Temporary mechanical circulatory support: Devices, outcomes, and future directions

Faced with a chronic donor shortage, clinicians and regulators both struggle to develop allocation systems which balance the challenges of waitlist mortality and donor availability. Most organ allocation systems across the globe have prioritized transplantation of patients supported on temporary mechanical circulatory support (tMCS) with regional variations. There are concerns that this approach might not produce optimal outcomes and is not without major drawbacks including lack of strict criteria for tMCS as bridge strategy, choice of optimal devices and wait time on tMCS. The current manuscript outlines characteristics and limitations of current devices used for tMCS as a bridging strategy. The outcomes of transplantation following device support are evolving and are highlighted as well. Lastly, the allocation schema for heart transplantation in various countries are reviewed and compared. Additionally, we propose key principles to guide changes in next iteration of donor allocation systems to balance waitlist mortality with optimal post-transplant outcomes. First, allocation should be on the basis of calculated scores which take into account a variety of pre-and post-transplant factors and cannot be easily manipulate by choice of support therapy. Next, time at high urgency statuses should be time-limited with strict criteria for renewal. Emphasis should be placed on the further refinement of durable mechanical support therapies. Patients on durable support need a pathway to qualify for transplantation in the absence of complications, and lastly, peer review of exceptions to organ allocation policy are critically important to ensure the appropriate allocation of donor organs.