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There are several potential outcomes of myocardial ischaemia. When ischaemia is severe and prolonged, irreversible damage occurs and there is no recovery of contractile function. Interventions aimed at reducing mechanical activity and oxygen demand either before ischaemia or during reperfusion have been shown to delay the onset of ischaemic damage and to improve recovery during reperfusion. When myocardial ischaemia is less severe but still prolonged, myocytes may remain viable but exhibit depressed contractile function. Under these conditions, reperfusion restores complete contractile performance. This type of ischaemia leading to a reversible, chronic left ventricular dysfunction has been termed `hibernating myocardium'. It is important clinically recognize hibernation as reperfusion of hibernating myocardium by angioplasty or heart surgery restores contraction and this correlates with long term survival. A third possible outcome after a short period of myocardial ischaemia is a transient post-ischaemic ventricular dysfunction, a situation termed `stunned myocardium'.

Arterial and coronary sinus difference for potassium, lactate, glucose, free fatty acids and creatine kinase was measured every 5 minutes in two patients undergoing successful intracoronary thrombolysis of left anterior descending occlusion. In the first patient, reperfusion, 160 minutes after the onset of pain, was followed by a transient and limited release of creatine kinase in the coronary sinus, improvement in the electrocardiogram and restitution of left ventricular contraction. In the second patient, reperfusion 365 minutes after the onset of pain, was also accompanied by a limited release of creatine kinase. Reocclusion of the left anterior descending coronary artery, however, necessitated further thrombolysis which led to a massive release of creatine kinase and permanent loss of wall-motion. It is suggested that, in this case, reperfusion damage had occurred. The arteriovenous differences showed a wash-out of potassium and lactate during reperfusion in each case. The interpretation of the entire sequence of arteriovenous changes, however, could be shown to depend critically on the state of regional perfusion.