Sickle cell disease: an inherited thrombophilia

Thrombophilia Screening: Not So Straightforward

Although inherited thrombophilias are lifelong risk factors for a first thrombotic episode, progression to thrombosis is multifactorial and not all individuals with inherited thrombophilia develop thrombosis in their lifetimes. Consequently, indiscriminate screening in patients with idiopathic thrombosis is not recommended, since presence of a thrombophilia does not necessarily predict recurrence or influence management, and testing should be selective. It follows that a decision to undertake laboratory detection of thrombophilia should be aligned with a concerted effort to identify any significant abnormalities, because it will inform patient management. Deficiencies of antithrombin and protein C are rare and usually determined using phenotypic assays assessing biological activities, whereas protein S deficiency (also rare) is commonly detected with antigenic assays for the free form of protein S since available activity assays are considered to lack specificity. In each case, no single phenotypic assay is capable of detecting every deficiency, because the various mutations express different molecular characteristics, rendering thrombophilia screening repertoires employing one assay per potential deficiency, of limited effectiveness. Activated protein C resistance (APCR) is more common than discrete deficiencies of antithrombin, protein C, and protein S and also often detected initially with phenotypic assays; however, some centres perform only genetic analysis for factor V Leiden, as this is responsible for most cases of hereditary APCR, accepting that acquired APCR and rare F5 mutations conferring APCR will go undetected if only factor V Leiden is evaluated. All phenotypic assays have interferences and limitations, which must be factored into decisions about if, and when, to test, and be given consideration in the laboratory during assay performance and interpretation. This review looks in detail at performance and limitations of routine phenotypic thrombophilia assays.

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

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

Comparison of thromboembolism outcomes in patients with sickle cell disease prescribed hormonal contraception

Patients with sickle cell disease (SCD) are at a risk of thromboembolism (TE), and use of hormonal contraception can further increase that risk. This study aims to assess patterns of hormonal contraceptive use and compare risk of contraception-related TE between combined hormonal contraceptives (CHCs) and progestin-only contraceptives (POCs). Patients with SCD aged between 12 and 44 years with a new prescription of a hormonal contraceptive in the Centers for Medicare and Medicaid Services Medicaid Analytic eXtract database (2006-2018) were followed up to 1 year. We identified 7173 new users: 44.6% initiated CHC and 55.4% initiated POC. Combined oral contraceptive pills (OCPs; 36.5%) and progestin-only depot medroxyprogesterone acetate (33.9%) were the most frequently prescribed agents. A total of 1.8% of contraception users had a new diagnosis of TE within 1 year of the first identified contraception prescription. There were no significant differences in TE event rates between CHC and POC users (17.2 and 24.7 events per 1000 person-years, respectively). In patients prescribed OCP, there were no differences in TE event rates based on estrogen dose or progestin generation. Transdermal patch had a 2.4-fold increased risk of TE as compared with that of OCP. Although limited by the retrospective study design and use of administrative claims data, this study found no significant differences in TE rates between new users of CHC and POC in patients with SCD. Careful evaluation of underlying TE risk factors should be considered for each patient with SCD before initiation of hormonal contraception.

Predisposing Factors and Incidence of Venous Thromboembolism among Hospitalized Patients with Sickle Cell Disease

Though patients with sickle cell disease (SCD) are at risk of developing venous thromboembolism (VTE), clear estimates of its incidence and predisposing factors in hospitalized SCD patients are not available. Therefore, this issue was addressed to facilitate an early diagnosis and initiate appropriate prophylactic and treatment strategies. A retrospective observational study was conducted on patients with SCD who were admitted to an academic center in Saudi Arabia over a 10-year period. We identified 1054 admissions of 394 patients with SCD. Of the 3% of patients identified with VTE, 50% experienced pulmonary embolism (PE), 34.3% exhibited deep vein thrombosis (DVT), 6.3% exhibited cerebral vein thrombosis, and 9.4% showed other forms of VTE. In pregnant SCD patients, 6.4% developed a VTE event during their hospital admission. Of the risk factors, high white blood cell count, length of stay, and presence of any additional risk factor for VTE was associated significantly with higher risk of VTE. In our study, this risk seems to be much lower, which is likely attributed to the use of VTE prophylactic strategies implemented in our center. Nevertheless, further studies are needed to establish the ideal prophylactic strategy in patients with SCD.

Impact of Genetic Variations on Thromboembolic Risk in Saudis with Sickle Cell Disease

BACKGROUND

Sickle cell disease (SCD) is a Mendelian disease characterized by multigenic phenotypes. Previous reports indicated a higher rate of thromboembolic events (TEEs) in SCD patients. A number of candidate polymorphisms in certain genes (e.g., FVL, PRT, and MTHFR) were previously reported as risk factors for TEEs in different clinical conditions. This study aimed to genotype these genes and other loci predicted to underlie TEEs in SCD patients.

