Pulmonary hypertension in sickle cell disease children under 10 years of age

Pulmonary hypertension in sickle cell disease

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

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Sickle cell nephropathy: insights into the pediatric population

The life expectancy of individuals with sickle cell disease has increased over the years, majorly due to an overall improvement in diagnosis and medical care. Nevertheless, this improved longevity has resulted in an increased prevalence of chronic complications such as sickle cell nephropathy (SCN), which poses a challenge to the medical care of the patient, shortening the lifespan of patients by 20-30 years. Clinical presentation of SCN is age-dependent, with kidney dysfunction slowly beginning to develop from childhood, progressing to chronic kidney disease and kidney failure during the third and fourth decades of life. This review explores the epidemiology, pathology, pathophysiology, clinical presentation, and management of SCN by focusing on the pediatric population. It also discusses the factors that can modify SCN susceptibility.

Chronic organ injuries in children with sickle cell disease

Median life expectancy of patients with sickle cell disease has increased to up to 55 years but there are still frequent cases of premature death, mostly in patients with pre-existing organ failure such as pulmonary hypertension, kidney injury, and cerebral vasculopathy. Most organ injuries remain asymptomatic for a long time and can only be detected through early systematic screening. Protocols combining assessment of velocities on transcranial Doppler and regular transfusions in patients with abnormal velocities have been demonstrated to dramatically reduce the risk of stroke. In contrast, no consensus has been reached on systematic screening or therapy for silent cerebral infarcts. The prognostic significance of increased tricuspid regurgitant jet velocity on echocardiography has not yet been identified in children, whereas increased albuminuria is a good predictor of kidney injury. Finally, screening for hip and eye disorder is recommended; however, different countries adopt different screening strategies. Hydroxyurea is probably of potential benefit in preventing chronic organ damage but this requires further study in order to be fully demonstrated. Efficacy and safety of the other new drugs available are also under investigation.

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.

Pulmonary hypertension and right ventricular function in Nigerian children with sickle cell anaemia

Background

Pulmonary hypertension (PH), a complication of sickle cell anaemia (SCA), results in considerable morbidity. This study aims to determine the prevalence and associations of echocardiography-suggested PH in children with SCA.

Methods

We performed a cross-sectional comparative study involving 100 systematically sampled SCA subjects 3–14 y of age in their steady state with matched haemoglobin AA phenotype controls. Clinical, laboratory and echocardiography data (including tricuspid regurgitation velocity [TRV], mean pulmonary arterial pressure [mPAP] and tricuspid annular plane systolic excursion [TAPSE]) were obtained from all patients. Statistical analyses were performed using SPSS version 22 (IBM, Armonk, NY, USA). A p-value <0.05 was considered statistically significant.

Results

Of the 100 SCA subjects studied, 22 (22%) had echocardiographic findings suggestive of PH compared with none in the controls. The median TAPSE was significantly lower in the PH group (2.55 cm [interquartile range {IQR} 2.2–2.8]) compared with the no PH group (2.77 cm [IQR 2.4–3.2]) (p=0.03). No significant correlation existed between mPAP and age, nor any laboratory parameters studied. The odds ratio (OR) suggested PH significantly increased with an increase in the frequency of hospitalizations for vaso-occlusive crises within a 12-month period (OR 15.15 [95% CI 1.57 to 146.35], p=0.02) and a lifetime history of blood transfusion (OR 5.44 [95% CI 1.09 to 27.24], p=0.04).

Conclusions

Echocardiography-suggested PH is common in children with SCA and is associated with poorer right ventricular function, frequent vaso-occlusive crises and blood transfusions.

Right ventricular function among South East Nigeria children with sickle cell anaemia

BACKGROUND

Sickle cell anaemia (SCA) is characterized by attendant ischemia-reperfusion injury especially to the heart.

METHODS

The aim of this work is to compare the right ventricular function of children with SCA in steady state (subjects) with those with haemoglobin AA genotype (controls), using echocardiography. It is a cross-sectional study, which echocardiographic measurements to assess right ventricular function among children with SCA and their controls.

