Elastic Properties of the Ascending Aorta in Patients with ?-Thalassemia Major

Iron overload, oxidative stress and vascular dysfunction: Evidences from clinical studies and animal models

Although iron is a metal involved in many in vital processes due to its redox capacity, body iron overloads lead to tissue damage, including the cardiovascular system. While cardiomyopathy was the focus since the 1960s, the impact on the vasculature was comparatively neglected for about 40 years, when clinical studies correlating iron overload, oxidative stress, endothelial dysfunction, arterial stiffness and atherosclerosis reinforced an "iron hypothesis". Due to controversial results from some epidemiological studies investigating atherosclerotic events and iron levels, well-controlled trials and animal studies provided essential data about the influence of iron, per se, on the vasculature. As a result, the pathophysiology of vascular dysfunction in iron overload have been revisited. This review summarizes the knowledge obtained from epidemiological studies, animal models and "in vitro" cellular systems in recent decades, highlighting a more harmful than innocent role of iron excess for the vascular homeostasis, which supports our proposal to hereafter denominate "iron overload vasculopathy". Additionally, evidence-based therapeutic targets are pointed out to be tested in pre-clinical research that may be useful in cardiovascular protection for patients with iron overload syndromes.

Assessment of Aortic Elasticity and the Doppler Tissue Echocardiography in Thalassemia Major Children

Cardiovascular diseases are the most common illness that needs special medical care in thalassemia particularly in children and adolescents. We aimed to compare aortic stiffness in thalassemia major and healthy children. The study included 65 asymptomatic thalassemia major 6 to 19-year–old children without known history of heart disease and 65 age- and sex-matched healthy controls. Arterial stiffness indices determined using two-dimensional (2D) and Doppler echocardiography. Data were analyzed by SPSS 20.0 with 0.05 as significant error. From the study, results showed that systolic (p = 0.009) and diastolic (p < 0.001) blood pressures were higher in controls. Left ventricular mass index (LVMI) was higher in patients (p < 0.001). Aortic stiffness index (p < 0.001), pulse pressure (p < 0.001), and pressure strain elastic modulus (p < 0.001) were higher in patients, while aortic strain (p < 0.002) and aortic distensibility (p < 0.001) were lower significantly. Aortic stiffness index was correlated with diastole aorta (p = 0.005), systole aorta (p < 0.001), and LVMI (p < 0.001). Strain was correlated with diastole aorta (p < 0.001). Pulse pressure was correlated with systolic blood pressure (p < 0.001), diastolic blood pressure (p = 0.002) significantly. Aortic distensibility was correlated with systolic blood pressure (p = 0.039) and diastole aorta (p < 0.001) significantly. The pressure strain elastic modulus was correlated only with diastole aorta (p = 0.029). Concluded, aortic stiffness index, pulse pressure, and pressure strain elastic modulus were higher in thalassemia children, while aortic strain and aortic distensibility were lower. This increase may result in reduction of mechanical efficiency of the heart. Therefore, assessment of aortic elastic properties as nontraditional cardiovascular risk factors may contribute to the identification of cardiovascular risks in children with thalassemia

Blockade of angiotensin AT1 receptors prevents arterial remodelling and stiffening in iron-overloaded rats

BACKGROUND AND PURPOSE

Damage to the vasculature caused by chronic iron-overload in both humans and animal models, is characterized by endothelial dysfunction and reduced compliance. In vitro, blockade of the angiotensin II AT₁ receptors reversed functional vascular changes induced by chronic iron-overload. In this study, the effect of chronic AT₁ receptor blockade on aorta stiffening was assessed in iron-overloaded rats.

EXPERIMENTAL APPROACH

Male Wistar rats were treated for 15 days with saline as control group, iron dextran 200 mg·kg^-1 ·day^-1 , 5 days a week (iron-overload group), losartan (20 mg·kg^-1 ·day^-1 in drinking water), and iron dextran plus losartan. Mechanical properties of the aorta were assessed in vivo. In vitro, aortic geometry and biochemical composition were assessed with morphometric and histological methods.

KEY RESULTS

Thoracoabdominal aortic pulse wave velocity (PWV) increased significantly, indicating a decrease in aortic compliance. Co-treatment with losartan prevented changes on PWV, β-index, and elastic modulus in iron-overloaded rats. This iron-related increase in PWV was not related to changes in aortic geometry and wall stress. but to increased elastic modulus/wall stress ratio, suggesting that a change in the composition of the wall was responsible for the stiffness. Losartan treatment also ameliorated the increase in aorta collagen content of the iron-overload group, without affecting circulating iron or vascular deposits.

