Primary percutaneous coronary intervention (PCI) is currently the treatment of choice for patients with acute ST elevation myocardial infarction (STEMI). Nevertheless, despite restoration of normal epicardial flow, myocardial perfusion remains impaired in approximately half of patients and is associated with a poor prognosis. A variety of invasive and non-invasive techniques have been proposed to evaluate microvascular perfusion and several invasive hemodynamic measures have been closely associated with microvascular damage.In order to improve microvascular perfusion after primary PCI, a variety of treatment strategies have been developed, such as adjunctive administration of glycoprotein IIb/IIIa inhibitors (GPIs). Although current ACC/AHA guidelines recommend that small molecule GPIs should be administered as a bolus followed by 18 hours of continuous infusion, changes in clinical practice may obviate the need for a maintenance infusion in current practice.