DISCOVERY: Diagnostic Data and Genetic Polymorphisms in ICD Patients.

Inclusion Criteria: * Implantation of a market approved Medtronic Dual-chamber ICD with long term clinical trends Cardiac Compass, * Subjects requiring the implantation of an ICD for primary prevention according to the current AHA/ACC/ESC guidelines, * Subject able to comply with the Clinical InvestigationPlan, * Subject is expected to remain available for follow-up visits, * Subject has signed the informed consent form within 10 days of implant, * The system implanted for this study is the first ICD implant for patient. Exclusion Criteria: * Women who are pregnant, or women of childbearing potential not on a reliable form of birth control, * Subject is enrolled in a concurrent study that may confound the results of this study, * Subject has a life expectancy less than two years, * Subject is post heart transplant or awaiting heart transplantation, * Subject is anticipated to demonstrate poor compliance, * Subjects with syndromes known to be associated with ion channel pathologies such as: * Long- or short-QT Syndrome * Brugada Syndrome * Catecholaminergic Polymorphic Ventricular Tachycardia (CPTV ).