2. The creation of the 2006 system

In the 1990s, UNOS classified heart transplant recipients using a two tiered system [8]. Those patients who necessitated either ICU care with inotropic infusions, support with MCS, or an IABP were given the highest priority, Status 1. The remaining patients were listed as Status 2. In 1999, the system was reappraised to include a Status 1A, 1B, and 2. In that era, mortality following LVAD implant reaches 5–10% per week [9]. Therefore, patients could be listed as 1A with ≤30 days of LVAD support. Alternatively, patients with >30 days of support and a device related complication could also be listed as 1A. This policy was subsequently revised in 2002 to permit listing any LVAD patient for 30 days once the treating physician determined they were "clinically stable." Criteria for listing patients as 1A just prior to the most recent change are listed in Table 1.

Status 1B was created for waiting list candidates with less urgent need for cardiac transplantation such as candidates stably waiting at home or in the hospital requiring intravenous inotrope or LVAD support. Active patients who were stable at home on oral medications were listed as Status 2 (Table 1).

Other important changes included in the 2006 revisions to the US allocation system included: (1) the integration of the allocation of pediatric hearts, (2) the institution of Geographic proximity in determining organ preference, and (3) utilizing ABO compatibility in determining generating priority. After initial offers to waiting list candidates in local or Donor Service Area (DSA) served by an organ procurement organization (OPO), offers then progressed to successive 500 mile geographic zones. Preference was given to ABO identical and then ABO compatible recipients within each status category and allocation proceeded to candidates eligible to receive a heart from any blood type donor after allocation to all compatible blood types.


Table 1. Indications for listing status prior to 2017.

Deciding which donor graft should be offered to which recipient requires a balancing act of important clinical and ethical issues. One must balance those at highest risk of dying while waiting, who also have the highest risk of post-transplant death, compared with those with improved likelihood of post-transplant survival. The mortality associated with different subgroups evolves over time. For example,Morality followingMCS implantation has significantly decreased over the last decade; while the use of MCS and ECMO have simultaneously burgeoned. A similar issue is the compromise for geographic equity. Cold ischemia should be minimized. Local donors of the highest acuity are first offered donor hearts. Compromises must be made when deciding if a less

The goal of heart allocation policy has remained to provide appropriate organs to those patients who were the "best" candidates with the shortest expected survival given geographic constraints. Fundamental rules of current practice were initially formed from small US heart transplant centers. Such rules were entertained without any clinical or physiological basis, simply "because they sounded good" [7]. The United States Heart Allocation system has evolved from its formal inception as a basic two tiered, local plus three zone system in 1989 to a three-tiered urgency based heart allocation system in 1998 [8–10]. Further modification occurred in 2006, integrating

In the 1990s, UNOS classified heart transplant recipients using a two tiered system [8]. Those patients who necessitated either ICU care with inotropic infusions, support with MCS, or an IABP were given the highest priority, Status 1. The remaining patients were listed as Status 2. In 1999, the system was reappraised to include a Status 1A, 1B, and 2. In that era, mortality following LVAD implant reaches 5–10% per week [9]. Therefore, patients could be listed as 1A with ≤30 days of LVAD support. Alternatively, patients with >30 days of support and a device related complication could also be listed as 1A. This policy was subsequently revised in 2002 to permit listing any LVAD patient for 30 days once the treating physician determined they were "clinically stable."

Criteria for listing patients as 1A just prior to the most recent change are listed in Table 1.

Status 1B was created for waiting list candidates with less urgent need for cardiac transplantation such as candidates stably waiting at home or in the hospital requiring intravenous inotrope or LVAD support. Active patients who were stable at home on oral medications were

Other important changes included in the 2006 revisions to the US allocation system included: (1) the integration of the allocation of pediatric hearts, (2) the institution of Geographic proximity in determining organ preference, and (3) utilizing ABO compatibility in determining generating priority. After initial offers to waiting list candidates in local or Donor Service Area (DSA) served by an organ procurement organization (OPO), offers then progressed to successive 500 mile geographic zones. Preference was given to ABO identical and then ABO compatible recipients within each status category and allocation proceeded to candidates eligible to receive a heart from

acute patient should be offered a heart over a farther patient of higher acuity.

pediatric allocation and refining geographic ordering of heart offers.

any blood type donor after allocation to all compatible blood types.

2. The creation of the 2006 system

36 Heart Transplantation

listed as Status 2 (Table 1).

Patients with restrictive diseases such as amyloidosis or those adults with congenital heart disease relied on prioritization based on "exception criteria." For a given patient, a transplant center must elect to request for an exception from a given region through a review board. This mechanism created the potential for regional variability in patient status due to regional practices and organ availability with resultant unequal access to transplantation.
