Elevated Transcranial Doppler Velocities Research Articles

Hydroxyurea Improves Intelligence Quotient Scores in Children with Sickle Cell Anemia and Elevated Transcranial Doppler Velocity

Introduction: Structural brain abnormalities resulting from sickle cell disease because of strokes, silent cerebral infarcts (SCI) and other biophysical characteristics of parenchymal damage from repeated sickling affect cognitive functioning. Hydroxyurea therapy reduces transcranial Doppler (TCD) velocities and improves SCI and other neurological outcomes in children with sickle cell anaemia. Hence the objectives of EXpanding Treatment for Existing Neurological Disease (EXTEND, NCT02556099), a phase 2 clinical trial, was to determine whether hydroxyurea titrated to maximum tolerated dose was effective in lowering transcranial Doppler (TCD) velocities and improving cognitive function in Jamaican children with sickle cell anemia (SCA) with increased stroke risk. Methods: Full-Scale Intelligence Quotient (FSIQ), verbal and nonverbal IQ were measured with the Wechsler Abbreviated Scale of Intelligence (WASI-II) at baseline and after 18 months of hydroxyurea treatment in 30 of the 43 enrolled children. Verbal Comprehension Index (VCI) was assessed using the Vocabulary and Similarities subtests. Perceptual Reasoning Index (PRI) was scored with the Block Design and Matrix Reasoning subtests. Members of the team conducting the tests were trained and test results were verified by an experienced member of the Epidemiology Research Unit, Caribbean Institute for Health Research. Participants were enrolled in the EXTEND trial based on a pre-treatment conditional or abnormal TCD velocity. They were assigned to one of three risk categories according to treatment status and stroke history at study enrollment: Group 1 (low stroke risk: no previous stroke, on hydroxyurea treatment n= 12), Group 2 (medium stroke risk: no previous stroke, no hydroxyurea, n=10) and Group 3 (High stroke risk: previous stroke, no hydroxyurea n=8). Anthropometric variables, including height and weight, were recorded as well as oxygen saturation and hematological variables. Differences in post treatment outcome were modelled using mixed linear regression. A p-value of <0.05 was considered statistically significant. Results: There was no difference in mean anthropometric values or gender distribution at baseline by stroke risk category groups (Table 1). The mean(sd) age in years of participants in Group 1 was 8.2(1.7), while for Group 2 the average age was 7.7(2.1) and for Group 3 it was 10.5(2.8). The mean age of Group 3 was significantly greater than Group 1. After 18 months of hydroxyurea treatment, participants were taking an average dose of 25 mg/kg/d, range 13.7 to 34.9 mg/kg/d. On treatment TCD velocities decreased by mean(sd) of 29.5 cm/sec (31.5). Hemoglobin (Hb) concentration was lowest in Group 3 but all groups showed increases during treatment with the rate of increase in Groups 2 and 3 being greater than Group 1 (p<0.001). Absolute neutrophil counts and absolute reticulocyte counts were not different by group, and both decreased significantly post treatment (p<0.001) (Table 1). At both time points, the VCI, PRI and FSIQ mean scores in Group 3 were low [Overall means(sd); 71(11.7), 71(12.6),69(11.6), respectively] and were significantly lower compared with Group 1 (p<0.001) (Table 1). While there was no significant effect of treatment on VCI and PRI scores, the mean FSIQ score increased on average by 2.9 units (95%CI 0.3, 5.4) post treatment among participants. Adjusting for age at enrollment had no effect on the improvement on FSIQ, however adjusting for changes in hemoglobin resulted in an increase in FSIQ by 3.3 units (95%CI -0.4, 7.0) which approached statistical significance (p=0.079). Conclusion: Participants treated with hydroxyurea at maximum tolerated dose for 18 months with or without a previous stroke had significant improvement in hematological variables and neuropsychological scores. Children with sickle cell anemia with high risk of stroke may benefit from routine neuropsychological testing, hydroxyurea treatment in addition to educational interventions.

Neurofilament light chain: A potential biomarker for cerebrovascular disease in children with sickle cell anaemia.

Cerebrovascular injury frequently occurs in children with sickle cell anaemia (SCA). Limited access to magnetic resonance imaging and angiography (MRI-MRA) in sub-Saharan Africa impedes detection of clinically unapparent cerebrovascular injury. Blood-based brain biomarkers of cerebral infarcts have been identified in non-SCA adults. Using plasma samples from a well-characterized cross-sectional sample of Ugandan children with SCA, we explored relationships between biomarker levels and MRI-detected cerebral infarcts and transcranial Doppler (TCD) arterial velocity. Testing was performed using a 4-plex panel of brain injury biomarkers, including neurofilament light chain (NfL), a central nervous system neuron-specific protein. Mean biomarker levels from the SCA group (n = 81) were similar to those from non-SCA sibling controls (n = 54). Within the SCA group, NfL levels were significantly higher in those with MRI-detected infarcts compared to no infarcts, and higher with elevated TCD velocity versus normal velocity. Elevated NfL remained strongly associated with MRI-detected infarcts after adjusting for sex and age. All non-SCA controls and SCA participants lacking MRI-detected infarcts had low NfL levels. These data suggest potential utility of plasma-based NfL levels to identify children with SCA cerebrovascular injury. Replication and prospective studies are needed to confirm these novel findings and the clinical utility of NfL versus MRI imaging.