RESULTS

The mean trans annular plane systolic excursion (TAPSE) in subjects, 28.24 ± 5.23 (Z score: 0.258 ± 1.10) was higher than that in control, 25.82 ± 3.59 (Z score: - 0.263 ± 0.80), and the difference in mean was statistically significant, (t = 2.703, p = 0.008). Significantly higher proportion of subjects with sickle cell anaemia had right ventricular dysfunction (Abnormal TAPSE), 25 (50.0%) when compared with those in control, 11 (22.0%), {χ2 = 8.5, p = 0.0035}. A higher proportion of subjects with sickle cell anaemia (25.5%) had Pulmonary hypertension (RVP) when compared with control (2.0%) and the difference in proportions was found to be statistically significant, (χ2 = 11.668, p = 0.001). The prevalence of right ventricular diastolic dysfunction in subjects was 9.8% while control was 0%.

CONCLUSION

Children with sickle cell anaemia present with right ventricular dysfunction. Prevalence of right ventricular systolic and diastolic dysfunction were higher in subjects. More of the subjects in this study (25.5%) had pulmonary hypertension.

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.

Doppler echocardiographic assessment of pulmonary artery pressure in children with sickle cell anaemia

Background

Pulmonary artery hypertension (PAH) is a known complication of patients with sickle cell disease (SCD). The prevalence of PAH has been reported to be high in children with SCD in developed countries. The mortality rate of patients with SCD who develop PAH is said to be 40% at 24 to 40 months after diagnosis. In Sub-Saharan Africa, particularly Nigeria, where the prevalence of SCD is high, there is a dearth of data on the prevalence of PAH in children with SCD. PAH may be a likely contributor to the unacceptably high mortality rate of children with SCD in Africa. The present study aimed to determine the pattern of pulmonary artery pressure in children with sickle cell anaemia (SCA) aged 1 to 12 years in their steady state using Doppler echocardiography in our environment.

Methods

Analytical, comparative and cross-sectional study. It was carried out at Lagos State University Teaching Hospital (LASUTH) over a period of seven months (31st August 2015 through 31st March 2016). A total of 400 children, aged 1 to 12 years were recruited following parental consent and assent. Two hundred children with SCA in steady state and 200 age and sex matched children with haemoglobin genotype AA who served as controls were studied. All subjects and controls had Doppler echocardiography performed on them by the author. PAH was defined as a pulmonary artery systolic pressure (PASP) of ≥30 mmHg at rest derived from the tricuspid regurgitant velocity (TRV) measured from Doppler echocardiography. This corresponds with TRV value of ≥2.5 m/s.

Results

The prevalence of PAH in children with SCA was 8% (n=16). None of the controls had PAH. The youngest subject with PAH was aged 2 years. The overall mean pulmonary artery pressure of children with SCA was significantly higher than that of controls (18.54±5.81 vs. 13.76±5.71 mmHg, P=0.000). The prevalence of PAH in children with SCA demonstrated an increase in trend with age.

Conclusions

The prevalence of PAH in children with SCA in steady state is high. This complication was noticed as early as the second year of life. It is recommended that all children with SCA should have periodic Doppler echocardiography for early detection of PAH.

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

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

The association of nocturnal hypoxia and an echocardiographic measure of pulmonary hypertension in children with sickle cell disease

BACKGROUND

Pulmonary hypertension (PH) is multifactorial in origin and may develop early in children with sickle cell disease (C-SCD). Potential etiologies are hemolysis-induced endothelial dysfunction, left ventricular (LV) dysfunction, and chronic hypoxia. Nocturnal hypoxia (NH) in C-SCD is known to be a sequela of obstructive sleep apnea (OSA). The primary objective of this study is to correlate polysomnographic evidence NH with echocardiographic measures of PH in C-SCD.

METHODS

We performed a retrospective chart review of 20 C-SCD (Hemoglobin SS), who had polysomnography and echocardiogram performed within a narrow time interval, and 31% of them had pre-existing cardiac conditions. Tricuspid regurgitant jet velocity (TRJV) ≥ 2.5 m/s was considered as an indicator of PH.

RESULTS

Twenty-five percent of the subjects had NH. Forty percent of C-SCD, predominantly male, had evidence of PH based on an elevated TRJV. Children with NH compared to non-NH had significantly worse baseline hypoxemia (p < 0.001), higher TRJV (p = 0.005), and higher LV end-diastolic diameters (p = 0.009). The severity of NH was influenced by OSA. However, PH was not associated with OSA or duration of hydroxyurea therapy.

