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Myocardial Technetium-99m-Teboroxime Uptake during Adenosine-Induced Hyperemia in Dogs with Either a Critical or Mild Coronary Stenosis: Comparison to Thallium-201 and Regional Blood Flow

Experimental Cardiology Laboratory, Division of Cardiology, Department of Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia

Correspondence: For correspondence or reprints contact: David K. Glover, Experimental Cardiology Laboratory, Box 500, University of Virginia Health Sciences Center, Charlottesville, VA 22908.

ABSTRACT

Experimental studies have shown ^99mTc-teboroxime to have a higher first-pass myocardial extraction, exceeding that of ²⁰¹TI with nearly linear initial myocardial uptake over a wide range of coronary flows. The goal of this study was to quantitatively compare teboroxime with ²⁰¹TI the assessment of a regional coronary flow imbalance when administered during adenosine vasodilation in dogs with either critical or mild LAD stenoses. Methods: Twenty-four anesthetized dogs with either critical (n= 10) or mild (n = 14) LAD stenoses were given an i.v. infusion of adenosine (300 µg/kg/min). When LCx flow was maximal, ²⁰¹TI, teboroxime and microspheres were simultaneously injected and the dogs were killed either 2 or 4 min later. Regional ²⁰¹TI, teboroxime activities and myocardial blood flow were determined by gamma well counting and ex vivo imaging of ^99mTc-teboroxime activity in myocardial heart slices was performed. Results: In both the critical and mild stenosis groups, the LAD/LCx zone ratios in dogs killed 2 min after tracer injection for both ²⁰¹TI (0.31 ± 0.07, 0.63 ± 0.05) and teboroxime (0.38 ± 0.09, 0.72 ± 0.04) significantly underestimated the microsphere flow ratio (0.18 ± 0.05, 0.43 ± 0.05) (p 0.01), but the degree of underestimation was greater for teboroxime compared with TI (p 0.05). Conclusion: In dogs with either critical or mild LAD stenoses, as early as 2 min after tracer injection, the ²⁰¹TI activity ratio more accurately assessed the adenosine-induced regional flow heterogeneity than did teboroxime. These results highlight the importance of an ultra-fast imaging protocol when using teboroxime with pharmacologic stress.

Key Words: thallium-201 • teboroxime • adenosine • hyperemia • coronary stenosis

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				D. A. Calnon, M. Ruiz, G. Vanzetto, D. D. Watson, G. A. Beller, and D. K. Glover Myocardial Uptake of 99mTc-N-NOET and 201Tl During Dobutamine Infusion : Comparison With Adenosine Stress Circulation, October 12, 1999; 100(15): 1653 - 1659. [Abstract] [Full Text] [PDF]