Outcomes of Status 2 Listing for Heart Transplantation by Qualifying Metric

Purpose: UNOS heart allocation allows exceptions to elevate allocation status for patients with medical urgency. Policy changes in 2018 aimed to reduce the number of Status 2 listings by exception1,2. The aim was to compare outcomes of patients with Status 2 exception to those qualifying for Status 2 with invasive devices.

Methods: Patients awaiting and undergoing heart transplantation (HT) in the current era (following October 18, 2018) were identified in the United Network for Organ Sharing registry. Patients were included for analysis if they qualified for Status 2 allocation at any time in the waitlist period. Patients < 18 years of age and those listed for or undergoing multiorgan transplant were excluded. Patients were grouped by the qualification criterion met for Status 2 allocation: IABP, percutaneous/endovascular device, or exception. Waitlist outcomes were HT and a competing outcome of death or deterioration requiring waitlist inactivation. Waitlist outcomes were evaluated using time since waitlist activation and time since Status 2 qualification. Cumulative incidence functions and competing-risks regression were used to model waitlist outcomes. Unadjusted 1-year post-transplant mortality was estimated using Kaplan-Meier analysis and compared using log-rank tests. Cox regression was used to estimate the risk-adjusted hazards for 1-year post-transplant mortality for Status 2 qualification criterions.

Results: Among 7,153 Status 2 waitlist candidates, 3,001 (42.0%) qualified for IABP, 820 (11.5%) for percutaneous/endovascular device, and 2,813 (39.3%) by exception. HT candidates who were Status 2 by exception were more likely to have congenital heart disease and restrictive or hypertrophic cardiomyopathy compared to those with IABP or percutaneous/endovascular devices (Table). On unadjusted analysis, HT candidates who qualified by exception were significantly less likely to undergo HT compared to those with IABP (Figure). Risk for waitlist death or delisting was not significantly different for patients qualifying for exception compared to other Status 2 patients. After risk adjustment, exception patients were less likely to undergo HT (HR 0.92, 95% CI [0.87-0.98], p=0.007) compared to patients with IABP with no significant difference in risk for waitlist death/deterioration compared to other Status 2 patients. Among patients who underwent HT, those listed by exception had significantly worse unadjusted 1-year survival compared to those with IABP and percutaneous/endovascular devices (89.4 vs 93.4 vs 94.4%, log-rank p< 0.001). After risk-adjustment, patients listed by exception had a significantly elevated risk for 1-year mortality compared to those with IABP (HR 1.52, 95% CI [1.23-1.88], p< 0.001) and those with percutaneous/endovascular devices (HR 2.02, 95% CI [1.32-3.11], p=0.001).

Conclusion: Exception requests comprise a substantial portion of Status 2 qualifications following the allocation policy change. Though not associated with an elevated risk for waitlist death or delisting, Status 2 qualification by exception independently predicts 1-year post-HT mortality. These findings may be of utility both in reappraisal of the allocation system and in patient risk stratification.

Identify the source of the funding for this research project: None