IMR Press / RCM / Volume 22 / Issue 1 / DOI: 10.31083/j.rcm.2021.01.230
Open Access Review
Impact of mechanical circulatory support on donor heart allocation: past, present, and future
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1 Division of Cardiac Surgery, Department of Surgery, Thomas Jefferson University, 19107 Philadelphia, USA

Academic Editor: Peter A. McCullough

Rev. Cardiovasc. Med. 2021, 22(1), 25–32; https://doi.org/10.31083/j.rcm.2021.01.230
Submitted: 28 October 2020 | Revised: 29 November 2020 | Accepted: 1 December 2020 | Published: 30 March 2021
Abstract

The United Network for Organ Sharing (UNOS) recently revised its heart allocation policy to address numerous shortcomings of the previous system. Implemented in 2018, the changes sought to reduce waiting list mortality, clearly define urgency status based on objective physiologic variables, decrease exemption requests, and introduce geographic modifications to ensure organ distribution favors the highest urgency candidates. In large part, UNOS policy revisions were driven by the growing use of continuous flow left ventricular assist devices (CF-LVADs) and the relevant device complications that led to an unacceptably high number of status exemptions. The new 6-tiered system assigns a comparatively lower urgency status to patients supported on CF-LVADs and higher urgency to patients supported on short-term mechanical circulatory assist (MCA) such as extracorporeal membrane oxygenation (ECMO) and intraaortic balloon pump (IABP) counterpulsation. LVAD use as bridge to transplant (BTT) therapy increased steadily throughout the preceding decade due to technological improvements and increased physician familiarity, but the recent policy changes introduce incentives for physicians to withhold this life-saving therapy in order to achieve higher urgency status for their patients. This paper will explore the technological evolution of MCA and the pertinent clinical trials that have led to their FDA approval as BTT and destination therapy. A review of the inception and development of the donor allocation system will be provided before examining available post-policy outcome data. Finally, we will highlight successes and shortcomings of the implemented changes before commenting on areas to potentially expand upon the existing policy.

Keywords
Ventricular assist
Mechanical circulatory assistt
UNOS heart allocation
LVAD
MCA
Destination therapy
Bridge-to-transplant
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