Abstract <p>One of the key problems of transplantation is the short period of safe hypothermic storage of a donor heart. A promising method of its prolongation is gas hypothermic preservation in mixtures of oxygen with carbon monoxide and other gas agents. However, the standardization of this approach requires the selection of conditions for cardiac arrest and washing it of blood before gas exposure. The aim of this work was to test the possibility of using the method of hyperbaric gas hypothermic preservation of the rat heart in combination with the use of Normacor cardioplegic solution mixed with the blood plasma substitute Gelofusine. An experimental study was conducted on isolated rat hearts (<i>n</i> = 30). Functional (contractility and heart rate) and morphological parameters were evaluated after 12 and 24 h of storage at 4°C and 6.5 atm pressure of a CO : O₂ (1 : 1) gas mixture. Three preparation protocols were compared: perfusion with Normacor® solution + Gelofusine at 37°C, perfusion with Custodiol solution at 4°C and storage without perfusion. It was shown that the combination Normakor® + Gelofusine ensures stable restoration of the contractile function of the heart (~50% of the native control) and its morphological preservation after 12 and 24 h of storage. After 12 h of storage, the “Normacor” group showed significantly better functional heart recovery results compared to the “Custodiol” group. Histological analysis revealed moderate and potentially reversible ischemic reperfusion injuries in all groups after 24 h of exposure to a gaseous medium. It was concluded that the combination of Normacor and Gelofusine solutions registered in Russia is an effective means of pretreatment of an organ for subsequent gas hypothermic preservation, which may contribute to the introduction of this approach into clinical practice to extend the shelf life of a donor heart.</p>