Quantitative T 2* assessment of acute and chronic myocardial ischemia/reperfusion injury in mice.
OBJECTIVE
Imaging of myocardial infarct composition is essential to assess efficacy of emerging therapeutics. T (2) (*) mapping has the potential to image myocardial hemorrhage and fibrosis by virtue of its short T (2) (*) . We aimed to quantify T (2) (*) in acute and chronic myocardial ischemia/reperfusion (I/R) injury in mice.


METHODS
I/R-injury was induced in C57BL/6 mice (n = 9). Sham-operated mice (n = 8) served as controls. MRI was performed at baseline, and 1, 7 and 28 days after surgery. MRI at 9.4 T consisted of Cine, T (2) (*) mapping and late-gadolinium-enhancement (LGE). Mice (n = 6) were histologically assessed for hemorrhage and collagen in the fibrotic scar.


RESULTS
Baseline T (2) (*) values were 17.1 ± 2.0 ms. At day 1, LGE displayed a homogeneous infarct enhancement. T (2) (*) in infarct (12.0 ± 1.1 ms) and remote myocardium (13.9 ± 0.8 ms) was lower than at baseline. On days 7 and 28, LGE was heterogeneous. T (2) (*) in the infarct decreased to 7.9 ± 0.7 and 6.4 ± 0.7 ms, whereas T (2) (*) values in the remote myocardium were 14.2 ± 1.1 and 15.6 ± 1.0 ms. Histology revealed deposition of iron and collagen in parallel with decreased T (2) (*) .


CONCLUSIONS
T (2) (*) values are dynamic during infarct development and decrease significantly during scar maturation. In the acute phase, T (2) (*) values in infarcted myocardium differ significantly from those in the chronic phase. T (2) (*) mapping was able to confirm the presence of a chronic infarction in cases where LGE was inconclusive. Hence, T (2) (*) may be used to discriminate between acute and chronic infarctions.
Department of Cardiology, University Medical Center Utrecht (UMCU), Utrecht, The Netherlands.
Eissa N E
EN
Aguor
Fatih
F
Arslan
Cees W A
CW
van de Kolk
Marcel G J
MG
Nederhoff
Pieter A
PA
Doevendans
Cees J A
CJ
van Echteld
Gerard
G
Pasterkamp
Gustav J
GJ
Strijkers
D000208:Acute Disease; D000818:Animals; D003094:Collagen / Q000737:chemistry; D004195:Disease Models, Animal; D005355:Fibrosis / Q000473:pathology; D006352:Heart Ventricles / Q000473:pathology; D006470:Hemorrhage / Q000175:diagnosis; D007501:Iron / Q000737:chemistry; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D009203:Myocardial Infarction / Q000150:complications / Q000473:pathology*; D015428:Myocardial Reperfusion Injury / Q000473:pathology*; D009206:Myocardium / Q000473:pathology; D013997:Time Factors
D003094:Collagen; D007501:Iron