Effect of the New Donor Heart Allocation System on Waitlist Mortality among All Candidates Listed with Mechanical Circulatory Support

Abstract

<h3>Purpose</h3> To evaluate the effect of the new donor heart allocation system on candidate waitlist morbidity and mortality in those listed with mechanical circulatory support (MCS). <h3>Methods</h3> The United Network for Organ Sharing (UNOS) database was queried for adults (≥18) listed for heart transplantation between October 2015 and September 2019. Candidates who were listed with any form of mechanical circulatory support (MCS) (intraaortic balloon pump (IABP), extracorporeal membrane oxygenation (ECMO), durable left ventricular assist device (LVAD), and others) were included. Candidates who did not have MCS at the time of listing or were listed between October 2017 and October 2018, were excluded to prevent inclusion of candidates who were listed under the old system and transplanted under the new system. <h3>Results</h3> Of the 4175 candidates included in this study, 2784 (66.7%) and 1391 (33.3%) were listed under the old and new system, respectively. Mean age and body mass index were similar, although candidates were slightly more likely to be female under the new system (23.0 vs. 20.4%, <i>p</i>=0.05). The proportion of inotrope-dependent candidates was significantly higher under the new system (24.4 vs. 18.5%, <i>p</i><0.01) although ventilator dependence did not differ significantly (4.0 vs. 3.6%, <i>p</i>=0.52). The distribution of MCS present at listing changed significantly as follows: IABP: +14.5%; ECMO: +2.1%; durable LVAD: -15.9%; and other: -0.7% (<i>p</i><0.01). Candidates listed under the new allocation were significantly less likely to experience death or worsening clinical condition on the waitlist (adjusted HR 0.61, 95% CI 0.47-0.78, <i>p</i><0.01) (Figure). <h3>Conclusion</h3> Candidates listed with MCS under the new donor heart allocation system experience less waitlist mortality. With regard to all candidates supported by MCS, the new system has achieved its goal.