CONCLUSIONS AND IMPLICATIONS

Losartan prevented the structural and functional indices of aortic stiffness in iron-overloaded rats, implying that inhibition of the renin-angiotensin system would limit the vascular remodelling in chronic iron-overload.

Prognostic evaluation of the elastic properties of the ascending aorta in dilated cardiomyopathy

BACKGROUND

Nowadays there is an increased interest in the role of aortic stiffness in the pathophysiology of heart failure (HF), as it is a major determinant of left ventricular (LV) performance. We aimed at assessing the predictive value of the aortic stiffness parameters, measured by echocardiography, in patients affected by nonischaemic dilated cardiomyopathy (DCM) regarding three end-points: death, HF rehospitalization, combined death or HF rehospitalization in a long-term follow-up.

MATERIALS AND METHODS

A total of 202 patients affected by nonischaemic DCM underwent an outpatient examination by echocardiography and blood pressure check at the brachial artery, in order to calculate aortic elastic properties (ie, compliance, distensibility, stiffness index, Peterson's elastic modulus, M-mode strain). ROC curves, Kaplan-Meier curves and multivariable Cox regressions (correcting for age, LV ejection fraction (LVEF), atrial fibrillation, cardiac resynchronization therapy (CRT)) were run to assess the predictive ability of aortic elastic properties against the 3 end-points.

RESULTS

Mean follow-up was 9.83 ± 2.80 years. 24.8% of patients died, while 34.7% were rehospitalized for HF cause and 44.6% experienced the combined end-point. LVEF did not correlate with aortic elastic properties. ROC curves and Kaplan-Meier curves were elaborated. Aortic stiffness did not predict death in our cohort. Otherwise, all aortic elastic properties predicted HF rehospitalization and combined death or HF rehospitalization, after correcting for age, LVEF, atrial fibrillation, CRT.

CONCLUSIONS

Elastic properties of the ascending aorta measured by echocardiography in patients with nonischaemic DCM predict long-term HF rehospitalization and combined death or HF rehospitalization, also after correcting for the confounding factors.

The reverse remodeling of the aorta in patients after renal transplantation - the value of aortic stiffness index: prospective echocardiographic study

BACKGROUND

Atherosclerosis is regarded as a combination of two major separate diseases: atherosis and sclerosis. Sclerotic component depends on deterioration of elastic properties of the aortic wall and is called aortic stiffness. The most valuable, non-invasive method of aortic stiffness assessment is echocardiography, which allows to calculate the aortic stiffness index (ASI). ASI is an independent predictor of all-cause and cardiovascular mortality in different groups of patients. The main aim of study was the assessment of the aortic reverse remodeling in patients with end-stage renal disease (ESRD) after renal transplantation (RT).

METHODS

Study group involved 42 patients aged 43.3 ± 12.6 years, including 19 women aged 49.9 ± 10.9 years and 23 men aged 41.5 ± 12.91 years, who have undergone RT from non-related renal transplant donors, The study protocol has been consisted of 5 stages: 1 week after RT, 3 months after RT, 6 months after RT, 1 year after RT and 3 years after RT. The echocardiographic examination was performed and measurements of Ao_max, Ao_min were done. On the base of obtained parameters ASI, aortic distensibility (AD) and aortic strain (AS) were calculated according to adequate formulas.

RESULTS

The improvement of indices characterizing the elastic properties of aorta were noted. These changes attained the statistically significant level only at the end of the observation. ASI just after RT was equal - 4.65 ± 1.58, three months after RT - 4.54 ± 1.49, six months after RT - 4.59 ± 1.61, one year after RT - 4.35 ± 1.21 and three years after RT - 3.35 ± 1.29, while AD reached respectively - 6.55 ± 3.76 cm²/dyn^-110^-6 just after RT, - 6.38 ± 3.42 cm²/dyn^-110^-6 three months after RT, - 6.53 ± 3.60 cm²/dyn^-110^-6 six months after RT, - 6.48 ± 2.79 cm²/dyn^-110^-6 one year after RT and - 8.03 ± 3.95 cm²/dyn^-110^-6 three years after RT. Noted AS values were equal - 6.61 ± 4.05%, just after RT, - 6.40 ± 3.58% three months after RT, - 6.56 ± 3.76%, six months after RT, - 6.45 ± 2.80% one year after RT, - 8.01 ± 3.97%. and three years after RT. The exact analysis of parameters concerning aortic function showed that to achieve ASI, AD and AS improvement, long time was needed, because the most significant changes of these indices were observed only between 1 year and 3 years after RT.

