title: A high loading dose of clopidogrel reduces myocardial infarct size in patients undergoing primary percutaneous coronary intervention: a magnetic resonance imaging study.
abstract: BACKGROUND
  We sought to determine whether a 600-mg loading dose of clopidogrel reduces myocardial infarct size compared with a 300-mg dose using contrast-enhanced magnetic resonance imaging in patients undergoing primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI).
  
  
  METHODS
  In 198 patients undergoing primary PCI for STEMI, contrast-enhanced magnetic resonance imaging was performed a median of 7 days after the index event. Infarct size was measured on delayed-enhancement imaging, and area at risk (AAR) was quantified on T2-weighted images.
  
  
  RESULTS
  Baseline characteristics were not significantly different between the 600-mg clopidogrel loading group (n = 117) and the 300-mg group (n = 81). The median infarct size was significantly smaller in the 600-mg group than in the 300-mg group (17.3% [8.9%-26.2%] vs 21.7% [12.9%-30.0%], P = .03). Myocardial salvage index ([AAR - infarct size] × 100/AAR) was greater in the 600-mg group than in the 300-mg group (47.7 [33.7-60.9] vs 32.0 [23.6-51.5], P < .01). Patients in the 600-mg group also had a significantly lower extent of microvascular obstruction and smaller number of segments with >75% of infarct transmurality than did those in the 300-mg group. After propensity score matching, the 600-mg group had smaller infarct size and greater myocardial salvage index compared with the 300-mg group. In multivariate analysis, the use of a 600-mg clopidogrel loading dose significantly reduced the risk of a large infarct (odds ratio 0.53, 95% CI 0.29-0.98, P = .04).
  
  
  CONCLUSIONS
  In patients undergoing primary PCI for STEMI, a 600-mg loading dose of clopidogrel reduced myocardial infarct size and improved myocardial salvage compared with a 300-mg loading dose.
authors.affiliation: Division of Cardiology, Department of Medicine, Seoul, Republic of Korea.
authors.forename: Young Bin
authors.initials: YB
authors.lastname: Song
authors.forename: Joo-Yong
authors.initials: JY
authors.lastname: Hahn
authors.forename: Hyeon-Cheol
authors.initials: HC
authors.lastname: Gwon
authors.forename: Sung-A
authors.initials: SA
authors.lastname: Chang
authors.forename: Sang-Chol
authors.initials: SC
authors.lastname: Lee
authors.forename: Yeon Hyeon
authors.initials: YH
authors.lastname: Choe
authors.forename: Seung-Hyuk
authors.initials: SH
authors.lastname: Choi
authors.forename: Jin-Ho
authors.initials: JH
authors.lastname: Choi
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Jae K
authors.initials: JK
authors.lastname: Oh
mesh_terms: D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D000077144:Clopidogrel; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000473:pathology* / Q000628:therapy; D009206:Myocardium / Q000473:pathology*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D016896:Treatment Outcome
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine