patients with Sickle Cell Disease: A Pharmacokinetics Study

OBJECTIVES

L-Glutamine is FDA-approved for sickle cell disease (SCD), yet the mechanism(s)-of-action are poorly understood. We performed a pharmacokinetics (pK) study to determine the metabolic fate of glutamine supplementation on plasma and erythrocyte amino acids in patients with SCD.

DESIGN

A pK study was performed where patients with SCD fasting for >8hours received oral L-glutamine (10 grams). Blood was analyzed at baseline, 30/60/90minutes/2/3/4/8 hrs. A standardized diet was administered to all participants at 3 established time-points (after 2/5/7hrs). A subset of patients also had pK studies performed without glutamine supplementation to follow normal diurnal fluctuations in amino acids.

SETTING

Comprehensive SCD Center in Oakland, California RESULTS: Five patients with SCD were included, three of whom performed pK studies both with and without glutamine supplementation. Average age was 50.6 ± 5.6 years, 60% were female, 40% SS, 60% SC. Plasma glutamine levels increased significantly after oral glutamine supplementation, compared to minimal fluctuations with diet. Plasma glutamine concentration peaked within 30-minutes of ingestion (p=0.01) before decreasing to a plateau by 2-hours that remained higher than baseline by 8hours. Oral glutamine also increased plasma arginine concentration, which peaked by 4-hrs (p=0.03) and remained elevated through 8-hrs. Erythrocyte glutamine levels began to increase by 8-hours, while erythrocyte arginine concentration peaked at 4-hours.

CONCLUSIONS

Oral glutamine supplementation acutely improved glutamine and arginine bioavailability in both plasma and erythrocytes. This is the first study to demonstrate that glutamine therapy increases arginine bioavailability and may provide insight into shared mechanisms-of-action between these conditionally-essential amino acids.

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.

Sickle Cell Disease-Induced Pulmonary Hypertension: A Review of Pathophysiology, Management, and Current Literature

Sickle cell disease is an inherited hemoglobinopathy leading to the synthesis of hemoglobin S. Hemoglobin S results in the formation of abnormal sickle-shaped erythrocytes that lead to hematologic abnormalities such as hemolytic anemia and increased risks of thrombosis. Another particular problem encountered with the disease is pulmonary hypertension. The objective of this narrative review is to discuss the prevalence, pathophysiology mechanisms, diagnostic techniques, treatment options, and prognostic indicators in the setting of sickle cell disease with pulmonary hypertension. Additionally, the review also highlights other advancements that are being investigated. Considering the significant morbidity, mortality, and prevalence of pulmonary hypertension in patients with sickle cell disease, it is important to account for the aforementioned domains in the future guidelines to provide optimal and individualized care to the high-risk individuals as well as reduce the progression of disease, morbidity, and mortality rates.

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.

Fluid overload due to intravenous fluid therapy for vaso-occlusive crisis in sickle cell disease: incidence and risk factors

Intravenous fluid therapy (IV‐FT) is routinely used in the treatment of vaso‐occlusive crises (VOCs), as dehydration possibly promotes and sustains erythrocyte sickling. Patients with sickle cell disease (SCD) are at risk of developing diastolic dysfunction and fluid overload due to IV‐FT. However, data on the adverse effects of IV‐FT for VOC is sparse. We aimed to evaluate the incidence and risk factors of fluid overload due to IV‐FT in patients with SCD. Consecutive hospitalisations for VOC treated with IV‐FT between September 2016 and September 2018 were retrospectively analysed. The median (interquartile range) age was 25·0 (18·3–33·8) years and 65% had a severe genotype (HbSS/HbSβ⁰‐thal). Fluid overload occurred in 21% of 100 patients. Hospital stay was longer in patients with fluid overload (6·0 vs. 4·0 days, P = 0·037). A positive history of fluid overload (P = 0·017), lactate dehydrogenase level (P = 0·011), and top‐up transfusion during admission (P = 0·005) were independently associated with fluid overload occurrence. IV‐FT was not reduced in 86% of patients despite a previous history of fluid overload. Fluid overload is frequently encountered during IV‐FT for VOC. IV‐FT is often not adjusted despite a positive history of fluid overload or when top‐up transfusion is indicated, emphasising the need for more awareness of this complication and a personalised approach.

Variation in pulmonary function tests among children with sickle cell anemia: a systematic review and meta-analysis

INTRODUCTION

the spectrum of pulmonary complications in sickle cell anemia (SCA) comprises mainly of acute chest syndrome (ACS), pulmonary hypertension (PH) and airway hyper-responsiveness (AHR). This study was conducted to examine the abnormalities in pulmonary function tests (PFTs) seen in children with SCA.

METHODS

electronic databases (Cochrane library, PubMed, EMBASE, Scopus, Web of Science) were used as data sources. Two authors independently reviewed studies. All case-control studies with PFT performed in patients with SCA and normal controls were reviewed. Pulmonary functions were assessed with the help of spirometry, lung volume and gas diffusion findings.

RESULTS

nine studies with 788 SCA children and 1101 controls were analyzed. For all studies, the pooled mean difference for forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, peak expiratory flow rate (PEFR), total lung capacity (TLC) and carbon mono-oxide diffusing capacity (DLCO) were -12.67, (95% CI: -15.41,-9.94), -11.69, (95% CI: -14.24, -9.14), -1.90, (95% CI: -4.32, 0.52), -3.36 (95% CI: -6.69, -0.02), -7.35, (95% CI: -14.97, -0.27) and -4.68, (95% CI -20.64, -11.29) respectively. FEV1 and FVC and were the only parameters found to be significantly decreased.

CONCLUSION

sickle cell anemia was associated with lower FEV1 and FVC, thus, supporting the role of routine monitoring for the progression of lung function decline in children with SCA with ACS. We recommend routine screening and lung function monitoring for early recognition of pulmonary function decline.

