Tricuspid regurgitation in patients with ?-thalassemia major

Pulmonary hypertension associated with thalassemia syndromes

Chronic hemolytic anemia has increasingly been identified as an important risk factor for the development of pulmonary hypertension (PH). Within the thalassemia syndromes, there are multiple mechanisms, both distinct and overlapping, by which PH develops and that differ among β-thalassemia major or intermedia patients. PH in β-thalassemia major correlates with the severity of hemolysis, yet in patients whose disease is well treated with chronic transfusion therapy, the development of PH can be related to cardiac dysfunction and the subsequent toxic effects of iron overload rather than hemolysis. β-Thalassemia intermedia, on the other hand, has a higher incidence of PH owing to the low level of hemolysis that exists over years without the requirement for frequent transfusions, while splenectomy is shown to play an important role in both types. Standard therapies such as chronic transfusion have been shown to mitigate PH, and appropriate chelation therapy can avoid the toxic effects of iron overload, yet is not indicated in many patients. Limited evidence exists for the use of pulmonary vasodilators or other therapies, such as l-carnitine, to treat PH associated with thalassemia. Here, we review the most recent findings regarding the pathogenic mechanisms, epidemiology, presentation, diagnosis, and treatment of PH in thalassemia syndromes.

Pulmonary hypertension in β thalassaemia

Pulmonary hypertension is one of the leading causes of morbidity and mortality in patients with haemolytic disorders and is a frequent finding in echocardiographic screening of patients with β thalassaemia. Substantial progress has been made in understanding of the multifactorial pathophysiology of pulmonary hypertension in β thalassaemia. Haemolysis, reduced nitric oxide bioavailability, iron overload, and hypercoagulopathy are among the main pathogenetic mechanisms. Various disease-directed therapeutic methods, such as transfusion, chelation, and splenectomy, have important roles in the development of pulmonary hypertension in β thalassaemia. Studies investigating the prevalence of pulmonary hypertension in β thalassaemia are mostly based on echocardiographic findings, and are thus limited by the scarcity of information derived from right heart catheterisation. Invasive pulmonary haemodynamic data are needed to clarify the true prevalence of pulmonary hypertension in β thalassaemia, to better understand the underlying pathophysiology and risk factors, and to define the optimum therapy for this devastating complication.

Sildenafil therapy in thalassemia patients with Doppler-defined risk of pulmonary hypertension

Pulmonary hypertension is a common but often overlooked complication associated with thalassemia syndromes. There are limited data on the safety and efficacy of selective pulmonary vasodilators in this at-risk population. We, therefore, designed a 12-week, open-label, phase 1/2, pilot-scale, proof-of-principle trial of sildenafil therapy in 10 patients with β-thalassemia and at increased risk of pulmonary hypertension based on an elevated tricuspid regurgitant jet velocity >2.5 m/s on Doppler-echocardiography. Variables compared at baseline and after 12 weeks of sildenafil treatment included Doppler-echocardiographic parameters, 6-minute walked distance, Borg Dyspnea Score, New York Heart Association functional class, pulmonary function, and laboratory parameters. Treatment with sildenafil resulted in a significant decrease in tricuspid regurgitant jet velocity by 13.3% (3.0±0.7 versus 2.6±0.5 m/s, P=0.04), improved left ventricular end systolic/diastolic volume, and a trend towards a improved New York Heart Association functional class. No significant change in 6-minute walked distance was noted. Sildenafil was well tolerated, although minor expected adverse events were commonly reported. The total dose of sildenafil (mg) was strongly correlated with percent change in nitric oxide metabolite concentration in the plasma (ρ=0.80, P=0.01). There were also significant increases in plasma and erythrocyte arginine concentrations. Our study suggests that sildenafil is safe and may improve pulmonary hemodynamics in patients at risk of pulmonary hypertension; however, it was not demonstrated to improve the distance walked in 6 minutes. Clinical trials are needed to identify the best treatment strategy for pulmonary hypertension in patients with β-thalassemia. (clinicaltrials.gov identifier: NCT00872170).

