Reproducibility of tricuspid regurgitant jet velocity measurements in children and young adults with sickle cell disease undergoing screening for pulmonary hypertension

The reproducibility of tricuspid regurgitant jet velocity (TRJV) measurements by Doppler echocardiography has not been subjected to systematic evaluation among individuals with sickle cell disease (SCD) undergoing screening for pulmonary hypertension. We examined sources of disagreement associated with peak TRJV in children and young adults with SCD. Peak TRJV was independently measured and interpreted a week apart by separate sonographers and readers, respectively, in 30 subjects (mean age, 15.8 ± 3.3 years) who provided 120 observations. We assessed intra‐/inter‐reader, intra‐/inter‐sonographer, sonographer‐reader, and within subject agreement using Intraclass Correlation Coefficient (ICC) and Cohen's kappa (κ). Agreement was examined graphically using Bland‐Altman plots. Although sonographers could estimate and measure peak TRJV in all subjects, readers designated tricuspid regurgitation nonquantifiable in 10–17% of their final interpretations. Intra‐reader agreement was highest (ICC = 0.93 [95% CI 0.86, 0.97], P = 0.0001) and within subject agreement lowest (ICC = 0.36 [95% CI 0.02, 0.64], P = 0.021) for single TRJV measurements. Similarly, intra‐reader agreement was highest (κ = 0.74 [95% CI 0.53, 0.95], P = 0.0001) and within subject lowest (κ = 0.14 [95% CI ?0.17, 0.46], P = 0.38) when sonographers and readers categorized TRJV measurements. On Bland‐Altman plots, absolute differences in observations increased with higher mean TRJV readings for intra‐/inter‐reader agreement. Peak TRJV measurements in individual children and young adults with SCD are affected by several sources of disagreement, underscoring the need for methodological improvements that ensure reproducibility of this screening modality for making clinical decisions in this population. Am. J. Hematol., 2010. © 2010 Wiley‐Liss, Inc.     

Tricuspid regurgitant jet velocity elevation and its relationship to lung function in pediatric sickle cell disease

Concerns about the morbidity and mortality associated with tricuspid regurgitant jet velocity (TRJV) elevation, which may indicate pulmonary hypertension (PHT), in adults with sickle cell disease (SCD) have prompted growing interest in screening the pediatric sickle cell population. The goals of our study were to estimate the prevalence of TRJV elevation and determine its relationship to pulmonary function in children and young adults with SCD at baseline. Seventy‐eight subjects (10–24 years old) with SCD underwent prospective screening by Doppler echocardiogram (ECHO), complete lung function evaluation, and laboratory testing as part of standard care at steady state. Tricuspid regurgitation was quantifiable in 68/78 (87%) subjects and peak TRJV was ≥2.5 m/sec in 26/78 (33.3%) evaluated. The frequency of obstruction, restriction, or abnormal gas exchange found on lung function evaluation was not significantly different in subjects with and without TRJV elevation. However, significant inverse correlations were observed between TRJV and both % predicted forced vital capacity (FVC) (r = ?0.29, P = 0.022) and oxygen saturation (r = ?0.26, P = 0.036). When compared to subjects without TRJV elevation, subjects with TRJV elevation had significantly lower % predicted forced expiratory volume in 1 sec (FEV₁) (78.9 ± 14.4 vs. 86.6 ± 13.0%, P = 0.023), FVC (82.8 ± 14.1 vs. 90.7 ± 12.9%, P = 0.017), and oxygen saturation (95.8 ± 3.2 vs. 97.5 ± 2.4%, P = 0.016). We found that the combination of low hemoglobin and low % predicted FVC best predicted TRJV elevation (χ² = 17.05, P = 0.001) in our cohort, correctly identifying 70% of cases and resulting in positive and negative predictive values of 60 and 74%, respectively. We conclude that in this young population with SCD, TRJV elevation that is not significantly associated with abnormal lung function is common at baseline. Pediatr Pulmonol. 2009; 44:281–289. © 2009 Wiley‐Liss, Inc.     

