title: Distinction of salvaged and infarcted myocardium within the ischaemic area-at-risk with T2 mapping.
abstract: OBJECTIVE
  Area-at-risk (AAR) measurements often rely on T2-weighted images, but subtle differences in T2 may be overlooked with this method. To determine the differences in oedema between salvaged and infarcted myocardium, we performed quantitative T2 mapping of the AAR. We also aimed to determine the impact of reperfusion time on T2 in the AAR.
  
  
  METHODS
  Twenty-two dogs underwent 2 h of coronary occlusion followed by 4 or 48 h of reperfusion before cardiac magnetic resonance imaging at 1.5 T. Late gadolinium enhancement images were used to define the infarcted, salvaged, and remote myocardium. T2 values from T2 maps and signal intensities on T2-weighted images were measured in the corresponding areas.
  
  
  RESULTS
  At both imaging time points, the T2 of the salvaged myocardium was longer than of remote (66.0 ± 6.9 vs. 51.4 ± 3.5 ms, P < 0.001 at 4 h, and 56.7 ± 7.3 vs. 48.1 ± 3.5 ms, P < 0.001 at 48 h). The T2 was also longer in the infarcted myocardium compared with remote at both 4 and 48 h (71.4 ± 7.6 ms, P < 0.01 vs. salvage and 64.0 ± 6.9 ms, P = 0.03 vs. salvage, both P < 0.001 vs. remote). The increase in T2 in the salvaged myocardium compared with remote was greater after 4 h than after 48 h (14.7 ± 5.6 vs. 8.7 ± 5.1 ms, P = 0.02).
  
  
  CONCLUSIONS
  T2 relaxation parameters are different in the infarcted and salvaged myocardium, and both are significantly longer than remote. Furthermore, the magnitude of increase in T2 was less in the salvaged myocardium after longer reperfusion, indicating partial resolution of oedema in the first 48 h after reperfusion.
authors.affiliation: Department of Health and Human Services, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bldg 10, RM B1D416, Bethesda, MD 20892-1061, USA Department of Medicine B, The Heart Center, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Sophia
authors.initials: S
authors.lastname: Hammer-Hansen
authors.affiliation: Department of Clinical Physiology, N2:01, Karolinska Institute and Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Ugander
authors.affiliation: Department of Health and Human Services, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bldg 10, RM B1D416, Bethesda, MD 20892-1061, USA.
authors.forename: Li-Yueh
authors.initials: LY
authors.lastname: Hsu
authors.affiliation: Department of Health and Human Services, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bldg 10, RM B1D416, Bethesda, MD 20892-1061, USA.
authors.forename: Joni
authors.initials: J
authors.lastname: Taylor
authors.affiliation: Department of Medicine B, The Heart Center, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Jens Jakob
authors.initials: JJ
authors.lastname: Thune
authors.affiliation: Department of Medicine B, The Heart Center, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Køber
authors.affiliation: Department of Health and Human Services, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bldg 10, RM B1D416, Bethesda, MD 20892-1061, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Kellman
authors.affiliation: Department of Health and Human Services, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bldg 10, RM B1D416, Bethesda, MD 20892-1061, USA araia@nih.gov.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Arai
mesh_terms: D000818:Animals; D055424:Cardiac-Gated Imaging Techniques; D003287:Contrast Media / Q000008:administration & dosage; D004195:Disease Models, Animal; D004285:Dogs; D004487:Edema / Q000473:pathology*; D019786:Gadolinium DTPA / Q000008:administration & dosage; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008863:Microspheres; D009203:Myocardial Infarction / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D015427:Reperfusion Injury / Q000473:pathology*
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA
keywords: Acute myocardial infarction; Area-at-risk; Magnetic resonance imaging; Myocardial ischaemia; Myocardial salvage