Ventriculo-vascular interactions in patients with beta thalassaemia major

Evaluation of carotid artery dynamics & correlation with cardiac & hepatic iron in β-thalassaemia patients

Background & objectives:

Early atherosclerosis and vascular complication have been described in thalassaemia patients. There is lack of data or guidelines regarding monitoring of vascular health in thalassaemia. This study was conducted to compare carotid artery structural and functional indices such as carotid artery intima-media thickness (CIMT), stiffness index (SI) and Young's elastic modulus (YEM) in β-thalassemia patients with age and sex matched controls, and to correlate these parameters with serum ferritin, cardiac iron, and hepatic iron.

Methods:

This cross-sectional study included 53 β-thalassaemia patients receiving regular blood transfusions. Carotid artery indices such as CIMT, SI, and YEM were calculated by duplex ultrasound and colour Doppler. Serum ferritin levels were measured by chemiluminescence. Cardiac and hepatic iron estimation were done using MRI T2* sequences analyzed by a special thalassaemia software.

Results:

Mean CIMT of cases and controls were 0.48 ± 0.04 and 0.44±0.02 mm, respectively and these were significantly different (P<0.001). Similarly significant differences were noted in SI and YEM of cases (2.45±0.79 and 96.12±34.85, respectively) as compared to controls (1.98±0.54 and 68.60±24.29, respectively) (P<0.001). There was significant inverse correlation between stiffness index and cardiac iron overload assessed by MRI cardiac T2* (P=0.03). Mean SI and YEM of cases were (2.1736 ± 0.2986 and 107.3± 41.6, respectively) significantly higher among non-splenectomized patients compared to splenectomized patients (2.0136 ± 0.263 and 86.9 ± 25.2, respectively) (P<0.05).

Interpretation & conclusions:

CIMT and arterial stiffness indices were significantly increased in β-thalassaemia patients compared to controls which was indicative of early atherogenic changes. This study supports the hypothesis that iron overload is a risk factor for early atherosclerosis and cardiovascular disease.

Vascular Dysfunction in Patients With Young β-Thalassemia

We aimed to study the endothelial dysfunction among children and adolescents with transfusion-dependent β-thalassemia using von Willebrand factor antigen (VWF:Ag) and flow cytometric analysis of circulating CD144+ endothelial microparticles (EMPs) and endothelial progenitor cells (CD34+VEGFR2+) and assess their relation to iron overload, erythropoietin and chelation therapy as well as echocardiographic parameters and carotid intima–media thickness. The VWF:Ag, EMPs, and CD34+VEGFR2+ cells were significantly higher among patients with β-thalassemia than controls ( P < .001). The type of chelation and patients’ compliance did not influence the results. No significant correlations were found between the studied vascular markers. Patients with evident heart disease had higher VWF: Ag, EMPs, and CD34+VEGFR2+ cells than those without. Carotid intima–media thickness was increased among patients but not correlated with vascular markers. We suggest that procoagulant EMPs and VWF: Ag are involved in cardiovascular complications in patients with young β-thalassemia. CD34+VEGFR2+ cells were further increased in response to tissue injury contributing to reendothelialization and neovascularization.

Early identification of cardiovascular involvement in patients with β-thalassemia major

The aim of the present study was to evaluate left ventricular myocardial deformation and carotid arterial stiffness using 2-dimensional strain and echo-tracking in patients with asymptomatic β-thalassemia major (β-TM) without significant myocardial iron overload to determine whether early subclinical cardiovascular abnormalities would be detectable. We enrolled 32 patients with β-TM (23 women, mean age 35 ± 8 years) and 33 healthy volunteers (20 women, mean age 35 ± 6 years). All subjects underwent echocardiography with 2-dimensional strain analysis (XStrain) and ultrasonography of the carotid arteries with measurement of the stiffness parameters (ProSound Alpha 10). Cardiac magnetic resonance imaging using a T2* algorithm (37.7 ± 5.6 ms) for the assessment of myocardial iron overload was performed in each patient. The clinical and standard echocardiographic parameters were comparable between the patients and healthy subjects. The global left ventricular longitudinal strain was significantly impaired in the patients compared with the controls (-17.9 ± 3.5% vs -24.3 ± 3.4%, p = 0.002), although the radial and circumferential strain values were similar between the 2 groups (p = NS for both). The carotid intima-media thickness was comparable between the patients and healthy subjects (0.67 ± 0.20 mm vs 0.66 ± 0.15 mm, p = NS). In contrast, the arterial stiffness was significantly increased in the patients compared with the controls (stiffness index 6.16 ± 1.31 vs 4.65 ± 0.82, p <0.001; arterial compliance 1.10 ± 0.26 vs 1.28 ± 0.30 cm(2)/mm Hg, p = 0.027; elastic modulus 74.1 ± 19.5 vs 59.1 ± 12.1 mm Hg, p = 0.001). In conclusion, cardiovascular abnormalities, although often subclinical, occur at an early stage of β-TM and also in the absence of significant iron overload. Thus, 2-dimensional strain and echo-tracking might be more accurate than standard echocardiography and vascular parameters in the early identification of cardiovascular involvement.