Clinical differences between children and adults with pulmonary hypertension and sickle cell disease

Pulmonary hypertension (PHT) is an important co-morbidity in sickle cell disease (SCD). Despite increasing research in adults, the prevalence and implication of this condition in children is unknown. Charts of 362 SCD patients followed at the Children's Hospital & Research Center Oakland were reviewed to determine clinical variables associated with obtaining echocardiographic screening for PHT, clinical associations of PHT, and associated mortality following diagnosis in adults and children with SCD. In this cohort, patients with underlying lung abnormalities or those on chronic transfusions were more likely to have echocardiograms, however the diagnosis of PHT was often unrecognized. A different clinical phenotype for PHT in adults versus children was identified. Associations with PHT for adults included age, renal and lung disease, hepatitis C, chronic transfusions, and a history of acute chest syndrome (ACS), with ACS being protective. Surprisingly, for children, a history of sepsis, along with a history of ACS, or obstructive lung disease were associated with PHT. Survival analysis found significant mortality for PHT, with a hazard ratio of 17·3 (95% confidence interval 4·9–60·4). The divergent clinical spectrum for PHT between adults and children may point to different age-specific mechanisms or biological expression of PHT.     

Cerebrovascular disease associated with sickle cell pulmonary hypertension

In patients with sickle cell disease, anemia is a recognized risk factor for stroke, death, and the development of pulmonary hypertension. We have proposed that hemolytic anemia results in endothelial dysfunction and vascular instability and can ultimately lead to a proliferative vasculopathy leading to pulmonary hypertension. Consistent with this mechanism of disease, we now report a case series of six patients with obliterative central nervous system vasculopathy who also have pulmonary hypertension and high hemolytic rate. These patients, identified in the course of a prospective screening study for pulmonary hypertension, presented with neurological symptoms prompting neuroimaging studies. Compared to 164 other patients of similar age in the screened population, those with newly diagnosed or clinically active cerebrovascular disease have significantly lower hemoglobin levels and higher levels of lactate dehydrogenase. A review of the literature suggests that many clinical, epidemiological, and physiological features of the arteriopathy of pulmonary hypertension closely overlap with those of stroke in sickle cell disease, both known to involve proliferative vascular intimal and smooth muscle hypertrophy and thrombosis. These cases suggest that cerebrovascular disease and pulmonary hypertension in sickle cell disease share common mechanisms, in particular, reduced nitric oxide bioactivity associated with particularly high-grade hemolysis. Clinicians should suspect occult cerebrovascular disease in sickle cell patients with pulmonary hypertension.     

Elevated tricuspid regurgitant jet velocity,reduced forced expiratory volume in 1 second,and mortality in adults with sickle cell disease

Cardiopulmonary disease is the leading cause of mortality in adults with sickle cell disease (SCD). Elevated tricuspid regurgitant jet velocity (TRJV) and reduced forced expiratory volume in 1 second (FEV₁) %predicted are associated with early mortality in SCD; however their relationship and combined effect on survival is unknown. We investigated the relationship between TRJV and FEV₁ %predicted, and their combined effect on mortality, in a retrospective cohort of 189 adults with SCD who underwent both pulmonary function testing and echocardiography. Nineteen (9.9%) of 189 patients died over a median follow‐up of 1.4 years; cardiopulmonary disease was the major cause of death in 52.6%. FEV₁%predicted was negatively associated with TRJV (Spearman rho, ?0.34, P < 0.001). Individuals with FEV₁%predicted ≤70% were more likely to have an elevated TRJV ≥2.5 m/second, compared to those with FEV₁%predicted >70% [45.8% versus 17.1%; odds ratio (OR) 4.1 (95% Confidence interval ([CI] 2.1–8.0); P = 0.001]. In a multivariable cox regression model, the combination of TRJV ≥2.5 m/second and FEV₁%predicted ≤70% predicted earlier mortality [hazard ratio (HR) 4.97 (95% CI 1.30‐18.91; P = 0.019)] after adjusting for age, sex, and nephropathy. Both FEV₁ %predicted ≤70% and TRJV ≥2.5 m/second were independently associated with nephropathy [OR 4.48 (95% CI 1.51–13.31); P = 0.004] and [OR 3.27 (95% CI 1.19–9.00); P = 0.017], respectively. In conclusion, pulmonary and cardiac impairment are associated with, and contribute to mortality in SCD. Therapies aimed at improving reduced FEV₁%predicted and elevated TRJV could improve survival in patients with SCD. Am. J. Hematol. 92:125–130, 2017. © 2016 Wiley Periodicals, Inc.     