METHODOLOGY

A multi-center genome-wide association study (GWAS) involving Saudi SCD adult patients with a history of TEEs (n = 65) and control patients without TEE history (n = 285) was performed. Genotyping used the 10× Affymetrix Axiom array, which includes 683,030 markers. Fisher's exact test was used to generate p-values of TEE associations with each single-nucleotide polymorphism (SNP). The haplotype analysis software tool version 1.05, designed by the University of Göttingen, Germany, was used to identify the common inherited haplotypes.

RESULTS

No association was identified between the targeted single-nucleotide polymorphism rs1801133 in MTHFR and TEEs in SCD (p = 0.79). The allele frequency of rs6025 in FVL and rs1799963 in PRT in our cohort was extremely low (<0.01); thus, both variants were excluded from the analysis as no meaningful comparison was possible. In contrast, the GWAS analysis showed novel genome-wide associations (p < 5 × 10-8) with seven signals; five of them were located on Chr 11 (rs35390334, rs331532, rs317777, rs147062602, and rs372091), one SNP on Chr 20 (rs139341092), and another on Chr 9 (rs76076035). The other 34 SNPs located on known genes were also detected at a signal threshold of p < 5 × 10-6. Seven of the identified variants are located in olfactory receptor family 51 genes (OR51B5, OR51V1, OR51A1P, and OR51E2), and five variants were related to family 52 genes (OR52A5, OR52K1, OR52K2, and OR52T1P). The previously reported association between rs5006884-A in OR51B5 and fetal hemoglobin (HbF) levels was confirmed in our study, which showed significantly lower levels of HbF (p = 0.002) and less allele frequency (p = 0.003) in the TEE cases than in the controls. The assessment of the haplotype inheritance pattern involved the top ten significant markers with no LD (rs353988334, rs317777, rs14788626882, rs49188823, rs139349992, rs76076035, rs73395847, rs1368823, rs8888834548, and rs1455957). A haplotype analysis revealed significant associations between two haplotypes (a risk, TT-AA-del-AA-ins-CT-TT-CC-CC-AA, and a reverse protective, CC-GG-ins-GG-del-TT-CC-TT-GG-GG) and TEEs in SCD (p = 0.024, OR = 6.16, CI = 1.34-28.24, and p = 0.019, OR = 0.33, CI = 0.13-0.85, respectively).

CONCLUSIONS

Seven markers showed novel genome-wide associations; two of them were exonic variants (rs317777 in OLFM5P and rs147062602 in OR51B5), and less significant associations (p < 5 × 10-6) were identified for 34 other variants in known genes with TEEs in SCD. Moreover, two 10-SNP common haplotypes were determined with contradictory effects. Further replication of these findings is needed.

Pregnancy outcomes in women with sickle cell disease in California

Adverse pregnancy outcomes occur frequently in women with sickle cell disease (SCD) across the globe. In the United States, Black women experience disproportionately worse maternal health outcomes than all other racial groups. To better understand how social determinants of health impact SCD maternal morbidity, we used California's Department of Health Care Access and Information data (1991-2019) to estimate the cumulative incidence of pregnancy outcomes in Black women with and without SCD-adjusted for age, insurance status, and Distressed Community Index (DCI) scores. Black pregnant women with SCD were more likely to deliver at a younger age, use government insurance, and live in at-risk or distressed neighborhoods, compared to those without SCD. They also experienced higher stillbirths (26.8, 95% confidence interval [CI]: 17.5-36.1 vs. 12.4 [CI: 12.1-12.7], per 1000 births) and inpatient maternal mortality (344.5 [CI: 337.6-682.2] vs. 6.1 [CI: 2.3-8.4], per 100 000 live births). Multivariate logistic regression models showed Black pregnant women with SCD had significantly higher odds ratios (OR) for sepsis (OR 14.89, CI: 10.81, 20.52), venous thromboembolism (OR 13.60, CI: 9.16, 20.20), and postpartum hemorrhage (OR 2.25, CI 1.79-2.82), with peak onset in the second trimester, third trimester, and six weeks postpartum, respectively. Despite adjusting for sociodemographic factors, Black women with SCD still experienced significantly worse pregnancy outcomes than those without SCD. We need additional studies to determine if early introduction to reproductive health education, continuation of SCD-modifying therapies during pregnancy, and increasing access to multidisciplinary perinatal care can reduce morbidity in pregnant women with SCD.

