The purpose of this study is to determine, relative to placebo, the effect of iron repletion therapy using intravenous (IV) ferric carboxymaltose on exercise capacity in patients with chronic heart failure and iron deficiency.

Inclusion Criteria:

• Iron deficient subjects with stable chronic heart failure (CHF) (NYHA II-III) on optimal background therapy for CHF
• Reduced left ventricular ejection fraction
• Capable of completing 6 minute walk test
• At least 18 years of age and with written informed consent prior to any study specific procedures

Exclusion Criteria:

• Erythropoietin stimulating agent (ESA) use, IV iron therapy and/or blood transfusion in previous 6 weeks prior to randomisation
• Exercise training program(s) in the 3 months prior to screening or planned in the next 6 months
• Chronic liver disease and/or elevated liver enzymes
• Vitamin B12 and/or serum folate deficiency
• Subject is not using adequate contraceptive precautions during the study
• Body weight ≤ 35 kg
• No other significant cardiac or general disorders that would compromise the ability to give informed consent and/or comply with study procedures