Context: Atheromatous and thrombotic embolization during percutaneous coronary intervention (PCI) in acute myocardial infarction is common and may result in microcirculatory dysfunction, the prevention of which may improve reperfusion success, reduce infarct size, and enhance event-free survival. Objective: To determine whether protection of the distal microcirculation from thromboembolic debris liberated during primary PCI results in improved reperfusion and decreased infarct size. Design, Setting, and Patients: Prospective randomized controlled trial at 38 academic and community-based institutions in 7 countries enrolling 501 patients aged 18 years or older with ST-segment elevation myocardial infarction (STEMI) presenting within 6 hours of symptom onset and undergoing primary PCI or rescue intervention after failed thrombolysis. Interventions: Patients were randomized between May 20, 2002, and November 21, 2003, to receive PCI with a balloon occlusion and aspiration distal microcirculatory protection system vs angioplasty without distal protection. Main Outcome Measures: Coprimary end points were ST-segment resolution (STR) measured 30 minutes after PCI by continuous Holter monitoring and infarct size measured by technetium Tc 99m sestamibi imaging between days 5 and 14. Secondary end points included major adverse cardiac events. Results: Among 252 patients assigned to distal protection, aspiration was performed in 97% (242/251), all angioplasty balloon inflations were fully protected in 79% (193/245), and visible debris was retrieved from 73% (182/250). Complete STR was achieved in a similar proportion reperfused with vs without distal protection (63.3% [152/240] vs 61.9% [148/239], respectively; absolute difference, 1.4% [95% confidence interval, -7.7% to 10.5%; P = .78]), and left ventricular infarct size was similar in both groups (median, 12.0% [n = 229] vs 9.5% [n = 208], respectively; P = .15). Major adverse cardiac events at 6 months occurred with similar frequency in the distal protection and control groups (10.0% vs 11.0%, respectively; P = .66). Conclusions: A distal balloon occlusion and aspiration system effectively retrieves embolic debris in most patients with acute STEMI undergoing emergent PCI. Nonetheless, distal embolic protection did not resultin improved microvascularflow, greater reperfusion success, reduced infarct size, or enhanced event-free survival.
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