Coronary Embolization and Myocardial Microinfarction: MR Imaging and Histopathologic Characterization

Abstract

Magnetic resonance imaging (MRI) has been proven to reliably assess regional perfusion and left ventricular (LV) function of microembolized myocardium. The visibility of microinfarct on delayed enhancement MRI (DE-MRI) is limited and dependent on technical and biological issues. Furthermore, MRI underestimates total microinfarct size compared with microscopy. MRI studies revealed that the presence of microemboli in pre-existing acute infarct delays infarct healing and magnifies LV remodeling. Discrimination of acute from chronic microinfarct is based on presence of inflammatory cells, edema and scar tissue, respectively. These noninvasive findings highlight the importance of prognostic utility of MRI and warrant larger clinical studies or registries to evaluate the significance of presence of focal microinfarct. Serial microscopic studies revealed that intravascular microemboli migrate into the extravascular space and this migration process is a function of time. This phenomenon may limit the use of microemboli therapy in occluding hemorrhagic blood vessels or treating tumors. Despite current standard of care, existing methods and therapies do not prevent coronary embolization nor reverse their deleterious effects.

Potentials, Limitations and Future Directions of MR Contrast Media in Ablation Therapies

“…T 1 and T 2 sequences with MR contrast media are useful for detecting and monitoring the evolution of fibrotic tissue after ablation [153,154]. The major obstacles in using MR contrast media at the present time are the dissociation of gadolinium from the chelates and nephrogenic systemic fibrosis.…”