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 for HF or acute coronary syndrome (including myocardial infarction), and to be valid, method of measurement should be in accordance with the protocol and the imaging exam should be made available to the Sponsor in digital format. In case several valid LVEF measurements are available, the closest to enrollment will be used for inclusion determination. * Clinically stable heart failure in the medical judgment of the investigator (i.e. no significant changes in medication, no worsening of symptoms, no unscheduled visits to the doctor's office) for the past 30 days and no hospitalization for heart failure or acute coronary syndrome (including myocardial infarction) in the past 40 days. * Reasonable expectation of meaningful survival for at least 1 year. Exclusion Criteria: * Participants with existing ICD or participant having an indication of ICD implantation for secondary prevention of sudden cardiac death. * Hospitalization for HF or for acute coronary syndrome in the previous 40 days. * Participants where a cardiac resynchronisation therapy (CRT) was planned or indicated. * Other indication for placement of device (sustained ventricular tachycardia, resuscitated sudden death, need for atrioventricular pacing). * NYHA class I or class IV symptoms at the time of study entry. * Participants with chronic renal insufficiency defined as serum creatinine ≥ 3 mg/dl (or ≥ 265.2 µmol/L). * American College of College-American Heart Association (ACC-AHA) class III or class IV (unstable) angina. * Known or suspected hypersensitivity/allergy to Iobenguane or to any of the excipients an Adreview (Iobenguane I-131 injection). * Participant who was pregnant or plans to become pregnant within 2 weeks after AdreView (Iobenguane I-123 Injection) administration. * Participant who had used any medication in the 2 weeks before AdreView (Iobenguane I-123 Injection) that could interfere with the test: e.g. but not limited to amitriptyline or derivatives, imipramine or derivatives, other antidepressants or drugs known or suspected to inhibit the norepinephrine transporter, antihypertensives that deplete norepinephrine stores or inhibit reuptake, sympathomimetic amines or cocaine. * Participants that had a medical condition that could interfere with the AdreView test (e.g. but not limited to left ventricular assist device (LVAD), or prior heart transplant). * Participants who participated in a clinical study involving a drug or device within 30 days prior to study entry and participants participating in any other clinical study. * Participants having serious non-cardiac medical condition associated with significant elevation of plasma catecholamines, including pheochromocytoma. * Participants with a clinical diagnosis of (or being treated for) Parkinson's disease or Multiple System Atrophy. * The participant had participated in a research study using ionizing radiation in the previous 12 months. * Participants previously randomized in this study.