Tc-99m sestamibi defect magnitude predicts the amount of viable myocardium after coronary reperfusion despite the presence of severe residual stenosis.
BACKGROUND
Whether technetium-99m-labeled methoxyisobutyl isonitrile (Tc-99m sestamibi) imaging early after reperfusion can detect the amount of salvaged viable myocardium in the presence of a severe residual stenosis remains controversial.


RESULTS
Nine dogs underwent total left anterior descending coronary artery (LAD) occlusion for 40 to 180 minutes followed by reperfusion through a flow-limiting stenosis. They were divided into 2 groups based on infarct size (group 1, <15% of risk area; group 2, > or =15%). Triphenyl tetrazolium chloride infarct size was measured by planimetry, and regional flow was quantified by radiolabeled microspheres. Mean infarct size was 9.3% +/- 3.0% of risk area in group 1 versus 51.1% +/- 4.8% in group 2 (P <.01). Tc-99m sestamibi was injected 30 minutes after reperfusion, when the LAD flows were comparable for group 1 (9 +/- 2 mL. min(-1)) and group 2 (9 +/- 1 mL. min(-1)). Left circumflex coronary artery flows were 33 +/- 5 and 32 +/- 9 mL. min(-1) for groups 1 and 2, respectively. Despite administration of Tc-99m sestamibi during diminished residual LAD flow after reperfusion, defect magnitude on ex vivo images in group 1 was significantly less severe than that in group 2, which had larger infarcts (0.71 +/- 0.02 vs 0.42 +/- 0.05, P <.01). This reflects greater salvage and more viability in group 1.


CONCLUSIONS
Resting perfusion imaging with Tc-99m sestamibi accurately determined viability of the infarct zone despite reperfusion through a residual stenosis. Tc-99m sestamibi imaging may prove useful in the clinical setting for the prediction of the amount of salvaged myocardium.
Takehana
K
K
Experimental Cardiology Laboratory, Cardiovascular Division, Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
Ruiz
M
M
Petruzella
F D
FD
Watson
D D
DD
Beller
G A
GA
Glover
D K
DK
D000818:Animals; D001783:Blood Flow Velocity; D003326:Coronary Circulation; D004285:Dogs; D006439:Hemodynamics; D008863:Microspheres; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000473:pathology*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi
D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi