Inclusion Criteria:  Age ≥ 18 years Informed, written consent Status post ICD implantation, including CRT-D Battery in EOL, ERM or ERI, ERT with indication for elective ICD generator replacement or patients presenting for electrical cardioversion for atrial arrhythmia.  Exclusion Criteria:  Age < 18 years Pregnancy Patients under guardianship or with mental disorders/disabilities Recent adequate and successful ICD shock therapy (within the past 12 months) Patients in the cardioversion arm with low battery (<1 year to ERI/RRT) Patients with intracardiac thrombus Participation in any other investigational study that may interfere with interpretation of the study and registry results Indications of an already compromised RV lead (Pacing impedance <200 or >2000 Ohm, Pacing threshold >5V/0.4ms, RV Sensing <4mV, HV impedance >80, presence of lead noise) Systems with recalled leads or leads known to have an elevated failure risk: Riata™ and Riata ST™ (St. Jude Medical, St. Paul, Minnesota, USA), Sprint Fidelis™ (Medtronic, Minneapolis, Minnesota, USA)