Longitudinal study of echocardiography‐derived tricuspid regurgitant jet velocity in sickle cell disease

Although echocardiography‐derived tricuspid regurgitant jet velocity (TRV) is associated with increased mortality in sickle cell disease (SCD), its rate of increase and predictive markers of its progression are unknown. We evaluated 55 subjects (median age: 38 years, range: 20–65 years) with at least two measurable TRVs, followed for a median of 4·5 years (range: 1·0–10·5 years) in a single‐centre, prospective study. Thirty‐one subjects (56%) showed an increase in TRV, while 24 subjects (44%) showed no change or a decrease in TRV. A linear mixed effects model indicated an overall rate of increase in the TRV of 0·02 m/s per year (P = 0·023). The model showed that treatment with hydroxycarbamide was associated with an initial TRV that was 0·20 m/s lower than no such treatment (P = 0·033), while treatment with angiotensin converting enzyme inhibitors and angiotensin receptor blockers was associated with an increase in the TRV (P = 0·006). In summary, although some patients have clinically meaningful increases, the overall rate of TRV increase is slow. Treatment with hydroxycarbamide may decrease the progression of TRV. Additional studies are required to determine the optimal frequency of screening echocardiography and the effect of therapeutic interventions on the progression of TRV in SCD.     

The 6-min walk test: an independent correlate of elevated tricuspid regurgitant jet velocity in children and young adult sickle cell patients

Elevation of echocardiography-determined tricuspid regurgitant jet velocity (TRV) predicts high systolic pulmonary artery pressure. The present study tested the hypotheses that elevated tricuspid regurgitant jet velocity is associated with both hemolysis and hypoxia and abnormal 6-min walk test (6MWT) results. This study aims to correlate elevated TRV with different clinical laboratory findings and 6MWT and to find the independent predictors of increased TRV. A prospective study of 80 patients aged 5–25 years old with sickle cell disease (SCD) under basal conditions and 40 matched controls was conducted. Hemolytic analysis was assessed by the levels of lactate dehydrogenase, serum bilirubin, and reticulocyte count. Oxygen saturation determination using pulse oximeter and 6MWT were done. The overall prevalence of elevated TRV (≥2.5 m/s) was 28.75 %. Associated risk factors were older age (r?=?0.28, p?=?0.01), longer duration of disease (r?=?0.25, p?=?0.025), higher reticulocytic count (r?=?0.344, p?=?0.002), lower O₂ saturation (r?=??0.574, p?=?0.0001), and shorter walked distance in 6MWT (r?=??0.75, p?=?0.0001). By multivariate logistic analysis, only the distance walked during 6MWT was the independent correlate of elevated TRV (odds ratio?=?0.85; 95 % CI?=?0.74 to 0.98 p?=?0.033). The study provides evidence for independent association of TRV with abnormal 6MWT results. The 6-min walk test can be used as noninvasive adjuvant tool for functional capacity assessment of SCD patients with elevated TRV.     

Relative systemic hypertension in patients with sickle cell disease is associated with risk of pulmonary hypertension and renal insufficiency

We analyzed entry data from 163 adult hemoglobin SS and Sbeta(0) thalassemia patients enrolled in the prospective Sickle Cell Pulmonary Hypertension Screening Study and stratified their ECHO-determined tricuspid regurgitant jet velocity (TRV) and serum creatinine concentration according to three systemic blood pressure categories. TRV was >or= 2.5 m/sec in 27% of the patients with systolic blood pressure (SBP) <120 mmHg and diastolic blood pressure (DBP) <70 mmHg, in 37% with SBP 120-139 mmHg or DBP 70-89 mmHg, and in 93% with SBP 140 mmHg or DBP 90 mmHg or higher (P<0.0005 for trend). Serum creatinine concentration was 1.0 mg/dL or higher in 7% of patients with SBP <120 mmHg and DBP <70 mmHg, in 17% with SBP 120-139 mmHg or DBP 70-89 mmHg and 50% with SBP 140 mmHg or DBP 90 mmHg or higher (P<0.0005 for trend). Over 2 years of follow-up, there were trends for more frequent progression to elevated TRV (P=0.073) or creatinine (P=0.037) values according to the higher systemic blood pressure categories. Our findings suggest that systemic SBP 120-139 mmHg or DBP 70-89 mmHg defines a category of relative systemic hypertension in patients with sickle cell disease that is associated with increased risk for pulmonary hypertension and renal dysfunction. Whether antihypertensive and/or nitric oxide donor therapy in sickle cell disease patients with relative hypertension prevents these and other complications should be determined by clinical trials.     

