Multivariate analysis of factors affecting waiting time to heart transplantation

Background. The growing clinical success of cardiac transplantation has resulted in a dramatic increase in the number of patients referred and subsequently listed for cardiac transplantation. Paradoxically, in the presence of a limited donor organ pool, such expansion has increased both the waiting time for transplantation and the number of patients dying while on the waiting list. Methods. We performed univariate and multivariate analyses of the waiting times of 301 patients listed for transplantation using a Cox proportional hazards model to evaluate the simultaneous effect of multiple variables on the waiting time of heart transplant candidates. Variables considered included age, sex, race, blood type, weight at listing, United Network for Organ Sharing (UNOS) status at listing, UNOS status at transplantation, and proportion of time on the waiting list as UNOS status 1. Results. The mean waiting time for patients ultimately having transplantation was 170.2 ± 206.0 days; the median waiting time was 103.5 days. Age, sex, weight, blood type, and percent of time as UNOS status 1 all had a significant impact on waiting time in the univariate analysis. By multivariate analysis, proportion of time as UNOS status 1, lower weight at listing, and blood type AB were all highly associated as predictors of a shorter waiting time. Weight at listing represented a continuous variable whose risk ratio for a shorter waiting time correlated in such a way that the risk of a longer waiting time increased 2.3 per 22.5-kg (50-pound) increase in weight. Blood types A and B, although associated with a shorter waiting time, correlated less strongly than the other three variables. Conclusions. Our findings from this multivariate analysis demonstrate that UNOS status, blood type, and weight were the variables that most strongly affected overall waiting time for transplantation. It is our hope to define more accurately a group of patients with both a high likelihood of a long waiting time and a prohibitive risk of death while on the waiting list, who therefore may benefit from surgical alternatives to transplantation.