AbstractA large infarct‐related artery (IRA), which mostly contains high‐burden thrombus formation (HBTF) and lipid pool‐like plaque contents, has been suggested to play a pivotal role in the no‐reflow phenomenon during primary percutaneous coronary intervention (p‐PCI). To reduce the thrombus burden of the IRA using the PercuSurge GuardWire device before intervention may be of crucial importance to preventing no‐reflow. The purposes of this study were to test the transradial application (TRA) of this new mechanical device and to determine its impact on prevention of no‐reflow during p‐PCI. From May to September 2002, the PercuSurge GuardWire device was utilized in 42 consecutive patients with acute myocardial infarction and large IRA (vessel size ≥ 3.5 mm with HBTF; group 1). From January to December 2000, p‐PCI was performed in large IRA (vessel size ≥ 3.5 mm) with HBTF using tranfemoral arterial approach in 101 consecutive patients (group 2). The angiographic and clinical outcomes of the two groups were compared in a chronologically consecutive manner. Successful reperfusion (final TIMI‐3 flow) was significantly higher in group 1 than in group 2 patients (95.2% vs. 79.1%; P = 0.005). Moreover, the combined incidence of vascular complications, post‐PCI thromboembolisms (defined as a distal embolism and a post‐PCI residual thrombus score of ≥ 3), and combined 30‐day major adverse cardiac events were significantly lower in group 1 than in group 2 patients (all P values < 0.05). In group 1 patients, post‐p‐PCI myocardial blush (MB) of ≥ 2 grades was found to be more than 88.0%. Furthermore, when compared with preintervention, thrombus scores were significantly reduced after aspiration (P = 0.0001), whereas the minimal lumen diameter (P = 0.0001), TIMI flow grade (P = 0.0001), and MB grade (P = 0.0001) had all significantly increased after aspiration using Export Aspiration Catheter. There were no significant differences in corrected TIMI frame count (P = 0.42), TIMI flow grade (P > 0.5), or MB grade (all P values > 0.5) between postaspiration and post‐PCI. The TRA of the PercuSurge GuardWire device during primary intervention of large IRA with HBTF was safe and feasible and provided benefits to patients. The initial successful reduction of the thrombus burden with this mechanical device before intervention can be translated into increased final TIMI‐3 flow, a combined MB of ≥ 2 grades, and fewer final thromboembolic events. Catheter Cardiovasc Interv 2004;61:503–511. © 2004 Wiley‐Liss, Inc.