CONCLUSIONS

There is a relationship between renal transplantation and improvement of the aortic elastic properties. The recovery of the renal function allows to initiate the reparative processes leading to at least partial restitution of the structure and features of the aorta, which is called reverse remodelling. Improvement of aortic wall elastic properties after renal transplantation is a continuous and prolonged process.

Assessment of Myocardial Performance Index and Aortic Elasticity in Patients With Beta-Thalassemia Major

BACKGROUND

This study aimed to assess myocardial performance index (MPI) and arterial elasticity indices in asymptomatic patients with beta-thalassemia major without known heart disease and to determine relationship between these indices and parameters indicating iron load of body.

METHODS

The study included 55 asymptomatic beta-thalassemia patients (median age: 20 years (10 - 48 years)) without known history of heart disease and 40 age- and sex-matched healthy controls. MPI and arterial elasticity indices were determined by using standard two-dimensional and Doppler echocardiography. Data were analyzed by SPSS for Windows version 20.0 (SPSS Inc., Chicago, IL, USA).

RESULTS

Left ventricular mass index (83.917 (50.62 - 144) and 68.37 (41.9 - 113.3)) and MPI (0.464 (0.33 - 0.68) and 0.431 (0.31 - 0.51)) were significantly higher in patients with beta-thalassemia when compared to control group (P < 0.001 and P = 0.006). Aortic elasticity indices were significantly higher while aortic strain and distensibility values were significantly lower in patients with beta-thalassemia compared to controls (all P values < 0.001). Positive correlations were detected between aortic stiffness index and platelet (r = 0.235; P = 0.019) and ferritin values (r = 0.328; P = 0.008). Presence of thalassemia (β = -0.729; P = 0.041) and higher platelet value (β = 0.235; P = 0.019) were significant determinants for increased aortic stiffness in linear regression analysis.

CONCLUSION

Arterial elasticity indices and MPI are impaired in patients with beta-thalassemia major and these parameters may be used to predict cardiovascular complications in asymptomatic patients with beta-thalassemia major.

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.

Vascular endothelial dysfunction in β-thalassemia occurs despite increased eNOS expression and preserved vascular smooth muscle cell reactivity to NO

Aims

The hereditary β-thalassemia major condition requires regular lifelong blood transfusions. Transfusion-related iron overloading has been associated with the onset of cardiovascular complications, including cardiac dysfunction and vascular anomalies. By using an untransfused murine model of β-thalassemia major, we tested the hypothesis that vascular endothelial dysfunction, alterations of arterial structure and of its mechanical properties would occur despite the absence of treatments.

Methods and Results

Vascular function and structure were evaluated ex vivo. Compared to the controls, endothelium-dependent vasodilation with acetylcholine was blunted in mesenteric resistance arteries of β-thalassemic mice while the endothelium-independent vasodilator (sodium nitroprusside) produced comparable vessel dilation, indicating endothelial cell impairment with preserved smooth muscle cell reactivity to nitric oxide (NO). While these findings suggest a decrease in NO bioavailability, Western blotting showed heightened expression of aortic endothelial NO synthase (eNOS) in β-thalassemia. Vascular remodeling of the common carotid arteries revealed increased medial elastin content. Under isobaric conditions, the carotid arteries of β-thalassemic mice exhibited decreased wall stress and softening due to structural changes of the vessel wall.

Conclusions

A complex vasculopathy was identified in untransfused β-thalassemic mice characterized by altered carotid artery structure and endothelial dysfunction of resistance arterioles, likely attributable to reduced NO bioavailability despite enhanced vascular eNOS expression.

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.

Aortic stiffness: current understanding and future directions

The aorta stiffens with aging, a process that is accelerated by arterial hypertension. Decreased arterial compliance is one of the earliest detectable manifestations of adverse structural and functional changes within the vessel wall. The use of different imaging techniques optimized for assessment of vascular elasticity and quantification of luminal and vessel wall parameters allows for a comprehensive and detailed view of the vascular system. In addition, several studies have also documented the prognostic importance of arterial stiffness (AS) in various populations as an independent predictor of cardiovascular morbidity and all-cause mortality. Measurement of AS by applanation tonometry with pulse-wave velocity has been the gold-standard method and is well-validated in large populations as a strong predictor of adverse cardiovascular outcomes. Because aortic stiffness depends on the prevailing blood pressure, effective antihypertensive treatment is expected to reduce it in proportion to the blood pressure reduction. Nevertheless, drugs lowering blood pressure might differ in their effects on structure and function of the arterial walls. This review paper not only will discuss the current understanding and clinical significance of AS but also will review the effects of various pharmacological and nonpharmacological interventions that can be used to preserve the favorable profile of a more compliant and less stiff aorta.

Impaired aortic stiffness and pulse wave velocity in patients with branch retinal vein occlusion

BACKGROUND

Aortic distensibility (AD) and pulse wave velocity (PWV) reflect arterial stiffness, which is linked to increased cardiovascular morbidity and mortality in different diseases such as atherosclerosis, hypertension, and diabetes mellitus, all of which are also common risk factors in patients with branch retinal vein occlusion (BRVO). In the present study, we aimed to determine whether arterial stiffness in different segments of the arterial tree is increased in patients with BRVO.

METHODS

The study group consisted of 35 patients with BRVO (20 female, 15 male, mean age: 55.9+/-6.8) and the age-matched control groups consisted of 19 patients with hypertension (9 female, 10 male, mean age: 55.2+/7.6) and 17 healthy subjects (9 female, 8 male, mean age: 53.4+/-9.6). Radial artery PWV was measured using a Pulse Wave Sensor HDI system, which measures non-invasively the radial pulse-wave recording with computer analysis of the diastolic decay, and provides separate assessment of the large arterial elasticity index (LAEI) and small artery elasticity index (SAEI). Aortic strain and AD was determined echocardiographically based on the relationship between changes in aortic diameter and pressure with each cardiac pulse. Patients with diabetes mellitus or inflammatory BRVO, and control patients with any occlusive vascular eye disease, were excluded. The results of the three groups were compared.

RESULTS

Compared to the subjects of the healthy control group, those with BRVO had lower LAEI (p<0.05). Both AD and aortic strain were significantly lower in the BRVO group than in both control groups (p<0.05 for both) and in the hypertensive control group than the healthy controls (p<0.05). The AD, LAEI and SAEI were positively correlated (p=0.021, r=0.307 and p=0.041, r=0.269 respectively).

CONCLUSIONS

The results of this study show that the arterial stiffness indices (large arterial elasticity index and aortic distensibility) are abnormal in patients with BRVO compared to the healthy and hypertensive controls. Arterial stiffness may play a role in the onset or progression of BRVO. Further studies are needed to determine the exact role of AS in the pathogenesis of BRVO, and to reveal its value in predicting systemic morbidity and mortality in patients with BRVO.

A comparison of echocardiographic techniques in determination of arterial elasticity in the pediatric population

BACKGROUND

Many methods are used to measure arterial elasticity in children using echocardiography. There is no data to support the equivalence of the different techniques. The goal of this study was to evaluate the reproducibility of several techniques used to measure arterial elasticity using echocardiography.

METHODS

Aortic distension in two different sites (arterial distension) through the cardiac cycle was measured by (four) two-dimensional (2D) and M-mode echocardiographic techniques in 20 children without significant structural heart disease. These measurements combined with noninvasive blood pressure measurements were used to calculate arterial elastic indices. Arterial elasticity was expressed in terms of distensibility and stiffness. Data were collected by two sonographers and interpreted by two reviewers. Paired Student's t-test and Pitman's test for equality of variance for correlated observations were used to detect differences between different sonographers, different reviewers, and different techniques.

RESULTS

No significant difference in the measured elasticity between sonographers or reviewers was observed. There was a somewhat increased variance in two of the four techniques evaluated. There was no significant difference in elasticity measured using different techniques to evaluate the same arterial site, although a significantly decreased elasticity was noted from measurements taken in the proximal ascending aorta as compared with the distal ascending aorta.

CONCLUSIONS

Many echocardiographic techniques produce reproducible measurements of arterial elasticity. There may be intrinsic differences in arterial elasticity between different segments of the ascending aorta, which have not been previously described in children with normal cardiac anatomy. Comparisons of data from separate studies must take these differences into account.