'Hot spot' detection of ischemic myocardium in vivo by gamma camera imaging

Robert D. Okada, Gerald Johnson, Kiem N. Nguyen, Zhonglin Liu, Barbara Edwards, Colin M. Archer, Timothy L. North, Adam C. King, James D. Kelly

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Background - 99Tc-HL91 is a new hypoxia imaging that demonstrates increase uptake and retention in globally hypoxic myocardium in vitro. The purpose of this study was to determine whether 99Tc-HL91 could detect regional ischemia in vivo by gamma camera imaging. Methods and Results - Eight open-chest dogs with left circumflex (LCx) stenoses were studied. Injection of 5 mCi of 99Tc-HL91 and microspheres was followed by imaging over 4 hours. Heart slices were imagined, then stained with triphenytetrazolium chloride (TTC), and tissues were well-counted. TTC staining demonstrated no injury. Mean LCx blood flow was 0.32±0.04 mL · min-1 · g-1, and mean left anterior descending coronary artery (LAD) flow was 0.96±0.02 mL · min-1 · g-1 (ratio, 0.33). 'Hot spots' were detected in 8 of 8 experiments in vivo within 60 minutes and improved over 4 hours. Region of interest analysis of LCx/LAD activity ratios demonstrated significant increases within 30 minutes (final ratios, 3.0;P<0.05). LCx and LAD washout curves demonstrated significant differences within 15 minutes. Washout curves were biexponential over 1 hour, followed by linear retention from 1 to 4 hours. Four-hour fractional retention was 0.12 for LAD and 0.44 for LCx (P<0.01). Myocardial flow versus tracer uptake demonstrated 2 phases: phase 1 (flow, 0.05 to 0.7 mL · min-1 · g-1) had an inverse linear correlation (r=0.80); phase 2, (flow,>0.7 mL · min-1 · g-1) had no correlation. ISchemic heart/liver ratios remained near 1.0 for 4 hours. Conclusions - 99Tc-HL91 positively identifies regional myocardial ischemia in a canine model using 99Tc imaging. Quantitative techniques allowed identification of ischemic myocardium within 15 minutes of tracer administration.

Original languageEnglish (US)
Pages (from-to)2557-2566
Number of pages10
Issue number25
StatePublished - Jun 30 1998


  • Hypoxia
  • Imaging
  • Ischemia
  • Myocardium
  • Technetium

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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