title: Contrast-enhanced magnetic resonance imaging of myocardium at risk: distinction between reversible and irreversible injury throughout infarct healing.
abstract: OBJECTIVE
  We sought to determine the relationship of delayed hyperenhancement by contrast magnetic resonance imaging (MRI) to viable and nonviable myocardium within the region at risk throughout infarct healing.
  
  
  BACKGROUND
  The relationship of delayed MRI contrast enhancement patterns to injured but viable myocardium within the ischemic bed at risk has not been established.
  
  
  METHODS
  We compared in vivo and ex vivo MRI contrast enhancement to histopathologic tissue sections encompassing the entire left ventricle in dogs (n = 24) subjected to infarction with (n = 12) and without (n = 12) reperfusion at 4 h, 1 day, 3 days, 10 days, 4 weeks and 8 weeks. In vivo MR imaging was performed 30 min after contrast injection.
  
  
  RESULTS
  The sizes and shapes of in vivo myocardial regions of elevated image intensity (828+/-132% of remote) were the same as those observed ex vivo (241 slices, r = 0.99, bias = 0.05+/-1.6% of left ventricle [LV]). Comparison of ex vivo MRI to triphenyltetrazolim chloride-stained sections demonstrated that the spatial extent of hyperenhancement was the same as the spatial extent ofinfarction at every stage of healing (510 slices, lowest r = 0.95, largest bias = 1.7+/-2.9% of LV). Conversely, hyperenhanced regions were smaller than the ischemic bed at risk defined by fluorescent microparticles at every stage of healing (239 slices, 35+/-24% of risk region, p<0.001). Image intensities of viable myocardium within the risk region were the same as those of remote, normal myocardium (102+/-9% of remote, p = NS).
  
  
  CONCLUSIONS
  Delayed contrast enhancement by MRI distinguishes between viable and nonviable regions within the myocardium at risk throughout infarct healing.
authors.affiliation: Northwestern University Medical School Feinberg Cardiovascular Research Institute, Department of Biomedical Engineering, Chicago, Illinois 60611-3008, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Fieno
authors.forename: R J
authors.initials: RJ
authors.lastname: Kim
authors.forename: E L
authors.initials: EL
authors.lastname: Chen
authors.forename: J W
authors.initials: JW
authors.lastname: Lomasney
authors.forename: F J
authors.initials: FJ
authors.lastname: Klocke
authors.forename: R M
authors.initials: RM
authors.lastname: Judd
mesh_terms: D000818:Animals; D004285:Dogs; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000473:pathology; D009206:Myocardium / Q000473:pathology*