CONCLUSION

Our study indicates that NH is associated with PH in C-SCD, and that screening for NH may help to identify C-SCD with higher morbidity risk.

How I treat hypoxia in adults with hemoglobinopathies and hemolytic disorders

Hemoglobinopathies are caused by genetic mutations that result in abnormal hemoglobin molecules, resulting in hemolytic anemia. Chronic complications involving the lung parenchyma, vasculature, and cardiac function in hemoglobinopathies result in impaired gas exchange, resulting in tissue hypoxia. Hypoxia is defined as the deficiency in the amount of oxygen reaching the tissues of the body and is prevalent in patients with hemoglobinopathies, and its cause is often multifactorial. Chronic hypoxia in hemoglobinopathies is often a sign of disease severity and is associated with increased morbidity and mortality. Therefore, a thorough understanding of the pathophysiology of hypoxia in these disease processes is important in order to appropriately treat the underlying cause and prevent complications. In this article, we discuss management of hypoxia based on three different cases: sickle cell disease, β-thalassemia, and hereditary spherocytosis. These cases are used to review the current understanding of the disease pathophysiology, demonstrate the importance of a thorough clinical history and physical examination, explore diagnostic pathways, and review the current management.

Changes in Bi-ventricular Function After Hematopoietic Stem Cell Transplant as Assessed by Speckle Tracking Echocardiography

Hematopoietic stem cell transplant (HSCT) is a therapeutic option for patients with sickle cell disease (SCD) and severe acquired aplastic anemia (SAA). HSCT may have beneficial effects on ventricular function in damaged myocardium. We hypothesized improvement in ventricular performance and pulmonary hypertension following HSCT with strain echocardiography in SCD and SAA. Echocardiographic strain and other standard functional data were obtained via retrospective cohort analysis of patients (n = 23) with SCD and SAA who underwent HSCT and were followed at a single center between 2000 and 2014. Left ventricular global longitudinal strain was below normal at baseline, and decreased significantly (from - 16.6 to - 11.1, P = 0.05) from pre-HSCT to the initial post-HSCT echocardiogram at 109 (SD ± 83) days. At 351 (SD ± 115) days, longitudinal strain improved significantly from initial decline (from - 11.1 to - 17.5, P = 0.009) but was comparable to baseline (P = 0.43). Other measurements of bi-ventricular function did not change significantly. Tricuspid regurgitation velocities as surrogates for pulmonary hypertension improved in the subset of patients with baseline elevated values although data points were limited. Abnormal myocardial systolic function was detected at baseline with strain imaging. HSCT was associated with initial worsening longitudinal strain values, followed by improvement to baseline levels by 1 year. Insufficient data exist on whether pulmonary hypertension improves after HSCT.

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.

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

INTRODUCTION

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

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.

Doppler-Defined Pulmonary Hypertension in Sickle Cell Anemia in Kurdistan, Iraq

To determine the frequency, clinical and laboratory associations of pulmonary hypertension in Iraqi Kurds with sickle cell anemia, a total of ninety four such patients attending a major hemoglobinopathy center in Iraqi Kurdistan were enrolled. All patients were re-evaluated clinically and had their blood counts, HbF, serum ferritin, LDH, renal and liver function assessed. Transthoracic Doppler echocardiography with measurement of tricuspid valve regurgitant jet velocity (TRV) was performed. A TRV in excess of 2.8 m/s was considered for the purposes of this study as indicative of pulmonary hypertension (PH). The prevalence of TRV in excess of 2.8m/s was 10.6%. By univariate analysis: significantly higher reticulocyte count, more frequent blood transfusions and pain episodes were encountered in the PH group as compared to the non-PH group (p = 0.001, 0.045 and 0.02 respectively). Moreover, PH patients had significantly higher mean right atrial area, left atrial size, E wave/A wave ratio and ejection fraction by echocardiography (p = 0.027, 0.037, <0.001 and 0.008 respectively). Except for reticulocyte count none of the other parameters remained significant by multivariate analysis (p = 0.024). In conclusion the current study revealed that pulmonary hypertension is rather frequent among Iraqi Kurds with sickle cell anemia, and identified reticulocyte count as an independently associated parameter with PH in this population. Future prospective studies including right heart catheterization and appropriate medical intervention are warranted.