Inflammatory status in pediatric sickle cell disease: Unravelling the role of immune cell subsets

Introduction: The mutation of the beta-globin gene that causes sickle cell disease (SCD) results in pleiotropic effects, such as hemolysis and vaso-occlusive crisis that can induce inflammatory mechanisms with deleterious consequences on the organism. Moreover, SCD patients display an increased susceptibility to infections. Few studies are currently available that evaluate a wide immunological profile in a pediatric population. This study proposes an evaluation of the immune profile in subjects with SCD in a pediatric population through a detailed analysis by flow cytometry. Methods and Materials: Peripheral blood samples from 53 pediatric patients with SCD (mean age 9.8 years, interquartile range 9 years) were obtained and then analyzed by flow cytometry, in order to evaluate changes in the immune populations compared to 40 healthy donors (mean age 7.3 years, interquartile range 9.5 years). Results: Our data showed an increase in neutrophils (with a reduction in the CD62L + subpopulation) and monocytes (with a decrease in HLA-DRlow monocytes) with normal values of lymphocytes in SCD patients. In the lymphocyte subpopulations analysis we observed lower values of CD4⁺ T cells (with higher number of memory and central memory T lymphocytes) with increased frequency of CD8⁺ T cells (with a predominant naive pattern). Moreover, we observed higher values of CD39⁺ Tregs and lower HLA-DR+ and CD39^- T cells with an increased Th17, Th1-17 and Th2 response. Conclusion: We observed immunological alterations typical of an inflammatory status (increase in activated neutrophils and monocytes) associated with a peculiar Treg pattern (probably linked to a body attempt to minimize inflammation intrinsic to SCD). Furthermore, we highlighted a T helper pathway associated with inflammation in line with other studies. Our data showed that immunological markers may have an important role in the understanding the pathophysiology of SCD and in optimizing targeted therapeutic strategies for each patient.

Systemic thrombolysis for acute central retinal artery occlusion in sickle cell disease: Case report

INTRODUCTION

In sickle cell disease (SCD), blood oxygen content is decreased due to anemia and the Hb-SS phenotype, in particular leads to an increased blood viscosity, which limits tissue oxygen delivery. Nonetheless, vasculopathy, correlating with daytime oxygen saturation,¹ thrombophilia and hyper coagulability are all underappreciated etiologies of stroke in SCD.² As a result, there is less known about the role of systemic thrombolysis for the management of acute stroke in SCD. Given the lack of studies and cases reviewed in literature, we describe a patient with SCD found to have an acute stroke treated with both intravenous (IV) alteplase and exchange transfusion.

RESULTS & DISCUSSION

We describe a 42-year-old African- American man with SCD (HbSS) who presented with an acute central retinal artery occlusion (CRAO) within an hour of onset and subsequently received IV thrombolysis with alteplase. His labs were significant for HbS 91%. He had no central vascular access to undergo emergent red blood cell (RBC) exchange so interventional radiology was consulted to minimize his bleeding risk after receiving tissue plasminogen activator (tPA). A right internal jugular catheter was placed with fluoro-guidance, resulting in minimal blood loss. After two sessions of RBC exchange, his HbS decreased to 26%. He reported an improvement of vision in his left eye the day following acute management and followed up with Hematology for secondary stroke prevention.

IMPLICATIONS

In reviewing this case, we recommend that current clinical trials for management of acute stroke including an acute CRAO carefully consider including patients with sickle cell disease to receive simultaneous IV thrombolysis and RBC exchange. The benefits outweigh the risk of a permanent disabling deficit with significant functional impairment. And while considering care plans tailored to the projected needs of acute care management for this patient population, we also recommend implementing healthcare models that improve access to preventative care in settings where the majority of children and adults with SCD live.

Investigation of thrombin generation assay to predict vaso-occlusive crisis in adulthood with sickle cell disease

Introduction

Sickle cell disease (SCD) is an inherited hemoglobinopathy disorder. The main consequence is synthesis of hemoglobin S leading to chronic hemolysis associated with morbidity. The aim of this study was to investigate Thrombin Generation Assay (TGA) to assess hypercoagulability in SCD and TGA parameters as biomarkers of vaso-occlusive crisis (VOC) risk and hospitalization within 1 year.

Materials and methods

We performed TGA in platelet poor plasma (PPP) with 1 pM of tissue factor and 4 μM of phospholipid-standardized concentration, in duplicate for patients and controls. We measured thrombomodulin (TM), soluble endothelial Protein C Receptor and Tissue Factor Pathway Inhibitor (TFPI).

Results

A total of 113 adult patients with SCD, 83 at steady state and 30 during VOC, and 25 healthy controls matched on age and gender were included. Among the 83 patients at steady state, (36 S/S-1 S/β⁰, 20 S/Sα³.⁷, and 19 S/C-7 S/β⁺) 28 developed a VOC within 1 year (median: 4 months [2.25–6]). We observed an increase of peak and velocity associated with a shortening of lagtime and time to peak (TTP) and no difference of endogenous thrombin potential (ETP) in patients compared to controls. TFPI (p < 0.001) and TM (p = 0.006) were significantly decreased. TGA confirmed hypercoagulability in all SCD genotypes and clinical status. The association of ETP > 1,207 nM.min and peak >228.5 nM presented a sensitivity of 73.5% and a specificity of 93.9% to predict VOC development within 1 year.