Stroke Prevention with Hydroxyurea Enabled through Research and Education: A Phase 2 Primary Stroke Prevention Trial in Sub-Saharan Africa

Introduction: Stroke is a severe complication of sickle cell anemia (SCA), with devastating sequelae. Transcranial Doppler (TCD) ultrasonography predicts stroke risk, but implementing TCD screening with suitable treatment for primary stroke prevention in low-resource environments remains challenging. SPHERE (NCT03948867) is a prospective phase 2 open-label hydroxyurea trial for SCA in Tanzania. Methods: After formal training and certification, local personnel screened children 2–16 years old; those with conditional (170–199 cm/s) or abnormal (≥200 cm/s) time-averaged mean velocities (TAMVs) received hydroxyurea at 20 mg/kg/day with dose escalation to maximum tolerated dose (MTD). The primary study endpoint is change in TAMV after 12 months of hydroxyurea; secondary endpoints include SCA-related clinical events, splenic volume and function, renal function, infections, hydroxyurea pharmacokinetics, and genetic modifiers. Results: Between April 2019 and April 2020, 202 children (average 6.8 ± 3.5 years, 53% female) enrolled and underwent TCD screening; 196 were deemed eligible by DNA testing. Most had numerous previous hospitalizations and transfusions, with low baseline hemoglobin (7.7 ± 1.1 g/dL) and %HbF (9.3 ± 5.4%). Palpable splenomegaly was present at enrollment in 49 (25%); average sonographic splenic volume was 103 mL (range 8–1,045 mL). TCD screening identified 22% conditional and 2% abnormal velocities, with hydroxyurea treatment initiated in 96% (45/47) eligible children. Conclusion: SPHERE has built local capacity with high-quality research infrastructure and TCD screening for SCA in Tanzania. Fully enrolled participants have a high prevalence of elevated baseline TCD velocities and splenomegaly. SPHERE will prospectively determine the benefits of hydroxyurea at MTD for primary stroke prevention, anticipating expanded access to hydroxyurea treatment across Tanzania.

Abstract TP150: Association Of Asymptomatic Cerebral Vasospasm With Outcomes In Aneurysmal Subarachnoid Hemorrhage

Cerebral vasospasm (cVSP) is a common complication in patients with aneurysmal subarachnoid hemorrhage (aSAH) and is associated with worse outcomes. However, clinical significance of asymptomatic cVSP remains poorly understood. We sought to determine the association between asymptomatic cVSP and hospital length of stay (LOS), duration of external ventricular drain (EVD), and functional outcome. We performed a retrospective cohort study of consecutive aSAH patients who were admitted to an academic referral center from 2016 to 2021. We included patients with confirmed aneurysmal etiology who received transcranial Doppler (TCD) with documented daily measurements. Multiple linear regression analysis was performed to test the association of asymptomatic cVSP (defined as elevated TCD velocities with no clinical correlation) and both hospital LOS and duration of EVD. Binary logistic regression analysis was used to test the association of asymptomatic cVSP and worse functional outcome (3-month modified Rankin scale 4-6). We included 223 patients (mean age 55.8 years [SD 13.4], 60% female, 70% white) with aSAH who survived hospitalization and had documented daily TCDs. Asymptomatic cVSP was seen in 32% of patients and delayed cerebral ischemia (DCI) was seen in 27% of patients. Only symptomatic cVSP was associated with prolonged hospital LOS (3.25 more days; p=0.034) independent of age, comorbidities, Hunt and Hess grades, modified Fisher scales, DCI, and other hospital complications. However, asymptomatic cVSP was associated with longer duration of EVD (3.78 more days; p=0.025) independent of common predictors including hydrocephalus and amount of cerebrospinal fluid daily output. Severity of vasospasm (ordinal variable: mild, moderate, or severe) was associated with longer duration of EVD (1.47 more days; p=0.016). Asymptomatic cVSP was not independently associated with worse functional outcome. In conclusion, isolated asymptomatic cVSP may not be associated with worse outcome but can contribute to interventions such as EVD prolongation. Clinical significance of asymptomatic cVSP and its management should be studied in multi-institutional prospective cohorts.

Stable to improved cardiac and pulmonary function in children with high-risk sickle cell disease following haploidentical stem cell transplantation.

Children with sickle cell disease (SCD) are at high-risk of progressive, chronic pulmonary and cardiac dysfunction. In this prospective multicenter Phase II trial of myeloimmunoablative conditioning followed by haploidentical stem cell transplantation in children with high-risk SCD, 19 patients, 2.0-21.0 years of age, were enrolled with one or more of the following: history of (1) overt stroke; (2) silent stroke; (3) elevated transcranial Doppler velocity; (4) multiple vaso-occlusive crises; and/or (5) two or more acute chest syndromes and received haploidentical transplants from 18 parental donors. Cardiac and pulmonary centralized cores were established. Pulmonary function results were expressed as percent of the median of healthy reference cohorts, matched for age, sex, height and race. At 2 years, pulmonary functions including forced expiratory volume (FEV), FEV1/ forced vital capacity (FVC), total lung capacity (TLC), diffusing capacity of lung for carbon monoxide (DLCO) were stable to improved compared to baseline values. Importantly, specific airway conductance was significantly improved at 2 years (p < 0.004). Left ventricular systolic function (fractional shortening) and tricuspid regurgitant velocity were stable at 2 years. These results demonstrate that haploidentical stem cell transplantation can stabilize or improve cardiopulmonary function in patients with SCD.

