Cardiac end-diastolic volume (A) and left ventricular (LV) mass (B) measured by in vivo MRI were higher, and cardiac CK flux (C) and ATP levels (D) measured by 31P MRS were lower in HF patients as compared to healthy subjects. Pathologic remodeling was associated with energy deficits as noted by correlations between LV mass and CK flux (E, p=0.033); LV mass and ATP levels (F, p=0.0084); end-diastolic volume and CK flux (G, p=0.0067); and end-diastolic volume and ATP levels (H, p=0.0022). Graphs show data points for individual participants. Data were tested for normality using the Kolmogorov-Smirnov test for normality and analyzed by two-tailed Student’s t-test (A-D) or a linear regression model (E-H) (n = 14 (healthy controls), 27 (heart failure patients). The error bars represent ±SEM.