What is the Role of Iron Supplementation in Heart Failure

January 8, 2021


By Varun Subashchandran

Peer Reviewed

Heart failure is a common health condition that is associated with significant morbidity and mortality. The American Heart Association estimates a prevalence of 6.2 million people in the United States between 2013 and 2016.1 In an international pooled analysis of 1506 patients with chronic heart failure, iron deficiency was identified in 50% of patients.2 This is of concern, as disorders of iron hemostasis lead to diminished iron circulation as well as functional iron in the form of hemoglobin.3 In an observational study of 157 patients with congestive heart failure, iron-deficient patients were observed to have decreased exercise tolerance and a 3-fold increased risk of mortality, regardless of anemia status.3 This is likely due to iron being a required component of metalloproteins involved in oxygen storage and oxidative phosphorylation.4,5 Iron deficiency leads to biochemical impairment in oxygen delivery, which likely leads to worse symptoms and outcomes in the setting of the preexisting structural impairment in oxygen delivery in patients with heart failure.

Thus, it seems that supplementation of iron in these patients should improve functional status and outcomes. Patients with iron deficiency anemia are generally treated with oral iron due to its efficacy, safety, and low cost.6 Additionally, intravenous (IV) iron has been shown to be associated with anaphylaxis and infection.6,7 One major disadvantage of oral iron is the increased rate of gastrointestinal side effects compared with IV iron, with one systematic review reporting an odds ratio (OR) of 3.05; 95% CI 2.07-4.48.8 Both the European Society of Cardiology (ESC) and the American College of Cardiology/American Heart Association/Heart Failure Society of America (ACC/AHA/HFSA) guidelines recommend testing all patients with heart failure for anemia and iron deficiency, defined as ferritin <100 µg/L or ferritin 100-299 µg/L with transferrin saturation <20%.9,10 Both sets of guidelines recommend treating iron-deficient patients with symptoms of heart failure. The ESC guidelines specifically recommend using IV ferric carboxymaltose; the ACC/AHA/HFSA guidelines recommend using IV iron but no specific formulation.9,10

The evidence for these guidelines stems from a variety of randomized controlled trials (RCT) that have studied iron supplementation in patients with heart failure. The most recent and largest meta-analysis reviewed 10 RCTs with a total of 1404 iron-deficient patients with systolic heart failure who underwent treatment with iron or placebo.11 This analysis showed that iron supplementation reduced hospitalization for worsening heart failure, OR 0.39; 95% CI 0.19-0.80, and the combined endpoint of death and heart failure hospitalization, OR 0.47; 95% CI 0.32-0.69. Zhou and colleagues also found that treatment with iron improved New York Heart Association (NYHA) class, peak oxygen consumption, 6-minute walk distance, and left ventricular ejection fraction. Eight out of the 10 RCTs analyzed in this study used IV iron formulations. Of the two trials that studied oral iron supplementation, IRON 5-HF, published in 2013,was terminated early after recruitment of only 23 patients.12 The second trial, IRONOUT HF, published in 2017, found no significant benefit of oral iron supplementation in patients with heart failure with reduced ejection fraction and iron deficiency.13 The limited follow-up of patients in this study, 16 weeks, may not have been enough to detect a longer-term benefit.

There is clear evidence indicating the significant overlap of heart failure and iron deficiency. Furthermore, supplementation with IV iron appears to improve symptoms and outcomes in these patients.  Both the European and American guidelines recommend testing for iron deficiency and IV repletion for those found deficient. While oral iron supplementation is not currently recommended, this is a result of a lack of data on the long-term benefit of oral iron supplementation in iron-deficient patients with heart failure, rather than a proven lack of long-term efficacy. Moving forward, large RCTs with adequate length of follow-up are needed to assess for any potential benefit of oral iron supplementation in heart failure patients.

Dr. Varun Subashchandran is a 4th year medical student at NYU Grossman School of Medicine

Peer reviewed by Dr. Adam Skolnicks, cardiology, NYU Langone Health

Image courtesy of Wikimedia Commons

References 

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