It is well known that in patients in whom myocardial reperfusion is absent or limited, despite adequate epicardial reperfusion, prognosis is poor and more severe left ventricular dysfunction can be expected in comparison to those patients in whom also microvascular reperfusion after PPCI is restored. Therefore, it is beyond doubt that knowledge about the actual state of the microvasculature and myocardial (re)perfusion shortly after PPCI, is important from a prognostic point of view.