Hydroxyurea to Reduce Stroke Risk in Tanzanian Children with Sickle Cell Anemia

Introduction: Sickle cell anemia (SCA) is highly prevalent in sub-Saharan Africa with &amp;gt;300,000 annual births, and substantial morbidity and mortality due to limited resources. The burden of stroke in this population is of particular concern, given the devastating clinical and neurocognitive sequelae of these events. Hydroxyurea, a potent disease modifying therapy for SCA, is safe and feasible for low-resource and malarial endemic countries within sub-Saharan Africa and when used at maximum tolerated dose (MTD), decreases the incidence of acute painful vaso-occlusive events, infections, malaria, transfusions, hospitalizations, and death. Whether hydroxyurea can prevent primary stroke in SCA within Africa has not yet been determined, due in part to lack of stroke screening programs using transcranial Doppler (TCD) ultrasonography. If effective, hydroxyurea would have even more therapeutic benefits for children with SCA, particularly in settings where blood is not available, affordable, or safe. We designed the Stroke Prevention with Hydroxyurea Enabled through Research and Education (SPHERE) trial to determine the stroke risk among Tanzanian children using TCD screening and to investigate the effects of hydroxyurea to reduce that risk. Methods: The SPHERE trial (NCT03948867) is a single center prospective phase 2 open-label screening and treatment pilot study at Bugando Medical Centre, a teaching and referral hospital in Mwanza, Tanzania. Children 2-16 years old with SCA consented to TCD screening by locally trained and certified examiners; recent febrile illness, red cell transfusion, or hospitalization were temporary exclusions. Study participants with maximum Time-Averaged Mean Velocity (TAMV) on TCD exam categorized as conditional (170-199 cm/sec) or abnormal (≥200 cm/sec) are offered hydroxyurea with escalation to MTD, while those with normal TCD screening exams will be rescreened annually. Hydroxyurea is initiated at ~20 mg/kg/day using 500 mg capsules and a weekly dosing calculator, then escalated every 8 weeks by 5 mg/kg/day up to 35 mg/kg/day. Children on hydroxyurea are seen monthly during dose escalation and every 3 months after reaching MTD. The primary endpoint is change in TCD velocity after 12 months of hydroxyurea therapy. Secondary endpoints include changes in splenic volume and filtrative function; change in renal function; incidence of infection, especially malaria; hydroxyurea pharmacokinetics; and genetic modifiers of disease including pharmacogenomics. Results: From April 2019 to April 2020, a total of 202 children underwent TCD screening, exceeding the projected enrollment pace and goal (Figure). The average age (mean ± SD) at enrollment was 6.8 ± 3.5 years, and 53% were female. A majority had previous dactylitis (75%), painful vaso-occlusive episode (93%), blood transfusion (68%), and malaria (89%). Recurrent hospitalization was common with 30% having &amp;gt;5 previous hospitalizations. Only 4% had previously used hydroxyurea. Baseline labs included hemoglobin = 7.8 ± 1.3 g/dL, HbF = 9.3 ± 5.4 %, and ANC = 5.5 ± 2.4 x 109/L. Baseline assessment revealed a palpable spleen in 46 children (23%), and most of these (29) were ≥5 cm below the costal margin. Abdominal ultrasonography documented splenic tissue in 91% of children with an average volume of 101 ± 123 mL (range 8-1045). TCD examinations were performed in all children at enrollment with average TAMV of 148 ± 27 cm/sec [median 144, IQR 130-169 cm/sec] with 76% normal, 21% conditional, 2% abnormal, and 1% inadequate exams. Of 47 children eligible for hydroxyurea for elevated TCD velocities, 45 successfully initiated treatment, while 1 lived too far away for regular visits, and 1 had low blood counts from acute splenic sequestration and died before initiating study treatment. Conclusion: Children with SCA in Tanzania have a high risk for primary stroke. Identification of elevated TCD velocities through screening by local trained certified examiners, coupled with initiation of hydroxyurea treatment with dose escalation to MTD, offers a feasible and affordable means by which to lower TCD velocities and reduce primary stroke risk. Now fully enrolled, SPHERE has built local clinical capacity, research infrastructure and high-quality TCD screening, and will prospectively determine the benefits of hydroxyurea for stroke prevention, as a prelude for expanding hydroxyurea access for children with SCA in Tanzania. Figure Disclosures No relevant conflicts of interest to declare.

Hydroxyurea Therapy to Prevent Incident Stroke Among Children with Sickle Cell Anaemia in Jamaica: The Extend Trial

Hydroxyurea Therapy to Prevent Incident Stroke Among Children with Sickle Cell Anaemia in Jamaica: The Extend Trial

Burden of neurological and neurocognitive impairment in pediatric sickle cell anemia in Uganda (BRAIN SAFE): a cross-sectional study

BackgroundChildren with sickle cell anemia (SCA) are highly susceptible to stroke and other manifestations of pediatric cerebral vasculopathy. Detailed evaluations in sub-Saharan Africa are limited.MethodsWe aimed to establish the frequency and types of pediatric brain injury in a cross-sectional study at a large SCA clinic in Kampala, Uganda in a randomly selected sample of 265 patients with HbSS ages 1–12 years. Brain injury was defined as one or more abnormality on standardized testing: neurocognitive impairment using an age-appropriate test battery, prior stroke by examination or transcranial Doppler (TCD) velocities associated with stroke risk in children with SCA (cerebral arterial time averaged mean maximum velocity ≥ 170 cm/second).ResultsMean age was 5.5 ± 2.9 years; 52.3% were male. Mean hemoglobin was 7.3 ± 1.01 g/dl; 76.4% had hemoglobin < 8.0 g/dl. Using established international standards, 14.7% were malnourished, and was more common in children ages 5–12. Overall, 57 (21.5%) subjects had one to three abnormal primary testing. Neurocognitive dysfunction was found in 27, while prior stroke was detected in 15 (5.7%). The most frequent abnormality was elevated TCD velocity 43 (18.1%), of which five (2.1%) were in the highest velocity range of abnormal. Only impaired neurocognitive dysfunction increased with age (OR 1.44, 95%CI 1.23–1.68), p < 0.001). In univariate models, malnutrition defined as wasting (weight-for-height ≤ −2SD), but not sex or hemoglobin, was modestly related to elevated TCD (OR 1.37, 95%CI 1.01–1.86, p = 0.04). In adjusted models, neurocognitive dysfunction was strongly related to prior stroke (OR 6.88, 95%CI 1.95–24.3, p = .003) and to abnormal TCD (OR 4.37, 95%CI 1.30, p = 0.02). In a subset of 81 subjects who were enriched for other abnormal results, magnetic resonance imaging and angiography (MRI/MRA) detected infarcts and/or arterial stenosis in 52%. Thirteen subjects (25%) with abnormal imaging had no other abnormalities detected.ConclusionsThe high frequency of neurocognitive impairment or other abnormal results describes a large burden of pediatric SCA brain disease in Uganda. Evaluation by any single modality would have underestimated the impact of SCA. Testing the impact of hydroxyurea or other available disease-modifying interventions for reducing or preventing SCA brain effects is warranted.

