The effects of serum iron level without anemia on long-term prognosis of patients with coronary heart disease complicated with chronic heart failure: a retrospective cohort study

The effects of serum iron level without anemia on long-term prognosis of patients with coronary heart disease (CHD) complicated with chronic heart failure (CHF) is still unclear. The objective of this study was to explore the effects of serum iron level without anemia on long-term prognosis of patients with CHD complicated with CHF. In this retrospective cohort study, 221 patients with CHD complicated with CHF were consecutively investigated. These patients were divided into three groups according to the tertiles of the serum iron level: low-iron group (n = 71), medium-iron group (n = 76) and high-iron group (n = 74). The overall serum iron without anemia was 13.0 +/- 5.50 mu mol/L and serum iron in each group was 7.58 +/- 1.63 mu mol/L, 11.94 +/- 1.79 mu mol/L, and 19.37 +/- 3.81 mu mol/L, respectively. Composite endpoint events were composed of major adverse cardiovascular and cerebrovascular events (MACCE), including recurrent heart failure, all-cause death, acute coronary syndrome (ACS) and ischemic stroke. The median follow-up duration was 239 days. After adjusting relevant confounding risk factors, we found that excessively low or high serum iron level is correlated to the MACCE in patients with CHD complicated with CHF and that the prognosis of patients with excessively high serum iron level is poorer than that of patients with excessively low serum iron level. We further revealed the effect of serum iron level on MACCE is U-shaped, but not linear relationship. Sensitivity analysis showed that the correlation between serum iron level and MACCE is stable. In addition, according to the test for interaction, the variables that modify the effect including CRP (P for interaction < 0.0001), diuretics (P for interaction = 0.0212) and antiplatelet drugs (P for interaction = 0.0167). This study showed that excessively low or high serum iron level without anemia is an independent risk factor of MACCE in patients with CHD complicating with CHF.