CHARACTERIZATION OF HIBERNATING AND STUNNED MYOCARDIUM

Both the hibernating and the stunned myocardium are characterized by reversible contractile dysfunction. In hibernating myocardium ischemia is still ongoing, 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 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 only causal 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 involves large parts of the left ventricle and thus impairs global left ventricular function, the extent of myocardial stunning can be reduced by inotropic stimulation, without inducing further damage to the myocardium. In the experimental setting, antioxidant agents, calcium antagonists and ACE inhibitors attenuate stunning, most effectively when administered before ischemia.