Echocardiographic markers of elevated pulmonary pressure and left ventricular diastolic dysfunction are associated with exercise intolerance in adults and adolescents with homozygous sickle cell anemia in the United States and United Kingdom

Subclinical Cardiac Dysfunction Is Associated With Extracardiac Organ Damages

Background: Several studies conducted in America or Europe have described major cardiac remodeling and diastolic dysfunction in patients with sickle cell disease (SCD). We aimed at assessing cardiac involvement in SCD in sub-Saharan Africa where SCD is the most prevalent.

Methods: In Cameroon, Mali and Senegal, SCD patients and healthy controls of the CADRE study underwent transthoracic echocardiography if aged ≥10 years. The comparison of clinical and echocardiographic features between patients and controls, and the associations between echocardiographic features and the vascular complications of SCD were assessed.

Results: 612 SCD patients (483 SS or Sβ⁰, 99 SC, and 19 Sβ⁺) and 149 controls were included. The prevalence of dyspnea and congestive heart failure was low and did not differ significantly between patients and controls. While left ventricular ejection fraction did not differ between controls and patients, left and right cardiac chambers were homogeneously more dilated and hypertrophic in patients compared to controls and systemic vascular resistances were lower (p < 0.001 for all comparisons). Three hundred and forty nine SCD patients had extra-cardiac organ damages (stroke, leg ulcer, priapism, microalbuminuria or osteonecrosis). Increased left ventricular mass index, cardiac dilatation, cardiac output, and decreased systemic vascular resistances were associated with a history of at least one SCD-related organ damage after adjustment for confounders.

Conclusions: Cardiac dilatation, cardiac output, left ventricular hypertrophy, and systemic vascular resistance are associated with extracardiac SCD complications in patients from sub-Saharan Africa despite a low prevalence of clinical heart failure. The prognostic value of cardiac subclinical involvement in SCD patients deserves further studies.

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.

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.

Exercise capacity and clinical outcomes in adults followed in the Cooperative Study of Sickle Cell Disease (CSSCD)

OBJECTIVES

To determine the factors associated with exercise capacity in adults with sickle cell disease (SCD) and its relationship to hospitalizations and mortality.

METHODS

A total of 223 participants in the Cooperative Study of Sickle Cell Disease (CSSCD) (64% female, 70% hemoglobin SS/Sβ⁰ thalassemia, mean age 43.3 ± 7.5 years) underwent maximal exercise testing using a treadmill protocol with a mean duration of 11.6 ± 5.2 minutes.

RESULTS

Female sex (β = -3.34, 95% CI [-1.80, -4.88], P < 0.001), older age (β = -0.14, 95% CI [-0.24, -0.04], P = 0.005), higher body mass index (β = -0.23, 95% CI [-0.37, -0.10]; P = 0.001), and lower hemoglobin (β = 0.56, 95% CI [0.08, 1.04], P = 0.02) were independently associated with lower fitness, while there was a trend with abnormal pulmonary function testing (β = -1.42, 95% CI [-2.92, 0.07]; P = 0.06). Lower percent-predicted forced expiratory volume in 1 second (FEV₁ ) was independently associated with lower fitness (β = 0.08, 95% CI [0.03, 0.13], P = 0.001). Genotype and hospitalization rates for pain and acute chest syndrome (ACS) prior to testing were not associated with exercise capacity. Baseline exercise capacity predicted neither future pain or ACS nor survival in our cohort. Adults with SCD tolerated maximal exercise testing.

CONCLUSIONS

Prospective studies are needed to further evaluate the impact of regular exercise and improved fitness on clinical outcomes and mortality in SCD.

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.

Diastolic dysfunction is associated with exercise impairment in patients with sickle cell anemia

BACKGROUND

Left ventricular diastolic dysfunction (DD) is an independent risk factor for mortality in sickle cell anemia (SCA) and is associated with increased extracellular volume (ECV) on cardiac MRI (CMR). Exercise impairment is common in SCA, but its causes and prognostic value are not well understood.

OBJECTIVE

To study the effects of DD and ECV on cardiopulmonary exercise test (CPET) in patients with SCA.

METHODS AND RESULTS

As part of a prospective study to characterize the cardiomyopathy of SCA (NCT02410811), 20 children and adults with SCA underwent CMR, echocardiography, and cycle ergometer CPET (age range 8-43 years). Maximum exercise was reached in 18 patients and 17 (94%) had reduced exercise capacity (%predicted VO₂ less than 80%). Six patients had DD and none had systolic dysfunction. Patients with DD had lower exercise capacity compared to patients with normal diastolic function (%predicted VO₂ 48.2 ± 9.1% vs. 61.2 ± 11.7%; P = 0.01). The z-score of left ventricular lateral E/e' ratio, which is a marker of DD, was negatively associated with %predicted VO₂ (r = -0.61, P = 0.01). All patients with moderate-to-severe exercise impairment (%predicted VO₂  < 60%) had lateral E/e' z-score > 2. In a multivariate analysis, lateral E/e' z-score was independently associated with %predicted VO₂ (P = 0.02). All participants had elevated ECV but the degree of elevation was not associated with exercise parameters.

CONCLUSION

Left ventricular DD is associated with decreased exercise capacity in SCA. Interventions to prevent or delay DD could improve exercise capacity, quality of life, and long-term outcomes in SCA.

Biomarker signatures of sickle cell disease severity

Identifying sickle cell disease patients at high risk of complications could lead to personalized treatment and better prognosis but despite many advances prediction of the clinical course of these patients remains elusive. We propose a system-type approach to discover profiles of multiple, common biomarkers that correlate with morbidity and mortality in sickle cell disease. We used cluster analysis to discover 17 signatures of 17 common circulating biomarkers in 2320 participants of the Cooperative Study of Sickle Cell Disease, and evaluated the association of these signatures with risk for stroke, pain, leg ulceration, acute chest syndrome, avascular necrosis, seizure, death, and trend of fetal hemoglobin and hemolysis using longitudinally collected data. The analysis shows that some of the signatures are associated with reduced risk for complications, while others are associated with increased risk for complications. We also show that these signatures repeat in two more contemporary studies of sickle cell disease and correlate with recently discovered biomarkers of pulmonary vascular disease. With replication and further study, these biomarker signatures could become an important and affordable precision medicine tool to aid treatment and management of the disease.

