Iron Deficiency in Heart Failure

Definition

Iron deficiency (ID) in heart failure is defined as ferritin <100 ng/mL (absolute ID) OR ferritin 100–300 ng/mL with transferrin saturation (TSAT) <20% (functional ID). This definition has been used consistently across major trials (CONFIRM-HF, AFFIRM-AHF, HEART-FID) and the 2021 ESC guideline.

The 2026 ESC guideline endorses TSAT <20% alone, on the grounds that the ferritin-based definition does not reliably identify absolute or functional deficiency, admits patients who are probably iron replete, and that ferritin is highly inflammation-sensitive. TSAT <20% is more sensitive and more specific, is associated with higher mortality independently of HF phenotype, and better identifies IV iron responders. The same guideline concedes the awkward consequence: every trial supporting the IV iron recommendation enrolled by the old definition, so the new definition is endorsed without trial evidence. (sources/HF-ESC-2026, rating: very high)

Key Concepts

Epidemiology and Pathophysiology

• Iron deficiency is present in ~30–50% of HFrEF and up to 50–80% of HFpEF patients; prevalence increases with NYHA class. (sources/HF-ESC-2021, rating: very high)
• Oral iron: IRONOUT HF RCT showed no improvement in exercise capacity in HFrEF with iron deficiency — oral iron is not recommended in HF (guidelines). (sources/HF-AHA-2022, rating: very high)
• Iron deficiency — even in the absence of anaemia — is independently associated with worse symptoms, exercise intolerance, and outcomes in HF (observational data). (sources/HF-ESC-2021, rating: very high)
• Mechanisms: myocardial mitochondrial dysfunction, impaired ATP production, skeletal muscle iron depletion, and neurohormonal dysregulation — all iron-dependent pathways independent of haemoglobin level. (sources/HF-update-ESC-2023, rating: very high)

Intravenous Iron — Evidence for Symptoms/QoL

• FAIR-HF (Anker et al., NEJM 2009; n=459; LVEF ≤45%): FCM vs placebo; primary PGA and NYHA class both significantly improved; 6MWT +35 m; independent of anaemia status. (sources/HF-ESC-2021, rating: very high)
• CONFIRM-HF (Ponikowski et al., EHJ 2015; n=304; LVEF ≤45%): FCM vs placebo over 52 weeks; 6MWT +18 m (P=0.002); HF hospitalizations reduced (HR 0.61); functional status improved. (sources/HF-update-ESC-2023, rating: very high)
• EFFECT-HF (van Veldhuisen et al., Circulation 2017; n=172): FCM improved peak VO2 vs usual care (+1.04 mL/kg/min; P=0.02). (sources/HF-update-ESC-2023, rating: very high)
• Guideline recommendation: IV iron (FCM or ferric derisomaltose) — ESC Class I, Level A for improvement of symptoms and exercise tolerance in HFrEF/HFmrEF with iron deficiency. (Upgraded from IIa in 2021 ESC Focused Update.) (sources/HF-update-ESC-2023, rating: very high)

Intravenous Iron — Evidence for Clinical Events (Hospitalizations/Mortality)

• AFFIRM-AHF (Ponikowski et al., Lancet 2020; n=1,132; acute HF + LVEF <50%): FCM at discharge vs placebo; primary composite (CV death + total HF hospitalizations) rate ratio 0.79 (95% CI 0.62–1.01; P=0.059) — near-significant; total HF hospitalizations RR 0.74 (P=0.013); CV death HR 1.07 (NS). Pre-specified sensitivity analysis excluding COVID-affected events: significant. (sources/HF-update-ESC-2023, rating: very high)
• IRONMAN (Kalra et al., Lancet 2022; n≈1,137; HF + LVEF <45%; 15% enrolled inpatient): Ferric derisomaltose vs usual care; recurrent HF hospitalizations + CV death rate ratio 0.82 (95% CI 0.66–1.02; P=0.070) — near-significant. Sensitivity analysis (adjusting for COVID): RR 0.76 (P=0.024). (sources/HF-update-ESC-2023, rating: very high)
• HEART-FID (Mentz et al., NEJM 2023; n=3,065; ambulatory HFrEF LVEF ≤40%): FCM vs placebo; hierarchical primary composite (death/HF hosp/6MWT) win ratio 1.10 (99% CI 0.99–1.23; P=0.02) — did not meet pre-specified threshold of p<0.01; main secondary (CV death/HF hosp) HR 0.93 (96% CI 0.81–1.06) — NS. (sources/fe-hf-heartfid-nejm-2023, rating: high)
• Guideline recommendation for hospitalisation reduction: ESC Class IIa, Level A — IV FCM or ferric derisomaltose to reduce risk of HF hospitalisation, based primarily on AFFIRM-AHF and IRONMAN. HEART-FID results do not currently change this recommendation but add nuance. (sources/HF-update-ESC-2023, rating: very high)

