title: Magnetic resonance imaging/magnetic resonance spectroscopy biomarkers evaluation of stunned myocardium in canine model.
abstract: OBJECTIVE
  To evaluate whether dynamic alterations in high-energy phosphate (HEP) occur in postischemic "stunned" myocardium (SM) in canine model and to investigate the correlation between HEP and cardiac function, using cine magnetic resonance imaging (cine-MRI) and phosphorus-31 magnetic resonance spectroscopy (31P-MRS).
  
  
  METHODS
  Dogs (n = 13) underwent cine MRI and 31P-MRS at 60 minutes, 8 days after 10 minutes full left anterior descending occlusion followed by reperfusion. The same MRI/MRS experiments were repeated on 5 reference animals (dogs without ischemic reperfusion) at the same time points to serve as internal reference myocardium (RM). After MR data acquisitions, the SM dogs (n = 3 at 60 minutes; n = 10 at 60 minutes and day 8) and RM dogs (n = 5) were euthanized and myocardial tissues were sampled for histologic study by triphenyltetrazolium chloride staining, hematoxylin and eosin staining, and electron microscopic examination.
  
  
  RESULTS
  The myocardial stunning at 60 minutes was confirmed by electron microscopy examinations from the 3 randomly chosen animals with SM. The phosphocreatine (PCr)/β- adenosine triphosphate (ATP) ratio of SM was significantly lower at 60 minutes than that at day 8 (1.07 ± 0.20 vs. 1.97 ± 0.28, P < 0.05). However, no significant difference was found between 60 minutes and day 8 in RM group (1.91 ± 0.14 at 60 minutes vs. 1.89 ± 0.16 at day 8, P > 0.05). At 60 minutes, the PCr/β-ATP ratio has significant difference between SM and RM groups; while at day 8, the ratio shows no significant difference between the 2 groups. The same results were obtained for left ventricle ejection fraction (LVEF). In SM group, LVEF has good correlation with myocardial PCr/β-ATP ratios at 60 minutes (R2 = 0.71, P < 0.05) and at day 8 (R2 = 0.73, P < 0.05), respectively.
  
  
  CONCLUSIONS
  The HEP alterations were confirmed by 31P-MRS in SM and there is a good correlation between PCr/β-ATP ratio and LVEF for SM at 60 minutes and recovered myocardium at day 8. The combined MRS/MRI method offers the potential to systematically assess the cardiac function, morphology, and metabolism of SM. These MRS/MRI biomarker datasets could be used to dynamically monitor therapeutic efficiency and predict cardiac events.
authors.affiliation: Department of Radiology, Xijing Hospital, Fourth Military Medical University, Xi'an, People's Republic of China.
authors.forename: Zhuoli
authors.initials: Z
authors.lastname: Zhang
authors.forename: Junxia
authors.initials: J
authors.lastname: Li
authors.forename: Shengyong
authors.initials: S
authors.lastname: Wu
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiangzhi
authors.initials: X
authors.lastname: Zhou
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Fan
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
authors.forename: Yi
authors.initials: Y
authors.lastname: Huan
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D000818:Animals; D015415:Biomarkers; D002316:Cardiotonic Agents / Q000378:metabolism; D004195:Disease Models, Animal; D004285:Dogs; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D017682:Myocardial Stunning / Q000378:metabolism / Q000473:pathology*; D010725:Phosphocreatine / Q000378:metabolism
chemical_list: D015415:Biomarkers; D002316:Cardiotonic Agents; D010725:Phosphocreatine; D000255:Adenosine Triphosphate