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(Circulation. 1997;95:1892-1899.)
© 1997 American Heart Association, Inc.

Articles

^99mTc-HL91

Effects of Low Flow and Hypoxia on a New Ischemia-Avid Myocardial Imaging Agent

Robert D. Okada, MD; Gerald Johnson, III, PhD; Kiem N. Nguyen, BS; Barbara Edwards, BS; Colin M. Archer, PhD; James D. Kelly, PhD

From the William K. Warren Medical Research Institute of the University of Oklahoma Health Sciences Center, Cardiology of Tulsa, Tulsa, and Amersham International (B.E., C.M.A., J.D.K.), Bucks, England.

Correspondence to Gerald Johnson III, PhD, William K. Warren Medical Research Institute, 6465 S Yale, Ste 1010, Tulsa, OK 74136.

Background ^99mTc-HL91 is a potential imaging agent that has demonstrated increased uptake in hypoxic tumor cells. The purpose of this study was to determine if ^99mTc-HL91 demonstrates increased uptake and retention in ischemic and hypoxic myocardium.

Methods and Results ^99mTc-HL91 (11.1 MBq) was infused over 10 minutes, followed by a 60-minute clearance phase. Activity was monitored by using an NaI detector. Three groups were studied using Krebs-Henseleit buffer (KH): controls (12 mL/min, n=6), low-flow ischemic (1 mL/min, n=7), and hypoxic (12 mL/min, n=8). Two groups were perfused with KH, red blood cells, and albumin: controls (6 mL/min, n=6) and low-flow ischemic (0.5 mL/min, n=6). For the KH hearts, the ^99mTc-HL91 peak uptake progressively increased from control (6.3±0.5 µCi, mean±SEM) to hypoxic (9.1±1.0 µCi) to low flow (44.0±2.6 µCi; P<.01). The peak uptake low-flow/control ratio was 7:1. Final retention increased progressively from control (0.8±0.1 µCi) to hypoxic (2.9±0.5 µCi) to low flow (10.9±1.3 µCi; P<.01). The final low-flow/control activity ratio was 13.6:1. Similar results were observed in the red blood cell–perfused control and low-flow groups.

Conclusions This study introduces a new myocardial "hot spot" imaging agent, ^99mTc-HL91. This agent demonstrates increased myocardial uptake and retention in hypoxic and low-flow ischemic models. Further in vivo imaging studies are warranted to determine the clinical potential of this agent.

Key Words: myocardium • radioisotopes • ischemia • hypoxia

This article has been cited by other articles:

				R. D. Okada, G. Johnson III, K. N. Nguyen, Z. Liu, B. Edwards, C. M. Archer, T. L. North, A. C. King, and J. D. Kelly 99mTc-HL91 : "Hot Spot" Detection of Ischemic Myocardium In Vivo by Gamma Camera Imaging Circulation, June 30, 1998; 97(25): 2557 - 2566. [Abstract] [Full Text] [PDF]