Ferumoxytol-Enhanced Cardiac Magnetic Resonance for Delineation of Hyperacute Intramyocardial Hemorrhage With Ex Vivo Validation

OBJECTIVES: Intramyocardial hemorrhage (IMH) is the most severe form of injury associated with reperfusion therapy during acute myocardial infarction (AMI). Although T2*-weighted cardiac MRI is regarded as the reference standard for IMH detection, its application is limited in the hyperacute phase. Ferumoxytol, an iron-based contrast agent characterized by potent T1-shortening and a long intravascular half-life, may enable earlier detection. This study assessed a T1-weighted approach using ferumoxytol-enhanced MRI (FE-MRI) for early detection of IMH after ischemia-reperfusion injury in a swine model. MATERIALS AND METHODS: IMH was induced in 22 Yorkshire swine using a closed-chest ischemia-reperfusion model with intracoronary collagenase administration. FE-MRI was performed immediately after reperfusion using T1-weighted cine imaging and serial T1 mapping with a modified Look-Locker inversion recovery (MOLLI) pulse sequence. Imaging findings were compared among IMH-positive (IMH+), IMH-negative (IMH-), and control animals. Results were validated through gross pathology, histology, and electron microscopy. RESULTS: Nine animals completed imaging, of which 5 were IMH+ and 4 IMH- based on histopathology and FE-MRI. In IMH+ animals, the T1 within hemorrhagic reperfused myocardium was significantly lower than remote myocardium [420.8 ms (380.5, 656.3) vs. 806.0 ms (781.0, 818.8); P