title: Magnetic resonance characterization of the peri-infarction zone of reperfused myocardial infarction with necrosis-specific and extracellular nonspecific contrast media.
abstract: BACKGROUND
  Because ischemically injured myocardium is frequently composed of viable and nonviable portions, a method to discriminate the two is useful for clinical management.
  
  
  RESULTS
  Ischemically injured myocardium was characterized with extracellular nonspecific (Gd-DTPA) and necrosis-specific (mesoporphyrin) MR contrast media in rats. Relaxation rates (R1) were measured on day 1 and day 2 by inversion-recovery echoplanar imaging. Spin-echo imaging was used to define contrast-enhanced regions and regional wall thickening. Gadolinium concentration, area at risk, and infarct size were measured at postmortem examination. DeltaR1 ratio (DeltaR1(myocardium)/DeltaR1(blood)) after administration of Gd-DTPA was greater in ischemically injured myocardium (1.20+/-0.15) than in normal myocardium (0.47+/-0.05, P<0.05), which was attributed to differences in gadolinium concentration and water content. The Gd-DTPA-enhanced region on day 2 was larger (32.8+/-0.9%) than true infarction as demonstrated by triphenyltetrazolium chloride (TTC) (24.6+/-1.4%, P<0.001, r=0.21). Bland-Altman analysis revealed that the Gd-DTPA-enhanced region overestimated true infarct size by 7.8+/-5.9%. On the other hand, the mesoporphyrin-enhanced region (26.9+/-1.8%, P=NS, r=0.87) and true infarct size were identical. The difference in the areas demarcated by the 2 agents is the peri-infarction. Systolic and diastolic MR images revealed no wall thickening in the mesoporphyrin-enhanced region (0.3+/-3.3%) but reduced thickening in the Gd-DTPA-enhanced rim (8.5+/-5.5%, P<0.05).
  
  
  CONCLUSIONS
  The Gd-DTPA-enhanced region encompasses both viable and nonviable portions of the ischemically injured myocardium. The Gd-DTPA-enhanced area overestimated infarct size, but the mesoporphyrin-enhanced area matched true infarct size. The salvageable peri-infarction zone can be characterized with double-contrast-enhanced and functional MR imaging; the mismatched area of enhancement between the 2 agents shows residual wall thickening.
authors.affiliation: Department of Radiology, University of California, San Francisco, Calif, USA. Maythem.Saeed@radiology.ucsf.edu
authors.forename: M
authors.initials: M
authors.lastname: Saeed
authors.forename: G
authors.initials: G
authors.lastname: Lund
authors.forename: M F
authors.initials: MF
authors.lastname: Wendland
authors.forename: J
authors.initials: J
authors.lastname: Bremerich
authors.forename: H
authors.initials: H
authors.lastname: Weinmann
authors.forename: C B
authors.initials: CB
authors.lastname: Higgins
mesh_terms: D000818:Animals; D003287:Contrast Media; D019786:Gadolinium DTPA; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008652:Mesoporphyrins; D008665:Metalloporphyrins; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000175:diagnosis*; D009206:Myocardium / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D003287:Contrast Media; D008652:Mesoporphyrins; D008665:Metalloporphyrins; C118579:gadophrin-2; D019786:Gadolinium DTPA