Conclusion

We have demonstrated a hypercoagulable state in SCD associated with chronic hemolysis. These preliminary findings suggest that TGA parameters, as ETP and peak, could be used to predict VOC development within 1 year.

Venous thromboembolism prophylaxis in hospitalized sickle cell disease and sickle cell trait patients

INTRODUCTION

Sickle trait (Hb SA) or sickle disease (Hb SS) carries increased risk of venous thromboembolism (VTE). Hb SS patients are young and lack common comorbid conditions that qualify them for VTE prophylaxis (VTEP).

METHODS

Retrospective, multicenter analysis of Hb SS/Hb SA adult patients between January 2013 and December 2018.

RESULTS

There were 803 Hb SA (525 patients) and 1020 Hb SS admissions (262 patients). VTEP use was similar between Hb SA and controls (42% vs. 46%; p-value = .06) and Hb SS and controls (45% vs. 42%; p-value = .13). Hb SS/Hb SA patients more frequently received more than half of prescribed doses of VTEP. In multivariate analysis, increasing age and longer hospitalizations were positive predictors. Odds of VTEP use varied with treatment site for Hb SS patients, whereas comorbid conditions, admission hemoglobin and platelet count were not predictive. By contrast, in Hb SA patients, comorbid conditions, higher admission hemoglobin, and higher admission platelet counts raised the odds of VTEP being offered.

CONCLUSIONS

VTEP is underused in Hb SS/Hb SA patients. There may be a trend toward offering more VTEP in Hb SS disease, but not in Hb SA patients, where VTEP prescribing is driven by comorbid conditions rather than genotype. Patient compliance does not appear to play a major role, but intercenter variability suggests provider education may improve VTEP use.

Thromboprophylaxis Reduced Venous Thromboembolism in Sickle Cell Patients with Central Venous Access Devices: A Retrospective Cohort Study

Sickle cell disease (SCD) induces a chronic prothrombotic state. Central venous access devices (CVADs) are commonly used for chronic transfusions and iron chelation in this population. CVADs are an additional venous thromboembolism (VTE) risk factor. The role of thromboprophylaxis in this setting is uncertain. The objectives are: (1) to determine whether thromboprophylaxis reduces VTE risk in SCD patients with CVAD and (2) to explore characteristics associated with VTE risk. We identified adults with SCD and CVAD intended for chronic use (≥3 months) at two comprehensive SCD centers. Thromboprophylaxis presence; type; intensity; and patient-, catheter-, and treatment-related VTE risk factors were recorded. Among 949 patients, 49 had a CVAD (25 without and 24 with VTE prophylaxis). Thromboprophylaxis type and intensity varied widely. Patients without thromboprophylaxis had higher VTE rates (rate ratio (RR) = 4.0 (95% confidence interval: 1.2−12.6), p = 0.02). Hydroxyurea was associated with lower VTE rates (RR = 20.5 (6.4−65.3), p < 0.001). PICC lines and Vortex and Xcela Power implantable devices were associated with higher rates compared with Port-a-Cath (RR = 5.8 (1.3−25.9), p = 0.02, and RR = 58.2 (15.0−225.0), p < 0.001, respectively). Thromboprophylaxis, hydroxyurea, and CVAD subtype were independently associated with VTE. The potentially protective role of thromboprophylaxis and hydroxyurea for VTE prevention in patients with SCD and CVAD merits further exploration.

Reduction in Prevalence of Thrombotic Events in Sickle Cell Disease after Allogeneic Hematopoietic Transplantation

Thrombosis is a recognized complication in sickle cell disease (SCD). Allogeneic hematopoietic cell transplantation (allo-HCT) remains the only curative options for patients with severe SCD phenotypes. There is limited data describing the effects of allo-HCT on recurrent thrombotic events (venous and arterial events). We evaluated 31 patients with SCD who have undergone allo-HCT with a median follow up of 34.5 months (range:13-115) post-transplant. No patient continued anticoagulation or anti-platelets after allo-HCT. There was an absolute difference of 32% [95% CI=12.3-32.2, p=0.002] in the prevalence of venous thromboembolic (VTE) events before and after allo-HSCT. In addition, there was an absolute 38.5% [95% CI=10.63-45.96, p=0.006] difference in the number of ischemic cerebrovascular accidents (CVA) before and after allo-HSCT. Patients with severe SCD who undergo allo-HCT are less likely to develop recurrent thrombotic events OR 0.22 [95% CI=0.058 - 0.83, p=0.025] when compared to a control cohort of patients matched for age and genotype. Following curative therapy with allo-HCT, there is a reduction in recurrent arterial and venous thrombosis in patients with severe SCD phenotypes.