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.

Sleep pathology characterization in sickle cell disease: case-control study

BACKGROUND

Children and adolescents with sickle cell disease (SCD) have a higher incidence of sleep pathology and obstructive sleep apnea syndrome (OSAS). The nocturnal hypoxemia is a risk to vaso-occlusive crisis among other SCD morbidities. Our aim was to compare polysomnography (PSG) results in a sample of children with SCD with a sample of children with suspected OSAS without SCD.

DESIGN AND METHODS

A retrospective study compared clinical and PSG parameters. A descriptive analysis and t-test were done considering P < 0.05 as significant.

RESULTS

PSG was done in 65 children with SCD and 65 control-children. Control sample was selected to be equal to SCD sample considering gender (53.8% were male), age (mean age was 9.4 years (SD ± 4.6) and AHI (mean 3.57 events/hr). Mean efficiency, latency and percentage of sleep phases in both groups showed no statistically significant differences. Mean SpO2 and minimum SpO2 were lower in SCD group and it was statistically significant (P < 0.01). Enuresis was more frequent in the SCD children group (35.4% vs. 6.2%, P < 0.01).

CONCLUSION

Comparing children with and without SCD, sleep architecture was similar in both groups and minimum SpO2 was significantly lower in SCD children although both groups had a similar AHI. This is an important issue in these children, so it is essential to have a sleep evaluation in order to prevent complications and co-morbidities.

Thalassemia major and sickle cell disease in adolescents and young adults

The increased longevity of patients with thalassemia and sickle cell disease (SCD) introduces new clinical challenges due to the accumulation of disease-related morbidity, psychosocial issues and health care adjustments. Patients with thalassemia major now live into adulthood without suffering heart failure but must confront delayed puberty, impaired fertility and progressive bone disease. The increased survival in SCD brings to the front previously unrecognized complications including pulmonary hypertension, silent cerebral infarcts and also reproductive dysfunction. Adolescents and young adults (AYAs) have age-related psychosocial needs in their transition from the pediatric health care environment to the adult system. In this review we present the uniquely age-related medical issues facing the AYA thalassemia and SCD cohort in their transition into adulthood.

Echocardiography-derived tricuspid regurgitant jet velocity is an important marker for the progression of sickle-cell disease

BACKGROUND

Although echocardiography-derived tricuspid regurgitant jet velocity (TRV) is associated with increased mortality in sickle-cell disease (SCD), it is unclear whether increased TRV is a marker of multiorgan disease due to systemic vasculopathy or related to increased pulmonary artery systolic pressure with episodes of multiple acute chest syndrome (ACS).

METHODS

Our study analyzed 148 consecutive patients with transthoracic echocardiography with TRV data, who came to our adult SCD Clinic at the Wake Forest Baptist Medical Center. For our analysis, we took TRV ≥ 2.5 m/s as elevated. Patients were followed on average for 9 years.

RESULTS

TRV ≥ 3 m/s was significantly associated with increased mortality (p < 0.001), thromboembolism (p < 0.001), hospitalization for ACS (p < 0.001), supraventricular arrhythmia (p = 0.028), right ventricular (RV) dilation, decreased hemoglobin and increased creatinine. Patients with a progressive increase in TRV during follow-up had increased mortality (36.7 vs. 8.6%, p = 0.007) and increased ACS (45 vs. 5.7%, p < 0.001). Death was independently associated with TRV ≥ 3 m/s (p = 0.023), ACS (p = 0.001) and increased RV basal diameter (p = 0.003).

CONCLUSIONS

TRV is an important global marker for the severity and progression of SCD, and carries a significant prognostic implication.

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.