Enlarged pulmonary artery on computed tomography and respiratory failure in sickle cell disease acute chest syndrome

Predicting the severity of acute chest syndrome is an important research priority in sickle cell disease. In this retrospective study of patients with acute chest syndrome, an enlarged pulmonary artery on computed tomography was associated with severe respiratory failure defined by the need for either noninvasive or mechanical ventilation.

Longitudinal effect of disease-modifying therapy on tricuspid regurgitant velocity in children with sickle cell anemia

Elevated tricuspid regurgitant velocity (TRV) ≥2.5 m/s is a predictor of disease severity in adults and children with sickle cell anemia (SCA), but how disease-modifying therapies (DMTs) affect this biomarker is incompletely understood. We investigated the effect of DMTs on TRV elevation in children. In a prospective single-center study, 204 subjects with HbSS or HbSβ0 thalassemia (mean age, 10.6 years; range, 5-18) had echocardiograms with assessment of TRV, with repeat evaluations after 2 years of observation. One-hundred and twelve participants received DMTs (hydroxyurea, n = 72; monthly erythrocyte transfusions, n = 40), 58 did not receive any DMT, and 34 were begun on hydroxyurea during this observation period. In the entire cohort, an increase in hemoglobin of 1.0 g/dL was associated with a 0.03-m/s decrease in TRV (P = .024), and a decrease in absolute reticulocyte count of 1.0 × 106/mL was associated with a 0.34-m/s decrease in TRV (P = .034). Compared with baseline, hydroxyurea exposure (continuous or newly started) was associated with an average 5% decline in mean TRV at the 2-year evaluation. Among participants newly started on hydroxyurea (mean treatment duration 1.2 ± 0.6 years), an increase in hemoglobin of 1.0 g/dL was associated with a 0.06-m/s decrease in TRV (P = .05). We conclude that hydroxyurea therapy may mitigate TRV elevation in children with SCA, possibly as a result of a reduction in hemolysis and improvement in anemia.

Tricuspid regurgitant jet velocity and myocardial tissue Doppler parameters predict mortality in a cohort of patients with sickle cell disease spanning from pediatric to adult age groups - revisiting this controversial concept after 16 years of additional evidence

Sickle cell disease (SCD) is a monogenic hemoglobinopathy associated with significant morbidity and mortality. Cardiopulmonary, vascular and sudden death are the reasons for the majority of young adult mortality in SCD. To better understand the clinical importance of multi-level vascular dysfunction, in 2009 we assessed cardiac function including tricuspid regurgitant jet velocity (TRV), tissue velocity in systole(S') and diastole (E'), inflammatory, rheologic and hemolytic biomarkers as predictors of mortality in patients with SCD. With up to 9 years of follow up, we determined survival in 95 children, adolescents and adults with SCD. Thirty-eight patients (40%) were less than 21 years old at initial evaluation. Survival and Cox proportional-hazards analysis were performed. There was 19% mortality in our cohort, with median age at death of 35 years. In the pediatric subset, there was 11% mortality during the follow up period. The causes of death included cardiovascular and pulmonary complications in addition to other end-organ failure. On Cox proportional-hazards analysis, our model predicts that a 0.1 m/s increase in TRV increases risk of mortality 3%, 1 cm/s increase in S' results in a 91% increase, and 1 cm/s decrease in E' results in a 43% increase in mortality. While excluding cardiac parameters, higher plasma free hemoglobin was significantly associated with risk of mortality (p=.049). In conclusion, elevated TRV and altered markers of cardiac systolic and diastolic function predict mortality in a cohort of adolescents and young adult patients with SCD. These predictors should be considered when counseling cardiovascular risk and therapeutic optimization at transition to adult providers.

Prognostic value of left ventricular longitudinal strain by speckle-tracking echocardiography in patients with sickle cell disease

Cardiovascular complications have been increasingly detected in patients with sickle cell disease (SCD). Two-dimensional speckle-tracking echocardiography (STE) detects early myocardial changes in a number of pathophysiological processes, which may be useful in SCD. This study was designed to examine the value of STE in predicting clinical outcome in adult patients with SCD. A total of 219 patients, mean age 33 ± 12 years were prospectively enrolled. Several clinical, laboratory and echocardiographic variables including left ventricular global longitudinal strain (LVGLS) by STE were assessed. The endpoint was a composite of the following events: (1) all-cause mortality, (2) three or more acute painful episodes that require hospitalization in one year, (3) acute chest syndrome and (4) hospitalization due to disease complication. The majority of the patients had enlargement of LV and left atrial (LA) with preserved ejection fraction. During the mean follow-up of 30 months, 69 patients (32%) had reached the endpoint, including eight deaths (3.7%). No difference was observed in the parameters of diastolic function comparing the patients with and without events. LVGLS ranged from - 12.25 to - 25.44 (mean - 20.26 ± 2.5), with higher values in the patients who had events compared with those who did not. In the multivariable analysis, higher LVGLS values were associated with adverse events (adjusted OR 1.25; 95% CI 1.04-1.51; p = 0.021), independently of the TR maximal velocity and LV ejection fraction. In patients with SCD, higher LV global longitudinal strain was a predictor of adverse outcome, independently of age, TR velocity and LV function.

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.

Sickle cell disease as a vascular disorder

INTRODUCTION

In sickle cell disease (SCD), hemoglobin S (HbS) red blood cells (RBCs) are characteristically deformed and inflexible. Often breaking down in the circulation, they exhibit increased adhesive properties with the endothelium and activated neutrophils and platelets, increasing the risk of occlusion of the microcirculation. SCD is categorized into two sub-phenotypes: hyperhemolytic, associated with priapism, leg ulcers, pulmonary hypertension, and stroke, and high hemoglobin/viscosity, which may promote vaso-occlusion-associated pain, acute chest syndrome, and osteonecrosis.

