title: The effects of dobutamine stress on cardiac mechanical synchrony determined by phase analysis of gated SPECT myocardial perfusion imaging in a canine model.
abstract: BACKGROUND
  Precise identification of left ventricular (LV) systolic mechanical dyssynchrony may be useful in optimizing the response to cardiac resynchronization therapy in heart failure (HF) patients. However, LV dyssynchrony is mostly measured at rest; patients often suffer from the HF symptoms during exercise.
  
  
  OBJECTIVE
  Our objective was to examine the impacts of stress on LV synchronism with phase analysis of gated SPECT myocardial perfusion imaging (GMPS) within a normal animal cohort.
  
  
  METHODS
  Stress was induced with different levels of dobutamine infusion in six healthy canine subjects. Hemodynamic properties were assessed by LV pressure measurements. Also, LV mechanical synchronism (coordination of LV septal and lateral wall at the time of contraction) was determined by phase analysis of GMPS using commercially available QGS software and in-house MHI4MPI software, with the thickening- and displacement-based method. Synchrony indexes in MHI4MPI included the septal-to-lateral delay and homogeneity index, derived from each of the two methods. Also, bandwidth, SD, and entropy (synchrony indexes) of the QGS software were assessed.
  
  
  RESULTS
  LVEF increased from 36.7% ± 8.7% at rest to 53.67% ± 12.34% at 20 μg · kg(-1) · minute(-1) (P < .001). Also, cardiac output increased from 3.67 ± 1.0 L · minute(-1) at rest to 8.4 ± 2.6 L · minute(-1) at 10 μg · kg(-1) · minute(-1) (P < .001). The same trend was observed for dP/dt max which increased from 1,247 ± 382.7 at rest to 5,062 ± 1,800 mm Hg · s(-1) at 10 μg · kg(-1) · minute(-1) (P < .01). Entropy decreased from 55.2% ± 8% at baseline to 43.5% ± 8.5% at 5 and 43.0% ± 3.7% at 10 μg · kg(-1) · minute(-1) dobutamine (P < .01). Thickening homogeneity index showed a difference from 91.7% ± 5.53% at rest to 98.2% ± 0.75% at 20 μg · kg(-1) · minute(-1) (P < .05).
  
  
  CONCLUSIONS
  Dobutamine stimulation could amplify the ventricular synchronism, and the thickening-based approach is more accurate than wall displacement for assessment of mechanical dyssynchrony in GMPS.
authors.affiliation: Department of Nuclear Medicine, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street, Montreal, QC, H1T 1C8, Canada.
authors.forename: Samaneh
authors.initials: S
authors.lastname: Salimian
authors.forename: Bernard
authors.initials: B
authors.lastname: Thibault
authors.forename: Vincent
authors.initials: V
authors.lastname: Finnerty
authors.forename: Jean
authors.initials: J
authors.lastname: Grégoire
authors.forename: François
authors.initials: F
authors.lastname: Harel
mesh_terms: D000818:Animals; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D004280:Dobutamine; D004285:Dogs; D005080:Exercise Test / Q000379:methods; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000187:drug effects; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014665:Vasodilator Agents; D016277:Ventricular Function, Left / Q000187:drug effects / Q000502:physiology*
chemical_list: D014665:Vasodilator Agents; D004280:Dobutamine