Iron deficiency in acute myocardial infarction (IDAMI): a pilot point-prevalence study

The prevalence of iron deficiency in patients with acute myocardial infarction (AMI) is poorly understood and may be of prognostic importance. Two definitions of iron deficiency are in common use, based on heart failure studies. One study of an AMI population included additional serum iron and ferritin-based definitions, providing prevalence estimates of 21% to 62% depending on the definition used.[1]

To estimate the prevalence of iron deficiency in a contemporary AMI population, according to two common definitions.

A point-prevalence study of consecutive patients with type one AMI at a tertiary cardiology centre in North East England between 24/04/2024 and 11/06/2024. Blood tests were collected on the day of AMI admission. We defined iron deficiency as 1) transferrin saturation (TSAT) <20% [1-3]; and 2) a composite of serum ferritin <100 µg/L or TSAT <20% with serum ferritin 100-299 µg/L.[4] For each definition, we report baseline characteristics according to sex, proportion of patients with type 2 diabetes mellitus, ST-elevation MI (STEMI) or non-ST-elevation MI (NSTEMI). We also provide summary data on iron, ferritin, TSAT, haemoglobin, mean cell volume, mean cell haemoglobin, haematocrit, and hypochromasia.

70 patients were recruited (mean age: 67 years, 27% female, 59% STEMI, 7% with a history of anaemia). TSAT was available for 67, and ferritin for 64 patients. Based on the TSAT <20% definition, 39 (58.2%) were iron deficient compared with 43 (67.2%) for the composite definition. Almost all female patients were iron deficient, regardless of the definition used. TSAT <20% appears to align best with other markers of iron deficiency, including lower serum iron and lower haemoglobin, than the composite definition.

Iron deficiency is common in patients with AMI, affecting over half of participants. Growing literature encourages a TSAT <20% definition, based on results from clinical trials of intravenous iron in patients with heart failure, rather than the composite definition in current heart failure guidelines.[2,3] The definition of TSAT <20% may more accurately represent the prevalence of iron deficiency in AMI because ferritin, unlike TSAT, is an acute phase reactant, which is likely to be elevated in AMI. We acknowledge that these findings from this small study require validation in larger studies, and that as ferritin and TSAT exhibit temporal changes, the optimal timing of measurement is unclear.

Baseline characteristics table