title: Arbutamine stress perfusion imaging in dogs with critical coronary artery stenoses: (99m)Tc-sestamibi versus (201)Tl.
abstract: Having previously shown that dobutamine reduces (99m)Tc-methoxyisobutylisonitrile (sestamibi [MIBI]) uptake in normal myocardium by elevating intracellular calcium, we hypothesized that arbutamine, which has less inotropic effect than dobutamine, might cause less reduction in MIBI uptake, thereby improving defect contrast. In this study using a canine model, we compared the effects of arbutamine stress on myocardial blood flow, myocardial MIBI uptake, and systolic thickening in the presence of a coronary artery stenosis.
  
  
  METHODS
  Arbutamine was infused (0.5-250 ng/kg/min) in 8 open-chest dogs with critical coronary stenoses that abolished flow reserve. At the time of peak arbutamine effect, MIBI (296 MBq), (201)Tl (27.75 MBq), and microspheres were coinjected. The dogs were killed 5 min later, and myocardial tracer activities and flow were quantified by well counting. Ex vivo imaging of heart slices was also performed.
  
  
  RESULTS
  Arbutamine increased mean heart rate, peak positive left ventricular pressure and its first time-derivative, and normal-zone myocardial thickening. Stenotic zone flow and thickening did not increase during arbutamine infusion. MIBI uptake versus flow was significantly lower than (201)Tl uptake at the same flow values. By imaging, defect magnitude (stenotic/normal) was greater for (201)Tl than MIBI (0.57 vs. 0.77; P < 0.001) [corrected].
  
  
  CONCLUSIONS
  In the presence of coronary stenoses that abolished regional flow reserve, myocardial uptake of MIBI, compared with (201)Tl, significantly underestimated the arbutamine-induced flow heterogeneity. The attenuation of MIBI uptake and diminished defect contrast during arbutamine stress were comparable with those previously reported for dobutamine stress.
authors: Experimental Cardiology Laboratory, Cardiovascular Division, Department of Medicine, University of Virginia Health System, Charlottesville, Virginia 22908-0500, USA. mrh2v@virginia.edu
authors: Mirta
authors: M
authors: Ruiz
authors: Kazuya
authors: K
authors: Takehana
authors: Frank D
authors: FD
authors: Petruzella
authors: Denny D
authors: DD
authors: Watson
authors: George A
authors: GA
authors: Beller
authors: David K
authors: DK
authors: Glover
mesh_terms: D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002395:Catecholamines / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects; D023921:Coronary Stenosis / Q000000981:diagnostic imaging*; D004285:Dogs; D006321:Heart / Q000000981:diagnostic imaging*; D006439:Hemodynamics / Q000187:drug effects; D011877:Radionuclide Imaging; D017256:Technetium Tc 99m Sestamibi; D013794:Thallium Radioisotopes
chemical_list: D002316:Cardiotonic Agents; D002395:Catecholamines; D013794:Thallium Radioisotopes; D017256:Technetium Tc 99m Sestamibi; C076559:arbutamine