Background : Primary percutaneous coronary intervention (PCI) in lesions with a large thrombus load increases the procedural complication rate such as no-reflow phenomenon and distal thromboembolization. To overcome this problem, we can use newly developed GuardWire Plus system(PercuSurge) for the protection of distal microvasculature. However there is no comparative study between distal protection device and glycoprotein IIbIIIa receptor blocker(GPIIb/IIIa-B) for protecting microvascular integrity. This study was designed to compare the efficacy of the PercuSurge Guardwire system and GPIIb/IIIa-B on the microvascular integrity assessed by myocardial contrast echocardiography (MCE) after primary PCI in patients with acute myocardial infarction (AMI). Methods : A total of 27 patients(16 men; age, 60짹12 years) with AMI < 12hours and complete occlusion of the infarct related artery were randomly divided into 2 groups : group A comprised 15 patients of AMI underwent primary PCI using PercuSurge System; and group B comprised 12 patients of AMI underwent primary PCI with pre-infusion of GPIIb/IIIa-B(Reopro). After successful PCI, we performed MCE(real time low mechanical index) using PESDA within 24 hours. The following parameters were compared in each group: A represents myocardial blood volume, 棺 represents the mean microbubble velocity, and A and 棺 represents myocardial blood flow(MBF). Results : The results were shown in the table. The baseline patient characteristics were similar in each group. Conclusion : GuardWire Plus system is more effective distal protection method than GPIIb/IIIa-B for the preservation of microvascular integrity during the primary PCI in patients with AMI.