Pediatric Natural Deaths

Autopsies are important in the investigation of childhood deaths. Most natural deaths are unlikely to come to the attention of the forensic pathologist, particularly in cases where death occurs in hospital. During the neonatal period (up to 28 days of age), deaths most commonly occur as a result of prematurity and related conditions, chromosomal abnormalities, or congenital malformations. Beyond the neonatal period, trauma-related deaths and sudden infant death syndrome are more common. In terms of natural acquired diseases of childhood, certain conditions are prevalent based on age and may be encountered at autopsy. Common acquired diseases that cause death in infants and children up to 5 years of age include pneumonia and other respiratory diseases, other infectious diseases, and malignancies. In older children, mortality due to natural disease declines substantially with trauma being the major cause of death, and malignancies the major cause of acquired disease. Sudden and/or unexpected deaths in which a natural disease state was previously unknown are most likely to come under the jurisdiction of the medical examiner or coroner and may be related to an underlying natural disease. Depending on the underlying disease process, the approach can differ, and therefore familiarity with common causes of death during childhood is important in order to focus the autopsy so that special techniques can be used along with obtaining proper ancillary testing to arrive at an accurate diagnosis and cause of death.

How does catalase release nitric oxide? A computational structure-activity relationship study

Hydroxyurea (HU) is the only FDA approved medication for treating sickle cell disease in adults. The primary mechanism of action is pharmacological elevation of nitric oxide (NO) levels which induces propagation of fetal hemoglobin. HU is known to undergo redox reactions with heme based enzymes like hemoglobin and catalase to produce NO. However, specific details about the HU based NO release remain unknown. Experimental studies indicate that interaction of HU with human catalase compound I produces NO. Presently, we combine flexible receptor-flexible substrate induced fit docking (IFD) with energy decomposition analyses to examine the atomic level details of a possible key step in the clinical conversion of HU to NO. Substrate binding modes of nine HU analogs with catalase compound I were investigated to determine the essential properties necessary for effective NO release. Three major binding orientations were found that provide insight into the possible reaction mechanisms for producing NO. Further results show that anion/radical intermediates produced as part of these mechanisms would be stabilized by hydrogen bonding interactions from distal residues His75, Asn148, Gln168, and oxoferryl-heme. These details will ideally contribute to both a clearer mechanistic picture and provide insights for future structure based drug design efforts.

Coagulation activation in children with sickle cell disease is associated with cerebral small vessel vasculopathy

Background

Thrombotic complications in Sickle Cell Disease (SCD) arise since infancy, but the role of the coagulation system in children has been poorly explored. To determine its role in the development of clinical complications in childhood we measured coagulation and endothelial parameters in children with SCD at steady state.

Methods

Markers of thrombin generation, fibrin dissolution and endothelial activation were evaluated in 38 children with SS-Sβ°, 6 with SC disease and 50 age and blood group matched controls. Coagulation variables were correlated with markers of hemolysis and inflammation, with the presence of cerebral and lung vasculopathy and with the frequency of clinical complications.

Results

SS-Sβ° patients presented higher levels of factor VIII, von Willebrand factor antigen (VWF:Ag) and collagen binding activity, tissue plasminogen activator antigen (t-PA:Ag), D-dimer, p-selectin, prothrombin fragment1+2 (F1+2) and lower ADAMTS-13:activity/VWF:Ag (p<0.05) compared to controls and SC patients. In SS-Sβ° patients coagulation variables correlated positively with markers of inflammation, hemolysis, and negatively with HbF (p<0.05). Patients with cerebral silent infarcts showed significant decrease in t-PA:Ag and ADAMTS-13 Antigen and a tendency toward higher D-dimer, F1+2, TAT compared to patients without them. D-dimer was associated with a six fold increased risk of cerebral silent infarcts. No correlation was found between coagulation activation and large vessel vasculopathy or other clinical events except for decreased t-PA:Ag in patients with tricuspid Rigurgitant Velocity >2.5m/sec.

Conclusions

SS-Sβ° disease is associated with extensive activation of the coagulation system at steady state since young age. ADAMTS-13 and t-PA:Ag are involved in the development of cerebral silent infarcts.

