Iron deficiency is an independent risk factor of increased myocardial energy expenditure in chronic heart failure patients.

Background: Chronic heart failure (CHF) is a major public health burden and is associated with high morbidity, mortality, and cost. Recent studies demonstrated iron metabolism and myocardial energy metabolism were altered in CHF patients. In this study, we aimed to analyze the effects and correlations of iron metabolism on myocardial energy metabolism in CHF.

Methods: One hundred and thirty patients with CHF [age: 66.2±11.5 years, males: 58.5% and New York Heart Association (NYHA) class (II/III/IV): 67/43/20] were included. Serum concentrations of ferritin, transferrin saturation (Tsat), and soluble transferrin receptor (sTfR) were quantified as the indexes of iron metabolism, and echocardiography was used to assess myocardial energy expenditure (MEE) levels. Iron deficiency (ID) was defined as ferritin <100 or 100-300 µg/L with Tsat <20%.

Results: Patients with CHF were divided into two groups based on iron status. The prevalence of ID in CHF was 36.9%, and increased with the severity of CHF, reaching 80.0% in those with NYHA class IV (NYHA class II/III/IV: 17.9% vs. 46.5% vs. 80.0%, P=0.000). The demographic characteristics [age, sex, body mass index (BMI), blood pressure, and heart rate] and hemoglobin (HGB) concentrations in two groups were similar (all P>0.05). MEE was significantly higher in the ID group (92.7±23.0 vs. 65.6±20.8 cal/min, P=0.000), while NYHA classes II and III was significantly higher in the ID group (71.6±16.4 vs. 60.3±14.8 cal/min, P=0.022; 88.9±10.4 vs. 69.1±20.1 cal/min, P=0.000). In univariable linear regression models, the presence of ID, higher NYHA class, increased N-terminal pro-B-type natriuretic peptide (NT-proBNP), sTfR, left ventricular internal diastolic diameter (LVIDd), as well as reduced ferritin, Tsat levels, and lower left ventricular ejection fraction (LVEF) were associated with elevated MEE levels (all P<0.05). In multivariable regression models, the presence of ID, reduced Tsat. and increased sTfR remained independent predictors of elevated MEE levels after adjustment for all variables that showed a significant association with MEE (all P<0.05).

Conclusions: The prevalence of ID is high in CHF and is associated with the severity of cardiac dysfunction. The presence of ID as well as reduced Tsat and increased sTfR concentrations are associated with elevated MEE levels in CHF.