AREAS COVERED

The sub-phenotypes are not completely distinct. Hemolysis may trigger vaso-occlusion, contributing to vascular complications. Targeting P-selectin, a key mediator of cross-talk between hyperhemolysis and vaso-occlusion, may be beneficial for vascular and vaso-occlusion-associated complications. English-language articles from PubMed on the topic of SCD and vaso-occlusive crises (VOCs) were reviewed from 1 January 2000 to 1 January 2019 using the search terms 'sickle cell disease,' 'vaso-occlusive crises,' and 'selectin.'

EXPERT OPINION

Besides targeting P-selectin, other strategies to counter VOCs and RBC sickling are being pursued. These include platelet inhibition to counter aggregation, intercellular adhesion, and thrombosis during VOCs; gene therapy to correct the homozygous missense mutation in the β-globin gene, causing polymerization of HbS; L-glutamine, possibly reducing oxidative stress in sickled RBCs; and fetal hemoglobin inducers.

Cardiovascular Sequelae of Sickle Cell Disease

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide. It is a multisystem disease that causes considerable patient morbidity. Despite advances in medical treatment, cardiopulmonary complications remain the most common cause of death in individuals with SCD. A growing body of evidence has shown that SCD results in a spectrum of cardiovascular complications through a variety of mechanisms, including chronic hemolysis, local tissue hypoxia, increased oxidative stress, and autonomic instability. Herein, we will examine the pathophysiology of sickle cell vasculopathy and discuss the spectrum of cardiovascular sequelae of the disease, while highlighting the impact of SCD on the cardiovascular health of the patients.

Low hemoglobin increases risk for cerebrovascular disease, kidney disease, pulmonary vasculopathy, and mortality in sickle cell disease: A systematic literature review and meta-analysis

Sickle cell disease (SCD) is characterized by deoxygenation-induced polymerization of hemoglobin in red blood cells, leading to hemolytic anemia, vaso-occlusion, and the development of multiple clinical complications. To characterize the clinical burden associated with differences in hemoglobin concentration and hemolysis measures, a systematic literature review of MEDLINE, EMBASE, and related meta-analyses was undertaken. For quantitative analyses related to hemoglobin concentration, pooled results were analyzed using random effects models to control for within-and between-study variability. To derive risk ratios associated with hemoglobin concentration change, we combined ratios of means from select studies, which reported hazard and odds ratios in meta-analyses for hemoglobin concentration-related outcomes and changes between groups. Forty-one studies were identified for inclusion based on relating hemoglobin concentration to clinical outcomes. Meta-analyses demonstrated that mean hemoglobin concentration was significantly lower in patients with cerebrovascular disease (0.4 g/dL), increased transcranial Doppler velocity in cerebral arteries (0.6 g/dL), albuminuria (0.6 g/dL), elevated estimated pulmonary artery systolic pressure (0.9 g/dL), and in patients that subsequently died (0.6 g/dL). In a risk reduction meta-analysis, modeled increased hemoglobin concentrations of 1 g/dL or greater resulted in decreased risk of negative clinical outcomes of 41% to 64%. In conclusion, chronic anemia is associated with worse clinical outcomes in individuals with SCD and even modest increases in hemoglobin concentration may be beneficial in this patient population. This systematic review has been registered on Prospero (Registration number CRD42018096860; https://www.crd.york.ac.uk/prospero/).

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.

Echocardiographic Screening of Cardiovascular Status in Pediatric Sickle Cell Disease

Although elevated right ventricular pressure and left ventricular diastolic dysfunction measured by echocardiogram are independent predictors of death in adults with sickle cell disease (SCD), the utility of routine echocardiographic screening in the pediatric population is controversial. We performed a 3-year retrospective review of children ≥ 10 years of age with SCD who underwent an outpatient transthoracic echocardiogram as part of a screening program. Of 172 patients referred for screening, 105 (61%) had a measurable tricuspid regurgitation jet velocity (TRV): median 2.4 m/s (IQR 2.3-2.5). Elevated right ventricular (RV) pressure (TRV ≥ 2.5 m/s, 25 mmHg), documented in 30% (32/105), was significantly associated with chronic transfusion therapy and elevated lactate dehydrogenase. Left ventricle (LV) dilation, documented in 25% (44/172), was significantly associated with lower hemoglobin, and higher reticulocyte count, lactate dehydrogenase level, and bilirubin level. There was no association between elevated right ventricular pressure or left ventricle dilation and indices of biventricular systolic or diastolic function. The one death in the cohort during the study period had normal echocardiographic findings. In conclusion, mild RV pressure elevation and LV dilation in children with SCD is associated with abnormal laboratory markers of disease severity, but not with ventricular dysfunction over the 3-year study period.

Renal abnormalities among children with sickle cell conditions in highly resource-limited setting in Ghana

