BACKGROUND: In-vivo explants in pigs are well-established to investigate myocardial function directly after transplantation. However, there is no functional data available for a longer time period after transplantation. We have established a pig model to investigate myocardial function 24 hours after orthotopic transplantation. MATERIALS AND METHODS: Orthotopic cardiac transplantations (HTx) in pigs were performed with a postoperative observation period of 24 hours (n = 6). To analyze myocardial function after transplantation, hemodynamical parameters (Swan-Ganz- and impedance-catheter data) as well as tissue and blood samples were obtained. Regional myocardial blood flow (RMBF) was assessed using fluorescent microspheres. RESULTS: The impedance-catheter parameters demonstrated a preserved contractility in both ventricles 24 hours post-transplantation. In contrast, cardiac output 24 hours after HTx was diminished by 50% as compared to the preoperative value. Conversely, pulmonary vascular resistance increased significantly. The RMBF was increased in both ventricles. Metabolic and histological analyses indicate myocardial recovery 24 hours after HTx with no irreversible damage. CONCLUSIONS: For the first time, we were able to establish a porcine model to investigate myocardial function 24 hours after heart transplantation. While the contractility of the transplanted hearts was well-preserved, impaired cardiac output was going along with an increase in pulmonary vascular resistance. Using this clinical relevant model, improvements of human cardiac transplantation and post-transplant contractile dysfunction, especially, could be investigated.