 Patients are enrolled in the registry up to 180 days post implantation of an Optim lead. Patients with OptimTM ICD leads and QuicksiteQuickflexQuickflex μQuartet LV leads are followed indefinitely following enrollment. Patients with other Optim leads are followed for a period of 60 months after OptimTM lead implantation. The follow-up plan for this registry is based on the established follow-up practices currently used by each of the respective registry centers. Patients are followed according to the centers standard follow-up schedule. 