Vitamin D deficiency, cardiac iron and cardiac function in thalassaemia major

Abstract

Vitamin D25-OH and D1-25OH levels were compared with cardiac R2* (1/T2*), left ventricular ejection fraction (LVEF), age, ferritin and liver iron in 24 thalassaemia major patients. Vitamin D25-OH levels were reduced in 13/24 patients while vitamin D1-25OH levels were often elevated. Vitamin D25-OH levels decreased with age (r(2) = 0.48) and with liver iron (r(2) = 0.20). Cardiac R2* was inversely related with the ratio of D25-OH to D1-25OH levels (r(2) = 0.42). LVEF was also proportional to the D25-OH/D1-25OH ratio (r(2) = 0.49). Vitamin D deficiency may be associated with cardiac iron uptake and ventricular dysfunction in thalassaemia major patients.

Fig 1

(A) Plot of cardiac R2^★ as a function of vitamin D25-OH levels. Cardiac R2^★ is proportional to cardiac iron. Vertical scale is logarithmic; cardiac R2^★ >50 Hz (shown by the horizontal grey line) indicates the threshold for detectable cardiac iron, corresponding to a T2^★ of less than 20 ms. Log-linear correlation has a negative slope with a r² of 0·44. Vitamin D25-OH levels of 50 nmol/l (vertical line) represents the lower limit of normal and 75 nmol/l indicates vitamin D ‘sufficiency’ (Dawson-Hughes et al, 2005). (B) Corresponding plot demonstrating the ratio of D25-OH to D1-25OH levels. A ratio less than 0·25 is associated with a sharp increase in detectable cardiac iron.

Fig 2

(A) Plot of left ventricular ejection fraction (LVEF) measured by MRI as a function of vitamin D25-OH levels. LVEF of 56% (shown by the horizontal grey line) indicates the threshold abnormal ejection fraction for non-iron overloaded thalassaemia major patients at our institution. Linear correlation has a positive slope with r² of 0·35. (B) Corresponding plot demonstrating the ratio of D25-OH to D1-25OH levels. All patients with LV dysfunction had a ratio less than 0·2.