Risk factors and mortality associated with an elevated tricuspid regurgitant jet velocity measured by Doppler-echocardiography in thalassemia: a Thalassemia Clinical Research Network report

An elevated tricuspid regurgitant jet velocity (TRV) is associated with hemolysis and early mortality in sickle cell disease, yet risk factors, clinical parameters, and mortality associated with this biomarker in thalassemia are poorly defined. This report summarizes the prevalence of an elevated TRV in 325 patients screened by Doppler echocardiography in the Thalassemia Clinical Research Network. A documented TRV was reported in 148 of 325 (46%) of patients. Average age was 25.9 years (range, 5-56 years) and 97% were transfusion-dependent. Mean TRV was 2.3 ± 0.4 m/s (range, 0.2-3.5 m/s). An abnormal TRV ≥ 2.5 m/s was identified in 49 of 148 (33%) of patients with a documented TRV, 5% (8/148), with a TRV ≥ 3.0 m/s, suggesting significant PH risk. Older age was strongly associated with a high TRV; however, 16% of children had a TRV ≥ 2.5 m/s. A history of splenectomy, hepatitis C, smoking, or high white blood cell count was associated with TRV elevation. In summary, an elevated TRV is noted in one-third of transfusion-dependent thalassemia patients with a documented value and develops in both children and adults. Age, splenectomy, hepatitis C, and smoking are significant univariate risk factors, with splenectomy surfacing as the dominant risk factor over time. Mortality was low in this cohort. Prospective longitudinal studies are needed. This study is registered at http://www.clinicaltrials.gov as NCT00661804.

Frequency of pulmonary hypertension in asymptomatic β-thalassemia major patients and the role of physiological parameters in evaluation

In this study, the authors aimed to evaluate the frequency of pulmonary hypertension (PHT) in asymptomatic thalassemia major (TM) patients, and to investigate the impact of pulmonary function test (PFT) and CO diffusion results on the evaluation of pulmonary hypertension. Data from 50 asymptomatic patients with TM over age 10 were evaluated. Pulmonary hypertension was diagnosed in 10 patients (20%). High tricuspid regurgitant jet velocity was found in 14% of adults and in 25% of children. Pulmonary function test including CO diffusion testing results were not different between the TM patients with or without pulmonary hypertension. In conclusion, PHT was frequent among TM patients even they were asymptomatic and although PFT results has shown lack of association, it should be investigated in larger population.

Pulmonary hypertension in thalassemia

Pulmonary hypertension (PH) is common in thalassemia and contributes to mortality. Advancing age and a history of splenectomy are major risk factors in this population. The etiology of PH is multifactorial, involving a complex interaction of platelets, the coagulation system, erythrocytes, and endothelial cells along with inflammatory and vascular mediators. The long-term effect of splenectomy, red cell membrane pathology, coagulation abnormalities, low nitric oxide (NO) bioavailability, excess arginase activity, platelet activation, oxidative stress, iron overload, and chronic hemolysis play a role. The process of hemolysis disables the arginine-NO pathway through the simultaneous release of erythrocyte arginase and cell-free hemoglobin. Both NO and its obligate substrate arginine are rapidly consumed. The biological consequences of hemolysis on NO bioavailability ultimately translate into the clinical manifestations of PH. Guidelines for the management of PH in thalassemia have not yet been established; however, clinical trials are ongoing in an effort to guide future therapy.

N-terminal natriuretic peptide and ventilation-perfusion lung scan in sickle cell disease and thalassemia patients with pulmonary hypertension