Exercise Therapy and Cardiovascular Toxicity in Cancer

Cardio-oncology is an emerging discipline focused predominantly on the detection and management of cancer treatment-induced cardiac dysfunction (cardiotoxicity), which predisposes to development of overt heart failure or coronary artery disease. The direct adverse consequences, as well as those secondary to anticancer therapeutics, extend beyond the heart, however, to affect the entire cardiovascular-skeletal muscle axis (ie, whole-organism cardiovascular toxicity). The global nature of impairment creates a strong rationale for treatment strategies that augment or preserve global cardiovascular reserve capacity. In noncancer clinical populations, exercise training is an established therapy to improve cardiovascular reserve capacity, leading to concomitant reductions in cardiovascular morbidity and its attendant symptoms. Here, we overview the tolerability and efficacy of exercise on cardiovascular toxicity in adult patients with cancer. We also propose a conceptual research framework to facilitate personalized risk assessment and the development of targeted exercise prescriptions to optimally prevent or manage cardiovascular toxicity after a cancer diagnosis.

Association of genetic variation in COMT gene with pain related to sickle cell disease in patients from the walk-PHaSST study

Background

Vaso-occlusive pain episodes (VOEs) are the hallmark of sickle cell disease (SCD), and our current understanding of disease biology, treatment, and psychological covariates does not adequately explain the variability of pain in SCD. Functional variants in catechol-O-methyltransferase (COMT) gene contribute to variability in pain perception, but their impact on pain perception in African American SCD patients is not well known.

Methods

We studied COMT single-nucleotide polymorphisms (SNPs) rs6269, rs4633, rs4818, rs4680, and rs165599 to determine their relationship to patient self-reported pain, the number of acute VOEs, and their impact on daily life and health care utilization in 438 hemoglobin SS patients who participated in the walk-PHaSST study.

Results

In women, two risk SNPs (rs4633 and rs165599) and the corresponding haplotype (ATCAA) were associated with increased frequency of pain-related emergency room visit.

Conclusion

COMT functional variants may predispose SCD patients to worse acute pain in women. The association of COMT variants with the intensity of self-reported acute pain warrants further genetic study of pain perception in SCD.

Vascular complications of sickle cell disease

Sickle cell disease (SCD) is a monogenetic disorder caused by a mutation in the β-globin gene HBB leading to polymerization of red blood cells causing damage to cell membranes, increasing its rigidity and intravascular hemolysis. Multiple lines of evidence suggest that SCD can be viewed as pan-vasculopathy associated with multiple mechanisms but driven by hemoglobin S polymerization. Here we review the pathophysiology, clinical manifestations and management strategies for cerebrovascular disease, pulmonary hypertension and renal disease associated with SCD. These "vascular phenotypes" reflect the systemic nature of the complications of SCD and are a major threat to the well-being of patients with the disorder.

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.

Longitudinal Analysis of Echocardiographic Abnormalities in Children With Sickle Cell Disease

BACKGROUND

Cardiac abnormalities have been described in echocardiograms of children with sickle cell disease (SCD). However, longitudinal studies investigating progression of echocardiographic abnormalities across the pediatric age spectrum in SCD are lacking.

METHODS

A retrospective longitudinal analysis of 829 echocardiograms from pediatric patients with SCD at steady-state was performed. Left heart parameters included left ventricular end-systolic, end-diastolic diameters, fractional shortening, and mass. Right ventricular pressure was estimated by tricuspid regurgitation gradient. Tricuspid regurgitation gradient ≥25 mm Hg, a z-score ≥2 for LV parameters and ≤-2 for left ventricular fractional shortening were considered abnormal.

RESULTS

Kaplan-Meier analysis revealed that echocardiographic abnormalities were detected by 5 years of age, and the cumulative incidence progressively increased throughout childhood. Age, male gender, HbSS and Sβ thalassemia genotype, white blood cell count, platelet count, total bilirubin, admissions for pain crises and acute chest syndrome were positively, whereas hemoglobin was negatively associated with cardiac abnormalities.

CONCLUSION

Cardiac abnormalities began early in childhood and progressively increased with age. Our study highlights the high cumulative incidence of cardiac abnormalities in children with SCD, which could represent a marker of disease severity.

Cardiorespiratory pathogenesis of sickle cell disease in a mouse model

The nature and development of cardiorespiratory impairments associated with sickle cell disease are poorly understood. Given that the mechanisms of these impairments cannot be addressed adequately in clinical studies, we characterized cardiorespiratory pathophysiology from birth to maturity in the sickle cell disease SAD mouse model. We identified two critical phases of respiratory dysfunction in SAD mice; the first prior to weaning and the second in adulthood. At postnatal day 3, 43% of SAD mice showed marked apneas, anemia, and pulmonary vascular congestion typical of acute chest syndrome; none of these mice survived to maturity. The remaining SAD mice had mild lung histological changes in room air with an altered respiratory pattern, seizures, and a high rate of death in response to hypoxia. Approximately half the SAD mice that survived to adulthood had an identifiable respiratory phenotype including baseline tachypnea at 7–8 months of age, restrictive lung disease, pulmonary hypertension, cardiac enlargement, lower total lung capacity, and pulmonary vascular congestion. All adult SAD mice demonstrated impairments in exercise capacity and response to hypoxia, with a more severe phenotype in the tachypneic mice. The model revealed distinguishable subgroups of SAD mice with cardiorespiratory pathophysiology mimicking the complications of human sickle cell disease.

Sleep and the Cardiovascular System in Children

Subspecialty pediatric practice provides comprehensive medical care for a range of ages, from premature infants to children, and often includes adults with complex medical and surgical issues that warrant multidisciplinary care. Normal physiologic variations involving different body systems occur during sleep and these vary with age, stage of sleep, and underlying health conditions. This article is a concise review of the cardiovascular (CV) physiology and pathophysiology in children, sleep-disordered breathing (SDB) contributing to CV morbidity, congenital and acquired CV pathology resulting in SDB, and the relationship between SDB and CV morbidity in different clinical syndromes and systemic diseases in the expanded pediatric population.

Cardiac Structural and Functional Changes Evaluated by Transthoracic and Tissue Doppler Echocardiography in Adult Patients with Sickle Cell Disease

One of the most common genetic blood disorders, resulting from inherited red blood cell disorders, is sickle cell disease (SCD) which is responsible for high death in adult patients with left ventricular diastolic dysfunction and pulmonary hypertension. Tissue Doppler Echocardiography (TDE) and transthoracic echocardiography (TTE) are two useful tools to assess the risk of SCD. The present study was conducted to evaluate the cardiac functions and structure using TDE and TTE among adult patients suffering from sickle cell anemia compare to normal samples.

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.

