Cellular and extracellular mechanisms causing myocardial stunning.

Myocardial stunning involves a profound and slowly recovering decrease in contractility that follows a brief but severe episode of ischemia (1). A report in this issue of the Journal of the American College of Cardiology (2) challenges the prevailing view that the mechanisms underlying stunning are cellular in origin. Interestingly, Chandrashekhar et al. (2) found there was little difference in the contraction of isolated myocytes removed either from stunned or from control hearts. Furthermore, Ca handling and Ca responsiveness were similar in myocytes from stunned or control hearts. Since stunning did not appear to be manifest at the cellular level, they concluded that the mechanisms underlying stunning are extracellular. This conclusion is provocative, since it conflicts with a large number of other studies that suggest that the mechanisms of stunning are cellular in origin. However, it must be acknowledged that Chandrashekhar et al. (2) do systematically and directly