The aim of this study was to determine the prevalence of pulmonary hypertension (PH) in sickle cell disease and thalassemia patients in relation to clinical and laboratory parameters of hemolysis and hemosidersosis, as well as plasma N-terminal pro-brain natriuretic peptide (NT-pro-BNP). The study also aimed to define the role of thromboembolic pulmonary artery (PA) obstruction in its etiology. Forty sickle cell disease and 30 thalassemia patients [15 beta-thalassemia major (beta-TM) and 15 beta-thalassemia intermedia (beta-TI)] were screened for PH defined as tricuspid regurgitant velocity (TRV) >2.5 m/sec and evaluated for PA obstruction using ventilation-perfusion lung scan (V/Q), together with measurement of their plasma levels of NT-pro-BNP. Patients were prospectively followed up for a mean of 18 +/- 6.1 months. The prevalence of PH was 37.5, 40.0 and 26.7% in sickle cell disease, beta-TI and beta-TM patients, respectively. Pulmonary hypertension patients were older, had longer disease duration, higher serum ferritin, serum lactate dehydrogenase (LDH) and NT-pro-BNP with lower hemoglobin (Hb) levels compared to patients without PH. N-terminal pro-BNP was positively correlated with duration of illness, TRV, LDH, serum ferritin, and negatively correlated with Hb levels. The strongest predictor for TRV was serum ferritin followed by the NT-pro-BNP level. Forty-six-point-seven percent of sickle cell disease patients with PH had either high or intermediate probability V/Q scan results compared to 10% of thalassemic patients with PH who had high probability V/Q scan results. Pulmonary hypertension is highly prevalent in young sickle cell disease and thalassemia patients, where elevated serum ferritin and NT-pro-BNP are the main indicators.

Update on thalassemia treatment in Taiwan, including bone marrow transplantation, chelation therapy, and cardiomyopathy treatment effects

Over the past few decades, Taiwan has seen striking improvements in the life expectancy of its 400 registered beta-thalassemia major (beta-TM) patients due mainly to adequate transfusion regimens and effective iron chelation therapy. Since 1995, Taiwanese citizens have enjoyed universal health care through National Health Insurance (NIH), receiving comprehensive treatment at minimal cost. In 1984, a national program for thalassemia prevention, control, and hematopoietic stem cell transplantation (HSCT) was initiated. Recent data show 1- and 2-year event-free survival rates of 85 and 78%, respectively. Chelation agents like deferoxamine (DFO), deferiprone (L1) and deferasirox (DFRA) are available in Taiwan, and therapy is tailored to individuals based on drug availability and tissue distribution of iron load. Intensive chelation regimens combining L1 and DFO are recommended in patients with cardiac complications, while DFRA has been found to be effective in reducing serum ferritin, with acceptable side effects. Here, we report advances in thalassemia treatment in Taiwan and suggest treatment guidelines.

Glutathione S-Transferase M1 Gene Polymorphisms are Associated with Cardiac Iron Deposition in Patients with β-Thalassemia Major

Patients with beta-thalassemia (thal) major are subject to peroxidative tissue injury by iron overload. Glutathione S-transferases work as antioxidants, and their activity is determined genetically. In this study, we used multiplex polymerase chain reaction (m-PCR) to analyze polymorphisms of two endogenous antioxidant agents, glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1), and to determine their roles in 41 patients with beta-thal major. Our results showed that the GSTM1 and GSTT1 null genotypes were not associated with any incidence of endocrine dysfunction (including diabetes mellitus, hypogonadism, hypothyroidism, and growth hormone deficiency), liver function, or impaired left ventricular ejection fraction (LVEF). The GSTM1 null genotype, but not the GSTT1 null genotype, was associated with a decreased signal intensity ratio on cardiac magnetic resonance imaging (MRI). Our results suggest that genetic variations of the GSTM1 enzyme are associated with cardiac iron deposition in patients with beta-thal major.

Delayed adverse vascular events after splenectomy in hereditary spherocytosis

BACKGROUND

It is probable that the variety and frequency of delayed adverse vascular events after splenectomy are underappreciated. Splenectomy is performed for a wide variety of conditions, and delayed postsplenectomy hazards are not often studied.

OBJECTIVE

To estimate the relative risk of adverse vascular events in members of hereditary spherocytosis families who have or have not had a splenectomy.

METHODS

Members of families in which hereditary spherocytosis exists were systematically questioned about adverse vascular events.

RESULTS

The cumulative incidence of arterial and venous events at age 70 years was greater in persons who had undergone a splenectomy for spherocytosis (arterial, 22% females, 32% males; venous, 20% females, 19% males) than in affected persons who did not undergo splenectomy (arterial, 3% females, 2% males; venous, 6% females, 4% males) or non-affected family members (arterial, 10% females, 17% males; venous, 4% females, 12% males). Affected subjects who undergo splenectomy are at greatly increased risk of arterial events as compared to affected subjects who do not undergo splenectomy [arterial, hazard ratio (HR) 7.2, 95% confidence interval (CI) 2.8-17.2; venous, HR 3.3, 95% CI 1.1-9.8].

