Ex Vivo Maintenance of Heart Viability: Comparison of Two Methods
Bridgen, Devin; Hagens, John; Brink, Rob; Gregg, Peter; Aridgides, Dan; Faghri, Ali
Currently established methods of tissue preservation for heart transplantation involve placing the harvested donor heart in a cold, nutrient-rich cardioplegic solution. Clinically, methods like these have only been shown to preserve heart tissue for a matter of hours. A new solution for tissue preservation developed by Transmedics Inc involves placing the heart in a chamber that mimics the physiological conditions of the human chest cavity. This solution maintains the heart in a beating state and pumps blood and nutrients through the myocardial circulation. This preservation technique has been clinically shown to improve the length of time that a heart can be preserved ex-vivo and when properly implemented, could theoretically preserve a donor heart indefinitely. A computer simulation using Finite-Element analysis was performed with the intention of comparing how well these two methods work to perfuse heart tissue with oxygen over a long period of time. As expected, it was shown that the Transmedics cart could keep the concentration of oxygen in the heart tissue at optimal levels indefinitely while the immersion technique could only keep the concentrations of oxygen in the tissue above healthy levels for around 5.5 hours. Investigations into the effect of temperature on each preservation technique found that the Transmedics preservation is most effective at 37 degrees Celsius, body temperature; while the immersion technique is most effective at 4 degrees Celsius. Though the Transmedics device was shown to be far superior in many areas, other considerations, like the cost and the ease of implementation of each technique have lead us to conclude that there are still certain situations in which tissue preservation by cooling is the best option for heart transplantation.