Outpatient inotropic therapy in heart transplant candidates: should its use influence waiting list priority status?

The use of outpatient intravenous inotropic therapy in heart transplant candidates is contentious. In addition to concerns about morbidity and mortality rates, the current United Network for Organ Sharing (UNOS) heart allocation system presently grants no waiting list priority status benefit to candidates who receive intravenous inotropic therapy in the outpatient setting (UNOS status 2), whereas identical therapy given in an intensive care unit setting does increase priority status (UNOS status 1). The goal of this study was to determine whether an increase in UNOS waiting list priority status is justified in heart transplant candidates receiving outpatient intravenous inotropic therapy by comparing the waiting list mortality of UNOS status 2 candidates on such therapy with that of UNOS status 2 candidates maintained on oral heart failure agents alone.

This is a retrospective analysis of the pretransplantation outcomes of heart transplant candidates initially listed as UNOS status 2, comparing 29 candidates receiving intravenous outpatient inotropic therapy (group 1) to 109 candidates maintained on oral heart failure agents alone (group 2).

The waiting list mortality was not significantly different between the two groups (group 1=7% vs group 2=20%, p=.18); however, group 1 patients had greater morbidity rates while awaiting transplantation than group 2 patients. A greater percentage of group 1 than group 2 patients clinically deteriorated to UNOS status 1 while awaiting transplantation (45% vs 11%), resulting in more group 1 patients undergoing transplantation overall, (59% vs 33%, p=.01) and more group 1 than group 2 patients undergoing transplantation at a higher priority status, UNOS status 1 (76% vs 33%, p=.003). Group 1 patients had more pretransplantation heart failure admissions (1.2 vs 0.6 admissions/total waiting period, p=.02) and longer hospital stays (26+/-39 vs 8.8+/-16 days, p=.03), spent a greater percentage of their total waiting time hospitalized (7% vs 2%, p=.003), and were more likely than group 2 patients to receive intravenous inotropic therapy during hospitalization (70% vs 25%, p=.001).

This study suggests that heart transplant candidates who require maintenance outpatient intravenous inotropic therapy represent a subgroup of UNOS status 2 candidates with greater waiting list morbidity, but no greater waiting list mortality than candidates who can be maintained on oral heart failure agents alone. However, the current UNOS heart allocation system provides for this increased illness acuity by assigning a higher priority status when necessary. A larger, prospective study is necessary to determine whether a true difference in waiting list mortality rates exists and if an increase in priority status is justified for UNOS status 2 candidates requiring maintenance inotropic therapy.