Cardiac resynchronization therapy (CRT) has been shown to reduce heart failure (HF), hospitalizations and death in patients with left ventricular ejection fraction (LVEF) <35% and wide QRS. CRT provides electromechanical resynchronization and improves LV systolic function. The induced LV reverse remodeling or near normalization in LVEF to ≥45% is associated with a significant reduction in the risk of subsequent life-threatening ventricular tachyarrhythmias (VTA). And at the time of replacement, the need for defibrillator back-up after an event-free first CRT-D service-life for patients with improved LVEF is a controversy question.

80% of Implantable Cardioverter Defibrillator (ICD) patients implanted for primary prevention do not experience VTA during the life-time of their first device.

So, regarding patients implanted with a CRT-D for primary prevention at the time of first implantation, the question is will they experience VTA after their device replacement by another CRT-D.

The objective of this study is to describe, in a population of patients who had a primary prevention ICD indication at first implantation of a CRT-D, the relevance defibrillator back-up after the replacement of the first CRT-D. For that, the rate of patients with at least one sustained VTA detected by the CRT-D or a conventional surface ECG will be assessed after the device replacement.

Furthermore, the association between the baseline characteristics of the CRT-D population after replacement and the risk of subsequent VTA will be explored after a minimum of two years FU.

Inclusion Criteria:

• Patient with primary prevention indication for defibrillation at the time of the first CRT-D implantation
• Patient implanted as first replacement by a CRT-D device (CRT-D by CRT-D)
• Lifetime of the previous CRT-D > 3 years
• Patient willing and able to comply with the protocol and who has provided written informed consent
• Patient whose medical situation is stable.

Exclusion Criteria:

• Patient with an ICD lead under advisory (e.g. Fidelis lead)
• Right or left ventricular leads exchange during CRT-D replacement
• Non functional atrial (except for patient with chronic AF) or right/left ventricular leads
• Life expectancy < 1 year
• Age < 18 years
• Pregnant woman or woman who plan to become pregnant during the trial
• Participation in another interventional clinical study

Patients initially implanted with a CRT-D (cardiac resynchronization therapy with defibrillator) device for primary prevention indication for defibrillation, requiring a device replacement by another CRT-D because of battery depletion