Iron-Based Contrast for the Heart: Clinical Promise of Ferumoxytol-Enhanced CMR

Ferumoxytol is an ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle that was originally approved by the U.S. FDA for treating iron deficiency anemia in patients with chronic kidney disease. It has since emerged as an off-label, versatile intravascular contrast agent for cardiovascular magnetic resonance (CMR) imaging, and in 2025, received FDA approval for brain imaging. This review provides an overview of ferumoxytol-enhanced CMR applications primarily focused on the heart, outlines its key imaging and pharmacokinetic properties, and summarizes its diagnostic safety profile.

Unlike gadolinium-based contrast agents (GBCAs), which rapidly wash out from the circulation, ferumoxytol has high r₁ and r₂ relaxivities and remains confined to the intravascular compartment for prolonged periods. Once metabolized by the reticuloendothelial system, its iron core is incorporated into the body's hematopoietic pathways. These unique properties enable steady-state and delayed-phase imaging, simplify complex imaging workflows, and facilitate accelerated multidimensional cardiac imaging methods. Emerging applications for ferumoxytol-enhanced CMR include myocardial perfusion assessment, multidimensional imaging, vascular and hemodynamic evaluation, and comprehensive structural heart disease imaging.

Ferumoxytol expands the clinical applications of CMR by enabling imaging techniques that are not feasible with conventional GBCAs and broadening imaging options for patients in whom GBCA administration may be less desirable based on individualized clinical risk-benefit assessment, including selected patients with renal insufficiency, very young children, and pregnant women.