Impact of organ prioritization for immunologic sensitization and waiting times for heart transplantation

Background: The Canadian status 4S category prioritizes highly sensitized patients with a calculated panel reactive antibody (CPRA) > 80% awaiting heart transplantation. We examined the effect of sensitization and status 4S and developed a predictive model to estimate waiting time in Canada.

Methods: A retrospective review was performed of patients listed for heart transplant at the Ottawa Heart Institute and Toronto General Hospital (Ontario, Canada). We evaluated the association of CPRA and priority listing status on waiting time and post-transplant outcomes. Waiting time risk factor analysis was performed using a multivariable parametric accelerated failure time model with a Weibull distribution.

Results: Of 394 patients listed (75% male, 51 ± 12 years), 291 (74%) received a transplant and 33 (8%) died waiting. The cumulative incidence of transplant decreased across higher CPRA groups but was similar for moderately and highly sensitized groups: 67%, 70%, 50%, and 40% at 12 months for CPRA 0%, 1% to 50%, 51% to 80%, and > 80%, respectively (p = 0.020). Status 4S patients experienced longer waiting times compared with other high priority status 3.5 and 4 and had increased risk of death on the waiting list (p = 0.014). Over a median follow-up of 2.4 years (interquartile range, 1.2-4.1), rejection occurred in 64 sensitized patients (24%) compared with 24 non-sensitized patients (9%; p = 0.019), but there was no difference in survival, allograft dysfunction, or cardiac allograft vasculopathy. A model predicting transplant waiting time, including CPRA, blood group, priority listing status, age, and weight, was developed and showed adequate discrimination and calibration.

Conclusions: Waiting time to heart transplant is increased for highly and moderately sensitized patients, suggesting the need to reevaluate the CPRA > 80% threshold for status 4S prioritization in Canada. Extended waiting times, despite 4S prioritization, supports consideration of additional factors to CPRA in ensuring equitable organ access for sensitized patients.