Hematopoietic stem-cell transplantation for sickle cell disease: current evidence and opinions

With rapidly expanding evidence of benefit reported by several groups, allogeneic hematopoietic stem-cell transplantation has become an acceptable treatment option for sickle cell disease. It is currently the only curative therapy available. Hematopoietic stem-cell transplantation was offered primarily as a therapeutic option for severe sickle cell disease in the context of myeloablative matched sibling donor transplants over the last two decades and helped to establish the benefits of transplantation for this disorder. While this approach provided proof of principle, the disadvantages and limitations of transplantation became evident along the way. It has been recognized that transplantation for sickle cell disease does not need to adhere strictly to the principles of transplantation for malignant disorders, such as achievement of full donor cell chimerism. As reviewed here, in recent years the transplant community has set out to explore ways to make stem-cell transplantation more available to patients with the disease, define indications and better timing, and offset toxicities with novel approaches to conditioning and better supportive care.

Prevalence of pulmonary arterial hypertension among sickle cell disease patients in Al Hassa

Background:

The prevalence of pulmonary arterial hypertension (PAH) in Saudi adults with sickle cell disease (SCD), the mechanism of its development, and its prospective prognostic significance are unknown.

Objective:

To assess the prevalence of PAH among sickle cell disease patients attended hematology outpatient clinic at King Fahad Hospital, Al Hassa, Saudi Arabia.

Methods:

Doppler echocardiography was performed for assessments of pulmonary- arterial systolic pressure (PASP) on 203 consecutive patients (102 men and 101 women) aged > 11 years, attending hematology clinic at King Fahad Hospital, Al Hassa, Saudi Arabia. Pulmonary hypertension was prospectively defined as a tricuspid regurgitant jet velocity (TRJV) of at least 2.5 m per second which can be estimate PASP equal or more than 25 mmHg.

Results:

Doppler-defined pulmonary arterial hypertension was diagnosed in 37.1% among 202 patients included in study (after one female patient was excluded) using a cutoff of PASP ≥25 mmHg.

Conclusion:

The prevalence of PAH among adults Saudis with SCD is higher than that reported from the developed countries. Further assessment using invasive techniques is required coupled employing analytical study design to predict the factors that favor the development of PAH among Saudi patients are required.

Unlocking the binding and reaction mechanism of hydroxyurea substrates as biological nitric oxide donors

Hydroxyurea is the only FDA approved treatment of sickle cell disease. It is believed that the primary mechanism of action is associated with the pharmacological elevation of nitric oxide in the blood; however, the exact details of this are still unclear. In the current work, we investigate the atomic level details of this process using a combination of flexible-ligand/flexible-receptor virtual screening coupled with energetic analysis that decomposes interaction energies. Utilizing these methods, we were able to elucidate the previously unknown substrate binding modes of a series of hydroxyurea analogs to hemoglobin and the concomitant structural changes of the enzyme. We identify a backbone carbonyl that forms a hydrogen bond with bound substrates. Our results are consistent with kinetic and electron paramagnetic resonance (EPR) measurements of hydroxyurea-hemoglobin reactions, and a full mechanism is proposed that offers new insights into possibly improving substrate binding and/or reactivity.

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

BACKGROUND

Noninvasively assessed pulmonary pressure elevations and left ventricular (LV) diastolic dysfunction are associated with increased mortality in adults with sickle cell disease, but their relationship to exercise intolerance has not been evaluated prospectively.

METHODS AND RESULTS

Echocardiography, 6-minute walk distance, hemolytic rate, and serum concentrations of ferritin and erythropoietin were evaluated in a cohort of 483 subjects with homozygous hemoglobin S in the U.S. and U.K. Walk-Treatment of Pulmonary Hypertension and Sickle Cell Disease with Sildenafil Therapy (Walk-PHaSST) study. Tricuspid regurgitation velocity, which reflects systolic pulmonary artery pressure, was 2.7 to <3.0 m/s (mean±SD, 2.8±0.1) in 26% of the subjects and ≥3.0 m/s (mean±SD, 3.4±0.4) in 11%. The LV lateral E/e' ratio, which has been shown to reflect LV filling pressure in other conditions but has not been studied in sickle cell disease, was significantly higher in the groups with tricuspid regurgitation velocity ≥2.7 m/s. Increased hemolysis (P<0.0001), LV lateral E/e' ratio (P=0.0001), blood urea nitrogen (P=0.0002), and erythropoietin (P=0.002) were independently associated with an increased tricuspid regurgitation velocity. Furthermore, female sex (P<0.0001), older age (P<0.0001), LV lateral E/e' ratio (P=0.014), and tricuspid regurgitation velocity (P=0.019) were independent predictors of a shorter 6-minute walk distance.

