The purpose of this study is to identify markers of increased risk for incident ventricular arrhythmias and cardiovascular events in patients already being treated with an implantable cardioverter-defibrillator (ICD) by exploring patient history and clinical findings, biological markers, ECG markers, and echocardiographic markers.

This is a multicenter prospective cohort study to assess the prognostic value of potential biomarkers for incident ventricular arrhythmias and cardiovascular events in patients with implantable cardioverter-defibrillator (ICD). In addition to information from the baseline visit and future study visits, the investigators will also register information from the patients medical records concerning comorbidities and previous medical events.

The data will be summarized with respect to demographic and baseline characteristics and risk markers/ measurements. The final diagnosis of incident cardiovascular events will be established by an adjudication committee with two senior physicians reviewing all information available on the patients, including information on the clinical outcome of the patient. The investigators will use multivariate statistical models to assess the individual performance of biomarkers/other tests.

Inclusion Criteria:

• Patients ≥ 18 years old
• Current treatment with an ICD
• Signed written informed consent before study commencement

Exclusion Criteria:

• Participation in other interventional clinical trial or previously included in the current study
• Patients not able to provide written informed consent
• Known or suspected, non-curable cancer,
• Neurological condition with short life expectancy; e.g. amyotropic lateral sclerosis (ALS)
• Patients unwilling or unable to comply with the protocol
• History of non-compliance to medical management and patients who are considered potentially unreliable by the Investigator
• History or evidence of alcohol or drug abuse with the last 12 months that may influence the participation of the patient in the study, as assessed by the Investigator during the screening phase
• Any surgical or medical condition, which in the option of the Investigator, will impair the ability of the patient to participate in the study

Patients treated with an ICD. Inclusion from outpatient clinic.