S-ICD® System IDE Clinical Study

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.