CONCLUSIONS

Echocardiography-estimated elevated pulmonary artery systolic pressure and LV lateral E/e' ratio were independently associated with poor exercise capacity in a large cohort of patients with sickle cell anemia. Controlled trials investigating whether strategies to prevent or delay pulmonary hypertension and/or LV diastolic dysfunction will improve exercise capacity and long-term outcomes in sickle cell anemia should be considered. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00492531.

Tricuspid regurgitant velocity elevation in a three-year old child with sickle cell anemia and recurrent acute chest syndromes reversed not by hydroxyurea but by bone marrow transplantation

Elevated Tricuspid Regurgitant Velocity (TRV) has been related to higher mortality in adults and to hemolysis, lower oxygen saturation during 6-minute walk test and acute chest syndrome (ACS) in children with sickle cell disease (SCD). Hydroxyurea (HU) has reduced TRV value in children and adults. We describe a three year old HbSS child with recurrent ACS, hypoperfusion of the left lung, mild hemolysis and persistent TRV elevation. TRV did not normalize after HU, despite improvement in clinical conditions and in baseline laboratory parameters related to hemolysis and blood viscosity, but normalized after bone marrow transplantation (BMT). Our experience suggests that in young patients, TRV reduction can be a positive concomitant effect of BMT.

Acute chest syndrome: sickle cell disease

Acute chest syndrome (ACS) is a common complication and reason for hospital admission in patients with sickle cell disease (SCD). It is also the most common cause of death in this patient population. Most of the time, the trigger for ACS in an individual patient cannot be identified. However, although infection is the most common identifiable cause for ACS, other important triggers are vaso-occlusive crisis (VOC) and asthma. This comprehensive review will focus on the pathogenesis, clinical characteristics, complications and treatment available to manage ACS. But importantly, this review will highlight new possible etiologies, with the goal of improving oxygenation and, therefore, a reduction in sickling and lung damage in this patient population.

Reconstructing sickle cell disease: a data-based analysis of the "hyperhemolysis paradigm" for pulmonary hypertension from the perspective of evidence-based medicine

The "hyperhemolytic paradigm" (HHP) posits that hemolysis in sickle disease sequentially and causally establishes increased cell-free plasma Hb, consumption of NO, a state of NO biodeficiency, endothelial dysfunction, and a high prevalence of pulmonary hypertension. The basic science underpinning this concept has added an important facet to the complexity of vascular pathobiology in sickle disease, and clinical research has identified worrisome clinical issues. However, this critique identifies and explains a number of significant concerns about the various HHP component tenets. In addressing these issues, this report presents: a very brief history of the HHP, an integrated synthesis of mechanisms underlying sickle hemolysis, a review of the evidentiary value of hemolysis biomarkers, an examination of evidence bearing on existence of a hyperhemolytic subgroup, and a series of questions that should naturally be applied to the HHP if it is examined using critical thinking skills, the fundamental basis of evidence-based medicine. The veracity of different HHP tenets is found to vary from true, to weakly supported, to demonstrably false. The thesis is developed that the HHP has misidentified the mechanism and clinical significance of its findings. The extant research questions identified by these analyses are delineated, and a conservative, evidence-based approach is suggested for application in clinical medicine.

Hematopoietic stem cell transplantation for sickle cell disease: current practice and emerging trends

Allogeneic HSCT controls sickle cell disease (SCD)-related organ damage and is currently the only curative therapy available. Over the last 2 decades, HSCT has been limited largely to myeloablative matched sibling donor (MSD) procedures that are feasible only in a minority of patients. As the natural history of the disease has evolved, it is clear that subsets of patients with severe disease are at risk for sudden death, devastating CNS and pulmonary complications, and debilitating vasoocclusive crises. For these patients, the benefits of transplantation can outweigh the risks if HSCT can be safely and successfully performed with low early and late toxicities. This review describes advances and ongoing investigation of HSCT for SCD from the perspectives of recipient age and presentation, donor stem cell source, intensity of conditioning, family and medical perspectives, and other variables that influence outcome. Ultimately, HSCT should be viewed as a viable treatment option for SCD on par with other therapies for select patients who can benefit from the procedure.