title: Impact of regional ventricular function, geometry, and dobutamine stress on quantitative 99mTc-sestamibi defect size.
abstract: BACKGROUND
  Serial myocardial perfusion imaging with 99mTc-sestamibi (MIBI) was used to evaluate infarct risk area and salvage after thrombolysis. The purpose of this investigation was to determine whether changes in MIBI defect size observed after reperfusion may result in part from distortion of regional and global left ventricular geometry.
  
  
  RESULTS
  Twenty-five open-chest dogs were subjected to either 15 minutes (groups 1A and 1B) or 3 hours (group 2) of left anterior descending coronary artery occlusion followed by 3 hours of reperfusion. MIBI was injected before occlusion (group 1A) or during occlusion (groups 1B and 2), and serial ECG-gated planar imaging was performed. Dobutamine was infused after 3 hours of reperfusion (groups 1B and 2) to transiently alter left ventricular size and function. Perfusion defect magnitude (DM) and extent (DE) were serially quantified with circumferential profile analysis of end-systolic (ES), end-diastolic (ED), and summed images. Flow was assessed with radiolabeled microspheres and correlated with myocardial MIBI activity. Myocardial thickening was assessed in the risk area with sonomicrometers. In group 1A dogs, ischemic dyskinesis produced large artifactual quantitative MIBI defects on ES images (DM, 9.3 +/- 1.3; DE, 27.8 +/- 6.0) that were significantly smaller on ED images (DM, 4.5 +/- 0.9, P < .05; DE, 4.4 +/- 2.3, P < .05). In addition, DM and DE correlated inversely with myocardial thickening on ES images (DM, r = -.84; DE, r = -.78) and summed images (DM, r = -.72; DE, r = -.61) but not ED images (DM, r = -.12; DE, r = -.15). An index of defect reduction derived from summed images correlated well with thickening fraction in stunned dogs (group 1B, r = .89) but poorly in infarcted dogs (group 2, r = .41) subjected to dobutamine stress.
  
  
  CONCLUSIONS
  99mTc-MIBI defect size may be affected by alteration of left ventricular geometry. Changes in regional function may confound analysis of risk area and myocardial salvage with serial 99mTc-MIBI imaging and may also affect defect size during pharmacological stress with dobutamine. Dobutamine 99mTc-MIBI imaging may be useful for distinguishing viable and nonviable myocardium.
authors.affiliation: Department of Internal Medicine, Yale University, School of Medicine, New Haven, Conn. 06510.
authors.forename: A J
authors.initials: AJ
authors.lastname: Sinusas
authors.forename: Q
authors.initials: Q
authors.lastname: Shi
authors.forename: P J
authors.initials: PJ
authors.lastname: Vitols
authors.forename: R C
authors.initials: RC
authors.lastname: Fetterman
authors.forename: P
authors.initials: P
authors.lastname: Maniawski
authors.forename: B L
authors.initials: BL
authors.lastname: Zaret
authors.forename: F J
authors.initials: FJ
authors.lastname: Wackers
mesh_terms: D000818:Animals; D003287:Contrast Media; D003326:Coronary Circulation / Q000187:drug effects; D004280:Dobutamine / Q000494:pharmacology*; D004285:Dogs; D006321:Heart / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006439:Hemodynamics / Q000187:drug effects; D009203:Myocardial Infarction / Q000503:physiopathology; D015425:Myocardial Reperfusion; D017682:Myocardial Stunning / Q000503:physiopathology; D011877:Radionuclide Imaging; D012307:Risk Factors; D017256:Technetium Tc 99m Sestamibi; D016276:Ventricular Function
chemical_list: D003287:Contrast Media; D004280:Dobutamine; D017256:Technetium Tc 99m Sestamibi