Abstract 4366548: Ferumoxytol Pharmacokinetics in Cardiac Magnetic Resonance

Introduction: Cardiac MRI (CMR) provides a non-invasive, radiation sparing assessment of anatomy and hemodynamics and is essential in caring for patients with congenital heart disease (CHD). Ferumoxytol (AMAG Pharmaceuticals) is an intravenously administered iron oxide nanoparticle that is FDA approved for the treatment of iron deficiency anemia but is increasingly used as an off-label MRI contrast agent. There are few studies assessing the effect of an iron-based contrast agent on circulating iron and iron stores in pediatric patients. Furthermore, patients with CHD may be cyanotic or have compensatory polycythemia, leading to increased iron burden. The objective of this study is to investigate the effect of radiologic dosing of Ferumoxytol on the iron stores of pediatric patients with CHD. Methods: A prospective observational study was performed on patients < 26 years of age undergoing ferumoxytol enhanced CMR (FE-CMR) at a large tertiary care center. Ferumoxytol dose was 4mg/kg administered intravenously over 15 minutes. Baseline evaluation of serum iron, transferrin, total iron binding capacity, ferritin and complete blood count were obtained within 24 hours prior to Ferumoxytol administration. Serial laboratory evaluations were performed at 3 follow up timepoints: 2-4 hours, 2-15 days, and 4-6 weeks post-contrast. Results: A total of 17 patients were enrolled. Two patients had low serum iron levels prior to FE-CMR while 15 patients had normal levels. Serum iron levels increased 2-4 hours after contrast but returned to normal or low normal levels in 2-9 days. Ferritin levels were not affected by ferumoxytol infusion. Transferrin levels and TIBC remained stable or decreased after ferumoxytol infusion. Average platelet levels before infusion were 281K/uL. No patients had an adverse reaction to infusion or clinical concern for iron toxicity. Conclusion: In pediatric patients with CHD, there is a marked increase in serum iron immediately after ferumoxytol infusion with return to baseline levels after several days. Ferumoxytol does not affect Ferritin levels. Transferrin levels and TIBC are normal or mildly decreased after infusion. This data suggests patients undergoing FE-CMR experience a transient increase in iron levels but no change to long term whole body iron levels. Further studies are needed to determine if these trends are statistically significant in a larger cohort.