Response to hypercapnia as a tool to assess cardiac recovery in a porcine model of DCD heart transplantation

The advent of normothermic, ex-situ heart perfusion (ESHP) enables new options for evaluation of cardiac grafts. Donation after circulatory death (DCD) is a promising solution to improve heart transplantation rates, but current ESHP evaluation approaches are recognized as suboptimal for DCD grafts. We aimed to develop a vascular function test for cardiac graft assessment during ESHP using a porcine model of DCD. Explanted hearts were perfused unloaded for 3 hours followed by left ventricular loading for 1 hour to measure cardiac recovery. During unloaded perfusion by pressure, hypercapnic vascular function tests were performed by briefly increasing CO₂ levels and measuring responses in coronary flow. Coronary flow was effectively increased, it correlated with several measures of cardiac recovery (p≤0.05 for all) and was not affected by adenosine infusion. Our data provide the first evidence of a vascular function test that may help to improve evaluation of DCD cardiac grafts and is amenable to implementation in current clinical protocols.