Changes in Care Delivery for Children With Sickle Cell Anemia During the COVID-19 Pandemic

BACKGROUND

Specialty care for children with sickle cell disease (SCD) may be disrupted during the coronavirus (COVID-19) pandemic. Our DISPLACE consortium includes 28 pediatric SCD centers.

METHODS

In May 2020, we surveyed the consortium on the impact of COVID-19 on their practice focusing on transcranial Doppler ultrasound, chronic red cell transfusions, telehealth, and COVID-19 testing.

OBSERVATION

Twenty-four DISPLACE providers completed the survey. Transcranial Doppler ultrasound screening decreased to 67% but chronic red cell transfusions remained at 96%. Most investigators (92%) used telehealth and 40% of providers had patients test positive for COVID-19.

CONCLUSION

The COVID-19 pandemic has affected routine care and necessitated changes in practice in SCD.

Invited Review: Optimal Management of Upper Extremity DVT: Is Venous Thoracic Outlet Syndrome Underrecognized?

BACKGROUND

UEDVT accounts for approximately 10% of all cases of deep vein thrombosis. In the most widely referenced general review of deep vein thrombosis (DVT the American Academy of Chest Physicians essentially recommend that upper extremity DVT (UEDVT) essentially be treated identically to that of lower extremity DVT, with anticoagulation being the default therapy. Unfortunately, the medical literature does not well differentiate between DVT in the arm and the leg, and does not emphasize the effects of the costoclavicular junction (CCJ) and the lack of effect of gravity, to the point where UEDVT due to extrinsic bony compression at the CCJ is classified as "primary."

METHODS

Comprehensive literature review, beginning with both Medline and Google Scholar searches in addition to collected references, then following relevant citations within the initial manuscripts studied. Both surgical and medical journals were explored RESULTS: It is proposed that effort thrombosis be classified as a secondary cause of UEDVT, limiting the definition of primary to that which is truly idiopathic. Other causes of secondary UEDVT include catheter- and pacemaker-related thrombosis (the most common cause, but often asymptomatic), thrombosis related to malignancy and hypercoagulable conditions, and the rare case of thrombosis due to compression of the vein by a focal malignancy or other space-occupying lesion. In true primary UEDVT and in those secondary cases where no mechanical cause is present or can be corrected, anticoagulation remains the treatment of choice, usually for three months or the duration of a needed catheter. However, evidence suggests that many cases of effort thrombosis are likely missed by a too-narrow adherence to this protocol.

CONCLUSIONS

Because proper treatment of effort thrombosis drops the long-term symptomatic status rate from 50% to almost zero and these are healthy patients with a long lifespan ahead, it is proposed that a more aggressive attitude toward thrombolysis be followed in any patient who has a reasonable degree of suspicion for venous thoracic outlet syndrome.

COVID-19 Infection and Acute Pulmonary Embolism in an Adolescent Female With Sickle Cell Disease

A previously healthy 20-year-old female presented to the emergency room in April 2020 with complaints of shortness of breath, chest pain, and cough. She was diagnosed with coronavirus disease 2019 (COVID-19) infection and pulmonary embolism (PE). Workup for anemia led to the diagnosis of sickle cell disease (SCD). Patients diagnosed with COVID-19 are at an increased risk for the development of PE and venous thromboembolism (VTE). Anticoagulation prophylaxis and escalation to treatment dosing are recommended in patients admitted with moderate to severe symptoms of COVID-19. PE and VTE are relatively uncommon in the pediatric and adolescent population. Most commonly, patients are diagnosed with thrombophilia or have an underlying hypercoagulable state such as with SCD. Also, symptoms of COVID-19 infection, acute chest syndrome (ACS), and PE can have overlapping features. In this report, we present a case of a late adolescent female with SCD, who was diagnosed with COVID-19, and whose condition was complicated with PE.

Hemolysis and Plasma Free Hemoglobin During Extracorporeal Membrane Oxygenation Support: From Clinical Implications to Laboratory Details

Venovenous and venoarterial extracorporeal membrane oxygenation (ECMO) are lifesaving supports that are more and more frequently used in critically ill patients. Despite of major technological improvements observed during the last 20 years, ECMO-associated hemolysis is still a complication that may arise during such therapy. Hemolysis severity, directly appreciated by plasma free hemoglobin concentration, may be present with various intensity, from a nonalarming and tolerable hemolysis to a highly toxic one. Here, we propose a review dedicated to extracorporeal membrane oxygenation (ECMO)-associated hemolysis, with a particular emphasis on pathophysiology, prevalence, and clinical consequences of such complication. We also focus on laboratory assessment of hemolysis and on the limits that have to be known by clinicians to prevent and manage hemolytic events.