CONCLUSION

There is a significant, long-lasting, increased risk of adverse arterial and venous thromboembolic events after splenectomy performed for hereditary spherocytosis. A review of the literature indicates that this is also true when splenectomy is performed for several other indications.

Influence of iron chelators on myocardial iron and cardiac function in transfusion-dependent thalassaemia: a systematic review and meta-analysis

Iron chelators have dramatically prolonged the life expectancy of patients with transfusion-dependent thalassaemia, but their precise clinical benefit in reducing the myocardial iron burden and improving cardiac function is unknown. This systematic review and meta-analysis included published clinical trials that assessed the efficacy of iron chelators in regularly transfused patients of thalassaemia major for two commonly reported outcomes - myocardial iron content and left ventricular ejection fraction (LVEF). The meta-analysis of 392 patients for myocardial iron content and 291 patients for LVEF showed that (i) iron chelators reduced cardiac iron content by 23.9% (95% confidence interval 17.3-29.8%); (ii) there was no significant difference between the amount of iron reduced by deferoxamine and deferiprone (P = 0.9504); and (iii) LVEF was not significantly influenced by iron chelators - summary Hedge's g 0.13 (95% confidence interval -0.10-0.36). A significant publication bias existed for LVEF (Egger's P = 0.049) but not for myocardial iron (Egger's P = 0.871). Our results indicate that iron chelators significantly reduce myocardial iron content. Further, the choice of deferoxamine versus deferiprone may rest on factors other than their efficacy to reduce cardiac iron load.

Successful Mitral Valve Replacement in a Patient with a Severe Form of β-Thalassaemia

beta-Thalassaemia is an inherited haemoglobin (Hb) disorder resulting in chronic haemolytic anaemia. The most anaemic patients require regular red blood cell (RBC) transfusions for survival but iron accumulation leads to multisystem dysfunction. Heart complications represent the leading cause of mortality in beta-thalassaemia patients. In this case report we present a successful mitral valve replacement (MVR) in a patient with a severe form of beta-thalassaemia.

Right Ventricular Function in Patients with Beta Thalassemia: Relation to Serum Ferritin Level

Cardiac dysfunction is a major cause of death in patients with beta thalassemia. Right ventricular (RV) contribution to cardiac morbidity and mortality in these patients has been suggested. We aimed to assess RV function in beta thalassemia (beta-Th) patients and to detect the relation of serum ferritin level to RV dysfunction. Thirty young patients with beta-Th and 15 age-matched normal subjects (NL) were included. We measured RV end diastolic and end systolic diameters (RVEDD and RVESD), RV % fractional shortening (RVFS), RV pressure (RVP), lateral and septal tricuspid annular systolic and diastolic tissue Doppler velocities (Sa, Ea, Aa & Ea/Aa), and RV myocardial systolic and diastolic velocities at the basal RV segment (RVSm, RVEm, RVAm & RVEm/Am). Serum ferritin level was measured in beta-Th patients who were divided accordingly into two groups; G1 with serum ferritin > or =2,000 microg/L and G2 with serum ferritin < 2,000 microg/L. Compared to NL subjects, beta-Th patients had significantly higher RVEDD, RVESD & RVP, lower RVFS, higher Aa, and lower Ea/Aa at lateral and septal tricuspid annular sites, higher RVAm and lower RVEm/Am. Patients with higher serum ferritin level (G1) had higher RVP, higher RVEDD and RVESD, lower Sa at the lateral annular site and lower RVSm than patients in G2. High serum ferritin level was significantly associated with pulmonary hypertension. We concluded that patients with beta-Th have RV diastolic dysfunction, pulmonary hypertension is common, and the presence of RV systolic dysfunction in these patients is related to the higher level of serum ferritin.

