Patients with diagnostic CMR images for assessment of LGE/fibrosis and evidence/presence of non-ischaemic myocardial fibrosis/scar will be randomized to the following treatment groups in a 1:1 ratio: ICD group or Optimal HF care group.

The primary objective of this study is to evaluate the hypothesis that implantable cardioverter defibrillator (ICD) therapy would decrease the risk of death from any cause in comparison to optimal heart failure (HF) care without ICD insertion in patients with NIDCM, left ventricular ejection fraction (LVEF) ≤35% and presence of myocardial fibrosis on cardiac magnetic resonance (CMR) imaging.

Inclusion Criteria:

• NIDCM (idiopathic or familial)*
• LVEF ≤35% and presence of fibrosis on CMR
• Diagnostic CMR scan
• Age ≥18 years
• Written informed consent
• Ability to give informed consent

Exclusion Criteria:

• ICM [previous myocardial infarction, previous percutaneous coronary intervention]
• Other cardiomyopathies (hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, restrictive cardiomyopathy, infiltrative cardiomyopathies [e.g. cardiac amyloidosis, cardiac sarcoidosis, hemochromatosis and iron overload cardiomyopathy], left ventricular non-compaction cardiomyopathy, reversible cardiomyopathies [Takotsubo syndrrome, peripartum cardiomyopathy, chemotherapy induced cardiomyopathy].
• Myocarditis
• Contraindication for CMR at study entry (including severe claustrophobia, pacemaker or ICD, metallic cerebral or intracranial implants, known allergy to gadolinium)
• Severe renal insufficiency (creatinine clearance <30 mL/min)
• Current pacemaker or defibrillator in situ
• Current indication for device therapy (e.g. secondary prophylaxis after aborted SCD)
• Renal impairment defined as an eGFR <30 milliliters
• Age <18 years
• Patients presenting with pregnancy
• Patients without informed consent
• Participation in another randomized trial
• Life expectancy <2 years