Mechanisms leading to reversible mechanical dysfunction in severe CAD: the alternatives to myocardial stunning

Patients with severe chronic coronary artery disease exhibit a highly altered myocardial pattern of perfusion, metabolism and mechanical performance. In this context, the diagnosis of stunning remains elusive not only because of methodological and logistic considerations, but also because of the pathophysiological characteristics present in the myocardium of these patients. In addition, a number of alternative pathophysiological mechanisms may act by mimicking the functional manifestations usually attributed to stunning. The present article reviews three of these mechanisms that could theoretically lead to reversible mechanical dysfunction in these patients: myocardial wall stress, the tethering effect, and myocardial expression and release of auto-and para-crine agents. Attention is focused on the role of these mechanisms in scintigraphically " normal " regions (i.e., regions usually showing normal perfusion, glucose metabolism and cellular integrity as assessed by nuclear imaging techniques) – in which stunning is usually considered-but these mechanisms could also operate over the whole viable myocardium. We hypothesize that reversion of these three mechanisms could partially explain the unexpected functional benefit after reperfusion recently highlighted by high spatial resolution imaging techniques.