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

In the US, mortality in sickle cell disease (SCD) increases after age 18-20 years. Biomarkers of mortality risk can identify patients who need intensive follow-up and early or novel interventions. We prospectively enrolled 510 SCD patients aged 3-20 years into an observational study in 2006-2010 and followed 497 patients for a median of 88 months (range 1-105). We hypothesized that elevated pulmonary artery systolic pressure as reflected in tricuspid regurgitation velocity (TRV) would be associated with mortality. Estimated survival to 18 years was 99% and to 25 years, 94%. Causes of death were known in seven of 10 patients: stroke in four (hemorrhagic two, infarctive one, unspecified one), multiorgan failure one, parvovirus B19 infection one, sudden death one. Baseline TRV ≥2.7 m/second (>2 SD above the mean in age-matched and gender-matched non-SCD controls) was observed in 20.0% of patients who died vs 4.6% of those who survived (P = .012 by the log rank test for equality of survival). The baseline variable most strongly associated with an elevated TRV was a high hemolytic rate. Additional biomarkers associated with mortality were ferritin ≥2000 μg/L (observed in 60% of patients who died vs 7.8% of survivors, P < .001), forced expiratory volume in 1 minute to forced vital capacity ratio (FEV1/FVC) <0.80 (71.4% of patients who died vs 18.8% of survivors, P < .001), and neutrophil count ≥10x10⁹/L (30.0% of patients who died vs 7.9% of survivors, P = .018). In SCD children, adolescents and young adults, steady-state elevations of TRV, ferritin and neutrophils and a low FEV1/FVC ratio may be biomarkers associated with increased risk of death.     

Functional capacity in children and young adults with sickle cell disease undergoing evaluation for cardiopulmonary disease

Although cardiopulmonary disease is associated with decreased functional capacity among adults with sickle cell disease (SCD), its impact on functional capacity in children with SCD is unknown. We evaluated 6‐min walk (6MW) distance in 77 children and young adults with SCD undergoing screening for cardiopulmonary disease. Of 30 subjects who also underwent cardiopulmonary exercise testing, we found evidence for decreased exercise capacity in a significant proportion. Exercise capacity was related to baseline degree of anemia and was significantly lower in subjects with a history of recurrent acute chest syndrome. We found that 6MW distance adjusted for weight and body surface area was shorter in subjects with restrictive lung disease but that only 6MW adjusted for weight remained significantly shorter when we controlled for baseline hemoglobin. Exercise capacity was not significantly different in subjects with and without cardiopulmonary disease. We conclude that restrictive lung disease is associated with shorter 6MW distances in children and young adults with SCD, but that variables associated with decreased exercise capacity, other than anemia, remain unclear. Our study underscores the importance of further delineating the direct pathophysiologic processes that contribute to decreased exercise capacity observed among individuals with SCD and cardiopulmonary disease. Am. J. Hematol., 2009. © 2009 Wiley‐Liss, Inc.     

Identification of genetic polymorphisms associated with risk for pulmonary hypertension in sickle cell disease

Up to 30% of adult patients with sickle cell disease (SCD) will develop pulmonary hypertension (pHTN), a complication associated with significant morbidity and mortality. To identify genetic factors that contribute to risk for pHTN in SCD, we performed association analysis with 297 single nucleotide polymorphisms (SNPs) in 49 candidate genes in patients with sickle cell anemia (Hb SS) who had been screened for pHTN by echocardiography (n = 111). Evidence of association was primarily identified for genes in the TGFβ superfamily, including activin A receptor, type II–like 1 (ACVRL1), bone morphogenetic protein receptor 2 (BMPR2), and bone morphogenetic protein 6 (BMP6). The association of pHTN with ACVRL1 and BMPR2 corroborates the previous association of these genes with primary pHTN. Moreover, genes in the TGFβ pathway have been independently implicated in risk for several sickle cell complications, suggesting that this gene pathway is important in overall sickle cell pathophysiology. Genetic variation in the β-1 adrenergic receptor (ADRB1) was also associated with pHTN in our dataset. A multiple regression model, which included age and baseline hemoglobin as covariates, retained SNPs in ACVRL1, BMP6, and ADRB1 as independently contributing to pHTN risk. These findings may offer new promise for identifying patients at risk for pHTN, developing new therapeutic targets, and reducing the occurrence of this life-threatening SCD complication.     

Five years of experience with hydroxyurea in children and young adults with sickle cell disease

The short-term beneficial effect of hydroxyurea (HU) in sickle cell disease (SCD) has been proven by randomized studies in children and adults. The Belgian registry of HU-treated SCD patients was created to evaluate its long-term efficacy and toxicity. The median follow-up of the 93 patients registered is 3.5 years; clinical and laboratory data have been obtained for 82 patients at 1 year, 61 at 2 years, 44 at 3 years, 33 at 4 years, and 22 after 5 years. On HU, the number of hospitalizations and days hospitalized dropped significantly. Analysis of the 22 patients with a minimum of 5 years of follow-up confirm a significant difference in the number of hospitalizations (P =.0002) and days in the hospital (P <.01), throughout the treatment when compared to prior to HU therapy. The probabilities of not experiencing any event or any vaso-occlusive crisis requiring hospitalization during the 5 years of treatment were, respectively, 47% and 55%. On HU, the rate per 100 patient-years of severe events was estimated to be 3.5% for acute chest syndrome, 1.2% for aplastic crisis, 0.4% for splenic sequestration; it was 0% for the 9 patients with a history of stroke or transient ischemic attack followed for an average of 4 years. No important adverse effect occurred. Long-term chronic treatment with HU for patients with SCD appears feasible, effective, and devoid of any major toxicity; in patients with a history of stroke, HU may be a valid alternative to chronic transfusion support. (Blood. 2001;97:3628-3632)     

