Myocardial Infarction as An Independent Predictor of Intramyocardial Hemorrhage in Acute Reperfused Myocardial Ischemic Rats

Background: In the previous studies, hemorrhage occurred only with the largest infarctions and studies confirmed a moderate correlation between the extent of necrosis and hemorrhage, but the extent of infarction size of these studies was limited. This study was to find the correlations between intramyocardial hemorrhage (IMH), myocardial infarction (MI), and myocardial edema (ME) from days 2 to 7 in a 7.0T MR scanner.Methods: The different degrees of myocardial ischemia were induced by occluding different sections of the proximal left anterior descending coronary artery (1–3 mm under the left auricle). T2*-mapping, T2-mapping and late gadolinium enhancement (LGE) sequences were performed on a 7.0T MR system at day 2 and 7. T2*- and T2-maps were calculated using a custom-made software. All areas were expressed as a percentage of the whole myocardial tissue of the left ventricle. The rats were divided into two groups based on the T2* results; MI with IMH was referred to as the +IMH group, while MI without IMH was referred to as the –IMH group.Results: The final experimental sample consisted of 25 rats in the +IMH group and 10 rats in the –IMH group. For the +IMH group. On day 2, There was a significant positive correlation between IMH size and MI size (r = 0.677, P<0.01), and a positive correlation between IMH size and ME size (r = 0.552, P<0.01). On day 7, There was a significant positive correlation between IMH size and MI size (r = 0.711, P<0.01), while no correlation was found between IMH size and ME size (r = 0.429, P = 0.097). Conclusions: Infarction size prior to reperfusion is a critical factor in determining whether a MI is hemorrhagic or non-hemorrhagic in rats.