We plan to study the concept of "energy starvation" in heart failure by evaluation of patients with nonischemic dilated cardiomyopathy (NIDCM) (heart failure with reduced heart pump function due to causes other than heart attack). We will use a combination of positron emission tomography and magnetic resonance imaging to study metabolism, anatomy, function, blood flow and efficiency, before and after 6 months' treatment with the drug spironolactone which blocks the deleterious effects of the hormone aldosterone on the myocardium (heart muscle).