International Study to Determine if AdreView Heart Function Scan Can be Used to Identify Patients With Mild or Moderate Heart Failure (HF) That Benefit From Implanted Medical Device

Inclusion Criteria: * Participants \>=18 years of age at the time dated informed consent was obtained. * Female participants must be pre-menarchal, surgically sterile (had a documented bilateral oophorectomy and/or documented hysterectomy), postmenopausal (cessation of menses for more than 1 year), non-lactating, or, if of childbearing potential, a serum or urine pregnancy test with the results known prior to AdreView (Iobenguane I-123 Injection) administration) was negative. * Participants willing and able to comply with all study procedures and a signed and dated informed consent was obtained before any study-procedure was carried out. * Heart failure NYHA class II or III for symptoms, participants with ischemic or non-ischemic heart disease, eligible for ICD implantation as per each site's standard of practice. * Non-ischemic dilated cardiomyopathy or ischemic heart disease of at least 3 months duration receiving guideline-directed optimal medical therapy. * 25%≤LVEF≤35%, performed within 3 months before or at time of enrollment, as measured by radionuclide ventriculography, or electrocardiogram \[ECG\]-gated SPECT myocardial perfusion imaging \[MPI\], or magnetic resonance imaging \[MR\], computed tomography \[CT\], or 3D or 2D echocardiography \[Simpson's or multidisc method only, M-mode echocardiography was not accepted\]. In case LVEF measurement was performed within 3 months before enrollment, measurement should be performed at least 40 days after a hospitalization …