Baseline serum ferritin predicts myocardial iron uptake following intravenous iron therapy - a hypothesis-generating study.

AIMS: Many patients with heart failure (HF) are iron-deficient. Intravenous (IV) iron therapy improves symptoms and reduces hospitalizations for HF. Several mechanisms have been proposed, including myocardial iron repletion. However, it is unknown if serum iron markers predict the extent of this repletion. To address this question, data from two clinical studies that evaluated changes in myocardial iron using cardiac magnetic resonance (CMR) were harnessed. METHODS AND RESULTS: The Myocardial-IRON trial measured change in myocardial iron, denoted by a decrease in CMR T1 and T2*, at 7 and 30 days after IV ferric carboxymaltose (FCM) in patients with iron deficiency (ID) and HF (n = 53). The STUDY trial measured myocardial and spleen iron at multiple timepoints after FCM in patients with ID without HF (n = 12). In this post-hoc analysis, we examined the association between baseline serum iron markers (transferrin saturation and ferritin) and change in myocardial iron in the weeks after FCM therapy. Changes in spleen iron were also examined, due its role as an intermediary in the redistribution of iron from iron-carbohydrate complexes such as FCM. In patients with or without HF, higher serum ferritin at baseline predicted lower rise in myocardial iron in the weeks after therapy with FCM. In contrast, higher serum ferritin at baseline predicted a greater rise in spleen iron. CONCLUSIONS: These data point towards the hypothesis that functional ID, which is characterized by elevated ferritin, could limit myocardial iron repletion after IV iron therapy, by favouring iron trapping in the spleen.