This prospective single-center study is an observational risk stratification trial in about 250 patients with standard indications for ICD treatment.

Implantable cardioverter defibrillators (ICD) have been shown to improve survival and current guidelines recommend their use for primary and secondary prevention of sudden cardiac death (SCD). However, a large number of patients never receive an appropriate therapy from their device. In contrast, electrical sorm and multiple ICD shocks occur in other patients.

Thus, identification of predictors for survival or ICD shocks is necessary for improved patient selection and optimized therapeutic strategies.

Risk stratification with electrocardiogram (ECG) and signal averaged ECG (SAECG), T-wave alternans (TWA) and Holter ECG including premature ventricular contractions (PVC), non-sustained VT (nsVT), heart rate variability (HRV), heart rate turbulence (HRT) and deceleration capacity, as well as clinical variables is possible, but not implemented in clinical routine in patients with ischemic or dilated cardiomyopathy and newly implanted ICD for primary or secondary prevention of SCD following current guidelines.

Patients will be prospectively followed and the predictive value of the risk markers mentioned above to predict all-cause mortality or appropriate ICD shocks will be investigated.

Inclusion Criteria:

• ischemic or dilated cardiomyopathy
• sinusrhythm
• ICD indication strictly following current guidelines (primary and secondary prevention of SCD)
• Age 18 years or older

Exclusion Criteria:

• no consent
• atrial fibrillation

Patients with ischemic or dilated cardiomyopathy and "standard indications" for ICD treatment. "Stamdard indications" are approved and strictly follow current guidelines, the decision on ICD implantation is based on left-ventricular ejection fraction or the history of malignant arrhythmia. i.e. secondary prevention of sudden cardiac death). Implantation procedure is performed at University Medical Center Goettingen.