The purpose of the Registry is to collect data on how Implantable Cardioverter Defibrillator (ICD) therapies and medications are being used by physicians to treat ventricular arrhythmias in order to better understand how to improve the clinical care of patients and effectiveness of ICD therapies.

Inclusion Criteria:

• Patients 18 years of age or older.
• Patients or legal guardians who are willing and able to sign a Permission for Access to and Use of Health Information in a Registry Form and, if required by an Institution's IRB, an Informed Consent.
• New or replacement implants of Medtronic market released single, dual or triple chamber ICDs including: GEM VR, GEM DR, GEM III AT, Marquis VR, Marquis DR, Maximo DR, Maximo VR, InSync ICD, InSync Marquis ICD and InSync II Marquis ICD.

Exclusion Criteria:

• Patients enrolled in a device study which effects programming and or treatment.