Background: Cold static storage (CSS) of hearts is limited to 6 hours from procurement to implantation. CSS lacks objective assessment of heart function prior to transplantation and prolonged CSS times induces oxidative phosphorylation, fatty acid metabolism pathways, and cell death; effects associated with primary graft dysfunction (PGD) post-transplantation. There have been attempts to prolong the preservation time to 12 hours experimentally using several perfusion methods. However, routinely successful normothermic ex vivo heart perfusion (NEVHP) for days would allow evaluation of organ function, organ treatment/recovery, near perfect matching, and making organ transplantation an elective procedure. Prolonged (>24hr) NEVHP could be used for gene therapy, immunomodulation, study and treatment of diseases, pharmacology, and physiology in isolated organs. We have previously demonstrated routinely successful NEVHP for 3 days using blood perfusate combined with plasma cross-circulation of the perfusate with a live animal. We determined that the critical “dose” of plasma exchange is 1mL/hr per gram of heart weight. Then we demonstrated successful 24hr NEVHP using plasma exchange without a paracorporeal animal. This study employs a novel perfusion protocol and system of NEVHP for the resuscitation and evaluation of hearts after 12 and 24h of CSS followed by transplantation.

Methods: Therteen (n=13) consecutive piglet hearts were procured from anesthetized pig using clinical protocols, flushed with cold UW solution, and stored in iced UW solution for 12 hours (n=5) and 24 hours (n=8) at 5°C. They were insturmented for NEVHP and perfused with 37°C blood-based perfusate at 0.7-1.0 mL/min per gram of cardiac tissue for 8 hours. The perfusate was continuously hemofiltered at 1 mL/hr per gram of cardiac tissue. Three hearts from the 24hr group were transplanted orthotopically in healthy pig recipients and function observed for 4 hours.

Results: All hearts regained normal function and metabolism within 10 minutes of NEVHP, which was sustained during the 8-hour test period. Three hearts were successfully transplanted, and cardiopulmonary bypass was weaned off with mild vasopressor support.

Conclusion: Hearts that underwent CSS for up to 24 hours can be routinely resuscitated to viable function using NEVHP. In addition, ex vivo perfusion allows for objective assessment of organ function prior to transplantation. Successful transplantation of these hearts corroborates adequate resuscitation and confirms viability after resuscitation using NEVHP.