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

Abstract

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. 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. 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. 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). 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.