The molecular basis for the prothrombotic state in sickle cell disease

The genetic and molecular basis of sickle cell disease (SCD) has long since been characterized but the pathophysiological basis is not entirely defined. How a red cell hemolytic disorder initiates inflammation, endothelial dysfunction, coagulation activation and eventually leads to vascular thrombosis, is yet to be elucidated. Recent evidence has demonstrated a high frequency of unprovoked/recurrent venous thromboembolism (VTE) in SCD, with an increased risk of mortality among patients with a history of VTE. Here, we thoroughly review the molecular basis for the prothrombotic state in SCD, specifically highlighting emerging evidence for activation of overlapping inflammation and coagulation pathways, that predispose to venous thromboembolism. We share perspectives in managing venous thrombosis in SCD, highlighting innovative therapies with the potential to influence the clinical course of disease and reduce thrombotic risk, while maintaining an acceptable safety profile.

Sickle Cell Disease: A Paradigm for Venous Thrombosis Pathophysiology

Venous thromboembolism (VTE) is an important cause of vascular morbidity and mortality. Many risk factors have been identified for venous thrombosis that lead to alterations in blood flow, activate the vascular endothelium, and increase the propensity for blood coagulation. However, the precise molecular and cellular mechanisms that cause blood clots in the venous vasculature have not been fully elucidated. Patients with sickle cell disease (SCD) demonstrate all the risk factors for venous stasis, activated endothelium, and blood hypercoagulability, making them particularly vulnerable to VTE. In this review, we will discuss how mouse models have elucidated the complex vascular pathobiology of SCD. We review the dysregulated pathways of inflammation and coagulation in SCD and how the resultant hypercoagulable state can potentiate thrombosis through down-regulation of vascular anticoagulants. Studies of VTE pathogenesis using SCD mouse models may provide insight into the intersection between the cellular and molecular processes involving inflammation and coagulation and help to identify novel mechanistic pathways.

Current Issues and Options for Hormonal Contraception in Adolescents and Young Adult Women With Sickle Cell Disease: An Update for Health Care Professionals

Women with sickle cell disease (SCD) are of particular concern regarding the significantly increased risk of pregnancy-related morbidity, mortality, and adverse outcomes. They have limited knowledge of pregnancy and childbirth risks, as well as of the benefits and risks of contraceptives. Thus, there is an urgent need for appropriate information about reproductive family planning to reduce unintended pregnancy. Any decision regarding the use of contraceptives has to be based on the efficacy and risk/benefit ratio of the method used. Both the World Health Organization (WHO) and the Centers for Disease Control (CDC) have developed, published, and updated evidence-based guidelines for medical providers for the use of contraceptives in patients with specific medical chronic conditions. This article provides an overview of the present knowledge on the use of contraceptives in women with SCD. We believe that the collaboration between health care professionals (hematologists, obstetricians, endocrinologists, and primary care providers) can play a major role in identifying the safer contraceptive method to abolish the risks of unintended pregnancy and preserve the health status of patients with SCD.

High incidence of venous thromboembolism recurrence in patients with sickle cell disease

Previous reports show increased incidence of venous thromboembolism [VTE, deep-vein thrombosis (DVT) and pulmonary embolus (PE)] in sickle cell disease (SCD) patients. The incidence, time course, and risk factors for VTE recurrence have been less well described. We determined the cumulative incidence of first VTE recurrence and bleeding in a cohort of SCD patients with incident VTE. Risk factors for recurrence and bleeding were also determined using multivariable Cox regression models, adjusting for gender, race/ethnicity, era of incident VTE, location and hospitalization-associated status of incident VTE, and SCD-related complications. Results are presented as adjusted hazard ratios (HR) and 95% confidence intervals (CI). Among 877 SCD patients with an incident VTE, the 1-year and 5-year cumulative incidence of recurrence was 13.2% (95% CI 11.0%-15.5%) and 24.1% (95% CI 21.2%-27.1%). Risk factors for VTE recurrence included more severe SCD (HR = 2.41; CI: 1.67-3.47), lower extremity DVT as the incident event (HR = 1.64; CI: 1.17-2.30), and pneumonia/acute chest syndrome (HR = 1.68; CI: 1.15-2.45). The cumulative incidence of bleeding was 4.9% (CI 3.5%-6.4%) at 6 months and 7.9% (CI: 6.2%-9.8%) at 1 year. More severe SCD (HR = 1.61; CI: 1.11-2.35) was associated with bleeding. The high incidence of VTE recurrence in patients with SCD suggests that extended anticoagulation may be indicated; however, this must be weighed against a relatively high risk of bleeding. Prospective, randomized studies of anticoagulation in SCD patients with VTE are needed.

