title: Myocardial magnetic resonance imaging contrast agent concentrations after reversible and irreversible ischemic injury.
abstract: BACKGROUND
  Discrepant reports have been published recently regarding the relationship of contrast-enhanced magnetic resonance image intensities to reversible and irreversible ischemic injury. Unlike image intensities, contrast agent concentrations provide data independent of the MRI technique. We used electron probe x-ray microanalysis (EPXMA) to simultaneously examine concentrations of Gd, Na, P, S, Cl, K, and Ca over a range of myocardial injuries. Methods and Results- Reversible and irreversible injury were studied in 38 rabbits divided into 4 groups defined by occlusion and reperfusion time, as well as time the animals were euthanized. Gd-DTPA was administered, and the hearts were excised and rapidly frozen, cryosectioned, freeze-dried, and examined by EPXMA in up to 3 regions: remote, infarcted, and at risk but not infarcted. Infarcted regions were defined by anti-myoglobin antibody or triphenyltetrazolium chloride staining. Regions at risk were defined by fluorescent microparticles administered during occlusion. Compared with remote regions, in acutely infarcted regions, Gd was increased (235+/-24%, P<0.005) in the same 50 x 100-microm areas in which Na was increased (154+/-5%, P<0.001) and K was decreased (52+/-8%, P<0.001). Similarly, in chronically infarcted regions, Gd was increased (472+/-78%, P<0.001) in areas in which Na was increased (332+/-28%, P<0.001) and K was decreased (47+/-5%, P<0.001). Also compared with remote regions, however, concentrations of Gd, Na, and K were not elevated after reperfusion in regions that were at risk but not infarcted (P=NS).
  
  
  CONCLUSIONS
  Regional elevations in myocardial MRI contrast agent concentrations are exclusively associated with irreversible ischemic injury defined histologically and by regional electrolyte concentrations.
authors.affiliation: Northwestern University Medical School Feinberg Cardiovascular Research Institute, Biomedical Engineering, Chicago, IL, USA.
authors.forename: Wolfgang G
authors.initials: WG
authors.lastname: Rehwald
authors.forename: David S
authors.initials: DS
authors.lastname: Fieno
authors.forename: Enn-Ling
authors.initials: EL
authors.lastname: Chen
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Kim
authors.forename: Robert M
authors.initials: RM
authors.lastname: Judd
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D002908:Chronic Disease; D003287:Contrast Media / Q000032:analysis*; D004577:Electron Probe Microanalysis; D019786:Gadolinium DTPA / Q000008:administration & dosage / Q000032:analysis*; D007700:Kinetics; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology*; D009206:Myocardium / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis; D011188:Potassium / Q000032:analysis; D011817:Rabbits; D011859:Radiography; D012964:Sodium / Q000032:analysis; D013455:Sulfur / Q000032:analysis
chemical_list: D003287:Contrast Media; D010758:Phosphorus; D002713:Chlorine; D013455:Sulfur; D012964:Sodium; D019786:Gadolinium DTPA; D011188:Potassium; D002118:Calcium