This clinical study is designed to evaluate the safety and effectiveness of the subcutaneous implantable defibrillator (S-ICD) System.

This clinical study is a prospective, non-randomized, multicenter clinical study without a control group conducted in the United States, Europe, and New Zealand.

Patients meeting eligibility criteria for implanting an S-ICD System will be enrolled in this clinical study, implanted with an S-ICD System, and followed prior to hospital discharge, and post-implant at 30 days, 90 days, and 180 days. After the 180-day post-implant follow-up visit, patients will continue to be followed semi-annually until study closure.

Eligible patients enrolled in this clinical study may also participate in the chronic conversion sub-study.

The safety endpoint will be evaluated through the use of a 180-day S-ICD System complication-free rate. The effectiveness endpoint will be evaluated using an induced ventricular fibrillation (VF) conversion efficacy rate. Spontaneous episodes and chronic conversion testing data will be evaluated using descriptive statistics to provide additional data supporting the continued chronic performance of the S-ICD System.

Inclusion Criteria:

• For patients without an existing transvenous device

  • Patient meets Class I, Class IIa or Class IIb indications/recommendations for ICD implantation per the current published guidelines at the time of enrollment

• For patients with an existing transvenous device

  • Patient requires replacement or revision of an existing implanted transvenous ICD system

• Age is ≥ 18 years

• An appropriate pre-operative ECG per template provided

Exclusion Criteria:

• Any condition which precludes the subject's ability to comply with the study requirements, including completion of the study.
• Females who are pregnant or lactating and pre-menopausal women who are unwilling to use adequate birth control for the duration of the study.
• Participation in any other investigational study without prior written consent from the study sponsor.
• Patients with a serious medical condition and life expectancy of less than one year.
• Patients with documented spontaneous and frequently recurring VT that is reliably terminated with anti-tachycardia pacing, unless the patient is not a candidate for a transvenous ICD system.
• Patients with existing epicardial patches or subcutaneous electrodes in the left thoracic quadrant.
• Patients with unipolar pacemakers or implanted devices that revert to unipolar pacing.
• Patients with severely impaired kidney function as measured by a Cockcroft-Gault Glomerular Filtration Rate (GFR) with an estimated GFR ≤ 29.