Post-conditioning reduces infarct size in an open-chest porcine acute ischemia-reperfusion model

Background: Timely reperfusion is a prerequisite for myocardial salvage; however, re-oxygenation of the ischemic myocardium initiates reperfusion injury. Post-conditioning diminishes the detrimental aftermath of an acute myocardial infarction through alleviation of reperfusion injury. Ischemic post-conditioning consists of a series of brief interruptions in the coronary blood supply that has to be applied within the first minutes after re-establishing the coronary flow. Methods: Sixteen female mixed Danish Landrace and Yorkshire pigs weighing 20 kg were included. The heart was exposed through a midline sternotomy. A snare was positioned around the left anterior descending coronary artery downstream of the second diagonal branch. After randomization to either no treatment (control group) or treatment by ischemic post-conditioning (post-conditioning group), the pigs underwent 45 min of ischemia and 180 min of reperfusion. The post-conditioning group had a post-conditioning algorithm applied consisting of 15 s of reperfusion alternating with 15 s of re-occlusion repeated 10 times. Results: The groups were comparable with regard to body weight, hemodynamics and the size of the area at risk. The post-conditioning group had an absolute reduction in infarct size of 18.1% [confidence interval (CI): 6.2: 30.0%] compared with the control group (P=0.0056). In the post-conditioning group, infarction developed in 39.6 +/- 12.0% (1 SD) of the area at risk compared with 57.8 +/- 10.2% (1 SD) in the control group. Conclusion: When ischemic post-conditioning was applied at reperfusion, we found an absolute reduction in infarct size of 18.1% presumably attributable to a diminished reperfusion injury. The model we have developed is suitable for further studies of this promising intervention.