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US Heart Allocation Policy: Current Issues and Possibilities for Fix


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Jon A. Kobashigawa, MD
Cedars-Sinai Heart Institute
Los Angeles, CA, USA
kobashigawaJ@cshs.org



US heart allocation policy has evolved considerably since the inception of the National Organ Transplant Act in 1984. An urgency-based system with concentric geographic zones was first adopted in 1988, with 2 priority statuses: Status 1, for all mechanical circulatory support (MCS) patients and those with inotropic dependency, and Status 2 for everyone else. Further modifications occurred in 1998 saw the introduction of a 3-tiered system, with Status 1A, the most urgent, intended for patients supported with MCS, mechanical ventilation, inotropic dependency with continuous hemodynamic monitoring, Status 1B for stable patients on ventricular assist devices (VADs) or inotrope infusions, and Status 2 for all others.

The current system, which was last modified in 2006, allows greater regional sharing of organs according to clinical urgency; thus, organs are now offered only to Status 1A/1B candidates locally (organ procurement area), then in the nearest concentric zone (500 mile radius) before being offered to Status 2 locally. Each policy change has sought to meet the government defined "Final Rule", which prescribes the difficult combination of equitable organ allocation (including across regions) while prioritizing according to objective severity of illness. Despite this, status 1A mortality in particular remains high [1].

Even with the most recent 2006 policy change, there remains regional heterogeneity in waiting times and number of transplants performed on higher urgency candidates. In particular, Region 1 of the US has demonstrated increased waiting times for status 1A patients [2], in part due to poor access to donors. In order to provide more equitable access, the Organ Procurement and Transplantation Network/United Network for Organ Sharing (OPTN/UNOS) Thoracic Committee is considering methods to enable broader regional sharing of hearts, either through the designation of geographical zones according to projected donor population, or greater priority for neighboring zone Status 1A patients over local Status 1B patients.

Since 2006, the widespread use of continuous-flow ventricular assist devices has prolonged survival and decreased mortality in waitlist patients [3], leading us to reconsider the urgency of transplanting stable VAD patients. The prolonged survival is reflected in the fact that waitlist numbers of Status 1A/1B patients have tripled since 2006 [1]. On the other hand, patients with VAD complications have been established to fare worse [4] and should remain highly prioritized.

Current policy development also seeks to assign higher priority to particular subgroups within Status 1A/1B that are at a disadvantage under the current system, with increased waitlist time and risk of mortality. These include those patients with restrictive cardiomyopathy [5], amyloidosis [6], congenital heart disease [7] and highly sensitized patients [8]. For highly sensitized patients, a uniformly standardized definition must be met, both in terms of unit of measurement (e.g. cPRA) and the method by which this measurement is obtained. For example, the Canadian definition of a highly sensitized patient is that of a patient possessing a panel reactive antibody (PRA) >80%, or PRA >20% with 3 prior positive crossmatches (in the setting of negative virtual or actual donor/recipient-specific crossmatch and appropriate size and blood-type of the prospective donor) [9].

How then, to be as fair as possible to all these subgroups? A heart allocation score, analogous to one used by our colleagues in lung transplantation, has been raised as a possibility. However, there are concerns about the length of time it would take to develop such a score, especially in a field that is so rapidly changing. In addition, there are fears that the data currently collected by the OPTN from transplant programs is incomplete and may lead to inappropriate scoring.

A multi-tiered system appears the most viable solution at present; one is currently in development by the OPTN/UNOS Heart Subcommittee, following the example set by our colleagues in the Eurotransplant countries, France, United Kingdom, and Canada. Such a system is overwhelmingly favored by centers across the United States [10], and would specify a clear prioritization level for each subgroup, reducing the need for status exceptions.

In summary, recent changes in the field of heart failure and transplantation have resulted in greater waitlist numbers, while status 1A mortality, although decreased, remains high. As it has done with each iteration, US heart allocation policy must inevitably continue to adapt to comply with the "Final Rule". Future policy must also address ethical issues such as multiple listing and retransplantation. For now, a further-tiered system with modified geographic zones appears to be the answer. ■

Disclosure Statement: Jon Kobashigawa, MD, is scientific medical advisor to TransMedics and Novartis, and discloses research grants and research support from Novartis, CareDx Inc and TransMedics.


References:

  1. Meyer D, Rogers J, Edwards L, et al. The future direction of the heart allocation system in the United States. Am J Transplant. 2014 [In Press].
  2. Schulze PC, Clerkin K, Kitada S, et al. Regional Differences in Recipient Waitlist Time and Pre-and Post-Transplant Mortality Following the 2006 UNOS Policy Changes in the Donor Heart Allocation Algorithm. JACC Heart Fail. 2014;2(2):166-177.
  3. Stewart GC, Givertz MM. Mechanical circulatory support for advanced heart failure: patients and technology in evolution. Circulation. 2012; 125(10):1304-15.
  4. Healy AH, Baird BC, Drakos SG, et al. Impact of ventricular assist device complications on posttransplant survival: an analysis of the United network of organ sharing database. Ann Thorac Surg. 2013;95(3):870-5.
  5. Singh TP, Milliren CE, Almond CS, et al. Survival benefit from transplantation in patients listed for heart transplantation in the United States. J Am Coll Cardiol. 2014;63(12):1169-78.
  6. Estep JD, Bhimaraj A, Cordero-Reyes AM, et al. Heart transplantation and end-stage cardiac amyloidosis: a review and approach to evaluation and management. Methodist Debakey Cardiovasc J. 2012;8(3):8-16.
  7. Kaufman BD, Shaddy RE. Immunologic considerations in heart transplantation for congenital heart disease.Curr Cardiol Rev. 2011;7(2):67-71.
  8. Stehlik J, Islam N, Hurst D, et al. Utility of virtual crossmatch in sensitized patients awaiting heart transplantation. J Heart Lung Transplant. 2009;28(11):1129-34.
  9. Canadian Cardiac Transplantation Network Status Criteria http://www.heartcentre.ca/documents/ListingStatusforCardiacTransplantationJan192010.pdf Accessed Sep 18, 2014.
  10. Kobashigawa J, Johnson M, Rogers J, et al. Report from a Forum on US Heart Allocation Policy. Am J Transplant. 2014 [In Press].



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