Modeling distribution of donor hearts to maximize early candidate survival

Abstract

Background: Priority for cardiac transplantation should reflect the relative waiting list mortality and operative mortality of outpatient candidates and critical candidates.

Methods and results: To determine how to distribute donor hearts for maximal overall survival, a Markov model of eight states was constructed from current statistics for outpatient sudden death, deterioration to critical status, operative mortality for outpatients, and operative mortality for critical candidates. Because the fraction of hearts offered to critical candidates varied, expected survival at 1 year was calculated. To determine the factors most critical in determining priority policy, current conditions were then varied over a fourfold range. Priority for critical candidates maximized overall candidate survival (with and without transplantation), increasing 1-year survival to 78% compared with 66% if hearts were offered only to outpatients. The benefit of giving priority to critical patients persisted when current group mortality rates were individually halved or doubled because these rates were still small compared with the 100% expected mortality of critical patients without transplantation. If the outpatient sudden death rate and the operative mortality for critical patients were doubled simultaneously, however, there was a slight negative impact on survival if critical candidates received priority. Regardless of changes in subgroup outcomes, the distribution of donor hearts had a relatively modest impact on survival because of the large excess of candidates.

Conclusions: Critical candidates for transplantation should continue to receive priority even if their operative mortality increases above current levels. However, postoperative outcomes must be assessed in relation to changing pretransplantation risks. Distribution of donor hearts will be most beneficial when it is possible to identify the waiting patients at greatest risk for sudden death and deterioration without transplantation.