Assessment of Myocardial Fibrosis in Cardiomyopathic Hamsters with Gadolinium-DTPA Enhanced Magnetic Resonance Imaging

RATIONALE AND OBJECTIVES: The authors investigated whether magnetic resonance (MR) imaging enhanced with gadolinium (Gd)-DTPA would be useful for assessment of myocardial fibrosis in cardiomyopathy. METHODS: The authors compared MR images of the excised heart after Gd-DTPA injection with histopathologic findings in 33 hamsters with cardiomyopathy of the Bio 14.6 strain and 26 healthy hamsters of various age groups and assessed localization of Gd-14C-DTPA by autoradiography in the myocardium of three hamsters with cardiomyopathy. RESULTS: The mean signal intensity ratios for the entire myocardium in hamsters with cardiomyopathy relative to that in healthy hamsters was significantly higher in a younger age group than in an older age group (1.30+/-0.09 versus 1.03+/-0.08, P < 0.001, respectively). This myocardial enhancement was more obvious in areas containing massive fibrosis in the early and mid stages than in the late stage. Autoradiograms of hamsters with cardiomyopathy showed patchy or linear increases in uptake, corresponding to the areas of myocardial fibrosis. Gadolinium-14C-DTPA radioactivity ratios of myocardial fibrosis to healthy myocardium were significantly higher in the early and mid stages than in the late stage (P < 0.01). CONCLUSIONS: Myocardial fibrosis with high cellularity and proliferation of vessels was delineated as an area enhanced with Gd-DTPA on MR images, and its signal intensity decreased with the late stage of myocardial fibrosis.