Tricuspid regurgitation velocity and other biomarkers of mortality in children, adolescents and young adults with sickle cell disease in the United States: The PUSH study

Updates in Pediatric Sickle Cell Lung Disease

Sickle cell lung disease presents a challenging care paradigm involving acute and chronic lower airway disease, sleep-disordered breathing, pulmonary vascular disease, and modification by environmental factors. Understanding the presentation, pathophysiology, and diagnostic approaches is essential for accurate identification and management. While significant progress has been made, there remains a need for research to develop effective treatments and interventions to decrease disease burden in these children. Additionally, the long-term impact of interventions on cardiopulmonary outcomes is unknown. Collaborative efforts among health care providers, researchers, advocacy groups, and policy makers are crucial to improving the lives of children with SCD.

Neutrophils in sickle cell disease: Exploring their potential role as a therapeutic target

Factors influencing the activation of neutrophils in SCD and the potential neutrophil-mediated ameliorating effects of therapies in SCD.

The range of haploidentical transplant protocols in sickle cell disease: all haplos are not created equally

The ideal curative therapy for sickle cell disease (SCD) must be applicable across all ages and include individuals with strokes and preexisting heart, lung, and kidney disease. Myeloablative, matched sibling donor hematopoietic stem cell transplant (HCT) for children with SCD has shown excellent outcomes over the past 3 decades but has been restricted due to the limited availability of a human leukocyte antigen-matched sibling donor (10%-15%) and increased treatment-related death in adults with myeloablative conditioning. To overcome these 2 significant barriers to curative therapy in SCD, related haploidentical HCT has become an active area of research. The use of related haploidentical donors (first- and second-degree relatives) increases the donor pool to at least 90% of those eligible across the life span. Importantly, most adults, even with strokes or significant comorbidities, can tolerate the nonmyeloablative conditioning regimen without treatment-related death. Since 2013, at least 3 related haploidentical HCT strategies have emerged as potential curative therapies for SCD: (1) a nonmyeloablative, T-cell replete, bone marrow transplant with thiotepa and posttransplant cyclophosphamide with a goal of complete donor chimerism; (2) a nonmyeloablative, in vivo T-cell depletion, using peripheral blood stem cells (PBSCs) with a goal of stable mixed donor-recipient chimerism; and (3) a myeloablative, ex vivo T-cell depletion using PBSCs and advanced-technology graft manipulation, with a goal of complete donor chimerism. We review the similarities, differences, outcomes, and gaps in knowledge with these 3 haploidentical HCT approaches for SCD.

Creating an automated contemporaneous cohort in sickle cell anemia to predict survival after disease-modifying therapy

The Food and Drug Administration requires contemporaneous controls to compare clinical outcomes for participants receiving experimental gene therapy or gene editing clinical trials. However, developing a contemporaneous cohort of rare diseases requires multiple person-hours. In a single referral center for sickle cell disease, we tested the hypothesis that we could create an automated contemporaneous cohort of children and adults with sickle cell anemia (SCA) to predict mortality. Data were obtained between 1 January 2004 and 30 April 2021. We identified 419 individuals with SCA with consistent medical care defined as followed continuously for >0.5 years with no visit gaps >3.0 years. The median age was 10.2 years (IQR, 1-24 years), with a median follow-up of 7.4 years (IQR, 3.6-13.5 years) and 47 deaths. A total of 98% (274 of 277) of the children remained alive at 18 years of age, and 34.3% (94 of 274) of those children were followed into adulthood. For adults, the median age of survival was 49.3 years. Treatment groups were mutually exclusive and in a hierarchical order: hematopoietic stem cell transplant (n = 22)>regular blood transfusion for at least 2 years (n = 56)>hydroxyurea for at least 1 year (n = 243)>no disease-modifying therapy (n = 98). Compared to those receiving no disease-modifying treatment, those treated with hydroxyurea therapy had a significantly lower hazard of mortality (hazard ratio = 0.38; P = 0.016), but no statistical difference for those receiving regular blood transfusions compared to no disease-modifying therapy (hazard ratio = 0.71; P = 0.440). An automated contemporaneous SCA cohort can be generated to estimate mortality in children and adults with SCA.

