Data on clinical events (admission for MI/ACS, admission for CHF, diagnostic angiography, revascularization, ICD device revision) will be collected by medical record review. Patients will be followed for a minimum of ten years or until death, cardiac transplantation or ventricular assist device implantation. A patient who experiences an appropriate ICD firing will have been considered to meet the primary endpoint of the study but will continue to be followed, particularly for the development of adverse events. We will continue to follow and leverage this population as well as enroll additional patients who have ICDs in place and are undergoing elective PG replacement for end-of-life indicators. The aims of this proposal are: