title: Assessment of diffuse myocardial fibrosis in rats using small-animal Look-Locker inversion recovery T1 mapping.
abstract: BACKGROUND
  The concentration of gadopentetate dimeglumine in myocardium and blood can be assessed from T1 measurements and can be used to calculate the extracellular volume (ECV) of the myocardium. We hypothesized that diffuse myocardial fibrosis in a small-animal model could be quantitatively assessed by measuring myocardial ECV using small-animal Look-Locker inversion recovery T1 mapping.
  
  
  RESULTS
  Sprague-Dawley rats (n=10) were subjected to continuous angiotensin-2 (AT2) infusion for 2 weeks via a subcutaneously implanted minipump system. Magnetic resonance imaging (MRI) was performed both before and after AT2 infusion. The MRI protocol included multislice cine imaging and before-and-after contrast small-animal Look-Locker inversion recovery T1 mapping and late gadolinium enhancement imaging. Myocardial ECV was calculated from hematocrit and T1 values of blood and myocardium. During the course of AT2 infusion, the mean±SD systolic blood pressure increased from 122±10.9 to 152±27.5 mm Hg (P=0.003). Normalized heart weight was significantly higher in AT2-treated animals than in control littermates (P=0.033). Cine MRI documented concentric left ventricular hypertrophy. Postcontrast myocardial T1 times were shortened after treatment (median [interquartile range], 712 [63] versus 820 [131] ms; P=0.002). Myocardial ECV increased from 17.2% (4.3%) before to 23.0% (6.2%) after AT2 treatment (P=0.031), which was accompanied by perivascular fibrosis and microscarring on myocardial histological analysis. There was a moderate level of correlation between ECV and collagen volume fraction, as assessed by histological analysis (r=0.69, P=0.013).
  
  
  CONCLUSIONS
  In a small-animal model of left ventricular hypertrophy, contrast-enhanced T1 mapping can be used to detect diffuse myocardial fibrosis by quantification of myocardial ECV.
authors.affiliation: Department of Congenital Heart Disease and Pediatric Cardiology, Deutsches Herzzentrum Berlin, Berlin, Germany. dmessroghli@dhzb.de
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Messroghli
authors.forename: Sarah
authors.initials: S
authors.lastname: Nordmeyer
authors.forename: Thore
authors.initials: T
authors.lastname: Dietrich
authors.forename: Olaf
authors.initials: O
authors.lastname: Dirsch
authors.forename: Elena
authors.initials: E
authors.lastname: Kaschina
authors.forename: Kostas
authors.initials: K
authors.lastname: Savvatis
authors.forename: Darach
authors.initials: D
authors.lastname: O h-Ici
authors.forename: Christoph
authors.initials: C
authors.lastname: Klein
authors.forename: Felix
authors.initials: F
authors.lastname: Berger
authors.forename: Titus
authors.initials: T
authors.lastname: Kuehne
mesh_terms: D000818:Animals; D001707:Biopsy, Needle; D003287:Contrast Media; D004195:Disease Models, Animal; D004719:Endomyocardial Fibrosis / Q000175:diagnosis*; D019786:Gadolinium DTPA; D007089:Image Enhancement / Q000379:methods*; D007150:Immunohistochemistry; D015918:Infusion Pumps, Implantable; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D009206:Myocardium / Q000473:pathology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA