title: Direct detection of regional myocardial ischemia with technetium-99m nitroimidazole in rabbits.
abstract: Conventional perfusion scintigraphy assesses disparities in regional myocardial blood flow but does not directly detect hypoxic tissue. Nitroimidazoles labeled with positron-emitting radionuclides have recently shown promise as direct markers of myocardial hypoxia. This study evaluates a new 99mTc-labeled nitroimidazole of potential benefit in standard myocardial scintigraphy.
  
  
  METHODS
  Technetium-99m-labeled nitroimidazole was administered to rabbits during the early reperfusion phase after 10 min (Group 1) or 60 (Group 2) min of coronary occlusion or after 10 min of a fixed coronary occlusion (Group 3). Tracer retention at 1 hr was assessed in relation to microsphere-determined blood flow during coronary occlusion and at tracer injection. The pattern of nitroimidazole retention on autoradiographs was then compared with the pattern of myocardial hypoperfusion defined by fluorescein photography to precisely define tracer localization.
  
  
  RESULTS
  The retention of nitroimidazole in Group 1 rabbits (brief occlusion) was independent of both occlusion and reperfusion blood flow and was uniformly distributed on the autoradiographs. In contrast, nitroimidazole retention in Groups 2 and 3 increased with the severity of hypoperfusion during the occlusion phase and precisely delineated the ischemic zone on all autoradiographs.
  
  
  CONCLUSIONS
  This 99mTc-labeled hypoxia-avid tracer delineates severe ischemia even after blood flow to the compromised myocardium has been restored. This class of compounds can potentially enhance the physiological assessment of patients with ischemic heart disease.
authors.affiliation: Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester, USA.
authors.forename: H
authors.initials: H
authors.lastname: Weinstein
authors.forename: C P
authors.initials: CP
authors.lastname: Reinhardt
authors.forename: J A
authors.initials: JA
authors.lastname: Leppo
mesh_terms: D000818:Animals; D001345:Autoradiography; D003326:Coronary Circulation; D005452:Fluoresceins; D006321:Heart / Q000000981:diagnostic imaging*; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging*; D009206:Myocardium / Q000473:pathology; D009593:Nitroimidazoles; D015609:Organotechnetium Compounds; D010781:Photography; D011817:Rabbits; D011877:Radionuclide Imaging; D013997:Time Factors; D014022:Tissue Survival
chemical_list: D005452:Fluoresceins; D009593:Nitroimidazoles; D015609:Organotechnetium Compounds; C082027:BMS 181321