title: Myocardial contractile reserve and perfusion defect severity with rest and stress dobutamine (99m)Tc-sestamibi SPECT in canine stunning and subendocardial infarction.
abstract: Myocardial contractile reserve and resting perfusion scintigraphy provide independent information to assess myocardial viability. The purpose of this study was to simultaneously evaluate both with (99m)Tc-sestamibi SPECT and low-dose dobutamine in canine stunning and subendocardial infarction (SEMI).
  
  
  METHODS
  Eighteen dogs were included in the study: 7 normal, 7 stunned, and 4 with SEMI. Closed-chest stunning and SEMI were produced by angioplasty balloon occlusion of the left anterior descending artery (20 and 90 min, respectively). Subsequent radiolabeled mircospheres confirmed reflow, and (99m)Tc-sestamibi was then administered at rest. Gated SPECT and MRI tagging were performed at rest and during low-dose dobutamine infusion (5 microg/kg/min). SPECT systolic wall thickening index (SWI) and MRI radial strain quantified myocardial contraction. Postmortem 2,3,5-triphenyltetrazolium chloride staining quantified SEMI.
  
  
  RESULTS
  Defect severity by SPECT in the anterior wall was mild and was not statistically different for the stunned versus SEMI groups (P = not significant). At rest, anterior wall SPECT SWI was significantly higher in the normal versus stunned groups (21.1 +/- 3.1 vs. 10.1 +/- 9.0; P = 0.0002) and the normal versus SEMI groups (21.1 +/- 3.1 vs. 2.6 +/- 6.0; P = 0.000002). With low-dose dobutamine, SWI increased significantly compared with rest for the stunned group (29.1 +/- 10.4 vs. 10.1 +/- 9.0; P = 0.000007) but did not increase significantly for the SEMI group (11.0 +/- 11.3 vs. 2.6 +/- 6.0; P = 0.09); SWI during low-dose dobutamine infusion for the stunned group was comparable to that for the normal group (29.1 +/- 10.4 vs. 28.2 +/- 7.0; P = 0.80). SWI also showed correlation with MRI radial strain (r = 0.42; P = 0.00015).
  
  
  CONCLUSIONS
  Defect severity for stunned myocardium and SEMI was mild and was not significantly different. Contractile reserve was significantly different in stunned myocardium and SEMI. (99m)Tc-Sestamibi SPECT at rest and with low-dose dobutamine is a promising new technique to simultaneously assess myocardial perfusion and contractile reserve.
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Outpatient Center, Johns Hopkins Medical Institutions, 601 N. Caroline Street, Baltimore, MD 21287, USA. bchin@jhmi.edu
authors.forename: Bennett B
authors.initials: BB
authors.lastname: Chin
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Esposito
authors.forename: Dara L
authors.initials: DL
authors.lastname: Kraitchman
mesh_terms: D000818:Animals; D003326:Coronary Circulation; D004280:Dobutamine; D004285:Dogs; D008279:Magnetic Resonance Imaging; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000503:physiopathology; D017682:Myocardial Stunning / Q000000981:diagnostic imaging* / Q000503:physiopathology; D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D019275:Radiopharmaceuticals; D004280:Dobutamine; D017256:Technetium Tc 99m Sestamibi