Sickle cell disease (SCD) is associated with progressive multi-organ failure especially, the brain and kidney and leads to high morbidity and mortality rate. The aim of this study was to determine the prevalence of renal abnormalities among children with SCD. This cross-sectional study recruited 212 sickling positive patients comprising of 96 Hb AS, 48 Hb SC, and 68 Hb SS phenotypes from the Pediatric Unit of Wassa Akropong Government Hospital, Wassa Akropong, Ghana. Early morning urine and venous blood samples were collected from each participant. Urinalysis was conducted and serum urea and creatinine levels were estimated. Estimate glomerular filtration rate (eGFR) was calculated using the Swartz equation. Classification of chronic kidney disease (CKD) was based on 'The Kidney Disease: Improving Global Outcomes (KIDIGO)' criteria. The mean age of the children were 7.90 years. Serum creatinine (p = 0.0310) and urea (p<0.0001) levels were significantly higher among Hb AS participants compared with Hb SS phenotype. The prevalent indicators of renal abnormalities were proteinuria (26.4%), urine granular cast (5.6%) and CKD (39.6%). Proteinuria, urine granular cast and CKD were most prevalent among Hb SS (47.1%, 11.8% and 73.5% respectively) compared with Hb SC (41.7%, 8.3%, and 45.8% respectively) and Hb AS (4.2%, 0.0%, and 14.5%) phenotypes, respectively. Sickle cell conditions were significantly associated with proteinuria (p<0.0001) and CKD (p = 0.0378). Children with Hb SS [aOR = 5.04, 95% CI (2.47-10.3); p<0.0001] and Hb SC [aOR = 3.14 95% CI (1.39-7.01); p = 0.0174] were at increased odds of developing CKD after adjusting for age, BMI and gender. Proteinuria and CKD are associated with sickle cell disease (Hb SC and Hb SS). Renal function should be routinely monitored for children with SCD.

Allogeneic Hematopoietic Stem Cell Transplantation for Adults with Sickle Cell Disease

Sickle cell disease (SCD) is an inherited red blood cell disorder that leads to substantial morbidity and early mortality. Acute and chronic SCD-related complications increase with older age, and therapies are urgently needed to treat adults. Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative therapy, but has been used less frequently in adults compared to children. This is, in part, due to (1) greater chronic organ damage, limiting tolerability to myeloablative conditioning regimens, (2) a higher rate of HSCT-related complications in adults versus children with SCD, and (3) limited coverage by public and private health insurance. Newer approaches using nonmyeloablative and reduced-intensity conditioning HSCT regimens have demonstrated better safety and tolerability, with high rates of stable engraftment in SCD adults. This review will focus on the impacts of HSCT, using more contemporary approaches to SCD-related complications in adults.

In-hospital Outcomes and Characteristics of Heart Failure in Sickle Cell Disease

Sickle cell disease (SCD) predominantly affects African-Americans (AAs) in the United States (US). Due to increasing life expectancy in developed countries, SCD-associated cardiomyopathy is typically seen in adults. The aim of this study was to distinguish hospitalization for this phenotype from traditional heart failure (HF) in AAs. We used the National Inpatient Sample (NIS) database to identify HF hospitalizations in AAs between 2005 and 2014 and stratified them according to SCD status. We compared the characteristics and outcomes before and after matching in a 1:3 ratio for age, gender, insurance, smoking status and admission year. Amongst the 1,195,718 HF admissions in AAs, SCD accounted for 7835. The age (mean ± SD) in the SCD cohort was significantly younger (45.66 ± 13.2) vs non-SCD (64.8 ± 15.2), p<0.001. SCD adults had significantly higher rates of pulmonary hypertension (PH), deep vein thrombosis, and pulmonary embolism while non-SCD adults had higher rates of cardiogenic shock and respiratory failure requiring intubation. The national hospitalization rate for HF in AAs increased from 151 to 257 per million between 2005 and 2011 before declining to 241 per million in 2014. There was a decrease in in-hospital mortality in AAs from 4.8% in 2005 to 3.6% in 2014. We also identified independent predictors of in-hospital mortality in SCD with HF. In conclusion, we described hospitalizations for an emerging heart failure phenotype in AAs. Although there is a national decreasing rate of HF hospitalizations in the US, this may not be reflective of the AA population.

Elevated tricuspid regurgitation velocity in congenital hemolytic anemias: Prevalence and laboratory correlates

Elevated tricuspid valve regurgitation jet velocity (TRV ≥ 2.5 m/s) is associated with mortality among adults with sickle cell disease (SCD), but correlative biomarkers are not studied according to treatment exposure or genotypes. To investigate the associations between biomarkers and TRV elevation, we examined the relationship between TRV and hemolytic, inflammatory, and cardiac biomarkers, stratified by disease-modifying treatments and SCD genotype. In total, 294 participants with SCD (mean age, 11.0 ± 3.7 years) and 49 hereditary spherocytosis (HS; mean age, 22.9 ± 19.75 years) were included for comparison and enrolled. TRV was elevated in 30.7% of children with SCD overall: 18.8% in HbSC/HbSβ⁺ -thalassemia, 28.9% in untreated HbSS/HbSβ⁰ -thalassemia, 34.2% in HbSS/HbSβ⁰ -thalassemia hydroxyurea-treated, and 57% in HbSS/HbSβ⁰ -thalassemia chronic transfusion treated. TRV was elevated in 10.7% and 27.8% in HS children and adults, respectively. In children with SCD, elevated TRV was correlated with hemoglobin (odds ratio [OR] = 0.78, P = 0.004), lactate dehydrogenase (LDH; OR = 2.52, P = 0.005), and N-terminal pro-brain natriuretic peptide (NT-pro BNP; OR = 1.003, P = 0.004). In multivariable logistic regression, adjusting for genotype, sex, hemolytic index, and treatment, hemoglobin concentration remained the only significant variable associated with elevated TRV in untreated HbSS/HbSβ⁰ -thalassemia participants. TRV was not associated with inflammatory markers, other markers of hemolysis, or NT-pro BNP in untreated HbSS/HbSβ⁰ -thalassemia. Neither hemoglobin nor LDH was associated with TRV in HbSC/HbSβ⁺ -thalassemia. These results suggest that elevated TRV is influenced by the degree of anemia, possibly reflecting sickling as part of the disease pathophysiology. Prospective studies should monitor hemoglobin concentration as children with SCD age into adulthood, prompting initiation of TRV screening and monitoring.

