Author + information
- Received March 6, 1989
- Revision received June 7, 1989
- Accepted June 21, 1989
- Published online December 1, 1989.
- Albert J. Sinusas, MD,
- Denny D. Watson, PhD,
- James M. Cannon Jr, ME and
- George A. Beller, MD, FACC∗
- ↵∗Address for reprints: George A. Beller, MD, Division of Cardiology, Box 158, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908.
The myocardial uptake of a new technetium-99m-labeled myocardial perfusion agent, methoxyisobutyl isonitrile (Tc-99m MIBI), and thallium-201 was correlated with microsphere flow in an open chest canine model of low coronary flow and postischemic dysfunction. Eighteen dogs were given an injection of thallium-201 (0.5 mCi) and Tc-99m MIBI (5 mCi) either after 40 min of partial left anterior descending artery occlusion (Group I, 10 dogs) or during reperfusion after 15 min of left anterior descending artery occlusion (Group II, 8 dogs). Regional dysfunction was documented during injection in both groups by quantitative two-dimensional echocardiography. Regional blood flow was assessed by radiolabeled microspheres. The heart was excised 15 min after radionuclide injection and the left ventricle divided into 96 segments for gamma well counting.
Among Group I dogs, central ischemic thallium-201 and Tc-99m MIBI activity (expressed as a percent of the activity in the corresponding nonischemic zone) was comparable, respectively, for endocardial (54 ± 17% and 52 ± 17%), mid-wall (71 ± 20% and 69 ± 17%) and epicardial (89 ± 13% and 94 ± 9%) segments and increased proportionally with flow. There was a good linear correlation among these endocardial segments between flow and both thallium-201 (r = 0.78) and Tc-99m MIBI (r = 0.85) activity. Among Group II dogs, central ischemic endocardial flow (59 ± 14%) was comparable to thallium-201 (70 ± 18%) and Tc-99m MIBI (74 ± 12%) activity. Similarly, relative endocardial flow in the intermediate ischemic region (71 ± 11%) was comparable to thallium-201 (77 ± 11%) and Tc-99m MIBI (81 ± 10%) activity.
Thus, myocardial uptake of Tc-99m MIBI and thallium-201 is comparable under conditions of low coronary flow and postischemic dysfunction and closely parallels flow alterations.
☆ This work was supported in part by Grant R01 HL-26205 from the National Heart, Lung, and Blood Institute, Bethesda, Maryland and E.I. Dupont de Nemours & Co., Inc., North Billerica, Massachusetts. Dr. Sinusas is the recipient of National Research Award 1 F32 HL07745-01 from the National Heart, Lung, and Blood Institute.
- Received March 6, 1989.
- Revision received June 7, 1989.
- Accepted June 21, 1989.