Microcirculation of intramyocardial hemorrhage caused by reperfused myocardial infarctions with ultrasmall superparamagnetic iron oxide cardiac magnetic resonance imaging

Background: The actual role of the coronary microcirculation, which is massively injured by myocardial infarction (MI), in intramyocardial hemorrhage (IMH) pathophysiology is still not fully understood. Purpose: To determine the change and distribution of microcirculation of myocardial edema (ME), IMH, MI, and the remote area of early reperfusion using 7.0-T cardiovascular magnetic resonance (CMR) in a rat model of acute MI. Material and Methods: Eight rats with 60-min myocardial ischemia followed by reperfusion were investigated. On days 2 and 7, after the acquisition of T2*-mapping and T2-mapping images, late gadolinium enhancement imaging was performed to evaluate the extent of myocardial ischemia after an injection of Gd-DTPA. On days 3 and 8, after the injection of ultrasmall superparamagnetic iron oxide (USPIO), T2*- and T2-mapping images were acquired. The R2 values of ME, IMH, MI, and remote areas were measured. Results: From days 2 to 3, R2 values increased in the IMH, MI, ME, and remote area (all P < 0.05) following administration of USPIO, while the delta R2 value of IMH and MI was larger than remote area (P < 0.05). From day 7 to day 8, there was no significant difference in the IMH, MI, ME, and remote area (all P > 0.05). Conclusion: Microvascular injury of IMH and MI is the most severe among all the studied myocardial injuries in the early reperfusion of MI, while microvascular density decreased during follow-up.