Outcome Comparison of 600-and 300-mg Loading Doses of Clopidogrel in Patients Undergoing Primary Percutaneous Coronary Intervention for ST-Segment Elevation Myocardial Infarction Results From the ARMYDA-6 MI (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty-Myocardial Infarction) Randomized Study

Objectives The purpose of this study was to compare 600- and 300-mg clopidogrel loading doses in patients with ST-segment elevation myocardial infarction (STEMI). Background Given the high thrombotic risk of patients with STEMI, greater platelet inhibition may improve outcome in those patients receiving percutaneous coronary intervention (PCI). Although observational data suggest that pretreatment with a 600-mg clopidogrel loading dose may be more effective than the 300-mg regimen in primary PCI, this hypothesis has never been tested in a randomized study. Methods A total of 201 patients undergoing primary PCI for STEMI randomly received a 600-mg (n = 103) or 300-mg (n = 98) clopidogrel loading dose before the procedure. The primary endpoint was the evaluation of the infarct size, defined as the area under the curve of cardiac markers. Results Infarct size was significantly lower in the high-dose regimen: median creatine kinase-myocardial band 2,070 ng/ml (interquartile range [IQR]: 815 to 2,847 ng/ml) versus 3,049 ng/ml (IQR: 1,050 to 7,031 ng/ml) in the 300-mg group, p = 0.0001; troponin-I 255 ng/ml (IQR: 130 to 461 ng/ml) versus 380 ng/ml (IQR: 134 to 1,406 ng/ml), p < 0.0001. In the 600-mg arm, Thrombolysis In Myocardial Infarction flow grade <3 after PCI was less frequent (5.8% vs. 16.3%, p = 0.031), left ventricular ejection fraction at discharge was improved (52.1 +/- 9.5% vs. 48.8 +/- 11.3%, p = 0.026), 30-day major adverse cardiovascular events were fewer (5.8% vs. 15%, p = 0.049), and bleeding/entry site complications were not increased (secondary endpoints). Conclusions In STEMI patients, pre-treatment with a 600-mg clopidogrel loading dose before primary PCI was associated with a reduction of the infarct size compared with a 300-mg loading dose, as well as with improvement of angiographic results, residual cardiac function, and 30-day major adverse cardiovascular events; further studies are warranted to evaluate impact of such strategy on survival. (J Am Coll Cardiol 2011; 58: 1592-9) (C) 2011 by the American College of Cardiology Foundation