Characterization of hibernating and stunned myocardium.

Both the hibernating and the stunned myocardium are characterized by reversible contractile dysfunction. In hibernating myocardium, perfusion is still reduced, whereas in stunned myocardium blood flow is fully or almost fully restored. Both the hibernating and the stunned myocardium retain an inotropic reserve. In hibernating myocardium the increase in contractile function is at the expense of metabolic recovery, whereas in the stunned myocardium no metabolic deterioration occurs during inotropic stimulation. Therefore, inotropic stimulation in combination with metabolic imaging may help not only to identify viable, dysfunctional myocardium but also to distinguish hibernating and stunned myocardium. The therapy of hibernating myocardium is to restore blood flow to the hypoperfused tissue. Myocardial stunning per se requires no therapy at all, since, by definition, blood flow is normal and contractile function will recover spontaneously. If, however, myocardial stunning is severe, and it involves large parts of the LV and thus impairs global LV function, it can be reversed with inotropic agents and procedures. In the experimental setting, anti-oxidant agents, calcium antagonists and ACE inhibitors attenuate stunning, but most effectively when administered before ischaemia.