CD34+ Hematopoietic Stem Cell Count Is Predictive of Vascular Event Occurrence in Children with Sickle Cell Disease

BACKGROUND/OBJECTIVES

Sickle cell disease (SCD) complications mostly result from vascular dysfunction, concerning systemic microvasculature and cerebral large vessels. The aim of this cohort study was to identify potential circulating biomarkers predictive for further vascular event occurrence in pediatric SCD.

METHODS

We consecutively enrolled 108 children with SCD at steady state, aged 3-18 years old (median 9.8 years). Hematology, coagulation, hemolysis, endothelial, platelet and vascular activation parameters were recorded at inclusion. Neurovascular and systemic vascular events were prospectively recorded during a mean follow-up period of 27 months.

RESULTS

Patients at steady state displayed significantly higher hemolysis and platelet activation markers, higher leukocyte, CD34+ hematopoietic stem cell and microvesicle counts, and a pro-coagulant profile compared to controls matched for age and ethnicity. Circulating endothelial cell or nucleosome level did not differ. During the follow-up period, 36 patients had at least one neurovascular (n = 12) or systemic vascular event (n = 25). In a multivariate model, high CD34+ cell count was the best predictor for the occurrence of a vascular event (OR 1.2 for 1000 cell/mL increase, 95% CI [1.049-1.4], p = 0.013, sensitivity 53%, specificity 84% for a threshold of 8675 cells/mL).

CONCLUSION

CD34+ cell count at steady state is a promising biomarker of further vascular event in children with SCD.

New Nitric Oxide Donor NCX 1443: Therapeutic Effects on Pulmonary Hypertension in the SAD Mouse Model of Sickle Cell Disease

Nitric oxide (NO) donors may be useful for treating pulmonary hypertension (PH) complicating sickle cell disease (SCD), as endogenous NO is inactivated by hemoglobin released by intravascular hemolysis. Here, we investigated the effects of the new NO donor NCX1443 on PH in transgenic SAD mice, which exhibit mild SCD without severe hemolytic anemia. In SAD and wild-type (WT) mice, the pulmonary pressure response to acute hypoxia was similar and was abolished by 100 mg/kg NCX1443. The level of PH was also similar in SAD and WT mice exposed to chronic hypoxia (9% O2) alone or with SU5416 and was similarly reduced by daily NCX1443 gavage. Compared with WT mice, SAD mice exhibited higher levels of HO-1, endothelial NO synthase, and PDE5 but similar levels of lung cyclic guanosine monophosphate. Cultured pulmonary artery smooth muscle cells from SAD mice grew faster than those from WT mice and had higher PDE5 protein levels. Combining NCX1443 and a PDE5 inhibitor suppressed the growth rate difference between SAD and WT cells and induced a larger reduction in hypoxic PH severity in SAD than in WT mice. By amplifying endogenous protective mechanisms, NCX1443 in combination with PDE5 inhibition may prove useful for treating PH complicating SCD.

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.

Pathophysiology of Sickle Cell Disease

Since the discovery of sickle cell disease (SCD) in 1910, enormous strides have been made in the elucidation of the pathogenesis of its protean complications, which has inspired recent advances in targeted molecular therapies. In SCD, a single amino acid substitution in the β-globin chain leads to polymerization of mutant hemoglobin S, impairing erythrocyte rheology and survival. Clinically, erythrocyte abnormalities in SCD manifest in hemolytic anemia and cycles of microvascular vaso-occlusion leading to end-organ ischemia-reperfusion injury and infarction. Vaso-occlusive events and intravascular hemolysis promote inflammation and redox instability that lead to progressive small- and large-vessel vasculopathy. Based on current evidence, the pathobiology of SCD is considered to be a vicious cycle of four major processes, all the subject of active study and novel therapeutic targeting: ( a) hemoglobin S polymerization, ( b) impaired biorheology and increased adhesion-mediated vaso-occlusion, ( c) hemolysis-mediated endothelial dysfunction, and ( d) concerted activation of sterile inflammation (Toll-like receptor 4- and inflammasome-dependent innate immune pathways). These molecular, cellular, and biophysical processes synergize to promote acute and chronic pain and end-organ injury and failure in SCD. This review provides an exhaustive overview of the current understanding of the molecular pathophysiology of SCD, how this pathophysiology contributes to complications of the central nervous and cardiopulmonary systems, and how this knowledge is being harnessed to develop current and potential therapies.

Lower than expected elevated tricuspid regurgitant jet velocity in adults with sickle cell disease in Nigeria

Background

Cardiopulmonary disease is a major cause of morbidity and mortality in persons with sickle cell disease (SCD). Tricuspid regurgitant jet velocity (TRJV) and predicted forced expiratory volume in 1 s (FEV1%) predicted are independently associated with death in SCD. The goal of this study was to determine the prevalence of elevated TRJV and the association, if any, between TRJV and FEV1% predicted among persons with sickle cell anaemia (SCA) in Nigeria.

Methods

Using a cross-sectional design, we enrolled 100 adult Nigerians (≥15 y) with SCA. We screened participants using Doppler echocardiogram to determine their TRJV and assessed their lung function with spirometry.

Results

The prevalence of elevated TRJV was 6%, with 74% of participants having low FEV1% predicted (<70%). TRJV was negatively correlated with FEV1%, but this finding was not statistically significant (Spearman's ρ=-0.0263, p=0.8058).

Conclusions

We found a low prevalence of elevated TRJV and a trend in association between TRJV and FEV1% predicted in Nigerian adults with SCA. Our findings underscore the need to explore further the relationship between SCD and cardiopulmonary disease in adults.

Advances in new drug therapies for the management of sickle cell disease

Introduction

Sickle cell disease (SCD) is an orphan disease in the United States, but is highly prevalent worldwide. Only two drugs, hydroxyurea and L-glutamine, are approved for this disease. With an improved understanding of the pathophysiology of SCD as well as the success of several recently approved drugs for other orphan diseases, there is an increased interest in the development of drugs for SCD.