Gene expression changes in sickle cell reticulocytes and their clinical associations

Transcriptional changes in compensatory erythropoiesis in sickle cell anemia (SCA) and their disease modulation are unclear. We detected 1226 differentially expressed genes in hemoglobin SS reticulocytes compared to non-anemic hemoglobin AA controls. Assessing developmental expression changes in hemoglobin AA erythroblasts for these genes suggests heightened terminal differentiation in early erythroblasts in SCA that diminishes toward the polychromatic to orthochromatic stage transition. Comparison of reticulocyte gene expression changes in SCA with that in Chuvash erythrocytosis, a non-anemic disorder of increased erythropoiesis due to constitutive activation of hypoxia inducible factors, identified 453 SCA-specific changes attributable to compensatory erythropoiesis. Peripheral blood mononuclear cells (PBMCs) in SCA contain elevated proportions of erythroid progenitors due to heightened erythropoiesis. Deconvolution analysis in PBMCs from 131 SCA patients detected 54 genes whose erythroid expression correlated with erythropoiesis efficiency, which were enriched with SCA-specific changes (OR = 2.9, P = 0.00063) and annotation keyword "ubiquitin-dependent protein catabolic process", "protein ubiquitination", and "protein polyubiquitination" (OR = 4.2, P = 7.5 × 10-5). An erythroid expression quantitative trait locus of one of these genes, LNX2 encoding an E3 ubiquitin ligase, associated with severe pain episodes in 774 SCA patients (OR = 1.7, P = 3.9 × 10-5). Thus, erythroid gene transcription responds to unique conditions within SCA erythroblasts and these changes potentially correspond to vaso-occlusive manifestations.

Associations of hemolysis and anemia with cardiopulmonary dysfunction in an adult sickle cell disease cohort

BACKGROUND

Hemolysis contributes to the anemia of sickle cell disease (SCD). Hemolysis and anemia are distinct but inter-related pathophysiological processes that underlie end-organ dysfunction in this condition. We hypothesized that real-world medical tests would reveal distinct contributions of hemolysis and anemia to certain cardiopulmonary changes in adults with SCD.

METHODS

We assessed laboratory and clinical tests of cardiopulmonary function obtained during routine delivery of care in 442 adult SCD patients. We characterized hemolysis by the first principal component (PC1) of reticulocyte percent, lactate dehydrogenase (LDH), aspartate amino transferase (AST) and total bilirubin- the hemolytic component. The relationships of hemoglobin concentration and hemolysis to organ dysfunction were analyzed by multiple regression and path analysis to identify independent associations.

RESULTS

Degree of hemolysis and degree of anemia both associated independently with elevated values for left atrial diameter (LAD) and left ventricular end-diastolic diameter (LVED), and with lower percent predicted forced expiratory volume in first second (FEV1). Degree of hemolysis, but not anemia, associated independently with low values for oxygen saturation, forced vital capacity (FVC), and total lung capacity (TLC)]. Path analysis reinforced the trend by multiple regression for association of both degree of hemolysis and anemia with elevated TRV but not with lower diastolic blood pressure.

DISCUSSION

Analysis of real-world clinical tests suggest that, although they are inter-related, the degrees of hemolysis and of anemia make independent contributions to cardiopulmonary dysfunction and that treatments that specifically target both aspects of sickle cell disease may be of maximal benefit.

Pulmonary hypertension screening in children with sickle cell disease

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Arginine Therapy and Cardiopulmonary Hemodynamics in Hospitalized Children with Sickle Cell Anemia: A Prospective, Double-blinded, Randomized Placebo-controlled Clinical Trial

Rationale: Acute changes in cardiopulmonary hemodynamics that include tricuspid regurgitant jet velocity (TRV) elevation measured by Doppler echocardiography are often encountered during sickle cell vasoocclusive pain and acute chest syndrome (ACS). Arginine and nitric oxide depletion develop in patients with these complications. Arginine administration may therefore improve nitric oxide bioavailability and potentiate pulmonary vasodilatation. Objectives: To evaluate effects of l-arginine supplementation on Doppler indices of cardiopulmonary hemodynamics in children with sickle cell anemia experiencing pain. Methods: This was a prospective, double-blinded, randomized placebo-controlled trial of oral arginine in children with sickle cell anemia age 5-17 years hospitalized with severe pain and/or ACS. Measurements and Main Results: Blood biomarkers and Doppler echocardiographic indices of cardiopulmonary hemodynamics were measured before and after supplementation. The mean change in TRV, pulmonary artery systolic pressure, mean pulmonary artery pressure, and other indices of cardiopulmonary hemodynamics were tested with paired Student's t test and correlated with markers of arginine bioavailability using Pearson correlation. Sixty-six children were randomized into arginine versus placebo groups. An elevated TRV ⩾ 2.5 m/s was seen in 40 (61%) patients. A Day 5 Doppler echocardiogram was performed in 47 patients who remained hospitalized. A greater reduction in median TRV occurred in the arginine group than placebo (22.2%, n = 22 vs. 3.8%, n = 25; p < 0.01). A larger percentage increase in global arginine bioavailability was associated with a lower TRV after 5 days of supplementation (r = -0.533; P = 0.001). Significant differences in multiple indices of cardiopulmonary hemodynamics and mean N-terminal pro B-type brain natriuretic peptide were also noted after arginine therapy. Conclusions: Oral arginine supplementation improves cardiopulmonary hemodynamics during sickle cell disease vasoocclusive pain and ACS.Clinical trial registered with Pan African Clinical Trial Registry https://pactr.samrc.ac.za/Search.aspx (PACTR201611001864290).

