Extramedullary hematopoiesis is associated with lower cardiac iron loading in chronically transfused thalassemia patients

The aim of this study was to evaluate, in a large cohort of chronically transfused patients, whether the presence of extramedullary hematopoiesis (EMH) accounts for the typical patterns of cardiac iron distribution and/or cardiac function parameters. We retrospectively selected 1,266 thalassemia major patients who had undergone regular transfusions (611 men and 655 women; mean age: 31.368.9 years, range: 4.2–66.6 years) and were consecutively enrolled within the Myocardial Iron Overload in Thalassemia network. The presence of EMH was evaluated based on steady-state free precession sequences; cardiac and liver iron overloads were quantified using a multiecho T2* approach; cardiac function parameters and pulmonary diameter were quantified using the steady-state free precession sequences; and myocardial fibrosis was evaluated using the late gadolinium enhancement technique. EMH was detected in 167 (13.2%) patients. The EMH1 patients had significantly lower cardiac iron overload than that of the EMH2 patients (P50.003). The patterns of cardiac iron distribution were significantly different in the EMH1 and EMH2 patients (P< 0.0001), with a higher prevalence of patients with no myocardial iron overload and heterogeneous myocardial iron overload and no significant global heart iron in the EMH1 group EMH1 patients had a significantly higher left ventricle mass index (P50.001) and a significantly higher pulmonary artery diameter (P50.002). In conclusion, in regularly transfused thalassemia patients, EMH was common and was associated with a thalassemia intermedia-like pattern of cardiac iron deposition despite regular transfusion therapy.