Impact of ABO-incompatible listing on wait-list outcomes among infants listed for heart transplantation in the United States: a propensity analysis

Abstract

Background: The purported advantage of ABO-incompatible (ABO-I) listing is to reduce wait times and wait-list mortality among infants awaiting heart transplantation. We sought to describe recent trends in ABO-I listing for US infants and to determine the impact of ABO-I listing on wait times and wait-list mortality.

Methods and results: In this multicenter retrospective cohort study using Organ Procurement and Transplant Network data, infants<12 months of age listed for heart transplantation between 1999 and 2008 (n=1331) were analyzed. Infants listed for an ABO-I transplant were compared with a propensity score-matched cohort listed for an ABO-compatible transplant through the use of a Cox shared-frailty model. The primary end point was time to heart transplantation. The percentage of eligible infants listed for an ABO-I heart increased from 0% before 2002 to 53% in 2007 (P<0.001 for trend). Compared with infants listed exclusively for an ABO-compatible heart, infants with a primary ABO-I listing strategy (n=235) were more likely to be listed 1A, to have congenital heart disease and renal failure, and to require extracorporeal membrane oxygenation. For the propensity score-matched groups (n=197 matched pairs), there was no difference in wait-list mortality; however, infants with blood type O assigned an ABO-I listing strategy were more likely to undergo heart transplantation by 30 days (31% versus 16%; P=0.007) with a less pronounced effect for infants with other blood types.

Conclusions: The proportion of US infants listed for an ABO-I heart transplantation has risen dramatically in recent years but still appears to be preferentially used for sicker infant candidates. The ABO-I listing strategy is associated with a higher likelihood of transplantation within 30 days for infants with blood group O and may benefit a broader range of transplantation candidates.

Figure 1

US trends in ABO-I listing of infants <6 months of age (age at which infants are generally presumed immunologically eligible for ABO-I HT) awaiting HT by year (A) and by region (B).

Figure 2

Competing outcomes for propensity-matched infants awaiting HT using an ABO-C (A) vs ABO-I (B) listing strategy.

Figure 3

Observed vs. expected proportion of infants receiving an ABO-I HT. The expected probability of ABO-I HT was calculated as the product of the probability of transplantation and the probability of receiving an ABO-I organ conditional on being transplanted for each blood type.