Relation between signal intensity on T2-weighted MR images and presence of microvascular obstruction in patients with acute myocardial infarction.
OBJECTIVE
In experimental animal models and human autopsy studies, hemorrhagic infarction caused by microvascular injury has been detected after coronary reperfusion. The purpose of this study was to determine whether detection of myocardial edema with T2-weighted MRI is influenced by the presence of microvascular obstruction.


METHODS
Thirty-seven patients underwent black-blood fat-suppressed T2-weighted, rest perfusion, and late gadolinium-enhanced MRI 5.4 +/- 3.1 days after the onset of acute myocardial infarction. On T2-weighted MR images, the signal intensity in relation to that of remote myocardium was determined in the late gadolinium-enhanced and periinfarction areas. Segment-based analysis was performed to determine whether the presence of microvascular obstruction influences the detection of myocardial edema.


RESULTS
The averaged signal intensity in the late gadolinium-enhanced area without microvascular obstruction was significantly higher than the signal intensity in remote normal myocardium (relative signal intensity, 1.83 +/- 0.50; p < 0.001). In contrast, the signal intensity in the microvascular obstruction area on T2-weighted images was not significantly different from the signal intensity in remote myocardium (relative signal intensity, 1.14 +/- 0.26). The percentages of late gadolinium-enhanced segments with high signal intensity on T2-weighted MR images were 95% (73/77) without microvascular obstruction and 30% (22/73) with microvascular obstruction.


CONCLUSIONS
With T2-weighted MRI, infarction-associated edema can be reliably detected in infarct lesions without microvascular obstruction. Microvascular obstruction, however, does not necessarily exhibit high signal intensity on T2-weighted MRI. Careful attention is required in interpretation of cardiac MR images of patients who have experienced acute myocardial infarction and undergone percutaneous coronary intervention. The findings on T2-weighted MR images can be substantial underestimates of the extent of acute myocardial infarction.
Mikami
Yoko
Y
Department of Radiology, Mie University Hospital, 2-174 Edobashi, Tsu, Mie 514-8507, Japan. yokomikami@gmail.com
Sakuma
Hajime
H
Nagata
Motonori
M
Ishida
Masaki
M
Kurita
Tairo
T
Komuro
Issei
I
Ito
Masaaki
M
D003331:Coronary Vessels / Q000473:pathology; D004489:Edema, Cardiac / Q000150:complications* / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D055806:Microvessels / Q000473:pathology*; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications* / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic