title: HL-91-technetium-99m: a new marker of viability in ischemic myocardium.
abstract: BACKGROUND
  Technetium 99m-HL91 is a new hypoxia imaging agent that demonstrates increased uptake in ischemic, viable myocardium. This study was performed to determine whether HL91 is taken up by nonviable myocardium.
  
  
  METHODS
  Twenty-three Krebs-Henseleit buffer-perfused, isolated rat hearts were studied. Tc-99m-HL91 300 microCi was infused over 10 minutes, followed by a 60-minute clearance. Myocardial activity was monitored by use of an NaI crystal. Four groups were studied: control (flow = 12 mL/min, n = 7), low flow (flow = 1 mL/min, n = 6), no flow/reflow (60 minutes no flow/60 minutes reflow before Tc-99m-HL91 infusion, flow = 12 mL/min, n = 5), and cyanide-treated (before Tc-99m-HL91 infusion, flow = 12 mL/min, n = 5). Injury was assessed by creatine kinase, transmission electron microscopy, and triphenyltetrazolium chloride.
  
  
  RESULTS
  Control (no injury) and cyanide-treated (severe injury) hearts demonstrated low uptake (6.3+/-0.5 mean+/-SEM and 5.7+/-1.2 microCi, respectively) and low 60-minute retention (13.8%+/-2.2% and 13.7%+/-3.9%, respectively). Low-flow hearts (minimal injury) demonstrated markedly increased uptake (43.5+/-2.8 microCi, P < .01) and increased 60-minute retention (33.2%+/-2.9%, P < .01) compared with control. No-flow/reflow hearts (moderate injury) demonstrated intermediate uptake (8.7+/-0.5 microCi, P < .05 to control), although retention was not significantly different (18.9%+/-3.5%, P = ns). Severely and rapidly injured myocardium demonstrated Tc-99m-HL91 peak uptake and retention indistinguishable from normal. Moderately injured myocardium demonstrated uptake intermediate between severely injured and low-flow-induced ischemic, viable myocardium.
  
  
  CONCLUSIONS
  Thus Tc-99m-HL91 is not taken up or retained in nonviable and irreversibly injured myocardium.
authors.affiliation: William K Warren Medical Research Institute of the University of Oklahoma Health Sciences Center, Tulsa 74136, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Okada
authors.forename: G
authors.initials: G
authors.lastname: Johnson
authors.forename: K N
authors.initials: KN
authors.lastname: Nguyen
authors.forename: L R
authors.initials: LR
authors.lastname: Carlson
authors.forename: D
authors.initials: D
authors.lastname: Beju
mesh_terms: D000818:Animals; D003326:Coronary Circulation; D003402:Creatine Kinase / Q000097:blood; D006321:Heart / Q000000981:diagnostic imaging*; D006439:Hemodynamics; D066298:In Vitro Techniques; D008297:Male; D008854:Microscopy, Electron; D017202:Myocardial Ischemia / Q000139:chemically induced / Q000000981:diagnostic imaging* / Q000473:pathology; D009206:Myocardium / Q000378:metabolism / Q000648:ultrastructure; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics; D010091:Oximes / Q000493:pharmacokinetics; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012966:Sodium Cyanide; D017725:Ventricular Pressure
chemical_list: D015609:Organotechnetium Compounds; D010091:Oximes; D019275:Radiopharmaceuticals; C105527:technetium Tc 99m 4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime; D003402:Creatine Kinase; D012966:Sodium Cyanide