The isolated heart is mounted and the left atrium is about to be cut for balloon insertion. A rabbit heart is pictured but the rat heart is mounted in an identical manner. Notice that a suture has been placed around a coronary branch which will be used to create regional ischemia. In the rabbit heart the epicardial coronary arteries can only be seen in situ while they are perfused with blood so the ligatures are best placed before removing the heart. Rat coronary branches cannot be seen either in situ or in vitro. Notice the jacketed chamber at the bottom of the picture into which the heart will be lowered.