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The new tiered allocation system for heart transplantation in the United States—a Faustian bargain

2019; Elsevier BV; Volume: 38; Issue: 8 Linguagem: Inglês

10.1016/j.healun.2019.05.010

1557-3117

A. Bernhardt,

Cardiac Structural Anomalies and Repair

See Related Article, page 858In the early 19th century, the German scientist and poet Johann Wolfgang von Goethe published his celebrated drama entitled Faust, A Tragedy. In this drama, Faust, frustrated by his inability to gain infinite knowledge, strikes a deal with the demon, Mephistopheles. In doing so, while Faust is pursuing his ambitions, tragedy befalls his beloved ones, which leaves him unfulfilled. Such a Faustian bargain is an example of intended good that results in less ideal outcomes. See Related Article, page 858 Recently, United Network of Organ Sharing (UNOS) changed the heart allocation policy in the United States.1UNOS/OPTNAdult Heart Allocation Changes.2018Google Scholar More categories have been introduced to better stratify the urgency for recipients of heart transplants. The idea behind these changes was to decrease mortality rates for recipients on the waiting list, while providing an opportunity to others for receiving organs. Concerned that the former 3-tier system did not prioritize enough urgency for these patients, UNOS has implemented a 6-tiered system with more specific guidelines for each tier. The new allocation system assigns patients on extracorporeal membrane oxygenation (ECMO) devices the highest priority. It is a hope that waitlist mortality may be reduced by these changes. However, these changes may result in worse aggregate outcomes after transplant. In a different approach to enhance organ allocation in EUROTRANSPLANT countries, a cardiac allocation score was developed and then revised in Germany.2Smits JM de Vries E De Pauw M et al.Is it time for a cardiac allocation score? First results from the Eurotransplant pilot study on a survival benefit-based heart allocation.J Heart Lung Transplant. 2013; 32: 873-880https://doi.org/10.1016/j.healun.2013.03.015Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar, 3Bernhardt AM Rahmel A Reichenspurner H The unsolved problem of organ allocation in times of organ shortage: the German solution?.J Heart Lung Transplant. 2013; 32: 1049-1051https://doi.org/10.1016/j.healun.2013.08.012Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar The idea behind the cardiac allocation score, similar to the established lung allocation score in lung transplantation, is to provide a happy medium between risk and benefit. Risk of mortality on the waiting list is measured based on the Seattle heart failure model and post-transplant outcomes are predicted by the Index for Mortality Prediction After Cardiac Transplantation score (IMPACT score). Patients who have a high urgency and a high chance of a successful post-transplant outcome will have the highest cardiac allocation score and are assigned the highest priority in the allocation process. The idea of a benefit score was bolstered by the observation that after establishment of the lung allocation score, waitlist mortality went down whereas post-transplant outcomes remained stable.4Smits JM Nossent G Evrard P et al.Lung allocation score: The Eurotransplant model versus the revised US model—A cross-sectional study.Transpl Int. 2018; 31: 930-937Google Scholar Durable ventricular assist devices are now seen as a viable, long-term alternative to transplant, at least in the first few years after implantation. Therefore, stable patients with ventricular assist device (VAD) without complications now are moved to a lower tier in the new US allocation system. This change reflects the technical and clinical improvements in outcomes in recent years, reaching a 2-year outcome exceeding 80% with current devices.5McGee E Danter M Strueber M et al.Evaluation of a lateral thoracotomy implant approach for a centrifugal-flow left ventricular assist device: The LATERAL clinical trial.J Heart Lung Transplant. 2019; 38: 344-351https://doi.org/10.1016/j.healun.2019.02.002Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar, 6Mehra MR Uriel N Naka Y et al.A fully magnetically levitated left ventricular assist device — Final Report.N Engl J Med. 2019; 380: 1618-1627https://doi.org/10.1056/NEJMoa1900486Crossref PubMed Scopus (580) Google Scholar As a result, these patients have less pressing needs for donor hearts than they did a decade ago. A change in the allocation protocols that enhances the priority given to patients on ECMO alters the incentive to use such devices. In the case that transplant candidates acutely decompensate and are in need of mechanical circulatory support devices, the transplant program has to decide if a short-term device or a durable device should be implanted. There is a risk that administrative and political reasons—and not primarily medical reasons—may influence the decision for the device. Registry data shows that heart transplant outcomes in patients who have had durable left ventricular assist device (LVAD) therapy are comparable with those without durable mechanical circulatory support.7Khush KK Cherikh WS Chambers DC et al.The International Thoracic Organ Transplant Registry of the International. Society for Heart and Lung Transplantation: Thirty-fifth adult heart transplantation Report—2018; focus theme: Multiorgan transplantation.J Heart Lung Transplant. 2018; 37: 1155-1168https://doi.org/10.1016/j.healun.2018.07.022Abstract Full Text Full Text PDF PubMed Scopus (289) Google Scholar However, those patients who have had transplants after ECMO therapy have a lower survival compared to patients with other bridging treatments before transplantation. This is an important finding because not only is there a recipient who is at risk of dying, but there is also a recipient on the waitlist who does not receive a donor heart in a timely manner. A study by Yin and colleagues8Yin MY Wever-Pinzon O Mehra MR et al.Post-transplant outcome in patients bridged to transplant with temporary mechanical circulatory support devices [e-pub ahead of print].J Heart Lung Transplant. 2019; 38: 858-869https://doi.org/10.1016/j.healun.2019.04.003Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar focuses on patients with temporary mechanical circulatory support compared with durable left ventricular assist devices. In this study on heart transplantation after short-term device treatment, the concerns are strengthened in that outcomes are lower compared with other bridging options and therefore, the authors develop a risk calculator to define the magnitude of outcome gaps that may be expected. However, the analysis is challenged by the small sample size of patients bridged by a temporary device, and such a calculator will need to be refined with more robust data in the future, and therefore, may not be ready for widespread use at this time. Presently, although the number of patients who have had transplants after short-term mechanical circulatory support is low, it is likely that the numbers of short-term devices implanted will be increasing under the new allocation system. The authors have tried to identify risk factors for dismal outcomes; however, unless these findings are confirmed in larger observations of transplants after temporary, short-term device therapy, results should neither be overinterpreted nor considered definitive in any way. Furthermore, not all temporary, short-term devices are the same. Cannula-based systems such as ECMO and CentriMag (Abbott, Abbott Park, IL), with and without an oxygenator, have a different risk profile than microaxial pumps. A partial-support device should also not be compared with a full-support device.9Werdan K Gielen S Ebelt H Hochman JS Mechanical circulatory support in cardiogenic shock.Eur Heart J. 2014; 35: 156-167https://doi.org/10.1093/eurheartj/eht248Crossref PubMed Scopus (309) Google Scholar Recently, the Impella 5.5 (ABIOMED, Danvers, MA) has been introduced in Germany after CE approval for 30 days. It was designed for axillary approach and allows full-support while the patient can be ambulated.10Bernhardt AM Hakmi S Sinning C Lubos E Reichenspurner H A newly developed transaortic axial flow ventricular assist device: Early clinical experience.J Heart Lung Transplant. 2019; 38: 466-467https://doi.org/10.1016/j.healun.2018.09.022Abstract Full Text Full Text PDF Scopus (11) Google Scholar Once introduced in the United States, such devices may have beneficial outcomes compared with ECMO therapy after transplantation but also should be considered for lower adverse events and mortality rates during short-term device therapy on the waiting list. Waitlist and transplant outcomes have to be evaluated and adjusted if needed in the near future. Transplant and mechanical circulatory support programs are encouraged to make the decision of device and treatment strategy based on medical reasons, expected survival on mechanical circulatory support, and expected waiting times based on the allocation rules. By considering these aspects, this may prevent the Faustian bargain of an intentional good ending in a tragedy. Alexander M. Bernhardt, MD has received honoraria, consultancy fees, and/or research support from Abbott, Abiomed, Medtronic, Novartis, and Orion Pharma.