Decreased Bleeding Incidence with Direct Oral Anticoagulants Compared to Vitamin K Antagonist and Low-Molecular-Weight Heparin in Patients with Sickle Cell Disease and Venous Thromboembolism

BACKGROUND

Venous thromboembolism (VTE) is a recognized complication of sickle cell disease (SCD), yet the optimal pharmacologic anticoagulant is unknown.

METHODS

A retrospective single-institution cohort study of patients with SCD complicated by first VTE from January 2009 through July 2017 was performed using ICD 9/10 codes. Data collected included the anticoagulant used, VTE recurrence, and incidence of bleeding.

RESULTS

109 patients with VTE were identified. SCD genotypes included HbSS in 92 (84%), HbSC in 13 (12%), and HbS-β+ thalassemia in 4 (4%). After the initial VTE event, 32 patients received a vitamin K antagonist (VKA), 34 for low-molecular-weight heparin (LMWH), and 43 for direct oral anticoagulants (DOACs). 16 patients (15%) experienced a clinically significant bleeding event, including 9 on VKA, 5 on LMWH, and 2 on DOACs. At a median follow-up of 11.8 (range, 3.4-60) months, 33 patients had a recurrent VTE, including 10 on VKA, 10 on LMWH, and 13 on DOACs (p = 0.833). Bleeding incidence was least with the DOACs, which were associated with fewer bleeding events (OR 0.22), and greatest with VKA (OR 1.55) (p < 0.05).

CONCLUSION

There was no difference between VTE recurrence and choice of anticoagulation in SCD patients with VTE. Bleeding events were lower for DOACs compared to VKA or LMWH.

Cardiovascular manifestations of sickle cell disease

Sickle cell disease (SCD) is the most frequent genetic haemoglobinopathy worldwide. Early childhood mortality has dramatically decreased in high-income countries, and most patients now survive beyond the 5th decade. However, in the aging SCD population, the morbidity related to chronic organ damage, especially kidney and heart, has become a major concern. While pulmonary hypertension has attracted most attention, it appears that this condition is frequently linked to left heart failure (HF). Accordingly, SCD-associated cardiomyopathy is emerging as a major cause of reduced quality of life and early mortality in these patients. The diagnosis of this particular phenotype of high-output HF is challenging. Exercise intolerance and dyspnoea in SCD patients are linked to multiple causes including chronic anaemia. Moreover, echocardiographic features are unusual and can be misinterpreted. The classical diagnosis algorithm for HF is generally not suitable in SCD patients, and HF is poorly recognized and mostly diagnosed at a late congestive stage in routine practice. Such patients need to be identified at an earlier stage of myocardial dysfunction via improved phenotyping. This constitutes the first step towards further investigations in SCD needed to improve the prognosis and the quality of life. This article provides an updated review of the recent advances in the pathophysiology and diagnosis, and in addition, perspectives of new therapeutic approaches in SCD-related cardiac manifestations.

Prevalence and risk factors for venous thromboembolism in children with sickle cell disease: an administrative database study

A hypercoagulable state resulting in increased venous thromboembolism (VTE) has been described in adults with sickle cell disease (SCD), but similar data for children are lacking. The objective of this retrospective cohort study was to describe the rate of VTE and risk factors associated with VTE in children with SCD across tertiary-care children's hospitals in the United States between the years 2009 and 2015. We used the Pediatric Health Information System database to investigate all pediatric patients with SCD admitted to 1 of 48 participating institutions between 1 January 2009 and 30 September 2015. International Classification of Disease, Ninth Edition, Clinical Modification codes were used to identify index thromboembolic events and chronic medical conditions known to be associated with VTE. Billing codes were used to identify central venous line (CVL) placement and pharmaceutical billing codes to identify estrogen containing oral-contraceptive use. Logistic regression analysis was used to study the association among unique patient characteristics, VTE, and death. 10 454 eligible subjects with SCD were identified. Median age (±interquartile range) of study cohort was 10 (±11) years. 181 subjects (1.7%) developed an index venous thromboembolic event during the study period. Median age at VTE diagnosis was 15.9 (±7.4) years. On multivariable logistic regression analysis, CVL placement, chronic renal disease, history of stroke, female sex, length of hospitalization, intensive care unit utilization, and older age were associated with VTE. After adjusting for other variables, VTE was independently associated with death. In summary, VTE can occur in pediatric patients with SCD. CVL placement is a modifiable risk factor for VTE development.

