title: Coronary Microembolization with Normal Epicardial Coronary Arteries and No Visible Infarcts on Nitrobluetetrazolium Chloride-Stained Specimens: Evaluation with Cardiac Magnetic Resonance Imaging in a Swine Model.
abstract: OBJECTIVE
  To assess magnetic resonance imaging (MRI) features of coronary microembolization in a swine model induced by small-sized microemboli, which may cause microinfarcts invisible to the naked eye.
  
  
  METHODS
  Eleven pigs underwent intracoronary injection of small-sized microspheres (42 µm) and catheter coronary angiography was obtained before and after microembolization. Cardiac MRI and measurement of cardiac troponin T (cTnT) were performed at baseline, 6 hours, and 1 week after microembolization. Postmortem evaluation was performed after completion of the imaging studies.
  
  
  RESULTS
  Coronary angiography pre- and post-microembolization revealed normal epicardial coronary arteries. Systolic wall thickening of the microembolized regions decreased significantly from 42.6 ± 2.0% at baseline to 20.3 ± 2.3% at 6 hours and 31.5 ± 2.1% at 1 week after coronary microembolization (p < 0.001 for both). First-pass perfusion defect was visualized at 6 hours but the extent was largely decreased at 1 week. Delayed contrast enhancement MRI (DE-MRI) demonstrated hyperenhancement within the target area at 6 hours but not at 1 week. The microinfarcts on gross specimen stained with nitrobluetetrazolium chloride were invisible to the naked eye and only detectable microscopically. Increased cTnT was observed at 6 hours and 1 week after microembolization.
  
  
  CONCLUSIONS
  Coronary microembolization induced by a certain load of small-sized microemboli may result in microinfarcts invisible to the naked eye with normal epicardial coronary arteries. MRI features of myocardial impairment secondary to such microembolization include the decline in left ventricular function and myocardial perfusion at cine and first-pass perfusion imaging, and transient hyperenhancement at DE-MRI.
authors.affiliation: Department of Radiology, Zhongshan Hospital, Fudan University and Shanghai Institute of Medical Imaging, Shanghai 200032, China.; Department of Medical Imaging, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Hang
authors.initials: H
authors.lastname: Jin
authors.affiliation: Department of Radiology, Zhongshan Hospital, Fudan University and Shanghai Institute of Medical Imaging, Shanghai 200032, China.; Department of Medical Imaging, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yun
authors.affiliation: Department of Cardiology, Zhongshan Hospital, Fudan University and Shanghai Institute of Cardiovascular Diseases, Shanghai 200032, China.
authors.forename: Jianying
authors.initials: J
authors.lastname: Ma
authors.affiliation: Department of Cardiology, Zhongshan Hospital, Fudan University and Shanghai Institute of Cardiovascular Diseases, Shanghai 200032, China.
authors.forename: Zhangwei
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Cardiology, Zhongshan Hospital, Fudan University and Shanghai Institute of Cardiovascular Diseases, Shanghai 200032, China.
authors.forename: Shufu
authors.initials: S
authors.lastname: Chang
authors.affiliation: Department of Radiology, Zhongshan Hospital, Fudan University and Shanghai Institute of Medical Imaging, Shanghai 200032, China.; Department of Medical Imaging, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Mengsu
authors.initials: M
authors.lastname: Zeng
mesh_terms: D000818:Animals; D017023:Coronary Angiography / Q000379:methods*; D003331:Coronary Vessels / Q000473:pathology*; D004195:Disease Models, Animal; D004617:Embolism / Q000473:pathology*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008863:Microspheres; D009200:Myocardial Contraction / Q000502:physiology; D009203:Myocardial Infarction / Q000473:pathology*; D009206:Myocardium / Q000473:pathology; D009580:Nitroblue Tetrazolium; D013194:Staining and Labeling; D013552:Swine; D020107:Troponin T / Q000097:blood; D016277:Ventricular Function, Left
chemical_list: D020107:Troponin T; D009580:Nitroblue Tetrazolium
keywords: Cardiac MR imaging; Coronary angiography; Myocardial contraction; Myocardial microinfarct