Hemolysis in sickle cell mice causes pulmonary hypertension due to global impairment in nitric oxide bioavailability

Pulmonary hypertension is a highly prevalent complication of sickle cell disease and is a strong risk factor for early mortality. However, the pathophysiologic mechanisms leading to pulmonary vasculopathy remain unclear. Transgenic mice provide opportunities for mechanistic studies of vascular pathophysiology in an animal model. By microcardiac catheterization, all mice expressing exclusively human sickle hemoglobin had pulmonary hypertension, profound pulmonary and systemic endothelial dysfunction, and vascular instability characterized by diminished responses to authentic nitric oxide (NO), NO donors, and endothelium-dependent vasodilators and enhanced responses to vasoconstrictors. However, endothelium-independent vasodilation in sickle mice was normal. Mechanisms of vasculopathy in sickle mice involve global dysregulation of the NO axis: impaired constitutive nitric oxide synthase activity (NOS) with loss of endothelial NOS (eNOS) dimerization, increased NO scavenging by plasma hemoglobin and superoxide, increased arginase activity, and depleted intravascular nitrite reserves. Light microscopy and computed tomography revealed no plexogenic arterial remodeling or thrombi/ emboli. Transplanting sickle marrow into wild-type mice conferred the same phenotype, and similar pathobiology was observed in a nonsickle mouse model of acute alloimmune hemolysis. Although the time course is shorter than typical pulmonary hypertension in human sickle cell disease, these results demonstrate that hemolytic anemia is sufficient to produce endothelial dysfunction and global dysregulation of NO.

Pulmonary hypertension in sickle cell disease: relevance to children

Pulmonary arterial hypertension (PAH), once considered a rare complication of sickle cell disease (SCD) and thalassemia, appears to be more common in adults with hemoglobinopathy than previously appreciated. On prospective screening of adults with SCD, approximately one-third of adults are found on echocardiography to have a tricuspid regurgitant jet velocity (TRV) of 2.5 m/s or higher, many of whom are asymptomatic. Dyspnea on exertion is the most common presenting symptom. This TRV abnormality is a marker for approximately 40% 3-year mortality in adults, and it is associated with laboratory values suggestive of more severe intravascular hemolysis. Release of hemoglobin and arginase from lysed red cells causes scavenging of nitric oxide (NO) and catabolism of L-arginine, the obligate substrate for NO synthase. The resulting impairment in NO bioavailability is associated with pulmonary vasoconstriction, endothelial dysfunction, thrombosis, and eventual development of plexogenic arterial lesions, the histological hallmark of all forms of PAH. Undoubtedly, additional pathophysiological mechanisms will also play a role in its multifactorial pathogenesis. Early data from children with SCD indicate a similar prevalence of elevated TRV, but the prognostic implications of this remain to be established. Individual patient diagnosis of PAH requires confirmation by right heart catheterization studies and individualized management. Hemolysis-associated PAH with impairments in NO bioavailability is being identified in thalassemia and other hemolytic disorders, and may be a general consequence of long-standing, severe intravascular hemolytic anemia.

Sickle cell leg ulcers: associations with haemolysis and SNPs in Klotho, TEK and genes of the TGF-beta/BMP pathway

Cutaneous leg ulcers are common in sickle cell anaemia and their risk might be genetically determined. Sickle cell anaemia patients were studied to examine the relationship of leg ulcers with haemolysis and with single nucleotide polymorphisms (SNPs) in candidate genes that could affect sickle vasoocclusion. Leg ulcer patients had lower haemoglobin levels and higher levels of lactate dehydrogenase, bilirubin, aspartate transaminase and reticulocytes than did control patients with sickle cell anaemia but without leg ulcers. Age-adjusted comparisons showed that sickle cell anaemia-alpha thalassaemia was more frequent among controls than cases. These results strongly suggested that the likelihood of having leg ulcers was related to the intensity of haemolysis. 215 SNPs in more than 100 candidate genes were studied. Associations were found with SNPs in Klotho, TEK and several genes in the TGF-beta/BMP signalling pathway by genotypic association analyses. KL directly or indirectly promotes endothelial nitric oxide (NO) production and the TEK receptor tyrosine kinase is involved in angiogenesis. The TGF-beta/BMP signalling pathway modulates wound healing and angiogenesis, among its other functions. Haemolysis-driven phenotypes, such as leg ulcers, could be improved by agents that reduce sickle erythrocyte density or increase NO bioavailability.