Pediatric Exercise Testing: Value and Implications of Peak Oxygen Uptake

Peak oxygen uptake (peakV˙O2) measured by clinical exercise testing is the benchmark for aerobic fitness. Aerobic fitness, estimated from maximal treadmill exercise, is a predictor of mortality in adults. PeakV˙O2 was shown to predict longevity in patients aged 7–35 years with cystic fibrosis over 25 years ago. A surge of exercise studies in young adults with congenital heart disease over the past decade has revealed significant prognostic information. Three years ago, the first clinical trial in children with pulmonary arterial hypertension used peakV˙O2 as an endpoint that likewise delivered clinically relevant data. Cardiopulmonary exercise testing provides clinicians with biomarkers and clinical outcomes, and researchers with novel insights into fundamental biological mechanisms reflecting an integrated physiological response hidden at rest. Momentum from these pioneering observations in multiple disease states should impel clinicians to employ similar methods in other patient populations; e.g., sickle cell disease. Advances in pediatric exercise science will elucidate new pathways that may identify novel biomarkers. Our initial aim of this essay is to highlight the clinical relevance of exercise testing to determine peakV˙O2, and thereby convince clinicians of its merit, stimulating future clinical investigators to broaden the application of exercise testing in pediatrics.

Pulmonary vascular and ventricular dysfunction in the susceptible patient (2015 Grover Conference series)

Pulmonary blood vessel structure and tone are maintained by a complex interplay between endogenous vasoactive factors and oxygen-sensing intermediaries. Under physiological conditions, these signaling networks function as an adaptive interface between the pulmonary circulation and environmental or acquired perturbations to preserve oxygenation and maintain systemic delivery of oxygen-rich hemoglobin. Chronic exposure to hypoxia, however, triggers a range of pathogenetic mechanisms that include hypoxia-inducible factor 1α (HIF-1α)-dependent upregulation of the vasoconstrictor peptide endothelin 1 in pulmonary endothelial cells. In pulmonary arterial smooth muscle cells, chronic hypoxia induces HIF-1α-mediated upregulation of canonical transient receptor potential proteins, as well as increased Rho kinase-Ca2+ signaling and pulmonary arteriole synthesis of the profibrotic hormone aldosterone. Collectively, these mechanisms contribute to a contractile or hypertrophic pulmonary vascular phenotype. Genetically inherited disorders in hemoglobin structure are also an important etiology of abnormal pulmonary vasoreactivity. In sickle cell anemia, for example, consumption of the vasodilator and antimitogenic molecule nitric oxide by cell-free hemoglobin is an important mechanism underpinning pulmonary hypertension. Contemporary genomic and transcriptomic analytic methods have also allowed for the discovery of novel risk factors relevant to sickle cell disease, including GALNT13 gene variants. In this report, we review cutting-edge observations characterizing these and other pathobiological mechanisms that contribute to pulmonary vascular and right ventricular vulnerability.

Genome-Wide Analysis Identifies IL-18 and FUCA2 as Novel Genes Associated with Diastolic Function in African Americans with Sickle Cell Disease

BACKGROUND

Diastolic dysfunction is common in sickle cell disease (SCD), and is associated with an increased risk of mortality. However, the molecular pathogenesis underlying this development is poorly understood. The aim of this study was to identify a gene expression profile that is associated with diastolic function in SCD, potentially elucidating molecular mechanisms behind diastolic dysfunction development.

METHODS

Diastolic function was measured via echocardiography in 65 patients with SCD from two independent study populations. Gene expression microarray data was compared with diastolic function in both study cohorts. Candidate genes that associated in both analyses were tested for validation in a murine SCD model. Lastly, genotyping array data from the replication cohort was used to derive cis-expression quantitative trait loci (cis-eQTLs) and genetic associations within the candidate gene regions.

RESULTS

Transcriptome data from both patient cohorts implicated 7 genes associated with diastolic function, and mouse SCD myocardial expression validated 3 of these genes. Genetic associations and eQTLs were detected in 2 of the 3 genes, FUCA2 and IL18.

CONCLUSIONS

FUCA2 and IL18 are associated with diastolic function in SCD patients, and may be involved in the pathogenesis of the disease. Genetic polymorphisms within the FUCA2 and IL18 gene regions are also associated with diastolic function in SCD, likely by affecting expression levels of the genes.

Sickle cell anemia mice develop a unique cardiomyopathy with restrictive physiology

Cardiopulmonary complications are the leading cause of mortality in sickle cell anemia (SCA). Elevated tricuspid regurgitant jet velocity, pulmonary hypertension, diastolic, and autonomic dysfunction have all been described, but a unifying pathophysiology and mechanism explaining the poor prognosis and propensity to sudden death has been elusive. Herein, SCA mice underwent a longitudinal comprehensive cardiac analysis, combining state-of-the-art cardiac imaging with electrocardiography, histopathology, and molecular analysis to determine the basis of cardiac dysfunction. We show that in SCA mice, anemia-induced hyperdynamic physiology was gradually superimposed with restrictive physiology, characterized by progressive left atrial enlargement and diastolic dysfunction with preserved systolic function. This phenomenon was absent in WT mice with experimentally induced chronic anemia of similar degree and duration. Restrictive physiology was associated with microscopic cardiomyocyte loss and secondary fibrosis detectable as increased extracellular volume by cardiac-MRI. Ultrastructural mitochondrial changes were consistent with severe chronic hypoxia/ischemia and sarcomere diastolic-length was shortened. Transcriptome analysis revealed up-regulation of genes involving angiogenesis, extracellular-matrix, circadian-rhythm, oxidative stress, and hypoxia, whereas ion-channel transport and cardiac conduction were down-regulated. Indeed, progressive corrected QT prolongation, arrhythmias, and ischemic changes were noted in SCA mice before sudden death. Sudden cardiac death is common in humans with restrictive cardiomyopathies and long QT syndromes. Our findings may thus provide a unifying cardiac pathophysiology that explains the reported cardiac abnormalities and sudden death seen in humans with SCA.

Sleep-disordered breathing and nocturnal hypoxemia in young adults with sickle cell disease

Sleep-disordered breathing (SDB) is reported in up to 69% of adolescents and children with sickle cell disease (SCD) [1], but data regarding the prevalence of SDB in adults with SCD are limited. In order to obtain a preliminary assessment of the frequency and degree of sleep-related hypoxemia and potential associations with cardiovascular function in adults with SCD, we conducted overnight sleep studies, 6-min walk tests, echocardiograms, and hematologic and chemistry panels, calculated the Pittsburgh sleep quality index (PSQI), and conducted fatigue- and health-related quality-of-life measurement in 20 young adults with SCD visiting a sickle cell clinic for routine care. Sleep apnea, defined as an apnea-hypopnea index (AHI) > 5 events/h, was found in 50% of patients. Traditional clinical indicators, such as obesity, the presence of snoring, and reported sleep complaints, did not reliably differentiate them. The patients with AHI > 5 had higher mean systolic blood pressure (p = 0.03), evidence of impaired left ventricular diastolic function (i.e., increased mitral valve E/A ratio, p = 0.05), a trend toward higher reduction in 6-min walk distances (p = 0.06), and lower health-related quality-of-life scores (p ≤ 0.01). Three of nine patients with more severe anemia (total Hb < 9.0) showed nocturnal hypoxemia in the absence of sleep apnea. As prolonged and frequent hypoxemic episodes likely increase risks for vaso-occlusive, cardiovascular, and neurologic complications of SCD, these results suggest that the prevalence and severity of SDB should be investigated further in studies of larger patient populations. If confirmed, these findings could identify opportunities to prevent or reduce nocturnal hypoxia and improve outcomes.