Cardiovascular function and treatment in β-thalassemia major: a consensus statement from the American Heart Association

This aim of this statement is to report an expert consensus on the diagnosis and treatment of cardiac dysfunction in β-thalassemia major (TM). This consensus statement does not cover other hemoglobinopathies, including thalassemia intermedia and sickle cell anemia, in which a different spectrum of cardiovascular complications is typical. There are considerable uncertainties in this field, with a few randomized controlled trials relating to treatment of chronic myocardial siderosis but none relating to treatment of acute heart failure. The principles of diagnosis and treatment of cardiac iron loading in TM are directly relevant to other iron-overload conditions, including in particular Diamond-Blackfan anemia, sideroblastic anemia, and hereditary hemochromatosis. Heart failure is the most common cause of death in TM and primarily results from cardiac iron accumulation. The diagnosis of ventricular dysfunction in TM patients differs from that in nonanemic patients because of the cardiovascular adaptation to chronic anemia in non-cardiac-loaded TM patients, which includes resting tachycardia, low blood pressure, enlarged end-diastolic volume, high ejection fraction, and high cardiac output. Chronic anemia also leads to background symptomatology such as dyspnea, which can mask the clinical diagnosis of cardiac dysfunction. Central to early identification of cardiac iron overload in TM is the estimation of cardiac iron by cardiac T2* magnetic resonance. Cardiac T2* <10 ms is the most important predictor of development of heart failure. Serum ferritin and liver iron concentration are not adequate surrogates for cardiac iron measurement. Assessment of cardiac function by noninvasive techniques can also be valuable clinically, but serial measurements to establish trends are usually required because interpretation of single absolute values is complicated by the abnormal cardiovascular hemodynamics in TM and measurement imprecision. Acute decompensated heart failure is a medical emergency and requires urgent consultation with a center with expertise in its management. The first principle of management of acute heart failure is control of cardiac toxicity related to free iron by urgent commencement of a continuous, uninterrupted infusion of high-dose intravenous deferoxamine, augmented by oral deferiprone. Considerable care is required to not exacerbate cardiovascular problems from overuse of diuretics or inotropes because of the unusual loading conditions in TM. The current knowledge on the efficacy of removal of cardiac iron by the 3 commercially available iron chelators is summarized for cardiac iron overload without overt cardiac dysfunction. Evidence from well-conducted randomized controlled trials shows superior efficacy of deferiprone versus deferoxamine, the superiority of combined deferiprone with deferoxamine versus deferoxamine alone, and the equivalence of deferasirox versus deferoxamine.

Circulating CD133(+)VEGFR2 (+) and CD34 (+)VEGFR2 (+) cells and arterial function in patients with beta-thalassaemia major

Arterial dysfunction has been documented in patients with beta-thalassaemia major. This study aimed to determine the quantity and proliferative capacity of circulating CD133(+)VEGFR2(+) and CD34(+)VEGFR2(+) cells in patients with beta-thalassaemia major and those after haematopoietic stem cell transplantation (HSCT), and their relationships with arterial function. Brachial arterial flow-mediated dilation (FMD), carotid arterial stiffness, the quantity of these circulating cells and their number of colony-forming units (CFUs) were determined in 17 transfusion-dependent thalassaemia patients, 14 patients after HSCT and 11 controls. Compared with controls, both patient groups had significantly lower FMD and greater arterial stiffness. Despite having increased CD133(+)VEGFR2(+) and CD34(+)VEGFR2(+) cells, transfusion-dependent patients had significantly reduced CFUs compared with controls (p = 0.002). There was a trend of increasing CFUs across the three groups with decreasing iron load (p = 0.011). The CFUs correlated with brachial FMD (p = 0.029) and arterial stiffness (p = 0.02), but not with serum ferritin level. Multiple linear regression showed that CFU was a significant determinant of FMD (p = 0.043) and arterial stiffness (p = 0.02) after adjustment of age, sex, body mass index, blood pressure and serum ferritin level. In conclusion, arterial dysfunction found in patients with beta-thalassaemia major before and after HSCT may be related to impaired proliferation of CD133(+)VEGFR2(+) and CD34(+)VEGFR2(+) cells.

Myocardial deformation in patients with Beta-thalassemia major: a speckle tracking echocardiographic study

BACKGROUND

Increasing data suggest that parameters of myocardial deformation are strong indices of ventricular systolic and diastolic function. We sought to determine myocardial deformation of the left ventricle and assess relationship of deformation rates with myocardial iron load in patients with beta-thalassemia major.