Areas covered

This review summarizes published studies of drug therapies and ongoing trials of novel agents.

Expert opinion

The development of drugs with different mechanisms of action offers opportunities for combination and individualized therapy in SCD. In addition to acute pain crisis, the evaluation of other SCD-related complications, exercise capacity, patient reported outcomes and validated surrogate endpoints are necessary to advance drug development. It is important to involve sites in sub-Saharan Africa and India, which have the highest burden of SCD, in trials of novel therapies.

Levels of Soluble Endothelium Adhesion Molecules and Complications among Sickle Cell Disease Patients in Ghana

BACKGROUND

Soluble adhesion molecules are involved in the gathering and joining of inflammatory cells to vascular endothelium. Therefore, they serve as potential markers of endothelial dysfunction in vascular diseases including sickle cell disease (SCD). In Ghana, there are scarcely any report on the levels of adhesion molecules among SCD patients. The current study aimed to determine plasma levels of ICAM-1, VCAM-1 and E-Selectin as markers of endothelial dysfunction in SCD patients in steady state, complications and controls.

METHODOLOGY

This was a cross-sectional study involving 60 HbAA controls, 46 HbSS steady state, 57 HbSS VOC, 18 HbSC VOC, 21 HbSS with leg ulcer and 11 HbSS with priapism. Blood samples were collected from all the study subjects (n = 213) and processed into plasma. The plasma levels of VCAM-1, ICAM-1 and E-Selectin concentrations of SCD patients and controls were measured using a double sandwich ELISA technique. Demographic information was also collected from the study subjects.

RESULTS

Levels of all soluble proteins (ICAM-1, VCAM-1 and E-Selectin) were significantly higher in HbSS steady-state patients compared to non-SCD controls (p < 0.001). Generally, SCD patients with complications had relatively higher levels of the soluble proteins compared to those in the steady-state. Of the SCD patients with complications, those with vaso-occlusion crisis (HbSS VOC) had relatively higher levels of ICAM-1, VCAM-1 and E-Selectin at (62.42 ng/mL &plusmn; 26.09), (634.99 ng/mL &plusmn; 324.31) and (236.77 ng/mL &plusmn; 114.40) respectively; Conclusion: Although levels of adhesion molecules were high in all the SCD patients with complications, those with vaso-occlusive crisis had higher levels. This might reflect an ongoing endothelial dysfunction in these patients. SCD patients with vaso-occlusive crisis presents with a more severe pathophysiology condition.

Pulmonary vascular endothelium: the orchestra conductor in respiratory diseases

The European Respiratory Society (ERS) Research Seminar entitled “Pulmonary vascular endothelium: orchestra conductor in respiratory diseases - highlights from basic research to therapy” brought together international experts in dysfunctional pulmonary endothelium, from basic science to translational medicine, to discuss several important aspects in acute and chronic lung diseases. This review will briefly sum up the different topics of discussion from this meeting which was held in Paris, France on October 27–28, 2016. It is important to consider that this paper does not address all aspects of endothelial dysfunction but focuses on specific themes such as: 1) the complex role of the pulmonary endothelium in orchestrating the host response in both health and disease (acute lung injury, chronic obstructive pulmonary disease, high-altitude pulmonary oedema and pulmonary hypertension); and 2) the potential value of dysfunctional pulmonary endothelium as a target for innovative therapies.

Nitric oxide pathology and therapeutics in sickle cell disease

Sickle cell disease is caused by a mutant form of hemoglobin that polymerizes under hypoxic conditions which leads to red blood cell (RBC) distortion, calcium-influx mediated RBC dehydration, increased RBC adhesivity, reduced RBC deformability, increased RBC fragility, and hemolysis. These impairments in RBC structure and function result in multifaceted downstream pathology including inflammation, endothelial cell activation, platelet and leukocyte activation and adhesion, and thrombosis, all of which contribute vascular occlusion and substantial morbidity and mortality. Hemoglobin released upon RBC hemolysis scavenges nitric oxide (NO) and generates reactive oxygen species (ROS) and thereby decreases bioavailability of this important signaling molecule. As the endothelium-derived relaxing factor, NO acts as a vasodilator and also decreases platelet, leukocyte, and endothelial cell activation. Thus, low NO bioavailability contributes to pathology in sickle cell disease and its restoration could serve as an effective treatment. Despite its promise, clinical trials based on restoring NO bioavailability have so far been mainly disappointing. However, particular "NO donating" agents such as nitrite, which unlike some other NO donors can improve sickle RBC properties, may yet prove effective.

What is the role of screening for pulmonary hypertension in adults and children with sickle cell disease?

Patient case: An 18-year-old male patient with homozygous hemoglobin SS disease was evaluated for progressive dyspnea and elevated tricuspid regurgitant jet velocity (TRV) on echocardiography. The patient's case is described in detail in Lancet¹ He had been treated with regular transfusions since childhood for stroke, had rare episodes of vaso-occlusive pain episodes, and did not take narcotic pain medications. He presented with progressive severe dyspnea on exertion and lower extremity edema. His laboratory tests were notable for a total hemoglobin level of 11.8 g/dL and hemoglobin S levels <30% but with 18% reticulocytes and elevated markers of hemolysis, such as high plasma levels of lactate dehydrogenase, aspartate amino transferase, and indirect bilirubin. The computed tomography scan of his chest in Figure 1A-B shows a large pulmonary artery, which has a greater diameter than his aorta, and a mosaic perfusion pattern, typical for severe pulmonary arterial hypertension. His Doppler echocardiographic study (Figure 1C) showed an unusually high TRV of 5.93 m/s, consistent with a calculated pulmonary artery systolic pressure of >140 mm Hg (4 times the TRV squared = 4V²). Additional images in Figure 1D show a dilated right ventricle and right atrium with a compressed left ventricle. The patient's right heart catheterization revealed a pulmonary artery systolic pressure of 147 mm Hg and diastolic pressure of 49 mm Hg; note that the normal values are ∼25/10 mm Hg.

Cardiovascular complications in patients with sickle cell disease

Sickle cell disease (SCD) is an autosomal recessive disease in which homozygosity for a single point mutation in the gene encoding the β-globin chain produces hemoglobin S molecules that polymerize within the erythrocyte during deoxygenation; the result is sustained hemolytic anemia and vaso-occlusive events. As patients live to adulthood, the chronic impact of sustained hemolytic anemia and episodic vaso-occlusive episodes leads to progressive end-organ complications. This scenario culminates in the development of 1 or more major cardiovascular complications of SCD for which there are no approved or consensus therapies. These complications include elevated pulmonary artery systolic pressure, pulmonary hypertension, left ventricular diastolic heart disease, dysrhythmia, sudden death, and chronic kidney disease with associated proteinuria, microalbuminuria, and hemoglobinuria. In patients with advancing age, cardiopulmonary organ dysfunction and chronic kidney injury have significant effects on morbidity and premature mortality. Over the last 15 years, a number of tests have been validated in multiple replicate cohort studies that identify patients with SCD at the highest risk of experiencing pulmonary and systemic vasculopathy and death, providing for screening strategies tied to targeted, more aggressive diagnostic and therapeutic interventions.

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.

Calpain-1 regulates platelet function in a humanized mouse model of sickle cell disease

One of the major contributors to sickle cell disease (SCD) pathobiology is the hemolysis of sickle red blood cells (RBCs), which release free hemoglobin and platelet agonists including adenosine 5'-diphosphate (ADP) into the plasma. While platelet activation/aggregation may promote tissue ischemia and pulmonary hypertension in SCD, modulation of sickle platelet dysfunction remains poorly understood. Calpain-1, a ubiquitous calcium-activated cysteine protease expressed in hematopoietic cells, mediates aggregation of platelets in healthy mice. We generated calpain-1 knockout Townes sickle (SSCKO) mice to investigate the role of calpain-1 in steady state and hypoxia/reoxygenation (H/R)-induced sickle platelet activation and aggregation, clot retraction, and pulmonary arterial hypertension. Using multi-electrode aggregometry, which measures platelet adhesion and aggregation in whole blood, we determined that steady state SSCKO mice exhibit significantly impaired PAR4-TRAP-stimulated platelet aggregation as compared to Townes sickle (SS) and humanized control (AA) mice. Interestingly, the H/R injury induced platelet hyperactivity in SS and SSCKO, but not AA mice, and partially rescued the aggregation defect in SSCKO mice. The PAR4-TRAP-stimulated GPIIb-IIIa (α_IIbβ₃) integrin activation was normal in SSCKO platelets suggesting that an alternate mechanism mediates the impaired platelet aggregation in steady state SSCKO mice. Taken together, we provide the first evidence that calpain-1 regulates platelet hyperactivity in sickle mice, and may offer a viable pharmacological target to reduce platelet hyperactivity in SCD.

Prospective evaluation of chronic organ damage in adult sickle cell patients: A seven-year follow-up study

Organ damage in sickle cell disease (SCD) is a crucial determinant for disease severity and prognosis. In a previous study, we analyzed the prevalence of SCD-related organ damage and complications in adult sickle cell patients. We now describe a seven-year follow-up of this cohort.All patients from the primary analysis in 2006 (n = 104), were included for follow-up. Patients were screened for SCD-related organ damage and complications (microalbuminuria, renal failure, elevated tricuspid regurgitation flow velocity (TRV) (≥2.5 m/seconds), retinopathy, iron overload, cholelithiasis, avascular osteonecrosis, leg ulcers, acute chest syndrome (ACS), stroke, priapism and admissions for vaso-occlusive crises (VOC) biannually. Upon 7 years of follow-up, progression in the prevalence of avascular osteonecrosis (from 12.5% to 20.4%), renal failure (from 6.7% to 23.4%), retinopathy (from 39.7% to 53.8%) was observed in the whole group. In HbSS/HbSβ⁰ -thal patients also progression in microalbuminuria (from 34% to 45%) and elevated TRV (from 40% to 48%) was observed while hardly any progression in the prevalence of cholelithiasis, priapism, stroke or chronic ulcers was seen. The proportion of patients with at least one episode of ACS increased in the group of HbSS/HbSβ⁰ -thal patients from 32% to 49.1%. In conclusion, 62% of the sickle cell patients in this prospective cohort study developed a new SCD-related complication in a comprehensive care setting within 7 years of follow-up. Although the hospital admission rate for VOC remained stable, multiple forms of organ damage increased substantially. These observations underline the need for continued screening for organ damage in all adult patients with SCD.

Pulmonary hypertension among 5 to 18 year old children with sickle cell anaemia in Nigeria

BACKGROUND

Pulmonary hypertension (PHT) is a significant cause of mortality in patients with sickle cell disease (SCD). Few studies on PHT in SCD have been carried out in children. This study aimed to estimate the prevalence of PHT in children with sickle cell anaemia (SCA) and determine its clinical and laboratory correlates.

METHODS

In this cross sectional study, evaluation involved obtaining bio-data, history and physical examination findings in 175 SCA subjects with haemoglobin genotype SS aged 5 to 18 years and 175 age and sex matched controls with haemoglobin genotype AA. PHT was determined using peak Tricuspid Regurgitant Velocity (TRV) obtained from echocardiography as a marker. Complete blood count (CBC), lactate dehydrogenase (LDH) assay, reticulocyte count, foetal haemoglobin (HbF) estimation as well as Human Immunodeficiency Virus (HIV) I and II, Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) screening were done for patients with SCA.