Ischemic stroke in children and young adults with sickle cell disease in the post-STOP era

The Stroke Prevention Trial in Sickle Cell Anemia (STOP) and Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP 2) trials established routine transcranial Doppler ultrasound (TCD) screening, with indefinite chronic red cell transfusions (CRCT) for children with abnormal TCD as standard of care. Implementation failures and limitations to the STOP protocol may contribute to continued ischemic stroke occurrence. In the “Post-STOP” study, we sought to assess the impact of the STOP protocol on the incidence of ischemic stroke in a multicenter cohort of former STOP and/or STOP 2 trial participants. A central team abstracted data for 2851 (74%) of the 3835 children who took part in STOP and/or STOP 2. Data included TCD and neuroimaging results, treatment, laboratory data, and detailed clinical information pertaining to the stroke. Two stroke neurologists independently confirmed each stroke using pre-specified imaging and clinical criteria and came to consensus. Among the 2808 patients who were stroke-free at the start of Post-STOP with available follow-up, the incidence of first ischemic stroke was 0.24 per 100 patient-years (95% CI, 0.18, 0.31), with a mean (SD) duration of follow-up of 9.1 (3.4) [median 10.3, range (0-15.4)] years. Most (63%) strokes occurred in patients in whom the STOP protocol had not been properly implemented, either failure to screen appropriately with TCD (38%) or failure to transfuse adequately patients with abnormal TCD (25%). This study shows that substantial opportunities for ischemic stroke prevention remain by more complete implementation of the STOP Protocol.     

Silent infarcts in young children with sickle cell disease

Silent infarcts have been reported most commonly in school-aged children with homozygous sickle cell disease (SCD-SS) and are associated with neurocognitive deficits. However, the prevalence of silent infarcts in younger children with SCD-SS is not well defined. In this retrospective study, brain magnetic resonance imaging and angiography (MRI/A) studies performed before 6 years of age in a cohort of children with SCD-SS were analysed and the prevalence of abnormalities was calculated. Clinical and laboratory parameters were compared between the groups with and without silent infarcts. Sixty-eight of 96 children in the cohort had brain MRI/A performed prior to age 6 years. Of the 65 who were neurologically asymptomatic, 18 (27·7%, 95% CI 17·3–40·2%) had silent infarcts (mean age 3·7 ± 1·1 years, range 1·3–5·9 years). Factors associated with silent infarcts included cerebral vessel stensosis by magnetic resonance angiography, lower rates of vaso-occlusive pain and acute chest syndrome and lower haemoglobin levels. The prevalence of silent infarcts in young children with SCD-SS is similar to that of older children and anaemia and severe vasculopathy may be risk factors.     

Hemolytic anemia-associated pulmonary hypertension in sickle cell disease

Pulmonary hypertension is one of the leading causes of death in adult sickle cell patients, with a prevalence of 20% to 40%. Although these patients have lower pulmonary pressures than patients with primary pulmonary hypertension, both groups suffer high 2-year mortality rates. Pulmonary hypertension may go undetected until the disease is advanced. Therefore, all adult patients with sickle cell disease should be screened with transthoracic Doppler echocardiogram and the tricuspid regurgitant jet (TRJ) velocity measured to estimate pulmonary artery pressures. A regurgitant jet (RJ) velocity of 2.5 m/s or higher establishes diagnosis and suggests a high risk of death (rate ratio of 10.1; CI= 2.2-47). Basic and epidemiologic studies suggest that pulmonary hypertension in sickle cell disease is mechanistically linked to chronic hemolytic anemia. Hemolysis results in the release of hemoglobin and arginase from the erythrocyte, increasing the consumption and decreasing the production of nitric oxide (NO), respectively. NO is a critical regulator of vasodilation and vascular homeostasis whose inactivation produces vasoconstriction and proliferative vasculopathy. Finally, we review suggested therapies including the established treatments and new pulmonary vasodilator and remodeling agents in the management of pulmonary hypertension in hemolytic anemias.