Association Between Periodic Limb Movements in Sleep and Cerebrovascular Changes in Children With Sickle Cell Disease.

Periodic limb movements (PLMs) have been associated with increased risk of stroke, but there is currently scarce research exploring this relationship in the setting of sickle cell disease (SCD). The aim of this study was to explore whether increased PLMs in children with SCD are associated with increased risk of cerebrovascular disease and to determine if there are any clinical or laboratory differences between children with SCD with elevated periodic limb movement index (PLMI) versus those with normal PLMI. This study is a comprehensive review of medical records of 129 children with SCD (aged ≤ 18 years) who had undergone polysomnography for evaluation of sleep-disordered breathing. Elevated PLMI (PLMI > 5 events/h) was present in 42% (54/129) of children with SCD. Children with elevated PLMI were found to have higher percentage of hemoglobin S, lower total iron, higher arousal index and tendency toward elevated transcranial Doppler velocity (P = .063, odds ratio = 3.9, 95% CI 0.93-16.22). While association between elevated PLMI and isolated cerebrovascular stenosis (P = .050, odds ratio 5.6, 95% CI 1.0-31.10) trended toward significance, there was significantly greater proportion of children with elevated PLMI who had cerebrovascular stenosis with Moyamoya disease (P = .046) as demonstrated by magnetic resonance imaging (MRI). The prevalence of elevated PLMI in children with SCD was higher than in previously published data. Elevated PLMI was significantly associated with greater rates of cerebrovascular disease as detected by MRI.

Correlating transcranial arterial Doppler velocities with haematologic parameters and haemolytic indices of Nigerian children with sickle cell anaemia.

Cerebral vasculopathy, elevated transcranial Doppler velocities and stroke are linked to excessive intravascular haemolysis in sickle cell anaemia. This study determined the prevalence and pattern of abnormal blood flow velocities in children with sickle cell anaemia from Northern Nigeria using transcranial Doppler and to correlate transcranial Doppler velocities with haematological and biochemical markers of haemolysis. Full blood count, reticulocyte count, fetal haemoglobin and some selected biochemical markers of haemolysis of 100 children with sickle cell anaemia were determined at steady state. The time-averaged mean of maximal velocities in four major intracranial blood vessels was measured using non-imaging transcranial Doppler, which were then classified according to the stroke prevention in sickle cell disease trial protocol. A simple linear correlation between time-averaged mean of maximal velocities in the four major intracranial vessels as the dependent variable and haematological and biochemical markers of haemolysis as independent variables was also determined at the significance level of 0.05. Abnormal transcranial Doppler velocities, classified as high risk, were found in 3% of the studied patients; 11% had intermediate risk while 84% had standard risk. Most high velocities were detected in the middle cerebral artery. The time-averaged mean of maximal velocities of middle cerebral artery positively correlated with total white blood cell count, absolute neutrophil count, platelet count, reticulocyte count, serum lactate dehydrogenase and total bilirubin, while it was negatively correlated with haematocrit and fetal haemoglobin levels. Our study showed low prevalence of abnormal transcranial Doppler velocities and low prevalence is unrelated to low markers of haemolysis in our study population.

Association of Matched Sibling Donor Hematopoietic Stem Cell Transplantation With Transcranial Doppler Velocities in Children With Sickle Cell Anemia

In children with sickle cell anemia (SCA), high transcranial Doppler (TCD) velocities are associated with stroke risk, which is reduced by chronic transfusion. Whether matched sibling donor hematopoietic stem cell transplantation (MSD-HSCT) can reduce velocities in patients with SCA is unknown. To determine the association of MSD-HSCT with TCD velocities as a surrogate for the occurrence of ischemic stroke in children with SCA. Nonrandomized controlled intervention study conducted at 9 French centers. Patients with SCA were enrolled between December 2010 and June 2013, with 3-year follow-up ending in January 2017. Children with SCA were eligible if younger than 15 years, required chronic transfusions for persistently elevated TCD velocities, and had at least 1 sibling without SCA from the same 2 parents. Families agreed to HLA antigen typing and transplantation if a matched sibling donor was identified or to standard care in the absence of a matched sibling donor. MSD-HSCT (n = 32), compared with standard care (n = 35) (transfusions for ≥1 year with potential switch to hydroxyurea thereafter), using propensity score matching. The primary outcome was the highest time-averaged mean of maximum velocities in 8 cerebral arteries, measured by TCD (TCD velocity) at 1 year. Twenty-five of 29 secondary outcomes were analyzed, including the highest TCD velocity at 3 years and normalization of velocities (<170 cm/s) and ferritin levels at 1 and 3 years. Sixty-seven children with SCA (median age, 7.6 years; 35 girls [52%]) were enrolled (7 with stroke history). In the matched sample, highest TCD velocities at 1 year were significantly lower on average in the transplantation group (129.6 cm/s) vs the standard care group (170.4 cm/s; difference, -40.8 cm/s [95% CI, -62.9 to -18.6]; P < .001). Of the 25 analyzed secondary end points, 4 showed significant differences, including the highest TCD velocity at 3 years (112.4 cm/s in the transplantation group vs 156.7 cm/s in the standard care group; difference, -44.3 [95% CI, -71.9 to -21.1]; P = .001); normalization rate at 1 year (80.0% in the transplantation group vs 48.0% in the standard care group; difference, 32.0% [95% CI, 0.2% to 58.6%]; P = .045); and ferritin levels at 1 year (905 ng/mL in the transplantation group vs 2529 ng/mL in the standard care group; difference, -1624 [95% CI, -2370 to -879]; P < .001) and 3 years (382 ng/mL in the transplantation group vs 2170 ng/mL in the standard care group; difference, -1788 [95% CI, -2570 to -1006]; P < .001). Among children with SCA requiring chronic transfusion because of persistently elevated TCD velocities, MSD-HSCT was significantly associated with lower TCD velocities at 1 year compared with standard care. Further research is warranted to assess the effects of MSD-HSCT on clinical outcomes and over longer follow-up. ClinicalTrials.gov Identifier: NCT01340404.

Associations of transcranial doppler velocity, age, and gender with cognitive function in children with sickle cell anemia in Nigeria

ABSTRACTChildren with sickle cell anemia (SCA) have elevated cerebral blood velocity relative to healthy peers. The primary aim of this study was to evaluate the association between cerebral blood velocity, measured by transcranial Doppler (TCD) ultrasound, age, and gender with cognitive function in children with SCA in Nigeria. Eighty-three children (Mage = 9.10, SD = 1.90 years; 55% female) with SCA in Nigeria completed cognitive assessments and a TCD ultrasound. The association between TCD velocity and measures of perceptual reasoning (Raven’s Progressive Matrices), working memory (WISC-IV Digit Span), and executive planning (Tower of London, TOL) were assessed. Results showed that elevated TCD velocity significantly predicted lower scores on TOL Time Violations and Total Problem-Solving Time when controlling for BMI, hemoglobin level, and parent education, suggesting that TCD velocity is related to the efficiency of executive function. Further, age was negatively related to children’s performance on the Ravens Matrices and TOL Total Correct, and boys showed greater deficits on the TOL Total Correct relative to girls. Moderation analyses for gender showed that there was a conditional negative association between TCD velocity and Digit Span for boys, but not for girls. Findings suggest that children with SCA in Nigeria with elevated TCD velocity are at risk for deficits in efficiency of executive planning, and boys with elevated TCD velocity are particularly at increased risk for deficits in auditory working memory. Implications of this study are important for interventions to reduce cerebral blood velocity and the use of TCD in this population.

Annual stroke incidence in Nigerian children with sickle cell disease and elevated TCD velocities treated with hydroxyurea.

Elevated transcranial Doppler (TCD) velocities accurately predict stroke risk in children with sickle cell disease (SCD). Chronic blood transfusion, the gold standard for primary stroke prevention, is faced with numerous challenges in Africa. Hydroxyurea (HU) has been shown to reduce elevated TCD velocities in children with SCD. To determine the effectiveness of HU in reducing the risk of primary stroke in a cohort of Nigerian children with SCD and elevated velocities treated with HU. Children with SCD and TCD velocities ≥170cm/sec treated with HU were prospectively followed with 3-monthly TCD and neurological evaluations for ≥12 months to determine the incidence of primary stroke. One hundred and four children, 53 males, and 51 females were enrolled into the study. Their ages ranged from 2 to 16 years with a mean of 6 years. At first TCD examination, velocities ranged from 173 to 260cm/sec with conditional and abnormal risk velocities in 60 (57.7%) and 44 (42.3%) children, respectively. Follow up ranged from 1 to 8 years with a mean of 3.6 years. Mean TCD velocities showed a significant decline from 198.2 (standard deviation [SD]=15.6) cm/sec to 169.3 (SD=21.4) cm/sec (P<0.001). One stroke event occurred in the cohort, giving a stroke incidence of 0.27/100 person years. HU significantly reduces TCD velocities in Nigerian children with SCD and elevated TCD velocities, with a corresponding reduction in the incidence of primary stroke. HU may represent a potential alternative for primary stroke prevention in low and middle income countries where the burden of SCD resides.