Cardiovascular complications and risk of death in sickle-cell disease

In sickle-cell disease, a point mutation in the β-globin chain causes haemoglobin to polymerise within erythrocytes during deoxygenation, altering red blood cell rheology and causing haemolysis. Improvements in health infrastructure, preventive care, and clinical treatments have reduced the morbidity and mortality of sickle-cell disease in developed countries. However, as these patients live longer, the chronic effects of sustained haemolytic anaemia and episodic vaso-occlusive events drive the development of end-organ complications. Cardiopulmonary organ dysfunction and chronic kidney injury have a large effect on morbidity and premature mortality, and typically accelerate in the second decade of life. These processes culminate in the development of pulmonary hypertension, left ventricular diastolic heart disease, dysrhythmia, and sudden death. In this Series paper, we review the mechanisms, clinical features, and epidemiology of major cardiovascular complications in patients with sickle-cell disease and discuss how screening and intervention could reduce their incidence.

The global burden of pulmonary hypertension in sickle cell disease: a systematic review and meta-analysis

Elevated tricuspid regurgitant jet velocity (TRJV) is a surrogate measure of pulmonary hypertension (PH) in persons with sickle cell disease (SCD). We sought to estimate the burden of PH in people living with sickle cell disease based on TRJV. From 2000 to 2015, we searched electronic databases for eligible publications and included 29 studies (n = 5358 persons). We used random effects modeling to determine the pooled estimate of elevated TRJV. The overall pooled prevalence of elevated TRJV was 23.5 %(95 % CI 19.5-27.4) in persons with SCD. The pooled prevalence of elevated TRJV in children and adults with SCD was 20.7 % (95 % CI 15.7--25.6) and 24.4 % (95 % CI 18.4-30.4), respectively. TRJV is prevalent among adults and children with SCD. Our finding support international recommendations that call for screening for PH in SCD patients.

Cardiomyopathy With Restrictive Physiology in Sickle Cell Disease

OBJECTIVES

The aim of this study was to identify a unifying cardiac pathophysiology that explains the cardiac pathological features in sickle cell disease (SCD).

BACKGROUND

Cardiopulmonary complications, the leading cause of adult death in SCD, are associated with heart chamber dilation, diastolic dysfunction, elevated tricuspid regurgitant jet velocity (TRV), and pulmonary hypertension. However, no unifying cardiac pathophysiology has been identified to explain these findings.

METHODS

In a 2-part study, we first examined patients with SCD who underwent screening echocardiography during steady state at our institution. We then conducted a meta-analysis of cardiac studies in SCD.

RESULTS

In the 134 patients with SCD studied (median age 11 years), significant enlargement of the left atrial volume was present (z-score 3.1, p = 0.002), shortening fraction was normal (37.6 ± 4.7%), and lateral and septal ratios of mitral velocity to early diastolic velocity of the mitral annulus (E/e') were severely abnormal in 8% and 14% of patients, respectively, indicating impaired diastolic function. Both TRV and lateral E/e' correlated with enlarged left atrial volume in SCD (p = 0.003 and p = 0.006, respectively). Meta-analysis of 68 studies confirmed significant left atrial diameter enlargement in patients with SCD compared with controls, evidence of diastolic dysfunction and enlarged left ventricular end-diastolic dimension with normal shortening fraction. The majority of patients with catheter-confirmed pulmonary hypertension had mild pulmonary venous hypertension consistent with restrictive cardiac physiology.

CONCLUSIONS

Patients with SCD have a unique form of cardiomyopathy with restrictive physiology that is superimposed on hyperdynamic physiology and is characterized by diastolic dysfunction, left atrial dilation, and normal systolic function. This combination results in mild, secondary, pulmonary venous hypertension and elevated TRV. Sudden death is common in other forms of restrictive cardiomyopathy. Our finding of this unique restrictive cardiomyopathy may explain the increased mortality rates and sudden death seen in patients with SCD with mildly elevated TRV.

Predictive models of six-minute walking distance in adults with sickle cell anemia: Implications for rehabilitation

BACKGROUND

Sickle cell anemia (SCA) is characterized by a broad spectrum of abnormalities that affect most body organs and systems. To date, there is few data on the influence of these patients' clinical characteristics on the functional exercise capacity.

AIM

To investigate the effect of the clinical complications on the functional exercise capacity of adult SCA patients.

METHOD

Cross-sectional study, where 45 SCA patients underwent clinical evaluations, echocardiography, pulmonary function testing, and determination of six-minute walking distance (6MWD).

RESULTS

A significant correlation (P < 0.001) was found between 6MWD and hemoglobin (Hb) level, tricuspid regurgitation velocity, forced vital capacity, acute chest syndrome, and diffusing capacity for carbon monoxide. The prediction model for 6MWD explained 67% of the 6MWD variability (P < 0.001).

CONCLUSIONS

Hemodynamics, cardiovascular function, pulmonary function, and episodes of acute lung injury seem to impact the 6MWD in adults with SCA.

Indications and Results of HLA-Identical Sibling Hematopoietic Cell Transplantation for Sickle Cell Disease

Although a number of published trials exist of HLA-identical sibling hematopoietic cell transplantation (HCT) for sickle cell disease (SCD) that span 2 decades, when and for whom this therapy should be pursued is a subject of debate. Assessments of the risks of transplant-related complications that include infertility and debilitating graft-versus-host disease and long-term quality of life after successful HCT are difficult to perform without prospective trials in transplant and nontransplant cohorts. However, it is possible to assess the risk of mortality and to compare published rates of survival in individuals with SCD treated and not treated by HCT. In this brief review, projections about mortality risk based on recent published reports are reviewed and summarized. The published data show overall survival and event-free survival rates of 95% and 92%, respectively, in children treated by HLA-identical sibling HCT. The overall survival rates in the Center for International Blood and Marrow Transplant Research (N = 412) and European Blood and Marrow Transplant (N = 487) registries were 91% and 95%, respectively. These results provide broad support for the therapeutic value of HLA-identical sibling HCT for children with SCD and serve as the basis for a strong recommendation in favor of the option of HCT when a suitable donor is available. The experience of HLA-identical sibling HCT in adults with SCD is limited but appears to be similar to results in children. These preliminary observations, however, warrant further investigation.

