Serum iron: a new predictor of adverse outcomes independently from serum hemoglobin levels in patients with acute decompensated heart failure.

Iron is an essential trace element in the body. However, in heart failure (HF), iron is only recognized as the cause of anemia. Actually, iron itself affects myocardial exercise tolerance and cardiac function via mitochondrial function. Therefore, it is necessary to clarify the pathological significance of iron in acute HF, irrespective of concomitant anemia. We investigated the impact of serum iron level at discharge on the prognosis of 615 patients emergently admitted with acute decompensated HF (ADHF). Patients were divided into two groups according to the median level of serum iron (62 µg/dL). The endpoint was the composite outcome, which included all-cause mortality and readmission for HF. During the mean follow-up period of 32.1 months, there were 333 events. Kaplan-Meier analysis showed that the incidence of the composite outcome was significantly higher in the Low iron group (P < 0.0001). In the multivariate analysis adjusted with factors including hemoglobin and ferritin levels, low serum iron was an independent predictor for the composite outcome (hazard ratio, 1.500; 95% confidence interval, 1.128-1.976; P = 0.0044). Low serum iron was an independent predictor of poor prognosis in ADHF, irrespective of hemoglobin or ferritin level, providing a new concept that iron may play a role in the pathophysiology of ADHF via non-hematopoietic roles.