Heart preservation

In clinical transplantation today, the donor heart is preserved with cold ischemic storage that gives safe preservation for 4 hours. Non-ischemic perfusion preservation is able to preserve the donor heart for 24 hours in pre-clinical studies. The aim of this thesis is to investigate: 1. how potassium, magnesium, and temperature affect the coronary artery contractility; 2. how much oxygen a cardioplegic heart consumes at different temperatures; and 3. if perfusion preservation is able to preserve coronary arterial endothelial and cardiac myocardial function.In study I, pre-stretched coronary arterial segments were studied in organ baths. Contractions were induced with 16 combinations of four different concentrations of potassium (16, 23, 30, and 127 mmol/L) at four different temperatures (37, 22, 15, 8 °C). Magnesium with concentrations from 0 - 20 mmol/L was used to attenuate the contraction induced with potassium (16, 23, 30, and 40 mmol/L) at 37 °C. The contractions caused by potassium can be minimized when combining hypothermia and/or elevated magnesium.In study II, a specially designed sealed perfusion system was used to investigate the oxygen consumption of aerobically perfused cardioplegic hearts. At 37°C , each 100 g of heart tissue consumes 1.1 mL/min oxygen at rest; and the oxygen consumption is reduced to 53%, 30%, 19%, and 15%, when the temperatures were 30, 22, 15, and 8 °C , respectively.In study III and IV, porcine hearts were perfused either 8 hours (continuously or intermittently) or 24 hours (with alternating pressures of 20 and 10 mmHg), using an oxygenated hyperkalemic perfusate containing erythrocytes, albumin, and hormones. The coronary arteries of the perfused hearts were investigated in organ baths and compared to fresh controls. The ventricular function of the 24 hours perfused hearts was similarly investigated. The intact coronary arterial endothelial function was preserved after both 8 hours and 24 hours of perfusion. The myocardial function was also fully preserved after 24 hours of perfusion.In conclusion, with well-established perfusion preservation, the heart can be safely preserved for 24 hours