All data will be entered into INTERMACS® through their web-based data entry system. Complete documentation and the Site User's Guide are contained at the data entry website (www.intermacs.org). INTERMACS (the Interagency Registry of Mechanical Assisted Circulatory Support) was formed as a partnership between the National Heart Lung, and Blood Institute (NHLBI), the FDA, Centers for Medicare and Medicaid Services (CMS), participating hospitals and industry (reference 7.2). It is the main MCS registry in the United States. In addition to its primary purpose, the validated database used by INTERMACS is also being made available as a service to other studies of mechanical circulatory support devices such as the BeneMACs study.