BACKGROUND: Diffuse interstitial fibrosis is present in diverse cardiomyopathies 
and associated with poor prognosis. We investigated whether magnetic resonance 
imaging-based T1 mapping could quantify the induction and pharmacological 
suppression of diffuse cardiac fibrosis in murine pressure-overload hypertrophy.
METHODS AND RESULTS: Mice were subjected to transverse aortic constriction or 
sham surgery. The angiotensin receptor blocker losartan was given to half the 
animals. Cine-magnetic resonance imaging performed at 7 and 28 days showed 
hypertrophy and remodeling and systolic and diastolic dysfunction in transverse 
aortic constriction groups as expected. Late gadolinium-enhanced magnetic 
resonance imaging revealed focal signal enhancement at the inferior right 
ventricular insertion point of transverse aortic constriction mice concordant 
with the foci of fibrosis in histology. The extracellular volume fraction, 
calculated from pre- and postcontrast T1 measurements, was elevated by 
transverse aortic constriction and showed direct linear correlation with 
picrosirius red collagen volume fraction, thus confirming the suitability of 
extracellular volume fraction as an in vivo measure of diffuse fibrosis. 
Treatment with losartan reduced left ventricular dysfunction and prevented 
increased extracellular volume fraction, indicating that T1 mapping is sensitive 
to pharmacological prevention of fibrosis.
CONCLUSIONS: Magnetic resonance imaging can detect diffuse and focal cardiac 
fibrosis in a clinically relevant animal model of pressure overload and is 
sensitive to pharmacological reduction of fibrosis by angiotensin receptor 
blockade. Thus, T1 mapping can be used to assess antifibrotic therapeutic 
strategies.