Pathophysiology and treatment of pulmonary hypertension in sickle cell disease

Pulmonary hypertension affects ∼10% of adult patients with sickle cell disease (SCD), particularly those with the homozygous genotype. An increase in pulmonary artery systolic pressure, estimated noninvasively by echocardiography, helps identify SCD patients at risk for pulmonary hypertension, but definitive diagnosis requires right-heart catheterization. About half of SCD-related pulmonary hypertension patients have precapillary pulmonary hypertension with potential etiologies of (1) a nitric oxide deficiency state and vasculopathy consequent to intravascular hemolysis, (2) chronic pulmonary thromboembolism, or (3) upregulated hypoxic responses secondary to anemia, low O2 saturation, and microvascular obstruction. The remainder have postcapillary pulmonary hypertension secondary to left ventricular dysfunction. Although the pulmonary artery pressure in SCD patients with pulmonary hypertension is only moderately elevated, they have a markedly higher risk of death than patients without pulmonary hypertension. Guidelines for diagnosis and management of SCD-related pulmonary hypertension were published recently by the American Thoracic Society. Management of adults with sickle-related pulmonary hypertension is based on anticoagulation for those with thromboembolism; oxygen therapy for those with low oxygen saturation; treatment of left ventricular failure in those with postcapillary pulmonary hypertension; and hydroxyurea or transfusions to raise the hemoglobin concentration, reduce hemolysis, and prevent vaso-occlusive events that cause additional increases in pulmonary pressure. Randomized trials have not identified drugs to lower pulmonary pressure in SCD patients with precapillary pulmonary hypertension. Patients with hemodynamics of pulmonary arterial hypertension should be referred to specialized centers and considered for treatments known to be effective in other forms of pulmonary arterial hypertension. There have been reports that some of these treatments improve SCD-related pulmonary hypertension.

Risk Factors of Pulmonary Hypertension in Brazilian Patients with Sickle Cell Anemia

This study was a prospective cross-sectional cohort study of 125 patients with sickle cell anemia (SS) between the ages of 16 to 60 years. Enrolled patients were followed-up prospectively for 15 months. Demographic, clinical, hematological and routine biochemical data were obtained on all patients. Six-minute walk test and Doppler Echocardiography were performed on all patients. A tricuspid regurgitant jet velocity (TRJV) < 2.5 m/sec was considered normal, 2.5 ≤ TRJV ≤ 3.0 was considered mild-moderate and > 3.0 m/sec, severe. Patients with abnormal TRJV were significantly older and more anemic, had significantly higher lactate dehydrogenase (LDH) levels, reticulocyte count and incidence of death. The logistic multimodal model implemented for the 125 patients indicated that age was the covariate that influenced the outcome of normal or abnormal TRJV with a cutoff age of thirty-two years. The survival rate for the group of patients with creatinine (Cr) > 1.0 mg/dL was lower than the group with Cr ≤ 1 and normal TRJV. A coefficient matrix showed that the LDH values were weakly correlated with the reticulocyte count but strongly correlated with hemoglobin suggesting that the TRJV values were not correlated with the hemolytic rate but with anemia. Ten patients died during the follow-up of whom 7 had TRJV > 2.5 m/sec. Acute chest syndrome was the most common cause of death followed by sepsis. In conclusion, this study shows that patients with SS older than thirty-two years with high LDH, elevated TRJV, severe anemia and Cr > 1 have poor prognosis and may be at risk of having pulmonary hypertension and should undergo RHC.

Prevention of Morbidity in sickle cell disease--qualitative outcomes, pain and quality of life in a randomised cross-over pilot trial of overnight supplementary oxygen and auto-adjusting continuous positive airways pressure (POMS2a): study protocol for a randomised controlled trial

BACKGROUND

Sickle cell anaemia (SCA) is an inherited disorder of haemoglobin. Patients experience long-term health care problems, affecting quality of life (QOL) including frequent acute pain, which is difficult to document in trials except as hospital admissions. Pilot data suggests that overnight respiratory support, either supplementary oxygen or auto-adjusting continuous positive airways pressure (APAP), is safe and may have clinical benefit. This pilot trial aims to determine which intervention is more acceptable to participants and whether there are other advantages of one over the other, e.g. in respiratory function or haematological parameters, before conducting the Phase 2 trial of overnight respiratory support funded by the National Institutes of Health Research.

METHODS/DESIGN

This is a pilot cross-over interventional trial with the order of interventions decided by simple randomization. Ten adults (age over 18 years) and 10 children (aged between 8 and 18 years) with homozygous sickle cell disease (haemoglobin SS, HbSS), recruited regardless of symptoms of sleep-disordered breathing, will undergo overnight pulse oximetry and will have two interventions, overnight oxygen and APAP, for a week each in randomised order with a washout week between interventions. Participants will complete online diaries via an iPad throughout the 29 days of the study and will complete QOL questionnaires and have measurement of haematology, biochemistry, spirometry and lung volumes (adults only) at 3 time points, at baseline and after each intervention, as well as in-depth semi-structured qualitative interviews after each intervention, carried out by an experienced psychologist. Both qualitative and statistical methods will be used to analyze the data. The primary outcome is qualitative data looking at participant experience from the transcribed interviews after each intervention. The participant's view on feasibility, acceptability and preference will specifically be explored. The QOL, laboratory and lung function data will be compared with baseline for each arm.

DISCUSSION

Patient and public involvement is an integral part of this trial and the key outcome is the qualitative result, which is dependent on obtaining good quality data to advise on participant feasibility, acceptability and preference. This is being addressed by using a standard interview. The development of a pain endpoint is another important outcome and collecting daily measurements is likely to be challenging. Research results will be used to inform design of the Phase 2 trial.

TRIAL REGISTRATION

ISRCTN46078697 18 July 2014.

Pulmonary Haemodynamics in Sickle Cell Disease Are Driven Predominantly by a High-Output State Rather Than Elevated Pulmonary Vascular Resistance: A Prospective 3-Dimensional Echocardiography/Doppler Study

AIMS

Patients with sickle cell disease have significant morbidity and mortality. Pulmonary hypertension is suggested to be an important contributor but its nature and severity in these patients and how best to non-invasively assess it are controversial. We hypothesised that a high-output state rather than primary pulmonary vascular pathology may be the major abnormality in sickle cell disease. This study aimed to evaluate the characteristics and severity of pulmonary hypertension in patients with sickle cell disease using detailed echocardiography.

METHODS AND RESULTS

We undertook a prospective study in 122 consecutive stable outpatients with sickle cell disease and 30 age, gender and ethnicity-matched healthy controls. Echocardiographic evaluation included 3D ventricular volumes, sphericity, tissue Doppler, and non-invasive estimation of pulmonary vascular resistance. 36% of patients had a tricuspid regurgitant velocity ≥2.5 m.s(-1) but only 2% had elevated pulmonary vascular resistance and the prevalence of right ventricular dysfunction was very low. Patients with raised tricuspid regurgitant velocity had significantly elevated biventricular volumes and globular left ventricular remodelling, related primarily to anaemia. In a subgroup of patients who underwent cardiac catheterization, invasive pulmonary haemodynamics confirmed the echocardiographic findings.

CONCLUSIONS

Elevated cardiac output and left ventricular volume overload secondary to chronic anaemia may be the dominant factor responsible for abnormal cardiopulmonary haemodynamics in patients with sickle cell disease. 3D echocardiography with non-invasive estimation of pulmonary vascular resistance represents a valuable approach for initial evaluation of cardiopulmonary haemodynamics in sickle cell disease.

Left ventricular remodeling in patients with sickle cell disease: determinants factors and impact on outcome

Cardiovascular complications have been increasingly detected as a result of prolonged longevity of patients with sickle cell disease (SCD). Previous studies have focused especially on pulmonary hypertension and its consequences on the right-side heart chambers, whereas factors associated with morphological changes in left ventricle (LV) remain poorly understood. This study was designed to identify clinical, laboratorial, and echocardiographic parameters associated with LV remodeling and its impact on outcome in SCD. Ninety patients aged 28 ± 7 years and 20 age- and gender-balanced healthy subjects were enrolled. Laboratory tests, electrocardiogram, and an echocardiogram with tissue Doppler imaging were performed in all patients. Patients with SCD had larger left and right heart chambers dimensions, LV mass, and tricuspid regurgitation (TR) velocity compared to health controls with similar demographic features. Despite chambers enlargement, systolic function of both ventricles was preserved. The mitral inflow velocities were higher in the patients than in controls, whereas septal and lateral annular motion velocities were normal, suggesting normal ventricular relaxation. SCD patients who were on hydroxyurea therapy and/or hypertransfusion had higher hemoglobin concentrations, but similar echocardiographic findings in comparison to those without treatment. Systolic blood pressure, ferritin concentration, TR velocity, and parameters of diastolic function were independently associated with increased LV mass. In addition, the predictors of adverse events were ferritin concentration, lactate dehydrogenase levels, and TR velocity. LV remodeling in SCD patients seems to be influenced by a combination of factors including blood pressure, ferritin concentration, TR velocity, and parameters of LV diastolic function, and was not associated with adverse outcomes.

Chronic transfusion therapy improves but does not normalize systemic and pulmonary vasculopathy in sickle cell disease

Tricuspid regurgitant (TR) jet velocity and its relationship to pulmonary hypertension has been controversial in sickle cell disease (SCD). Plasma free hemoglobin is elevated in SCD patients and acutely impairs systemic vascular reactivity. We postulated that plasma free hemoglobin would be negatively associated with both systemic and pulmonary endothelial function, assessed by flow-mediated dilation (FMD) of the brachial artery and TR jet velocity, respectively. Whole blood viscosity, plasma free hemoglobin, TR jet, and FMD were measured in chronically transfused SCD pre- and posttransfusion (N = 25), in nontransfused SCD (N = 26), and in ethnicity-matched control subjects (N = 10). We found increased TR jet velocity and decreased FMD in nontransfused SCD patients compared with the other 2 groups. TR jet velocity was inversely correlated with FMD. There was a striking nonlinear relationship between plasma free hemoglobin and both TR jet velocity and FMD. A single transfusion in the chronically transfused cohort improved FMD. In our patient sample, TR jet velocity and FMD were most strongly associated with plasma free hemoglobin and transfusion status (transfusions being protective), and thus consistent with the hypothesis that intravascular hemolysis and increased endogenous erythropoiesis damage vascular endothelia.

Reduced fitness and abnormal cardiopulmonary responses to maximal exercise testing in children and young adults with sickle cell anemia

Physiologic contributors to reduced exercise capacity in individuals with sickle cell anemia (SCA) are not well understood. The objective of this study was to characterize the cardiopulmonary response to maximal cardiopulmonary exercise testing (CPET) and determine factors associated with reduced exercise capacity among children and young adults with SCA. A cross-sectional cohort of 60 children and young adults (mean 15.1 ± 3.4 years) with hemoglobin SS or S/β(0) thalassemia and 30 matched controls (mean 14.6 ± 3.5 years) without SCA or sickle cell trait underwent maximal CPET by a graded, symptom-limited cycle ergometry protocol with breath-by-breath, gas exchange analysis. Compared to controls without SCA, subjects with SCA demonstrated significantly lower peak VO2 (26.9 ± 6.9 vs. 37.0 ± 9.2 mL/kg/min, P < 0.001). Subjects demonstrated slower oxygen uptake (ΔVO2/ΔWR, 9 ± 2 vs. 12 ± 2 mL/min/watt, P < 0.001) and lower oxygen pulse (ΔVO2/ΔHR, 12 ± 4 vs. 20 ± 7 mL/beat, P < 0.001) as well as reduced oxygen uptake efficiency (ΔVE/ΔVO2, 42 ± 8 vs. 32 ± 5, P < 0.001) and ventilation efficiency (ΔVE/ΔVCO2, 30.3 ± 3.7 vs. 27.3 ± 2.5, P < 0.001) during CPET. Peak VO2 remained significantly lower in subjects with SCA after adjusting for age, sex, body mass index (BMI), and hemoglobin, which were independent predictors of peak VO2 for subjects with SCA. In the largest study to date using maximal CPET in SCA, we demonstrate that children and young adults with SCA have reduced exercise capacity attributable to factors independent of anemia. Complex derangements in gas exchange and oxygen uptake during maximal exercise are common in this population.

A Sickle Cell Disease Patient with Severe Tricuspid Regurgitation and Early Developed Pulmonary Hypertension

Pulmonary hypertension (PH) worsens the mortality of the patients with sickle cell disease (SCD). The exact mechanism of PH development/progression in SCD, including the role of tricuspid regurgitation (TR), remains unclear. We herein report an unusual SCD case, complicated by chronic thromboembolic disorder, who developed severe TR and an accelerated progression of PH. Tricuspid valve surgery significantly ameliorated the patient's symptoms and reduced hospital readmission. The early detection and management of the reversible disorder accelerating the PH development in SCD patients may alter the clinical course, improve the quality of life, and potentially affect the long-term outcome.

Exercise-Induced Abnormal Increase of Systolic Pulmonary Artery Pressure in Adult Patients With Sickle Cell Anemia: An Exercise Stress Echocardiography Study

BACKGROUND

Pulmonary hypertension (PH) at rest is a risk factor for death in patients with sickle cell anemia (SCA). Exercise echocardiography (EE) can detect latent PH. We sought to investigate the occurrence of exercise-induced abnormal response of systolic pulmonary artery pressure (SPAP) in adult patients with SCA and normal SPAP at rest, and to identify the independent predictors of this abnormal response.

