The study is expected to be conducted at up to 20 centers located in the United States. Up to 400 subjects will be enrolled to yield up to 200 eligible subjects that meet screening criteria. This study will be conducted in subjects with an implanted, commercially available, Medtronic, CRT-D device. Each enrolled subject will be followed every 2 months from time of enrollment to end of the study.The study will end after the last enrolled subject completes the 12-month follow-up.