Wednesday, February 19, 2014

The effects of dobutamine stress on cardiac mechanical synchrony determined by phase analysis of gated SPECT myocardial perfusion imaging in a canine model.

The effects of dobutamine stress on cardiac mechanical synchrony determined by phase analysis of gated SPECT myocardial perfusion imaging in a canine model.
J Nucl Cardiol. 2014 Jan 9;
Authors: Salimian S, Thibault B, Finnerty V, Grégoire J, Harel F

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.
OBJECTIVES: 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.

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