METHODS

The left ventricular longitudinal, circumferential, and radial myocardial deformation was determined using speckle tracking echocardiography in 42 thalassemia patients aged 24.4 +/- 6.4 years. The results were compared with those of 38 age-matched controls. The rates of longitudinal and circumferential deformation were correlated with cardiac T2* magnetic resonance findings.

RESULTS

Compared with controls, patients had significantly greater global systolic radial strain (P = 0.001), but similar global systolic longitudinal (P = 0.12) and circumferential strain (P = 0.84). On the other hand, patients had significantly lower longitudinal systolic strain rate (SR) (P = 0.019), longitudinal early diastolic SR (P = 0.036), and circumferential early diastolic SR (P = 0.04) than controls. The cardiac T2* findings correlated positively with longitudinal (r = 0.44, P = 0.004) and circumferential early diastolic SR (r = 0.37, P = 0.019), but not with the respective systolic SRs and left ventricular ejection fraction (all P > 0.05). Patients with iron overload (T2*< 20 msec), compared to those without, had significantly lower longitudinal (1.45 +/- 0.33/sec vs. 1.76 +/- 0.27/sec, P = 0.002) and circumferential (1.01 +/- 0.31/sec vs. 1.22 +/- 0.31/sec, P = 0.03) early diastolic SR.

CONCLUSIONS

Patients with beta-thalassemia major have reduced longitudinal systolic SR, longitudinal early diastolic SR, and circumferential early diastolic SR. The rates of diastolic deformation in the longitudinal and circumferential dimensions are inversely related to myocardial iron overload.

Disease knowledge and treatment adherence among patients with thalassemia major and their mothers in Taiwan

AIMS

The current study had three aims: (i) to examine disease knowledge in both thalassemia major patients and their mothers; (ii) to understand the relationships between disease knowledge and treatment adherence in thalassemia major patients; and (iii) to explore the importance of selected factors in predicting patients' knowledge about thalassemia major.

BACKGROUND

Patients with thalassemia major must be treated with life-long blood transfusions. Evidence suggests that patients with more knowledge/information about their illnesses adhere more readily to treatment schedules. However, there has been little evaluation of knowledge and treatment adherence in thalassemia major patients.

DESIGN AND METHODS

A cross-sectional correlational survey design and purposive sampling were used. Thirty-two thalassemia major patients (mean age 17.5 years) and 32 mothers (mean age 40.5 years) were recruited.

RESULTS

On a scale ranging from 0-20, the average of the patients' disease knowledge about thalassemia major was 15.19 and the average of their mothers' disease knowledge was 16.44. The scores for the patients' disease knowledge about thalassemia major were positively correlated with follow-up visit adherence (r = 0.690, p < 0.001) and with desferrioxamine infusion adherence (r = 0.791, p < 0.001). 95.6% of variance in patients' knowledge was explained by a model that included mothers' knowledge (beta = 0.901, p < 0.001), follow-up visit adherence (beta = 0.084, p = 0.140) and annual household income (beta = 0.042, p < 0.387).

CONCLUSIONS

The positive association between knowledge and treatment adherence and factors of patients' knowledge indicate the need for systematic education for patients and caregivers to improve adherence to treatment.

RELEVANCE TO CLINICAL PRACTICE

Improvement of the quality of patient care, reinforcement of medical education and enhanced efforts by clinical staff to provide practical knowledge to patients with thalassemia major should significantly improve patient adherence to treatment.

Characterization of circulatory disorders in beta-thalassemic mice by noninvasive ultrasound biomicroscopy

Beta-thalassemia is an inherited hematological disease caused by a decrease or absence of production of beta-globin that requires chronic therapeutic interventions. This condition leads to important arterial and venous thromboembolic events, transitory ischemic attacks, and microcirculatory obstructions, indicative of circulatory disturbances. To investigate the presence of microcirculatory disorders without the confounding effect of treatments, we used beta-thalassemic mice with typical clinical characteristics of human beta-thalassemia major. One impediment to the understanding of microcirculatory physiology, in particular for beta-thalassemic mice, has been the lack of an appropriate noninvasive imaging approach. We thus developed a novel noninvasive high-frequency ultrasound imaging method to evaluate murine vascular hemodynamic properties. In our beta-thalassemic mice, total peripheral vascular resistance was significantly increased (P < 0.01) compared with wildtype littermates, whereas mean blood pressure, heart rate, and cardiac output were similar (P = nonsignificant). Importantly, the vascular hemodynamics in beta-thalassemic mice were significantly affected according to the Pourcelot indexes measured in the common carotid artery and abdominal aorta (P < 0.01 and P < 0.05, respectively). Hence, our beta-thalassemia characterization of vascular hemodynamics by noninvasive ultrasonic approaches proves the existence and provides unique quantitative assessment of microcirculatory flow disturbances in those mice.