Different effects of partial pressure in a high-pressure gaseous mixture of carbon monoxide and oxygen for rat heart preservation

We maintained the function of an extracted rat heart after 24–48 h preservation in a high-pressure gaseous mixture of carbon monoxide (CO) and oxygen (O2). Here, we assessed the effects of different partial pressures of hyperbaric CO and O2 for 24–48 h at 4 °C on rat heart preservation and compared conditions including immersion in University of Wisconsin solution. Preserved hearts were transplanted into recipient rats via heterotopic cervical heart transplantation for in vivo evaluation and perfused using the Langendorff system for ex vivo evaluation. The survival rate of transplanted hearts was 100% at postoperative day 7 in the CO + O2 (PCO:PO2 = 1.5:2.0 atm) group but only 33% in the CO + O2 (PCO:PO2 = 2.0:1.5 atm) group. Langendorff system and histopathological analysis revealed that the left ventricular pressure of preserved hearts in the CO + O2 (PCO:PO2 = 1.5:2.0 atm) group was better than the CO + O2 (PCO:PO2 = 2.0:1.5 atm). We demonstrate that exposure of rat hearts to hyperbaric CO and O2 is superior to the immersion method and that partial pressure of hyperbaric CO and O2 is crucial to preservation.