99mTc-HL91: "hot spot" detection of ischemic myocardium in vivo by gamma camera imaging.

Abstract

BACKGROUND:

99mTc-HL91 is a new hypoxia imaging agent that demonstrates increased uptake and retention in globally hypoxic myocardium in vitro. The purpose of this study was to determine whether 99mTc-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 99mTc-HL91 and microspheres was followed by imaging over 4 hours. Heart slices were imaged, then stained with triphenyltetrazolium chloride (TTC), and tissues were well-counted. TTC staining demonstrated no injury. Mean LCx blood flow was 0.32+/-0.04 mL x min(-1) x g(-1), and mean left anterior descending coronary artery (LAD) flow was 0.96+/-0.02 mL x min(-1) x 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 ratio, 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 x min(-1) x g(-1)) had an inverse linear correlation (r= -0.80); phase 2, (flow, >0.7 mL x min(-1) x g(-1)) had no correlation. Ischemic heart/liver ratios remained near 1.0 for 4 hours.

CONCLUSIONS:

99mTc-HL91 positively identifies regional myocardial ischemia in a canine model using 99mTc imaging. Quantitative techniques allowed identification of ischemic myocardium within 15 minutes of tracer administration.

• Authors: R D Okada, G Johnson 3rd, K N Nguyen, Z Liu, B Edwards, C M Archer, T L North, A C King, J D Kelly
• Journal: Circulation (Circulation) Vol. 97 Issue 25 Pg. 2557-66 (Jun 30 1998) ISSN: 0009-7322 [Print] United States
• PMID: 9657477 (Publication Type: Journal Article)

Chemical References

• Contrast Media
• Organotechnetium Compounds
• Oximes
• Radiopharmaceuticals
• technetium Tc 99m 4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime

Topics

• Animals
• Contrast Media
• Dogs
• Gamma Cameras
• Myocardial Ischemia (diagnosis)
• Organotechnetium Compounds
• Oximes
• Radiopharmaceuticals