Dear Purnima, I send you two articles, where isolated rat hearts were perfused by Langendorff technique. One of them is a model of regional ischemia by occlusion of the left anterior descending coronary artery and other by global ischemia, the latter model is easier because it is accomplished by closing the flow of Ringer's solution through the aorta.
For using murine model consult the following website: https://www.ncbi.nlm.nih.gov/pubmed/24747599
The first suggested model is OK. The Langendorff model if not perfused with a red cells suspension is already (when perfused with Krebs) a chronic ischemic model. Metabolism in the Krebs perfused model has nothing to do with what occurs in the first model. Your choice.