Etiology and clinical implications of microvascular dysfunction in patients with acute myocardial infarction.

In patients with acute myocardial infarction (MI), coronary microvasculatures are often damaged irreversibly due to myocardial ischemia and reperfusion, and flow to the previously ischemic myocardium is markedly reduced, a phenomenon known as the "no-reflow phenomenon". Percutaneous coronary intervention (PCI) may accelerate embolization of plaque gruels and microthrombi to the microvessels, which further reduces tissue perfusion. The extent of the no-reflow zone correlates with infarct size, and it has additional prognostic information. Recent advances in imaging modalities have enabled us to diagnose the no-reflow phenomenon and to assess the mechanisms of the no-reflow phenomenon. Pharmacological interventions and catheter-based devices to retrieve embolic materials have been proposed, and some of them are associated with improvement in clinical outcomes. Thus, we should keep in mind that only the achievement of complete microvascular perfusion is associated with better functional and clinical outcomes in patients with acute MI.