Clinical manifestations of myocardial stunning.

The phenomenon of myocardial stunning has been observed in all animal species studied. The possible occurrence of myocardial stunning in man has been demonstrated after either regional ischemia (such as exercise-induced angina, vasospastic or unstable angina) or after global ischemia (i.e., after cardioplegic arrest during cardiac surgery, or cardiac arrest, or heart transplantation). Finally, it may also be observed in patients with acute myocardial infarction, subjected to recanalization therapy, because viable myocardium, salvaged by reperfusion, may remain stunned, with delayed contractile recovery. Occurrence of stunning may aggravate hemodynamic conditions in already unstable patients, and it may lead to underestimation of the extent of myocardium salvaged by thrombolysis. Repeated episodes of stunning may lead to a condition of apparently 'chronic' contractile dysfunction that may be difficult to differentiate from hibernation, because of the technical difficulties in accurately measuring myocardial blood flow in patients, and because both phenomena may coexist and overlap in the same patient. In addition, recent evidence suggests that repeated episodes of stunning may lead to a progressive worsening of the residual contractile dysfunction and to longer recovery times, and it has thus been suggested, and it is much debated, that hibernation might at least in part be the consequence of repetitive episodes of stunning.