title: Collateral circulation formation determines the characteristic profiles of contrast-enhanced MRI in the infarcted myocardium of pigs.
abstract: OBJECTIVE
  To investigate the relationship between the collateral circulation and contrast-enhanced MR signal change for myocardial infarction (MI) in pigs.
  
  
  METHODS
  Pigs underwent permanent ligation of two diagonal branches of the left anterior descending artery. First-pass perfusion (FPP) MRI (for detecting myocardial perfusion abnormalities) and delayed enhancement (DE) MRI (for estimating myocardial infarction) using Gd-DTPA were performed at 2 h, 7 d and 4 weeks after the coronary occlusion. Myocardial blood flow (MBF) was evaluated using nonradioactive red-colored microspheres. Histological examination was performed to characterize the infarcts.
  
  
  RESULTS
  Acute MI performed at 2 h afterwards was characterized by hypoenhancement in both FPP- and DE-MRI, with small and almost unchanged FPP-signal intensity (SI) and DE-SI due to negligible MBF. Subacute MI detected 7 d afterwards showed small but significantly increaseing FPP-SI, and was visible as a sluggish hyperenhancement in DE-MRI with considerably higher DE-SI compared to the normal myocardium; the MBF approached the half-normal value. Chronic MI detected at 4 weeks afterwards showed increasing FPP-SI comparable to the normal myocardium, and a rapid hyperenhancement in DE-MRI with even higher DE-SI; the MBF was close to the normal value. The MBF was correlated with FPP-SI (r=+0.94, P<0.01) and with the peak DE-SI (r=+0.92, P<0.01) at the three MI stages. Remodeled vessels were observed at intra-infarction and peri-infarction zones during the subacute and chronic periods.
  
  
  CONCLUSIONS
  Progressive collateral recovery determines the characteristic profiles of contrast-enhanced MRI in acute, subacute and chronic myocardial infarction in pigs. The FPP- and DE-MRI signal profiles not only depend on the loss of tissue viability and enlarged interstitial space, but also on establishing a collateral circulation.
authors.affiliation: 1] Department of Vascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China [2] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [3] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.affiliation: 1] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [2] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5.
authors.forename: Bo
authors.initials: B
authors.lastname: Xiang
authors.affiliation: National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6.
authors.forename: Hung-yu
authors.initials: HY
authors.lastname: Lin
authors.affiliation: Department of Cardiovascular Surgery, the First Affiliated Hospital, Harbin Medical University, Harbin 150001, China.
authors.forename: Hong-yu
authors.initials: HY
authors.lastname: Liu
authors.affiliation: 1] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [2] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5 [3] Cardiac Science Program, Institute of Cardiovascular Science, St Boniface General Hospital, Winnipeg, Manitoba, Canada R2H 2A6.
authors.forename: Darren
authors.initials: D
authors.lastname: Freed
authors.affiliation: 1] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [2] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5 [3] Cardiac Science Program, Institute of Cardiovascular Science, St Boniface General Hospital, Winnipeg, Manitoba, Canada R2H 2A6.
authors.forename: Rakesh C
authors.initials: RC
authors.lastname: Arora
authors.affiliation: 1] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [2] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5.
authors.forename: Gang-hong
authors.initials: GH
authors.lastname: Tian
mesh_terms: D000818:Animals; D003097:Collateral Circulation; D003287:Contrast Media; D019786:Gadolinium DTPA; D009203:Myocardial Infarction / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D013552:Swine
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA
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