Ischemic Time Greater Than Four Hours is Associated with Increased Mortality among Candidates Listed and Transplanted under the New Donor Heart Allocation System

Abstract

<h3>Purpose</h3> Wider regional sharing of donor hearts under the new allocation system has led to significantly longer ischemic times (IT). Prior reports suggest longer IT increase the risk of post-heart transplantation (HTx) mortality. We sought to determine the effect of IT on HTx survival under the new allocation system. <h3>Methods</h3> The United Network for Organ Sharing (UNOS) database was queried for all candidates listed and transplanted from October 2018 to March 2020. Recipients were stratified into quartiles based on organ IT. Univariate analysis was performed using the Kaplan-Meier method. The adjusted association between IT and post-HTx survival was assessed using Cox proportional hazards models. <h3>Results</h3> A total of 2696 HTx recipients were included in this study. Median ischemic time was 3.5 hours (interquartile range 2.8-4.0). 180-day post-HTx survival was 94.4% for recipients with IT <2.8 hours (quartile 1), 93.5% for IT between 2.8 and 3.5 hours (quartile 2), 93.6% for IT between 3.5 and 4.0 hours (quartile 3), and 91.4% for IT >4 hours (quartile 4) (log-rank <i>p</i>=0.15) (Figure 1). Compared to quartile 1, quartiles 2 and 3 achieved similar post-HTx survival (quartile 2: aHR 1.21, 95% CI 0.78-1.88, <i>p</i>=0.41; quartile 3: aHR 1.24, 95% CI 0.80-1.93, <i>p</i>=0.337), although hazard of death was significantly higher in quartile 4 (aHR 1.55, 95% CI 1.02-2.35, <i>p</i>=0.04). <h3>Conclusion</h3> HTx recipients with IT greater than 4 hours may be at higher risk of mortality under the new donor heart allocation system. Offers with longer IT require careful consideration for acceptance.