3 The procedure
3.1 Normothermic extracorporeal preservation aims to keep the donor's heart beating outside the body, using a perfusion machine that delivers warm oxygenated blood supplemented with catecholamine, nutrients and electrolytes. This technique aims to decrease the amount of damage that occurs to the heart after removal, by reducing the rate of tissue deterioration compared with conventional cold ischaemic storage. The aim is to improve clinical outcomes for the recipient. The technique was initially used to preserve hearts donated after brainstem death, but has recently been adapted to preserve hearts donated after circulatory death (death that has been diagnosed and confirmed using cardio‑respiratory criteria). This overview considers only normothermic extracorporeal preservation of hearts donated after brainstem death.
3.2 In this procedure, the donor heart is inspected and arrested with cold cardioplegia solution before being removed. After removal, the heart is placed in a perfusion machine and re‑animated. The perfusion machine comprises a blood reservoir (which stores the donor's blood), pulsatile-flow pump, blood oxygenator, blood warming unit and monitoring equipment. Oxygenated blood from the reservoir is warmed and pumped into the aorta, perfusing the coronary arteries of the donor heart. Coronary venous blood drains into the right atrium, through the coronary sinus, and passes into the right ventricle. The blood flows through the pulmonary artery, into the oxygenator, and passes back into the reservoir. Aortic pressure, coronary flow, blood temperature and heart rate are all monitored. Immediately before the transplantation procedure, the heart is arrested with cold cardioplegia solution and disconnected from the perfusion machine. It is then implanted into the recipient. This procedure has been used to store donor hearts for up to 8 hours before transplantation.