Is stunned myocardium ischemic on a microvascular level?

Stunned myocardium generally has normal resting flow and most studies have documented normal flow reserve. "Vascular stunning" (reduced vasodilator capacity) can be produced by ischemia, but the duration required is longer than that required to produce mechanical stunning. The two phenomenon can therefore be dissociated and are essentially unrelated. Nevertheless, despite evidence of normal microvascular patency in stunned myocardium, there are observations consistent with the existence of microvascular foci of ischemia, possibly related to vascular spasm or constriction, and this may explain the finding that increased flow in stunned myocardium may partially, or even largely, reverse the mechanical dysfunction. The "microvascular spasm" hypothesis may explain a significant portion of the dysfunction of stunned myocardium and deserves further study.