Abstract 10378: Characterization of Changes in Cardiac Structure and Function in Mice Treated With Anthracyclines Using Serial Cardiac Magnetic Resonance Imaging

Abstract

Introduction: Anthracyclines are a standard chemotherapeutic agent. However, the anthracyclines are associated with a late reduction in left ventricular ejection fraction (LVEF) and heart failure. Pathologically, anthracycline-induced cardiotoxicity (AIC) is characterized by the development of cardiac edema and fibrosis and cardiac magnetic resonance (CMR) is the gold-standard imaging technique for edema and fibrosis. Hypothesis: We hypothesized that a) cardiac edema and fibrosis would be detected by CMR after anthracyclines and b) edema and fibrosis would provide prognostic information. Methods: We performed a longitudinal CMR and histological study of 45 wild-type mice randomized to doxorubicin (DOX, n=30, 5 mg/kg/week for 5 weeks) or placebo (n=15). Measurements were performed at baseline, 5, 10, and 20 weeks after DOX or placebo. Measures of interest were LVEF, myocardial edema and fibrosis. Edema was assessed by T2 mapping, fibrosis by calculating the extracellular volume (ECV) from pre- and post-contrast T1 measurements. Results: In DOX-treated mice vs. placebo, myocardial edema at 5 weeks was increased (T2 values of 32±4 vs. 21±3 ms, P<0.05, Fig. A), while LVEF was unchanged. At 10 weeks, there was a reduction in LVEF (54±6 vs. 63±5% μL, P<0.05) and an increase in myocardial fibrosis (ECV of 0.34±0.03 vs. 0.27±0.03, P<0.05, Fig. B). There was a correlation between T2 measures and cardiac water weight (r=0.79, P=0.007, Fig. C) and between the ECV and histological myocardial fibrosis (r=0.90, P<0.001; Fig. D). Both the early increase in edema and the sub-acute increase in fibrosis predicted the late DOX-induced mortality (P<0.001, Fig. E and F). Conclusions: Our data suggest that, in mice, CMR can detect the early increase in edema and sub-acute increase in fibrosis after anthracyclines, that an increase in edema precedes a reduction in LVEF, that the increase in edema and fibrosis are linked and both are predictive of late animal mortality.