Cardiac energetics in patients with chronic heart failure and iron deficiency: an in‐vivo  (31)P magnetic resonance spectroscopy study

AIMS: Iron deficiency (ID) is prevalent and adverse in chronic heart failure (CHF) but few human studies have explored the myocardial mechanism(s) that potentially underlie this adversity. Because mitochondrial oxidative phosphorylation (OXPHOS) provides over 90% of the hearts adenosine triphosphate (ATP), and iron is critical for OXPHOS, we hypothesized that patients with CHF and ID would harbour greater cardiac energetic impairments than patients without ID. METHODS AND RESULTS: Phosphorus magnetic resonance spectroscopy was used to quantify the phosphocreatine (PCr) to ATP (PCr/ATP) ratio, an index of in‐vivo cardiac energetics, in CHF patients and healthy volunteers. Cardiac structure and function was assessed from magnetic resonance short stack cines. Patients with (n = 27) and without (n = 12) ID, and healthy volunteers (n = 11), were similar with respect to age and gender. The PCr/ATP ratio was lower in patients with ID (1.03 [0.83–1.38]) compared to those without ID (1.72 [1.51–2.26], p < 0.01) and healthy volunteers (1.39 [1.10–3.68], p < 0.05). This was despite no difference in cardiac structure and function between patients with and without ID, and despite adjustment for the presence of anaemia, haemoglobin levels, cardiac rhythm, or New York Heart Association (NYHA) class. In the total CHF cohort, the PCr/ATP ratio correlated with ferritin levels (rho = 0.4, p < 0.01), and was higher in NYHA class I than class II or III patients (p = 0.02). CONCLUSION: Iron deficiency is associated with greater cardiac energetic impairment in patients with CHF irrespective of anaemia and cardiac structure and function. Suppression of cardiac mitochondrial function might therefore be a mechanism via which ID worsens human CHF.