Beyond Categorical Tiers: Improving Measurement of Medical Urgency as the Foundation for Heart Allocation Reform.
The United States heart allocation system prioritizes transplant candidates using therapy-based categorical urgency tiers that measure treatment decisions rather than biological risk. This miscalibration is associated with observable downstream issues: status exception rates exceeding 40% of adult listings, systematic escalation of temporary mechanical circulatory support in hemodynamically stable candidates, missed opportunities for myocardial recovery, and structural inequities in access. This review argues that meaningful reform requires a sequenced agenda: developing validated continuous urgency scores grounded in objective biological variables for both adult and pediatric candidates, reforming the exception process through standardized prospectively applied criteria, and building a new allocation policy using accurate inputs.