METHODS AND RESULTS

Forty-four adult patients with SCA and normal SPAP at rest (tricuspid regurgitant jet flow velocity [TRV] <2.5 m/sec) were studied and divided into 2 groups: exhibiting normal SPAP after treadmill EE (TRV ≤ 2.7 m/sec) (G1), and exhibiting abnormal exercise-induced increase of SPAP (TRV > 2.7 m/sec) (G2). TRV cutoff points at rest and during EE were based on data from healthy-matched control subjects. Abnormal response of SPAP with exercise occurred in 57% of the sample (G2), with mean TRV level of 3.39 ± 0.41 m/sec (range 2.8-4.5 m/sec), significantly higher than those of G1 (2.29 ± 0.25 m/sec, range 2.0-2.7 m/sec; P < 0.001). Multivariate analysis identified TRV value in resting conditions ≥2.25 m/sec (P < 0.05), left atrial volume index ≥41 mL/m² (P < 0.05), and a E/e'-waves ratio ≥6.3 (P < 0.05) as independent predictors of exercise-induced increase of SPAP.

CONCLUSION

We concluded that adult patients with SCA and normal SPAP at rest may exhibit abnormal exercise-induced increase in SPAP, which was independently related to resting TRV levels, and indices of diastolic impairment and left ventricular filling pressure.

Elevated pulse pressure is associated with hemolysis, proteinuria and chronic kidney disease in sickle cell disease

A seeming paradox of sickle cell disease is that patients do not suffer from a high prevalence of systemic hypertension in spite of endothelial dysfunction, chronic inflammation and vasculopathy. However, some patients do develop systolic hypertension and increased pulse pressure, an increasingly recognized major cardiovascular risk factor in other populations. Hence, we hypothesized that pulse pressure, unlike other blood pressure parameters, is independently associated with markers of hemolytic anemia and cardiovascular risk in sickle cell disease. We analyzed the correlates of pulse pressure in patients (n  =  661) enrolled in a multicenter international sickle cell trial. Markers of hemolysis were analyzed as independent variables and as a previously validated hemolytic index that includes multiple variables. We found that pulse pressure, not systolic, diastolic or mean arterial pressure, independently correlated with high reticulocyte count (beta  =  2.37, p  =  0.02) and high hemolytic index (beta  =  1.53, p = 0.002) in patients with homozygous sickle cell disease in two multiple linear regression models which include the markers of hemolysis as independent variables or the hemolytic index, respectively. Pulse pressure was also independently associated with elevated serum creatinine (beta  =  3.21, p  =  0.02), and with proteinuria (beta  =  2.52, p  =  0.04). These results from the largest sickle cell disease cohort to date since the Cooperative Study of Sickle Cell Disease show that pulse pressure is independently associated with hemolysis, proteinuria and chronic kidney disease. We propose that high pulse pressure may be a risk factor for clinical complications of vascular dysfunction in sickle cell disease. Longitudinal and mechanistic studies should be conducted to confirm these hypotheses.

Reduction of the six-minute walk distance in children with sickle cell disease is correlated with silent infarct: results from a cross-sectional evaluation in a single center in Belgium

Background

The 6-minute walk test (6MWT) is used in adults and children affected by a wide range of chronic diseases to evaluate their sub-maximal exercise capacity. It reflects the global response of various physiological systems in a situation simulating a daily life activity.

Methods

We analyzed factors affecting the 6MWT in 46 Sickle Cell Disease children. Forty-two were treated with hydroxyurea (HU). Patients with normal test (>80% of the age-standardized predicted value) were compared to patients with abnormal test (≤80%). Baseline hematological values, clinical events, cerebrovascular disease, cardio-pulmonary parameters and disease-modifying treatment were compared according to the performance of the test.

Results

Among the 46 patients, 14 had an abnormal 6MWT. In univariate analysis, both groups were similar for biological and clinical data. Six of the 14 patients with an abnormal 6MWT had silent infarct (SI) compared to 6/32 with a normal test (P = 0.09). When excluding chronically transfused patients, 4 of the 11 patients with an abnormal 6MWT had SI compared to 1/26 (P = 0.02). Baseline pulse oximetry was normal in both groups but slightly lower in patients with abnormal 6MWT (P = 0.02). No patient presented exercise-induced desaturation. In multivariate analysis, the only factor associated with abnormal 6MWT was the presence of SI (P = 0.045).

Conclusions

In our cohort of 46 patients characterized by high exposure rate to HU and by the absence of severe cardiopulmonary disease, the sole factor independently associated with 6MWT was the presence of SI. The lower exercise capacity of children with SI may reflect some subclinical neurological impairment as they do not differ by hemoglobin level or cardiopulmonary parameters.

Cellular, pharmacological, and biophysical evaluation of explanted lungs from a patient with sickle cell disease and severe pulmonary arterial hypertension

Pulmonary hypertension is recognized as a leading cause of morbidity and mortality in patients with sickle cell disease (SCD). We now report benchtop phenotyping from the explanted lungs of the first successful lung transplant in SCD. Pulmonary artery smooth muscle cells (PASMCs) cultured from the explanted lungs were analyzed for proliferate capacity, superoxide (O2 (•-)) production, and changes in key pulmonary arterial hypertension (PAH)-associated molecules and compared with non-PAH PASMCs. Upregulation of several pathologic processes persisted in culture in SCD lung PASMCs in spite of cell passage. SCD lung PASMCs showed growth factor- and serum-independent proliferation, upregulation of matrix genes, and increased O2 (•-) production compared with control cells. Histologic analysis of SCD-associated PAH arteries demonstrated increased and ectopically located extracellular matrix deposition and degradation of elastin fibers. Biomechanical analysis of these vessels confirmed increased arterial stiffening and loss of elasticity. Functional analysis of distal fifth-order pulmonary arteries from these lungs demonstrated increased vasoconstriction to an α1-adrenergic receptor agonist and concurrent loss of both endothelial-dependent and endothelial-independent vasodilation compared with normal pulmonary arteries. This is the first study to evaluate the molecular, cellular, functional, and mechanical changes in end-stage SCD-associated PAH.

First successful lung transplantation for sickle cell disease with severe pulmonary arterial hypertension and pulmonary veno-occlusive disease

Little is known about the use of lung transplantation in the management of sickle cell disease-associated pulmonary arterial hypertension (SCD-PAH). We present clinical and pathological data and report the first successful outcome of bilateral lung transplantation in a patient with severe SCD-PAH and pulmonary veno-occlusive disease (PVOD). We discuss the complexities of multidisciplinary planning and management of lung transplantation in patients with SCD-associated pulmonary vascular complications. This case reports the first documented successful lung transplant and first case of PVOD in a patient with SCD-PAH.

