Early Vascular Aging and Subclinical Myocardial Deformation in Children with β-Thalassemia Major: The Role of Asymmetric Dimethylarginine

Background: Children with β-thalassemia major (β-TM) survive longer due to advances in transfusion and chelation therapy; however, cardiovascular complications have emerged as a leading cause of long-term morbidity. Chronic hemolysis, oxidative stress, and iron overload may promote early endothelial dysfunction and premature vascular aging, yet their impact on myocardial deformation in pediatric patients remains incompletely characterized. Objectives: To evaluate subclinical myocardial dysfunction and arterial stiffness in children with β-TM and to investigate hemolysis-related changes in asymmetric dimethylarginine (ADMA) and L-arginine as biomarkers of endothelial dysfunction in relation to cardiovascular involvement. Methods: Twenty-four children with β-TM and 20 age-matched healthy controls were included. Cardiac structure and myocardial deformation were assessed by conventional echocardiography, tissue Doppler imaging, and speckle-tracking strain analysis. Arterial stiffness was evaluated using oscillometric pulse wave analysis and bilateral carotid intima–media thickness (CIMT). Serum ADMA and L-arginine levels were measured, and hemoglobin, reticulocyte count, and ferritin levels were recorded. Results: Children with β-thalassemia major demonstrated significantly increased arterial stiffness compared with controls, including higher PWV (4.61 ± 0.37 vs. 4.38 ± 0.31), AIx@75 (augmentation index at 75 bpm) (28.5 ± 8.34 vs. 22.8 ± 6.51), left CIMT [0.45 (0.39–0.51) vs. 0.41 (0.38–0.46)], and right CIMT [0.43 (0.39–0.54) vs. 0.40 (0.34–0.46)]. In addition, patients exhibited reduced global longitudinal strain (−19.3 ± 2.91 vs. −21.84 ± 1.91), prolonged isovolumetric relaxation time [53 (37–71) vs. 45 (37–55)], and elevated E/Em (8.44 ± 2.19 vs. 6.92 ± 1.10). ADMA levels were significantly higher in patients (0.54 ± 0.19 vs. 0.39 ± 0.22) and were positively associated with reticulocyte counts and inversely correlated with hemoglobin levels. In addition, both ADMA and ferritin levels were positively correlated with arterial stiffness indices and left ventricular filling pressures. Conclusions: Children with β-thalassemia major exhibit features suggestive of early cardiovascular aging, including impaired myocardial deformation, diastolic involvement, and increased arterial stiffness. The observed association between ADMA levels and markers of hemolysis, vascular stiffness, and myocardial deformation highlights the potential involvement of endothelial dysfunction in premature myocardial–vascular remodeling. These findings suggest that ADMA may serve as a promising biomarker for early cardiovascular risk in pediatric β-thalassemia major; however, further longitudinal and multi-center studies are needed to confirm its clinical utility for risk stratification.