Impact of the United Network for Organ Sharing allocation criteria changes on temporary mechanical circulatory support use as a bridge to transplant

Temporary mechanical circulatory support (tMCS) devices such as intra-aortic balloon pumps, veno-arterial extracorporeal membrane oxygenation, and percutaneous ventricular assist devices, play a major role in supporting patients with end-stage heart failure and bridging them to transplant. In 2018, the United Network for Organ Sharing heart allocation criteria was modified by increasing the number of statuses in the heart transplant waitlist to differentiate and favor the sickest patients awaiting transplantation. Within this new system, patients with tMCS devices receive the highest priority statuses. While the 2018 allocation system has reduced waitlist times and mortality for the highest-priority patients, some studies have shown a concomitant rise in the utilization of tMCS devices as bridge to transplant after its enaction. In this narrative review, we describe these changes in tMCS utilization and provide insights on how the upcoming creation of a continuous distribution allocation system may further impact these trends.