Abstract: Objective To investigate the protective effect and safety of coronary sinus retroperfusion (CSR) with aortic oxygenated blood for acute myocardial ischemia during off-pump beating heart surgery in pigs. Methods Eighteen pigs were subjected to 120 min of acute myocardial ischemia by ligation of the lateral anterior descending branch (LAD) of the coronary artery followed by 60 min of reperfusion by lifting LAD ligation. The pigs were divided into 3 groups after the above operation, including a control group (group 1) and low- and high-pressure retroperfusion groups (groups 2 and 3), and in the latter two groups the pigs received 60 min of aorta-coronary sinus shunt retroperfusion (ACSSR) following 60 min of ischemia with self- or manually inflated balloon-tipped cannula inserted to induce low or high-pressure, respectively. The left ventricular function and measurements of coronary sinus nitric oxide (NO), endothelin-1 (ET-1) and infarct size were recorded. Results Three hours after ischemia, the maximal left ventricular pressure increment to reduction rates in groups 2 and 3 were much higher than those of group 1, with also higher NO and lower ET-1 concentrations in the coronary sinus blood. The infarct size was reduced by 45% and 61% in groups 2 and 3, respectively, as compared with that of group 1. Conclusion ACSSR can reduce left ventricular systolic and diastolic dysfunction, protect coronary endothelial function, and reduce infarct size for rescue of the acutely ischemic myocardium in pigs during off-pump beating heart surgery.