title: Prognostic significance of microvascular obstruction by magnetic resonance imaging in patients with acute myocardial infarction.
abstract: BACKGROUND
  The extent of microvascular obstruction during acute coronary occlusion may determine the eventual magnitude of myocardial damage and thus, patient prognosis after infarction. By contrast-enhanced MRI, regions of profound microvascular obstruction at the infarct core are hypoenhanced and correspond to greater myocardial damage acutely. We investigated whether profound microvascular obstruction after infarction predicts 2-year cardiovascular morbidity and mortality.
  
  
  RESULTS
  Forty-four patients underwent MRI 10 +/- 6 days after infarction. Microvascular obstruction was defined as hypoenhancement seen 1 to 2 minutes after contrast injection. Infarct size was assessed as percent left ventricular mass hyperenhanced 5 to 10 minutes after contrast. Patients were followed clinically for 16 +/- 5 months. Seventeen patients returned 6 months after infarction for repeat MRI. Patients with microvascular obstruction (n = 11) had more cardiovascular events than those without (45% versus 9%; P=.016). In fact, microvascular status predicted occurrence of cardiovascular complications (chi2 = 6.46, P<.01). The risk of adverse events increased with infarct extent (30%, 43%, and 71% for small [n = 10], midsized [n = 14], and large [n = 14] infarcts, P<.05). Even after infarct size was controlled for, the presence of microvascular obstruction remained a prognostic marker of postinfarction complications (chi2 = 5.17, P<.05). Among those returning for follow-up imaging, the presence of microvascular obstruction was associated with fibrous scar formation (chi2 = 10.0, P<.01) and left ventricular remodeling (P<.05).
  
  
  CONCLUSIONS
  After infarction, MRI-determined microvascular obstruction predicts more frequent cardiovascular complications. In addition, infarct size determined by MRI also relates directly to long-term prognosis in patients with acute myocardial infarction. Moreover, microvascular status remains a strong prognostic marker even after control for infarct size.
authors.affiliation: Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Md, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Wu
authors.forename: E A
authors.initials: EA
authors.lastname: Zerhouni
authors.forename: R M
authors.initials: RM
authors.lastname: Judd
authors.forename: C H
authors.initials: CH
authors.lastname: Lugo-Olivieri
authors.forename: L A
authors.initials: LA
authors.lastname: Barouch
authors.forename: S P
authors.initials: SP
authors.lastname: Schulman
authors.forename: R S
authors.initials: RS
authors.lastname: Blumenthal
authors.forename: J A
authors.initials: JA
authors.lastname: Lima
mesh_terms: D000368:Aged; D003327:Coronary Disease / Q000150:complications / Q000175:diagnosis; D005260:Female; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008833:Microcirculation / Q000473:pathology*; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000473:pathology*; D011379:Prognosis; D012720:Severity of Illness Index