Why HEART-FID vs AFFIRM-AHF Differ

• Patient risk profile: HEART-FID placebo arm had 17.3 CV events/100 pt-yr vs 47.1 in AFFIRM-AHF — ~2.7× lower baseline risk, reducing absolute treatment effect.
• Enrollment timing: AFFIRM-AHF treated patients at discharge from acute HF admission (high-risk transition window); HEART-FID treated stable ambulatory patients.
• TSAT baseline: Higher mean TSAT at enrollment in HEART-FID, suggesting less severe iron deficiency.
• COVID-19 pandemic: Majority of HEART-FID patients enrolled during 2020–2021; reduced hospitalization rates across all arms.
• Statistical threshold: HEART-FID required p<0.01 (FDA special protocol agreement); actual P=0.02 would be significant under standard p<0.05.
• Dose timing: HEART-FID dosed every 6 months based on iron indexes; AFFIRM-AHF front-loaded post-discharge with fixed algorithm.

Contradictions / Open Questions

• Class I recommendation (symptoms/QoL) vs HEART-FID neutral events endpoint: The ESC Class I upgrade for IV iron (symptoms) was based on FAIR-HF/CONFIRM-HF/EFFECT-HF. HEART-FID, the largest and most rigorously powered events trial, failed to show significant benefit — raising the question of whether benefit in ambulatory patients is real and whether benefit is confined to the peri-acute discharge window. (sources/fe-hf-heartfid-nejm-2023, rating: high; sources/HF-update-ESC-2023, rating: very high)
• Optimal iron deficiency definition: Ferritin-based criteria (used in all major trials) vs TSAT <20% alone (bone marrow–validated): recent scientific statements suggest TSAT <20% is more biologically meaningful. Mixed criteria enrollment in trials may have diluted treatment effect by including patients who were not truly iron-deficient. (sources/fe-hf-heartfid-nejm-2023, rating: high)
• HFpEF: evidence gap: HEART-FID enrolled LVEF ≤40%; AFFIRM-AHF/IRONMAN included up to LVEF <50%. No trial has specifically demonstrated hospitalization or mortality benefit from IV iron in HFpEF. ESC recommendation explicitly notes that further evidence in LVEF >50% is needed. (sources/fe-hf-heartfid-nejm-2023, rating: high)
• Interaction with SGLT2 inhibitors: Only 8% of HEART-FID patients were on SGLT2 inhibitors; the incremental benefit of IV iron on top of modern quadruple GDMT (ARNi + BB + MRA + SGLT2i) is not established. (sources/fe-hf-heartfid-nejm-2023, rating: high)

Connections

• Related to entities/HFrEF — primary clinical context; iron deficiency management section
• Related to entities/Heart-Failure — broader HF syndrome
• Related to entities/HFpEF — evidence gap for IV iron
• Related to concepts/Cardiorenal-Syndrome — CKD affects iron metabolism and ferritin interpretation

Sources

• sources/HF-ESC-2026
• sources/HF-ESC-2021
• sources/HF-update-ESC-2023
• sources/HF-AHA-2022
• sources/fe-hf-heartfid-nejm-2023