| Summary: | 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.
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