Boston Scientific Post Market Subcutaneous-Implantable Cardioverter Defibrillator (S-ICD) Registry

Main study: Inclusion Criteria 1. Age \>/= 18yrs 2. Eligible for implantation of an S-ICD system per local clinical guidelines or currently implanted with an S-ICD system (Software (SW) version 1.59.0 or later) 3. Willing and able to provide written informed consent or have informed consent as provided by a legal representative Exclusion Criteria: 1. Participation in any other investigational study that may interfere with interpretation of the Registry results 2. Incessant ventricular tachycardia and/or spontaneous, frequently recurring ventricular tachycardia that is reliably terminated with anti-tachycardia pacing 3. Patients with unipolar pacemakers or implanted devices that revert to unipolar pacing Extension Phase Sub-study: Inclusion Criteria 1. Subjects who are actively enrolled in the EFFORTLESS S-ICD Registry OR Subjects who completed the 5-year follow-up in the EFFORTLESS S-ICD Registry. All clinical events, spontaneous and induced episode data and system replacement or revision data since the last EFFORTLESS S-ICD Annual Follow-Up of the main study must be available in medical files or equivalent. 2. Subjects who are actively implanted with an S-ICD pulse generator (SQ-RX, EMBLEM or EMBLEM MRI) and an S-ICD electrode (Q-TRAK or EMBLEM) or any other future commercial available versions 3. Willing and able to provide written informed consent or have informed consent as provided by a legal representative and willing to participate in all testing and follow-ups as described the Sub-Study protocol 4. Age 18 or above, and of legal age to give informed consent specific to national laws Exclusion Criteria 1. Subjects with device replacement from the S-ICD to a transvenous ICD 2. Subjects with unipolar pacemakers or implanted devices that revert to unipolar pacing 3. Subjects that are participating in any other investigational study that may interfere with interpretation of the Registry results, without the written approval of Boston Scientific