PURPOSE: Transmedic Organ Care System (OCS) allows preservation of the donor heart by perfusing the organ at 34°C in a beating state and providing additional assessment options. The perfusion protocols as established by the manufacturer is valid for adult human hearts, using coronary flows in the 8-900ml/min range guided by lactate measurements. Higher flow can facilitate higher degrees of cardiac oedema which can be associated with diastolic dysfunction, and generel impairment of contractility of the heart. The aim of the study is to establish the optimal coronary flow in a juvenile porcine heart, similar in size to the adult human heart, that minimizes oedema and still meets the metabolic requirements.

METHODS: 18 pigs in the range of 60-70kg was used for the trial and randomized into three groups with a coronary flow of 6-, 7- or 800ml/min for 180 minuts. After intubation and propofol/fentanyl anesthesia was induced, median sternotomy was performed and the heart prepared for harvest. Immediately after crossclamp 1000ml of HTK Custodiol cardioplegia was administered, and the heart prepared as per protocol for the human heart. The heart was connected a OCS-based system and randomized to one of three regimens: a coronary flow of 6-, 7- or 800ml/min for 180 minutes at 34 degree celsius, with the pressure autoregulated to 65mmHg. The pump flow was adjusted to give the desired coronary flow. Haemodynamic parameteres were continously recorded, arterial and venous lactates sampled every 30 minutes. Biopsies taken form the apex of the left ventricle and the heart was weighed after 180 minuts of perfusion.

RESULTS: Our primary endpoint was met, as the weight gain in the 800ml/min group was significantly higher than the 600ml/min group (103g +/-20g vs 72g +/- 15g, p<0.05). There were no significant difference in the final lactate (relative to the initial levels) after three hours of perfusion. All hearts had end arterial lactate under 5.0 mmol/l. At the end of the perfusion, Troponin T levels in the blood and pathohistological examination of the biopsies showed no significant differences between the groups.

CONCLUSION: We found a lower degree of oedema formation in the 600ml/min perfusion group, but similar metabolic response as the group with higher flows. . We suggest using this slightly reduced flow when investigating juvenile porcine hearts in an ex-vivo perfusion model.