Risk factors for death in 632 patients with sickle cell disease in the United States and United Kingdom

Background

The role of pulmonary hypertension as a cause of mortality in sickle cell disease (SCD) is controversial.

Methods and Results

We evaluated the relationship between an elevated estimated pulmonary artery systolic pressure and mortality in patients with SCD. We followed patients from the walk-PHaSST screening cohort for a median of 29 months. A tricuspid regurgitation velocity (TRV)≥3.0 m/s cuttof, which has a 67–75% positive predictive value for mean pulmonary artery pressure ≥25 mm Hg was used. Among 572 subjects, 11.2% had TRV≥3.0 m/sec. Among 582 with a measured NT-proBNP, 24.1% had values ≥160 pg/mL. Of 22 deaths during follow-up, 50% had a TRV≥3.0 m/sec. At 24 months the cumulative survival was 83% with TRV≥3.0 m/sec and 98% with TRV<3.0 m/sec (p<0.0001). The hazard ratios for death were 11.1 (95% CI 4.1–30.1; p<0.0001) for TRV≥3.0 m/sec, 4.6 (1.8–11.3; p = 0.001) for NT-proBNP≥160 pg/mL, and 14.9 (5.5–39.9; p<0.0001) for both TRV≥3.0 m/sec and NT-proBNP≥160 pg/mL. Age >47 years, male gender, chronic transfusions, WHO class III–IV, increased hemolytic markers, ferritin and creatinine were also associated with increased risk of death.

Conclusions

A TRV≥3.0 m/sec occurs in approximately 10% of individuals and has the highest risk for death of any measured variable.

The study is registered in ClinicalTrials.gov with identifier

NCT00492531

Severe nocturnal and postexercise hypoxia in children and adolescents with sickle cell disease

Hypoxia is a common feature in children with sickle cell disease (SCD) that is inconsistently associated with painful crises and acute chest syndrome. To assess the prevalence and risk factors of hypoxia, we recorded daytime, nocturnal, and postexercise pulse oximetry (SpO₂) values in 39 SCD patients with a median age of 10.8 years. Median daytime SpO₂ was 97% (range, 89%–100%), and 36% of patients had daytime hypoxia defined as SpO₂<96%. Median nocturnal SpO₂ was 94.7% (range, 87.7%–99.5%), 50% of patients had nocturnal hypoxia defined as SpO₂≤93%, and 11(37%) patients spent more than 10% of their total sleep time with SpO₂<90%. Median postexercise SpO₂ was 94% (range, 72%–100%) and 44.7% of patients had postexercise hypoxia defined as an SpO₂ decrease ≥3% after a 6-minute walk test. Among patients with normal daytime SpO₂, 35% had nocturnal and 42% postexercise hypoxia. Compared to 9 patients without daytime, nocturnal, or postexercise hypoxia, 25 patients with hypoxia under at least one of these three conditions had greater anemia severity (P = 0.01), lower HbF levels (P = 0.04), and higher aspartate aminotransferase levels (P = 0.03). Males predominated among patients with postexercise hypoxia (P = 0.004). Hypoxia correlated neither with painful crises nor with acute chest syndrome. Of 32 evaluable patients, 6 (18.8%) had a tricuspid regurgitation velocity ≥2.6 m/s, and this feature was associated with anemia (P = 0.044). Median percentage of the predicted distance covered during a 6-minute walk test was 86% [46–120]; the distance was negatively associated with LDH (P = 0.044) and with a past history of acute chest syndrome (P = 0.009). In conclusion, severe episodes of nocturnal and postexercise hypoxia are common in children with SCD, even those with normal daytime SpO₂.

An official American Thoracic Society clinical practice guideline: diagnosis, risk stratification, and management of pulmonary hypertension of sickle cell disease

BACKGROUND

In adults with sickle cell disease (SCD), an increased tricuspid regurgitant velocity (TRV) measured by Doppler echocardiography, an increased serum N-terminal pro-brain natriuretic peptide (NT-pro-BNP) level, and pulmonary hypertension (PH) diagnosed by right heart catheterization (RHC) are independent risk factors for mortality.

METHODS

A multidisciplinary committee was formed by clinician-investigators experienced in the management of patients with PH and/or SCD. Clinically important questions were posed, related evidence was appraised, and questions were answered with evidence-based recommendations. Target audiences include all clinicians who take care of patients with SCD.

RESULTS

Mortality risk stratification guides decision making. An increased risk for mortality is defined as a TRV equal to or greater than 2.5 m/second, an NT-pro-BNP level equal to or greater than 160 pg/ml, or RHC-confirmed PH. For patients identified as having increased mortality risk, we make a strong recommendation for hydroxyurea as first-line therapy and a weak recommendation for chronic transfusions as an alternative therapy. For all patients with SCD with elevated TRV alone or elevated NT-pro-BNP alone, and for patients with SCD with RHC-confirmed PH with elevated pulmonary artery wedge pressure and low pulmonary vascular resistance, we make a strong recommendation against PAH-specific therapy. However, for select patients with SCD with RHC-confirmed PH who have elevated pulmonary vascular resistance and normal pulmonary capillary wedge pressure, we make a weak recommendation for either prostacyclin agonist or endothelin receptor antagonist therapy and a strong recommendation against phosphodiesterase-5 inhibitor therapy.

CONCLUSIONS

Evidence-based recommendations for the management of patients with SCD with increased mortality risk are provided, but will require frequent reassessment and updating.

Differences in the clinical and genotypic presentation of sickle cell disease around the world

Sickle cell disease (SCD), caused by a mutation in the β-globin gene HBB, is widely distributed in malaria endemic regions. Cardiopulmonary complications are major causes of morbidity and mortality. Hemoglobin SS (Hb SS) represents a large proportion of SCD in the Americas, United Kingdom, and certain regions of Africa while higher proportions of hemoglobin SC are observed in Burkina Faso and hemoglobin Sβ-thalassemia in Greece and India. Coinheritance of α-thalassemia and persistence of hemoglobin F production are observed in highest frequency in certain regions of India and the Middle East. As confirmed in the PUSH and Walk-PHaSST studies, Hb SS, absence of co-inheriting alpha-thalassemia, and low hemoglobin F levels tend to be associated with more hemolysis, lower hemoglobin oxygen saturations, greater proportions of elevated tricuspid regurgitant jet velocity and brain natriuretic peptide, and increased left ventricular mass index. Identification of additional genetic modifiers will improve prediction of cardiopulmonary complications in SCD.