Updated clinical models for VTE prediction in hospitalized medical patients

Venous thromboembolism (VTE) occurring in hospitalized medical patients is associated with increased length of hospitalization, high rate of acute care hospital transfer, longer inpatient rehabilitation and multiplication of health-care costs. Identification of acutely ill hospitalized medical patients eligible for thromboprophylaxis is a sophisticated process. Global VTE risk stems from the combination of predictors related with the acute medical illness, comorbidities, associated treatments and patients' intrinsic risk factors. Emerging clinical risk factors related to underlying pathologies should be considered when VTE risk is assessed. The Padua Prediction Score (PPS), the International Medical Prevention Registry on Venous Thromboembolism (IMPROVE-RAM) and the Geneva Risk Score are three robust risk assessment models (RAM) which underwent extensive external validation in cohorts of acutely ill hospitalized medical patients. The development of the IMPROVE bleeding risk assessment model and the identification of D-Dimer increase as a biomarker-predictor of VTE are some steps forward for personalized thromboprophylaxis. The beneficial impact of the RAMs in VTE prevention is already seen by the decrease of in-hospital VTE rates when RAMs are incorporated in electronic alert systems.

Pulmonary Embolism in Children

Pulmonary embolism (PE) in children is a rare condition with potential for high mortality. PE incidence is increasing owing to increased survival of children with predisposing conditions, increased use of central venous catheters, and improved awareness and recognition. Although pediatric PE is distinct from adult PE, management guidelines in children are extrapolated from the adult data. Treatment includes thrombolysis or thrombectomy, and pharmacologic anticoagulation. Ongoing clinical trials are evaluating the use of direct oral anticoagulants in children. Further research is required to develop pediatric-specific evidence-based guidelines for diagnosis and management of PE.

Inflammation in sickle cell disease

The primary β-globin gene mutation that causes sickle cell disease (SCD) has significant pathophysiological consequences that result in hemolytic events and the induction of the inflammatory processes that ultimately lead to vaso-occlusion. In addition to their role in the initiation of the acute painful vaso-occlusive episodes that are characteristic of SCD, inflammatory processes are also key components of many of the complications of the disease including autosplenectomy, acute chest syndrome, pulmonary hypertension, leg ulcers, nephropathy and stroke. We, herein, discuss the events that trigger inflammation in the disease, as well as the mechanisms, inflammatory molecules and cells that propagate these inflammatory processes. Given the central role that inflammation plays in SCD pathophysiology, many of the therapeutic approaches currently under pre-clinical and clinical development for the treatment of SCD endeavor to counter aspects or specific molecules of these inflammatory processes and it is possible that, in the future, we will see anti-inflammatory drugs being used either together with, or in place of, hydroxyurea in those SCD patients for whom hematopoietic stem cell transplants and evolving gene therapies are not a viable option.

How I diagnose and treat venous thromboembolism in sickle cell disease

The incidence of venous thromboembolism (VTE) in adult patients with sickle cell disease (SCD) is high. However, overlapping features between the clinical presentation of VTE and SCD complications and a low index of suspicion for thrombosis can influence patient management decisions. VTE in SCD can therefore present management challenges to the clinical hematologist. Herein, we present 3 distinct clinical vignettes that are representative of our clinical practice with SCD patients. These vignettes are discussed with specific reference to the hypercoagulable state in SCD patients, recent VTE diagnosis and anticoagulant therapy guidelines from the general population, and evaluation of the risk of bleeding as a result of long-term exposure to anticoagulant therapy. We examine current diagnostic and treatment options, highlight limitations of the existing clinical prognostic models that offer personalized guidance regarding the duration of anticoagulation, and propose a clinical approach to guide the decision to extend anticoagulation beyond 3 months.

Prasugrel hydrochloride for the treatment of sickle cell disease

INTRODUCTION

Therapeutic options for sickle cell disease (SCD) are limited and, currently, only one drug (hydroxyurea) has FDA approval for the treatment of adult SCD. While this genetic disease is caused by hemoglobin polymerization, subsequent downstream events trigger platelet activation, vaso-occlusion and the disease's complex pathophysiology. Areas covered: The oral thienopyridine, prasugrel hydrochloride, irreversibly inhibits the P2Y12 receptors, inhibiting ADP-dependent platelet activation. We discuss recent clinical trials evaluating the pharmokinetics of prasugrel and its potential for use in SCD. Expert opinion: Prasugrel administration in SCD appears to be well tolerated and safe. However, although this drug modestly inhibits platelet activity in these patients, administration of prasugrel to a large group of children and adolescents for up to 24 months failed to convincingly reduce vaso-occlusive complications. Speculatively, prasugrel may be of occasional use for off-license purposes in patients unable or unwilling to take hydroxyurea (particularly in 12-17-year olds). Although there is currently no prospect of prasugrel being licensed for use in SCD, the success of on-going trials of other antiplatelet agents in SCD might lead to further trials of prasugrel in SCD.