title: The histology of viable and hibernating myocardium in relation to imaging characteristics.
abstract: OBJECTIVE
  This study characterizes the histology of myocardium predicted to be hibernating using three different imaging techniques to explain the discordance among them.
  
  
  BACKGROUND
  Both radionuclide and functional imaging techniques were used to assess myocardial hibernation. The former have high sensitivity and the latter high specificity for predicting functional recovery.
  
  
  METHODS
  Nineteen patients underwent thallium-201 and 99m-technetium tetrofosmin myocardial perfusion imaging, and dobutamine magnetic resonance imaging (MRI), prior to coronary bypass grafting. Criteria for predicted hibernation for each technique were defined before operation. Postoperative criteria for scar and true hibernation were also defined. Biopsies were analyzed for myocyte volume fraction (MVF), glycogen deposition and pathologic cell features.
  
  
  RESULTS
  Thallium was most sensitive in predicting hibernation (88%) and MRI most specific (84%); and, although there was good agreement between thallium and tetrofosmin (85%), agreement between MRI and thallium (59%) or tetrofosmin (59%) was poor. For each technique, MVF was higher in segments predicted to be hibernating rather than scar (p < 0.05). The MVF was higher where both thallium and MRI predicted hibernation (0.77+/-0.07) than in segments predicted by thallium alone (0.69+/-0.13, p < 0.05). Proven hibernating segments had a higher MVF than scar (0.72+/-0.11 vs. 0.6+/-0.26, p < 0.05).
  
  
  CONCLUSIONS
  Preservation of myocyte fraction is an important determinant of functional recovery after revascularization. A higher myocyte fraction is required to maintain contractile reserve than to achieve significant tracer uptake. This explains the higher sensitivity of radionuclide imaging compared with dobutamine MRI in the identification of myocardial hibernation.
authors.affiliation: Department of Cardiac Imaging, Royal Brompton Hospital and Imperial College School of Medicine, London, United Kingdom.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Gunning
authors.forename: Raffi R
authors.initials: RR
authors.lastname: Kaprielian
authors.forename: John
authors.initials: J
authors.lastname: Pepper
authors.forename: Dudley J
authors.initials: DJ
authors.lastname: Pennell
authors.forename: Mary N
authors.initials: MN
authors.lastname: Sheppard
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Severs
authors.forename: Kim M
authors.initials: KM
authors.lastname: Fox
authors.forename: S Richard
authors.initials: SR
authors.lastname: Underwood
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D004280:Dobutamine; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D017682:Myocardial Stunning / Q000175:diagnosis / Q000473:pathology*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013318:Stroke Volume / Q000502:physiology; D013793:Thallium
chemical_list: D004280:Dobutamine; D013793:Thallium