 - Legally utilized MCSD implanted on or after March 1, 2006; every consented patient who receives an eligible MCSD at a participating center will be enrolled, regardless of reason i.e., bridge-to-recovery, bridge-to-alternative bridge, bridge-to-clinical improvement for transplant eligibility, bridge-to-transplant, destination therapy. Beginning June 1, 2014, and with lnstitutional Review Board approval, participating sites may enroll patients under a waiver of informed consent and authorization. 