The study is a prospective multicenter registry. Consecutive patients with indications of implant / replacement or upgrade of implantable cardioverter defibrillator (ICD) will be enrolled.

The primary objective of the study is to determine the predictors of appropriate anti-tachycardia therapy (with shock) in a non-selected population of patients implanted with an ICD.

Secondary objectives of the study are:

• the incidence of anti-tachycardia therapies;
• the predictors of inappropriate therapy and onset of arrhythmia burden;
• the adherence to the current guidelines in the Italian clinical practice;
• the predictors of heart failure (HF) onset and response to cardiac resynchronization therapy (CRT).

Inclusion Criteria:

• Patient implanted with a Subcutaneous (S)- Ventricular Chamber (VR)- Dual Chamber (DR) - or Cardiac Resynchronization Therapy (CRT) Defibrillator (this study will utilize all the market released CRT-D or VR/DR-ICD systems and leads)
• Patient is willing and able to sign an authorization to use and disclose health information or an Informed Consent
• Patient must be able to attend all required follow-up visits at the study center for at least 12 months

Exclusion Criteria:

• Patient is participating in another clinical study that may have an impact on the study endpoints
• Women who are pregnant or plan to become pregnant

This study requires patients implanted with a defibrillator that meet all inclusion/exclusion criteria.