Assessment of intramyocardial hemorrhage in acute reperfused myocardial infarction using 7.0T

Methods 10 Sprague Dawley rats (female, 250-300g) underwent ligation of the left anterior descending or circumflex coronary arteries for 60 minutes, followed by reperfusion for 48 hours. The rats were then scanned at 7.0T MR (BRUKER BIOSPEC 70/30, Germany), using T2 mapping(TR/ TE=1500ms/10,20,30ms, MTX=192×192, FOV=50×50mm, slice thickness=1.5mm) and LGE(TR/TE=5.2ms/1.8ms, FA=25°, MTX=256×256, FOV=50×50mm, slice thickness=1.5mm).The T2 mapping images were created using a custom-made software, written by Matlab. The T2 values of edema, hemorrhage, and remote myocardium were then calculated using a ImageJ software, along with the determination of presence and size of hemorrhage. All datas were assessed by 2 radiologists who were blinded to the pathology results. The hearts were dissected after the CMR study for pathological analysis. Left ventricular sections of the specimens, matched well with T2 mapping slices, were assessed for hemorrhage and its size. The pathological stains including hematoxylin-eosin and Prussian blue staining were assessed for red blood cells exudation and acute hemorrhage respectively by an experienced pathologist. Results One rat died undergoing CMR. 55 of all 72 pathological sections of left ventricles (LV) showed myocardial infarction that matched well with the hyperintense area in LGE MRI (Figure 1B,D). Myocardial hemorrhage pathologically occurred in 44 sections, corresponded with hypointense area in 41 image slices on T2 mapping (Figure 1A,C,E). Prussian blue staining of all hemorrhagic sections was negative (Figure 1F). 4 slices with hypointense area on T2 mapping showed no hemorrhage on pathological sections. On the section bassis, the sensitivity and specificity for hemorrhage on T2 mapping were 93% and 85% respectively, and the positive and negative predictive values were 91% and 89% respectively (Table 1). The T2 values of edema, hemorrhage, and remote myocardium were 47.2±9.4ms, 27.9 ±5.2ms, 21.3±4.4ms respectively, and all three values had significant differences (p<0.05).The size of hemorrhage calculated on T2 mapping corresponded with that on pathological sections(6.1%±0.02 vs 6.3%±0.02, p=0.46).