Objective: β-Thalassemia major (TM) is an inherited hemoglobin disorder resulting in chronic hemolytic anemia, and regular lifelong transfusion therapy remains the mainstay in the treatment of patients. Cardiac involvement is the leading cause of death in patients with β-TM. The association between vitamin D deficiency and left ventricular systolic and diastolic dysfunction has been previously demonstrated in the literature. Speckle-tracking echocardiography (STE) is feasible and valid for the evaluation of cardiac function via an assessment of the longitudinal deformation of the myocardium through the cardiac cycle. Our study aims to evaluate the effect of vitamin D deficiency on myocardial deformation and functions in children with thalassemia major by STE.
Methodology: In this prospective study, 33 patients with β-TM, receiving regular blood transfusions, and undergoing iron chelation therapy were enrolled in April 2018-January 2020. Vitamin D and ferritin levels, cardiac magnetic resonance (MR) T2* value, conventional echocardiography, and speckle tracking were evaluated. LV regional circumferential, and longitudinal strain values were measured. Vitamin D levels considered <20ng/ml, 20–30ng/ml, >30ng/ml as deficient, insufficient, and sufficient, respectively. Myocardial functions of patients with vitamin D deficiency or insufficiency were evaluated by STE before and after vitamin D replacement.
Results: The mean age of patients was 15.4±3.09 years; the male/female ratio was 18/15, and mean ferritin levels were 2017±1573ng/ml. Vitamin D level deficiency was detected in 30 (90%) and insufficient in 3 (10%) of our patients. Cardiac T2* value was normal in 21 patients and 12 patients had iron accumulation on cardiac T2* MR. The mean of left ventricular ejection fraction (LVEF) was 64±4.7%, and the mean left ventricular shortening fraction (LVSF) was 34.2±3.8% before vitamin D replacement, and LVEF was 65.1±5.2% and LVSF 35±3.7% after vitamin D replacement (p>0.05). The mean left ventricle global longitudinal strain (LVGLS) was 19±2.7% before replacement and 24±2.7% after replacement (p: 0.04). The left ventricle global circumferential strain (LVGCS) was 20±2.8% before replacement and 25±3.8% after replacement (p: 0.03). While there was no significant difference in right ventricular functions before and after vitamin D replacement, but a statistically significant increase was observed in parameters showing left ventricular diastolic functions after replacement. There was a significant improvement in the global longitudinal strain of left ventricular after vitamin D replacement.
Conclusion: Vitamin D deficiency is frequently observed in patients with β-TM. It is reported that vitamin D deficiency causes decreased contractility and leads to an increase in cardiac iron involvement accordingly cardiomyopathy in these patients. Speckle tracking echocardiography could be used as a feasible method for evaluating subclinical myocardial dysfunction in patients with β-TM. In patients with β-TM, diastolic functions are primarily affected in the case of cardiac toxicity. In our study, we observed that our patients’ diastolic functions had improved after vitamin D replacement therapy.