RESULTS

The mean peak TRV of subjects with SCA and controls was 2.2 ± 0.4 m/s and 1.9 ± 0.3 m/s respectively and prevalence of PHT among children with SCA and controls was 22.9% and 2.3% respectively. PHT in SCA correlated negatively with body mass index, haematocrit and haemoglobin.

CONCLUSION

This study affirms that PHT prevalence is high in children with SCA in Nigeria. Cardiovascular examination for signs of PHT is recommended for children with SCA and if required, further echocardiographic assessment from as early as five years.

Predictors of mortality in adults with Sickle cell disease admitted to intensive care unit in Bahrain

OBJECTIVE

Sickle cell disease (SCD) is one of the most common genetic blood disorders in Bahrain. However, there is a paucity of data regarding the clinical presentation of SCD patients who require ICU admission. This study aimed to describe the epidemiological data of SCD patients admitted to the ICU and to identify predictors of mortality in order to help intensivists identify patients at most risk.

METHOD

This study used a retrospective, descriptive, and correlational design. Records of 210 SCD patients admitted to the ICU in Salmaniya Medical Complex (SMC) were reviewed.

RESULTS

210 patient with SCD were admitted to ICU during study period. The main reason for ICU admission was acute chest syndrome. The mortality rate of SCD patients in the ICU was 12.7%. The four significant predictors of mortality were age, number of previous hospitalizations, length of stay, and need of renal replacement therapy. Non-survivors were older than survivors (M=38.6 vs. M=30.3years, U=1685, z=-2.2, P=0.025), were less frequently hospitalized (M=19 vs. M=46 times, U=1274, z=-3.7, P=0.000), had shorter lengths of stay in the ICU (M=3.1 vs. M=5.5days, U=1145, z=-4, P=0.000), and more likely to require renal replacement therapy the p=0.0297 than the survivors. The combined effect of these predictors was modelled with cox regression and found to be statistically significant. Gender, presence of comorbid conditions, level of hemoglobin on admission, and need for blood transfusions were not found to be predictors for mortality.

CONCLUSION

Acute chest syndrome was the main reason for SCD patients to be admitted to the ICU. Older age, less frequent hospitalization, shorter stays in the ICU, and the need for renal replacement therapy were found to be indicators of high mortality rate SCD patients.

Differences of microparticle patterns between sickle cell anemia and hemoglobin SC patients

Sickle cell anemia (SCA) and hemoglobin SC (HbSC) disease are the two most common forms of sickle cell disease (SCD), a frequent hemoglobinopathy which exhibits a highly variable clinical course. Although high levels of microparticles (MPs) have been consistently reported in SCA and evidence of their harmful impact on the SCA complication occurrences have been provided, no data on MP pattern in HbSC patients has been reported so far. In this study, we determined and compared the MP patterns of 84 HbSC and 96 SCA children, all at steady-state, using flow cytometry. Most of circulating MPs were derived from platelets (PLTs) and red blood cells (RBCs) in the two SCD syndromes. Moreover, we showed that HbSC patients exhibited lower blood concentration of total MPs compared to SCA patients, resulting mainly from a decrease of MP levels originated from RBCs and to a lesser extent from PLTs. We did not detect any association between blood MP concentrations and the occurrence of painful vaso-occlusive crises, acute chest syndrome and pulmonary hypertension in both patient groups. We also demonstrated for the first time, that whatever the considered genotype, RBC-derived MPs exhibited higher externalized phosphatidylserine level and were larger than PLT-derived MPs.

Intravascular hemolysis and the pathophysiology of sickle cell disease

Hemolysis is a fundamental feature of sickle cell anemia that contributes to its pathophysiology and phenotypic variability. Decompartmentalized hemoglobin, arginase 1, asymmetric dimethylarginine, and adenine nucleotides are all products of hemolysis that promote vasomotor dysfunction, proliferative vasculopathy, and a multitude of clinical complications of pulmonary and systemic vasculopathy, including pulmonary hypertension, leg ulcers, priapism, chronic kidney disease, and large-artery ischemic stroke. Nitric oxide (NO) is inactivated by cell-free hemoglobin in a dioxygenation reaction that also oxidizes hemoglobin to methemoglobin, a non-oxygen-binding form of hemoglobin that readily loses heme. Circulating hemoglobin and heme represent erythrocytic danger-associated molecular pattern (eDAMP) molecules, which activate the innate immune system and endothelium to an inflammatory, proadhesive state that promotes sickle vaso-occlusion and acute lung injury in murine models of sickle cell disease. Intravascular hemolysis can impair NO bioavailability and cause oxidative stress, altering redox balance and amplifying physiological processes that govern blood flow, hemostasis, inflammation, and angiogenesis. These pathological responses promote regional vasoconstriction and subsequent blood vessel remodeling. Thus, intravascular hemolysis represents an intrinsic mechanism for human vascular disease that manifests clinical complications in sickle cell disease and other chronic hereditary or acquired hemolytic anemias.

Hydroxycarbamine: from an Old Drug Used in Malignant Hemopathies to a Current Standard in Sickle Cell Disease

While hydroxycarbamide (hydroxyurea, HU) has less and fewer indications in malignant hemopathies, it represents the only widely used drug which modifies sickle cell disease pathogenesis. Clinical experience with HU for patients with sickle cell disease has been accumulated over the past 25 years in Western countries. The review of the literature provides increasing support for safety and efficacy in both children and adults for reducing acute vaso-occlusive events including pain episodes and acute chest syndrome. No increased incidence of leukemia and teratogenicity was demonstrated. HU has become the standard-of-care for sickle cell anemia but remains underused. Barriers to its use should be identified and overcome.