Objectives: Intramyocardial hemorrhage (IMH) is the most severe form of injury associated with reperfusion therapy during acute myocardial infarction (AMI). Although T 2 *-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 T 1 -shortening and a long intravascular half-life, may enable earlier detection. This study assessed a T 1 -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 T 1 -weighted cine imaging and serial T 1 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 T 1 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 0.05). Gross and microscopic findings confirmed extravasated erythrocytes and disrupted myocardial architecture, consistent with hemorrhagic injury. Conclusions: This proof-of-concept study demonstrates the feasibility and potential of T 1 -weighted FE-MRI as a unique approach for detecting IMH immediately after ischemia-reperfusion injury. Early identification of IMH by FE-MRI may facilitate translational efforts to develop and evaluate targeted therapies that reduce IMH burden and improve post-AMI outcomes.
Pogosyan et al. (Tue,) studied this question.