Late gadolinium-enhancement cardiac magnetic resonance identifies postinfarction myocardial fibrosis and the border zone at the near cellular level in ex vivo rat heart.
BACKGROUND
using a resolution 1000-fold higher than prior studies, we studied (1) the degree to which late gadolinium-enhancement (LGE) cardiac magnetic resonance tracks fibrosis from chronic myocardial infarction and (2) the relationship between intermediate signal intensity and partial volume averaging at distinct "smooth" infarct borders versus disorganized mixtures of fibrosis and viable cardiomyocytes.


RESULTS
sprague-Dawley rats underwent myocardial infarction by coronary ligation. Two months later, rats were euthanized 10 minutes after administration of 0.3 mmol/kg intravenous gadolinium. LGE images ex vivo at 7 T with a 3D gradient echo sequence with 50×50×50 μm voxels were compared with histological sections (Masson trichrome). Planimetered histological and LGE regions of fibrosis correlated well (y=1.01x-0.01; R(2)=0.96; P<0.001). In addition, LGE images routinely detected clefts of viable cardiomyocytes 2 to 4 cells thick that separated bands of fibrous tissue. Although LGE clearly detected disorganized mixtures of fibrosis and viable cardiomyocytes characterized by intermediate signal intensity voxels, the percentage of apparent intermediate signal intensity myocardium increased significantly (P<0.01) when image resolution was degraded to resemble clinical resolution consistent with significant partial volume averaging.


CONCLUSIONS
these data provide important validation of LGE at nearly the cellular level for detection of fibrosis after myocardial infarction. Although LGE can detect heterogeneous patches of fibrosis and viable cardiomyocytes as patches of intermediate signal intensity, the percentage of intermediate signal intensity voxels is resolution dependent. Thus, at clinical resolutions, distinguishing the peri-infarct border zone from partial volume averaging with LGE is challenging.
Schelbert
Erik B
EB
Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Md. 20892-1061, USA.
Hsu
Li-Yueh
LY
Anderson
Stasia A
SA
Mohanty
Bibhu D
BD
Karim
Syed M
SM
Kellman
Peter
P
Aletras
Anthony H
AH
Arai
Andrew E
AE
D000208:Acute Disease; D000818:Animals; D002908:Chronic Disease; D003287:Contrast Media; D005355:Fibrosis; D019786:Gadolinium DTPA; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology*; D009206:Myocardium / Q000473:pathology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D013997:Time Factors
D003287:Contrast Media; D019786:Gadolinium DTPA