T.R. Harris1, K. Tracy1, Y. Shishido1, M. Cortelli1, M. Petrovic1, E. Simonds1, V. Simon1, W. Tucker1, B. Petree1, R. Ukita1, C. Demarest1, G. Coyan1, A. Shah1, M. Bacchetta1 1Vanderbilt University Medical Center, Cardiac Surgery, Nashville, TN, USA
Introduction: The demand for heart allografts for transplant vastly exceeds supply; subsequently, efforts to increase the donor pool include normothermic regional perfusion and donation after circulatory death. Donation after circulatory death (DCD) allografts experience two ischemic hits, lending them vulnerable to ischemia-reperfusion injury, whereas asystolic warm ischemic time (aWIT). To assess the function of heart allografts after DCD, the purpose of the study was to design a porcine model with the goal of a controlled aWIT.
Methods:
Yorkshire/Landrace (N=13) pigs (62.73 ± 6.56kg) were anesthetized using ketamine, tiletamine-zolazepam, xylazine and isoflurane. Hemodynamic monitoring was assessed using a femoral arterial line. Femoral arterial and venous cannulae (15-18Fr) were placed to procure 1.5L whole blood to be used for isolated heart evaluation on an ex vivo heart perfusion platform, with synchronous isovolumetric crystalloid resuscitation. Anesthesia was transitioned to total intravenous anesthesia, using midazolam, propofol and fentanyl. An adequate plane of anesthesia was assessed after 20 minutes via jaw tone, palpebral and pain reflex. Circulatory arrest was induced via vecuronium and extubation. Hemodynamic parameters were recorded every 5 minutes. Once asystolic or with evidence of pulseless electric activity, a sternotomy was performed. The heart is isolated, and the aortic root is cannulated. After 10 minutes of aWIT, hearts were flushed with 2L St. Thomas cardioplegia solution, with simultaneous venting of the venae cavae and left atrium. After sufficient flushing, the heart is procured for further assessment. Hearts are subsequently reperfused using a Langendorff ex vivo heart perfusion model, whereas physiologic, thermal, and functional parameters are assessed.
Results:
All porcine models demonstrated sufficient planes of anesthesia, as verified by a veterinarian. Average total WIT, defined as extubation to cardioplegia was 21±3 min; functional warm ischemic time, defined as SBP≤ 50 to cardioplegia, was 13±2.6 min; and agonal phase, defined as extubation to asystole was 10.3±2.1 min. Asystolic WIT was consistently 10 minutes across all hearts. Blood collection averaged 1.5L of autologous blood with synchronous crystalloid reperfusion through a venous cannula.
Conclusion:
In summary, we have designed a consistent model for procurement of DCD hearts to be evaluated for functional, histologic and metabolomic analyses. Further work is to utilize this platform for evaluation of various models of DCD procurement, storage and reperfusion models.