This study is to demonstrate the prognostic usefulness of assessment of myocardial sympathetic innervation, as determined by the heart to mediastinum (H/M) ratio on planar 123I mIBG imaging as either normal or abnormal, for identifying heart failure (HF) subjects at higher risk of experiencing an adverse cardiac event. Daniel S. Berman, MD 7088 Cardiac Imaging- SPECT Congestive Heart Failure 04/30/2008 Name: Justin Henderson Phone: (310) 423-2116 E-mail: HendersonJS@cshs.org