Myocardial Iron Loading in Patients with Thalassemia Major on Deferoxamine Chelation

Abstract

Background: Heart failure secondary to myocardial iron loading remains the leading cause of death in thalassemia major (TM). We used cardiovascular magnetic resonance (CMR) to assess the prevalence of myocardial iron overload and ventricular dysfunction in a large cohort of TM patients maintained on conventional chelation treatment with deferoxamine. Methods: A mobile CMR scanner was transported from London, UK, to Sardinia, Italy where 167 TM patients were assessed for myocardial iron loading, B-natriuretic peptide (BNP), and ferritin. In patients with myocardial iron loading CMR assessments of ventricular function were also made. Results: Myocardial iron loading (T2 * < 20 ms) was present in 108 (65%) patients, which was severe (T2 * < 8 ms) in 22 (13%). Impaired (<56%) left ventricular (LV) ejection fraction (EF) was present in 5%, 20% and 62% of patients with mild, moderate or severe iron loading. Increasing myocardial iron was related to impaired LVEF (Rs = 0.57, p < 0.001), weakly related to serum ferritin (Rs = −0.34, p < 0.001), and not related to liver iron (Rs = 0.11, p = 0.26). BNP was weakly related to myocardial iron (Rs = −0.35, p < 0.001) and was abnormal in only 5 patients. Conclusions: Myocardial siderosis was found in two-thirds of thalassemia major patients on maintenance deferoxamine treatment. This was combined with a high prevalence of impaired LV function, the severity of which tracked the severity of iron deposition. BNP was not useful to assess myocardial siderosis.

The relationship between myocardial t2* and left ventricular volumetric and functional parameters in thalassemia major patients

“…Cross sectional analysis has demonstrated a poor correlation between the cardiac T2* value and the LIC in the literature (10,31,32). Despite the significant negative correlation between the heart T2* value and the liver R2 value, the correlation was weak, with a wide scatter of values, indicating that cardiac T2* measurement is essential for predicting cardiac complications and the associated risk of death.…”

Glutathione S‐transferase gene polymorphism and cardiac iron overload in thalassaemia major

“…The MRI T2* parameter has proven to be a fast, simple, robust parameter and, although it has not been calibrated with chemical measurements of endomyocardial iron in humans, growing indirect evidence suggests that it reflects cardiac iron. In chelated patients, myocardial iron is usually inversely related to the compliance with chelation, whereas no significant correlation with liver iron and serum ferritin concentration measured at the time of T2* assessment was found (Tanner et al, 2006). However, in a subset of patients, low T2* values occur despite a history of good compliance with chelation therapy, suggesting the possible role of genetic factors in cardiac iron deposition.…”

A decisional algorithm to start iron chelation in patients with beta thalassemia

“…1 However, in nonchronically-transfused thalassemia patients, ferritin hepatosecretion does not match liver iron accumulation and neither is serum ferritin representative of extrahepatic siderosis. [1][2][3][4] These inherent limitations in viewing serum ferritin as a reliable marker of iron overload have led us to consider other plasma factors that might be more pertinent to the etiopathology of iron overload and relevant for initiating treatment and assessing its long-term efficacy. 5 Here, we considered labile plasma iron (LPI), the major redox-active and readily chelatable fraction of non-transferrin-bound iron (NTBI), as a more direct marker of impending tissue iron overload and, therefore, as a potential indicator for the initiation of chelation therapy.…”