In the United States, the allocation of donor organs is accomplished under the supervision of the United Network of Organ Sharing (UNOS), a private organization under contract to the federal government. The United States is divided geographically into 11 regions for donor heart allocation. Under UNOS policy, thoracic organs are distributed on the basis of blood type, medical urgency, and time on the waiting list. The physiologic limit of approximately 4 hours of ischemic out-of-body time for hearts precludes a national sharing of donor hearts. Currently, the highest priority for patients to receive donor organs is assigned according to the severity of illness. Each candidate awaiting heart transplantation is assigned a status corresponding to the medical urgency of the candidate who is to receive a heart transplant. For a candidate who is 18 years of age or older at the time of listing, medical urgency is assigned as follows (UNOS policy …