Changes in Transcranial Doppler Flow Velocities in Children with Sickle Cell Disease: The Impact of Hydroxyurea Therapy

Hydroxyurea (HU) was recently described as a substitute for chronic transfusion for children with sickle cell disease (SCD) and abnormal transcranial Doppler (TCD) velocities who have received at least 1 year of transfusions. However, the role of HU in reverting elevated TCD velocities in patients not treated with transfusion is still debatable. The objective of the study was to examine whether HU influences the progression of TCD velocities in children with SCD. Children with SCD with at least 2 TCDs not less than 6 months apart were evaluated over 51 months. Time-averaged maximum mean (TAMM) velocities for the initial and the last transcranial Doppler examinations were noted and differences compared between HU and HU-naive groups. Overall, 68.8% of the HU-group with elevated TCD velocities compared with 40.0% of the HU-naive experienced TCD reversal (P = .047). A higher proportion of the HU-naive group, 7 (14.3%) versus 9.8% of the HU group experienced TCD conversion. Those with initial conditional velocities in the HU-group experienced a significant reduction in TAMM velocities (from 176.8 ± 5.3 to 162.7 ± 13.9 cm/s, difference of 14.1 cm/s; P = .001) unlike those in the HU-naive group (176.3 ± 5.3 to 170.0 ± 18.6 cm/s, difference of 6.3 cm/s; P = .148). The change in the TAMM velocities was also significantly higher among the HU-group (14.1 ± 12.4 cm/s versus 6.3 ± 18.5 cm/s, P = .015). Our data suggest a beneficial role of HU in TCD velocity reduction in patients not treated with chronic transfusions, particularly among those with initial conditional TCD velocities.

Stroke Avoidance for Children in REpública Dominicana (SACRED): Protocol for a Prospective Study of Stroke Risk and Hydroxyurea Treatment in Sickle Cell Anemia

BackgroundIn the Dominican Republic, where the burden of sickle cell anemia (SCA) is high, many children lack access to routine screening and preventative care. Children with SCA are at risk for stroke, an event that leads to significant morbidity and mortality. In the United States, screening via transcranial Doppler (TCD) identifies children with SCA at highest stroke risk, allowing early intervention with blood transfusions. The need for indefinite transfusions for primary stroke prevention limits their practicality in limited-resource countries. Hydroxyurea has been shown to lower TCD velocities and to prevent conversion from conditional (170 to 199 cm/sec) to abnormal (greater than or equal to 200 cm/sec) velocities. In resource-limited settings, implementation of a TCD screening program, coupled with hydroxyurea therapy, could reduce the burden of SCA and stroke.ObjectiveThe aims of the Stroke Avoidance for Children in REpública Dominicana (SACRED) trial are (1) to screen children with SCA for stroke risk using TCD and to determine the prevalence of elevated velocities in a cross-sectional sample; (2) to identify clinical and laboratory correlates of elevated velocities; and (3) to obtain longitudinal data on the natural history of TCD velocities and to measure therapeutic effects of hydroxyurea.MethodsThis prospective trial, designed and conducted by Cincinnati Children’s Hospital Medical Center (CCHMC) and Hospital Infantil Robert Reid Cabral (HIRRC) with Centro de Obstetricia y Ginecología, includes a baseline cross-sectional epidemiological survey of the distribution of TCD velocities across a large cohort of children with SCA in the Dominican Republic. Children with conditional velocities are eligible to begin protocol-directed hydroxyurea if laboratory criteria are met. The treatment schedule begins with a fixed-dose of approximately 20 mg/kg/day for 6 months, after which it escalates to maximum tolerated dose (MTD). All participants undergo longitudinal annual TCD evaluation, while those on hydroxyurea have semi-annual evaluations during the 3-year study period. Data are collected using an Internet-based Research Electronic Data Capture (REDCap) system with forms translated into Spanish; both remote and on-site monitoring are used.ResultsTo date, 122 children with SCA have enrolled in SACRED including 85 (69.7%, 85/122) with normal, 29 (23.8%, 29/122) with conditional, 5 (4.1%, 5/122) with abnormal, and 3 (2.5%, 3/122) with inadequate TCD velocities. Of the 29 children with conditional TCD velocities, 17 (59%, 17/29) have initiated hydroxyurea per protocol, with plans for escalation to MTD.ConclusionsThe SACRED trial will provide novel epidemiologic data about the prevalence of children with SCA and increased stroke risk in the Dominican Republic. The study also includes an investigation of the impact of hydroxyurea at MTD on elevated TCD velocities, as well as clinical and laboratory parameters. The design and implementation of SACRED reflect a successful international institutional partnership, one that features local capacity building and training in research methods and clinical care. The trial’s results have important implications for screening and prevention of primary stroke in children with SCA living in resource-limited settings.Trial RegistrationClinicalTrials.gov NCT02769845; https://www.clinicaltrials.gov/ct2/show/NCT02769845 (Archived by WebCite at http://www.webcitation.org/6qf6n0Egh)

First Report on Elevated Transcranial Doppler Ultrasound Velocities As First Stroke Risk and Their Association with Hemoglobin F Expression in Saudi Arabian Pediatric Sickle Cell Patients

Introduction: Sickle cell disease (SCD) is one of the most common inherited hemoglobinopathies in Middle East and specifically Saudi Arabia which leads to vaso-occlusive, hematological and infectious crises, including stroke as one of the common complications (1,2). Primary prevention of the first stroke is carried out by risk assessment using transcranial Doppler (TCD) ultrasound and providing blood transfusions to SCD patients with higher than 199 cm/sec TCD velocities (3). Furthermore, althoughhigher HbF expression is also associated with less severity of the SCD, no studies are available about association of HbF with TCD flow velocities and hence risk of stroke in SCD (4). This study has been carried out to identify SCD patients at high risk of stroke based on TCD results, and to determine the association between Hb-F levels and blood velocity using TCD results.Patients and Methods: Cross-sectional study included 56 pediatric SCD patients. TCD ultrasounds were performed at diagnosis for assessment of first stroke risk and then after every 6 months for follow-up studies. Patients with elevated TCD velocities given monthly packed RBCs transfusions to have HbS level around 40% (5,6). Data analysis was performed by "Statistical Package for the Social Sciences (SPSS, Version 17.0)".Results:In our patient population, male to female ratio was 1.33:1 (32 males, 24 females) and mean age was 7.5 ± 3.42 years (range: 2-14 years). Seven (12.5%) patients had TCD velocities higher than or equal to 200 cm/second, with mean age of 4.7±1.4 years and mean HbF 7.5±3.8, which were significantly different from patient group with normal flow velocities (mean age of 7.8±3.4 years; mean HbF 20±15.9). Patients with higher TCD velocities receiving blood transfusion got velocities in normal range within 6-12 months. Most importantly, normal TCD flow velocities were significantly associated with higher HbF expression and vice versa. As protective role of HbF in sickle cell patients is well established (11;13) and inducing the HbF expression in such patients using medications like hydroxyurea (20) or by genetically modifying the silencing of fetal γ-globin gene have been long standing goal in treatment of sickle cell disease (21), our findings about correlation of higher TCD flow velocities with lower HbF expression (and vice versa) and hence higher risk of first stroke in sickle cell patients provides a new direction for assessing the risk for vasculopathy in SCD patients.Discussion/Conclusions:Low prevalence of SCD patients with higher TCD velocities in our study population is in accordance with previous studies (5). Risk of first stroke was clinically manageable by 6-12 months of regular PRBCs transfusions, per established clinical practice (6). Moreover, normal TCD flow velocities and hence lower risk of stroke was significantly associated with the higher hemoglobin F expression and vice versa. As protective role of HbF in sickle cell patients is well established (4) and inducing the HbF expression in such patients have been long standing goal in treatment of sickle cell disease (7), our findings about correlation of higher TCD flow velocities with lower HbF expression (and vice versa) and hence higher risk of first stroke in sickle cell patients provides a new direction for assessing the risk for vasculopathy in SCD patients.

Hydroxyurea for sickle-cell anaemia in Africa: mind the gap.

Hydroxyurea for sickle-cell anaemia in Africa: mind the gap.

Abstract T P370: Blood Transfusions in Pediatric Sickle Cell Disease Normalize Cerebral Blood Flow While Maintaining Constant Cerebral Oxygen Metabolism

Background: Chronic blood transfusions (Tx) reduces stroke risk in pediatric sickle cell disease (SCD). Cerebral blood flow (CBF) is elevated in SCD, likely representing a compensatory mechanism to maintain cerebral oxygen metabolism (CMRO2) in the setting of reduced arterial oxygen content (CaO2) from chronic anemia. When exhausted compensatory mechanisms are unable to meet oxygen demands, stroke ensues. We measured MR-derived CBF and oxygen extraction fraction (OEF) pre- and post-Tx, hypothesizing that Tx ‘resets’ the CBF baseline by increasing CaO2 via increased hemoglobin (Hb), while maintaining cerebral oxygen delivery and metabolism. Methods: SCD children on chronic Tx were enrolled in a prospective, observational MRI study. MR-CBF and MR-OEF were acquired before and 2 hours after exchange Tx. MR-CBF and MR-OEF were measured using pseudocontinuous arterial spin labelling and a novel asymmetric spin echo sequence, respectively. CaO2 =1.35 x [Hb] x SaO2. CMRO2 = CaO2 x CBF x OEF. Results: Two SCD children underwent MRI pre- and post-Tx (six more are anticipated prior to ISC). For subject #1 (18 yo F with overt stroke), mean global CBF was 128 and 98 ml/min/100g pre- and post-Tx, respectively, indicating a 24% CBF reduction. For subject #2 (6 yo F with elevated transcranial Doppler velocities), mean global CBF was 189 and 129 ml/min/100g pre- and post-Tx, respectively, a 32% CBF reduction (Fig). Both Hb and CaO2 were increased after Tx, resulting in unchanged oxygen delivery (CaO2 x CBF) post-Tx. Moreover, OEF and CMRO2 were not significantly different pre- and post-Tx, consistent with our hypothesis that CBF increases to maintain oxygen delivery. Conclusions: Elevated CBF is likely a compensatory mechanism to maintain constant oxygen delivery in SCD children who have chronically low CaO2. In our subjects, Tx improved CaO2, allowing CBF to normalize. This reduced hemodynamic stress likely contributes to the lower stroke risk in chronically transfused SCD children.

Association of Annexin A5 Resistance with Silent Infarct in Sickle Cell Disease

Background: In sickle cell disease (SCD) abnormally shaped RBCs interact with white blood cells and the endothelium, leading to a vasculopathy and thrombotic/ prothrombotic complications such as stroke and pulmonary hypertension. About 10 % of patients with a thrombotic event in the general population will have the presence of an antiphospholipid (aPL) antibody (Andreoli et al. 2013). One proposed mechanism for the thrombophilic nature of aPL antibodies is the disruption of annexin A5. Annexin A5 is a potent anticoagulant protein that has an affinity to phospholipids. In the presence of aPL antibodies, annexin A5 is unable to form its crystallized anticoagulant shield (annexin A5 resistance). There is a paucity of data which assesses the association of aPL antibodies with vasculopathic complications of SCD, and there have been no studies investigating the annexin A5 resistance assay (A5R). We designed a pilot study assessing aPL antibody levels and A5R in a pediatric sickle cell population.Methods: Patients with a history of stroke, abnormal transcranial doppler (TCD) and elevated TR gradient by echocardiography (>25mm of Hg) were eligible. A5R, lupus anticoagulant- DRRVT, anti β2GP1, anti phosphatidylserine and anti cardiolipin antibody (IgG, IgA, IgM) assays were performed on samples obtained prospectively when patients were at a steady state (at least 4 weeks after an acute event). A5R measures coagulation times in the presence and absence of annexin A5. Resistance to the anticoagulant effects of annexin is expressed as a reduction in this ratio (Rand et al. 2004). Statistical analysis assessed multiple variables including age, gender, hemoglobin, reticulocyte count, LDH, hydroxyurea therapy, transfusion therapy, elevated TR gradient, stroke and silent stroke. Univariate analysis and multivariate logistic regression was performed with abnormal annexin A5 as the outcome variable.Results:There were a total of 39 patients: 12 patients with a history of stroke, 6 with an elevated TCD velocity and 15 patients with an elevated TR gradient. Of the 27 patients that did not have a stroke, 25 had a screening MRI in the prior year, and 9 of these patients had silent infarcts. Only 1 of 39 patients had elevated anticardiolipin IgG antibodies and 1 had an abnormal lupus coagulant (DRVVT). In contrast, 5/39 patients (12.8%) had low or abnormal annexin A5 resistance, 7/39 (18%) were in the borderline range and 27/39 (69%) were normal. This frequency of abnormality was unexpected in the antiphospolipid antibody and lupus anticoagulant negative population. None of the patients, except the one with the positive lupus anticoagulant, developed any thrombotic events in 3.5 years of follow up. None of the patients with overt stroke or abnormal TCDs had an abnormal A5R. Multivariate logistic regression analyses showed statistically significant association of hemoglobin (p= 0.037, OR 0.25, CI 0.07-0.92)), age (p =0.047, OR 1.43, CI 1.01-2.04) and silent infarct (p =0.015, OR 28.5, CI 1.9-420.5) with abnormal annexin A5 resistance. A multivariate analysis using linear regression with annexin A5 resistance as a continuous outcome variable (Table 1), showed persistence of the significant association of silent infarcts (p =0.037).Conclusion: We report an association between annexin A5 resistance and low hemoglobin, older age and presence of silent infarct in a subgroup of SCD patients. Prevalence of abnormal aPL antibody assays and lupus anticoagulant was strikingly low in this cohort. A potential role for perturbed annexin A5 resistance in the pathophysiology of silent infarction in SCD will need to be evaluated further in carefully designed prospective studies and may be a novel therapeutic target.Table 1Hemoglobin, Age and Silent Stroke are Associated with Abnormal Annexin A5 ResistanceCharacteristicOdds RatioOdds Ratio Confidence Intervalp-valueHemoglobin*0.250.07-0.920.037Reticulocyte count0.770.54-1.080.13LDH1.000.99-1.000.51Age*1.431.01-2.040.047Monocyte count1.001.00-1.000.34Silent infarct*28.51.9-420.50.015Stroke0.470.05-4.880.53Elevated TR gradient0.340.03-3.490.36Gender0.470.05-4.880.53Allosensitization0.560.05-5.860.63HU vs no treatment0.460.03-6.930.58Transfusion vs no treatment0.180.01-4.260.29 DisclosuresNo relevant conflicts of interest to declare.

Safety and Long-Term Effects of Splenectomy At the Age of Two for Acute Splenic Sequestration in Sickle Cell Disease: A Retrospective Review

AbstractAbstract 4758 Objective:Despite improved awareness and education about acute splenic sequestration (ASS) in sickle cell disease (SCD), such episodes remain potentially fatal and treatment options are limited. We report our local experience in children splenectomized at the age of two by evaluating long term complications related to sepsis, thrombosis and iron overload. Methods:Retrospective charts review of children with SCD and a history of ASS who underwent total splenectomy between 1996 and 2012 at Ste-Justine Hospital in Montreal, Canada. T-test and Fisher's exact test were used for statistical analysis. Results:20 patients were included in the study. Median age at splenectomy was 2 years old (range: 2–9 y.o). Median post-splenectomy follow-up was 4 years (range: 1month–16 years). 7 patients (35%) had limited fever in the postoperative setting, including one requiring antibiotics for pneumonia. Median length of stay was 4 days (range: 2–8 days). Three patients were hospitalised for documented sepsis at extended follow-up: two for salmonella at 1 and 12 years post splenectomy, while the third had hemophilus influenzae sepsis five months post-op but also within two months of a sibling cord blood transplantation. Platelet count increased within one month of surgery, and remained elevated at 6 and 12 months post splenectomy (p<0.001 at 1, 6 and 12 months compared to pre-surgery). Deep venous thrombosis was documented in one patient 4 years post splenectomy during hospitalisation for pain crisis. The thrombosis resolved with a three months treatment with enoxaparin. Thrombophilia work-up was negative. 75% of patients were on a transfusion program prior to splenectomy for a median duration of 13 months (11–20 months). Preliminary evaluation of iron overload in seven patients revealed a decrease in ferritinemia in all but two. One patient remained with severe iron overload and still requires oral chelation therapy. HbSS and HbS-Bthal splenectomized patients were more likely to be placed on hydroxyurea (HU) therapy than non-splenectomized patients with an odds ratio of 3 (11/20 vs 39/136 of our local population, p=0.023; 95% CI 1.17–7.9). 2 patients are on a regular transfusion program for elevated transcranial Doppler velocities. One patient underwent match sibling allogeneic transplantation. Conclusion:Our data suggest that performing total splenectomy at a very young age is a well-tolerated and efficacious treatment modality for children with severe and/or recurrent ASS. Performing splenectomy at a younger age may avoid unnecessarily extended transfusion programs and contribute to lessen the degree of iron overload. We consider ASS as a marker of SCD severity, as illustrated by the high rate of HU use in splenectomized patients. Whether splenectomy leads to biological modification contributing to increased SCD severity should be further studied. Concerns over possible increased thrombotic risk should also be further evaluated. Disclosures:No relevant conflicts of interest to declare.