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Iron's Cardiac Role Beyond Haemoglobin — EECC MCQ

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ModerateGeneral CardiologyIron's Cardiac Role Beyond HaemoglobinEECC

A 70-year-old man with HFrEF on GDMT develops a new finding of iron deficiency (ferritin 60 microg/L, TSAT 14%). He asks whether his iron deficiency could be contributing to his HF symptoms beyond anaemia. His Hb is 128 g/L (normal). What is the role of iron in cardiomyocytes?

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Correct answer: B — Iron is essential for mitochondrial energy production in cardiomyocytes — iron deficiency impairs oxidative phosphorylation and reduces cardiac contractility INDEPENDENTLY of haemoglobin; this is why iron replacement improves HF symptoms even in non-anaemic patients

Iron's role extends far beyond haemoglobin synthesis: (1) mitochondrial function: iron is a cofactor for cytochrome c oxidase and other electron transport chain enzymes — cardiomyocytes are extremely mitochondria-rich (>30% of cell volume); iron deficiency directly impairs oxidative phosphorylation and ATP production; (2) myoglobin: intracellular oxygen storage and transport within cardiomyocytes requires iron-containing myoglobin; (3) citric acid cycle: aconitase (iron-sulphur cluster enzyme). This explains why iron deficiency impairs cardiac function INDEPENDENTLY of anaemia — and why iron replacement improves symptoms, exercise capacity, and hospitalisations even in non-anaemic HF patients (FAIR-HF: ~50% of participants were non-anaemic and benefited equally). The ESC 2023 HF Guidelines define iron deficiency as ferritin <100 OR ferritin 100-299 with TSAT <20% — the threshold is LOWER than the general population definition because of the critical cardiac need for iron.

Reference: ESC (2023): HF Guidelines; FAIR-HF