Why myocardial stunning is clinically important.

Stunning has been described in every species studied so far, and there is no reason to suspect that humans are the exception. The exact prevalence and severity of stunning in humans remain unknown because of our inability to diagnose this condition. In most cases, stunning probably does little harm. However, it seems plausible that in a minority of cases, stunning can be quite detrimental and even life-threatening by causing hemodynamic instability that requires intensive monitoring, pharmacological and/or mechanical circulatory support, and prolonged hospitalization with its attendant costs (Table 1). Recognition of stunning in these cases may pay handsome dividends, since this form of contractile dysfunction can be completely corrected with inotropic therapy. Furthermore, the notion that contractility can be reversibly depressed for prolonged periods of time is critical in order to properly manage patients with severe left ventricular dysfunction and/or cardiogenic shock after acute infarction or cardiac surgery, in whom the decision as to whether to implement and maintain vigorous pharmacological and/or mechanical circulatory support for extended periods of time obviously depends upon whether or not the ventricular dysfunction is reversible (Table 1). Quick and reliable diagnostic techniques for detecting stunning in these cases are clearly essential. In addition, the lack of immediate improvement in regional myocardial function after therapeutic revascularization (e.g., thrombolysis in acute infarction) would be difficult to interpret without recognition of the phenomenon of stunning (Table 1). Diagnosis of stunning in these cases is important to decide whether to perform PTCA on the infarct-related vessel. Regardless of all of the above, stunning is likely to be a factor contributing to the progressive decrease in regional function and/or cardiac dedifferentiation observed in patients with chronic, reversible wall motion abnormalities (Table 1). This may turn out to be the major clinical importance of myocardial stunning.