Sickle cell disease as an accelerated aging syndrome

Sickle cell disease (SCD) is characterized by vaso-occlusion, hemolysis, and systemic manifestations that form the hallmark of the disease. Apart from morbidity, SCD is also associated with increased mortality and decreased quality of life. Aging is a natural phenomenon that is associated with changes at cellular, tissue, and organ levels, in addition to the loss of physical fitness, increased susceptibility to diseases, and a higher likelihood of mortality. Some of the cellular mechanisms involved in normal (or physiological) aging include abnormalities of sphingolipids (ceramides) and reduced length of the telomere. These changes have also been documented in SCD. Cellular, organs, and physical manifestations of SCD resemble an accelerated aging syndrome. Sickle erythrocytes also acquire morphological features similar to that of aged normal erythrocytes and are thus picked up early by the macrophages for destruction. Brain, kidney, heart, innate and adaptive immune system, and musculoskeletal system of patients with SCD exhibit morphological and functional changes that are ordinarily seen in the elderly in the general population. Stroke, silent cerebral infarcts, cardiomegaly, heart failure, pulmonary hypertension, nephropathy with proteinuria, osteopenia, osteoporosis, osteonecrosis, gout, and infections are exceedingly common in SCD. In this review, we have attempted to draw parallels between SCD and accelerated aging syndromes.

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

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

Evidence-Based Minireview: In young children with severe sickle cell disease, do the benefits of HLA-identical sibling donor HCT outweigh the risks?

In case 1, a 14-month-old male child with sickle cell disease (SCD) was referred for evaluation for an allogeneic hematopoietic stem cell transplant (HCT). The patient had a history of dactylitis 3 times in his first year of life and febrile episodes twice at the consult. His 4-year-old sister was found to be human leukocyte antigen (HLA) identical. The patient was started on hydroxyurea (HU) at 2.5 years of age. His parents again sought consultation when he was 5 years old because of concerns about his medical condition. At the time, the patient had experienced 2 vaso-occlusive pain episodes (VOEs) requiring hospitalization during the previous 2 years. He had also experienced intermittent pain crises requiring rest at home for 2 to 3 days. The child has not attended school in person due to the COVID-19 pandemic. The family is considering HCT but is ambivalent about it because of potential toxicity. In case 2, an 8-year-old female child is 3 years out from HCT for SCD from her HLA-identical sibling. Before HCT, despite receiving HU, she had experienced >5 VOEs requiring hospitalization and 2 episodes of acute chest syndromes in the previous 3 years. She had also been missing almost 50 days of school days each year. After HCT, she is now attending school regularly and participating in all normal age-appropriate activities. The parents believe that HCT has been transformative in their child's life.

Mortality and Causes of Death From Sickle Cell Disease in The Netherlands, 1985-2017

In the Netherlands, between 1985 and 2007 secular changes in the health care of patients with sickle cell disease (SCD) have taken place, such as penicillin prophylaxis, vaccination programs and stroke prevention. We investigated the number and causes of death in a cohort of 298 SCD patients, established in 2007, before introduction of neonatal screening, to determine preventable deaths. All patients were diagnosed with SCD before the age of 18 (median age at diagnosis 5.1 y). Their vital status was determined up to January 2017. After a total follow-up period of 4565 patient years and a median time of follow-up of 15 years for all patients, 230 patients (77%) were still alive, 45 patients (15%) were lost to follow-up and a total of 23 patients (8%) had died. Estimated survival to 18 years was 92% with a global mortality rate of 0.48 deaths/100 patient years. Leading causes of death were infection (35%) followed by neurologic complications (22%) and death in the course of a painful episode (13%). Nine of the 20 known causes of death were preventable. These results strongly suggest the benefit of comprehensive care measures for patients with SCD in the Netherlands to further prevent morbidity and mortality.

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

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

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

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