P5659How does mechanical dyssynchrony affect the efficiency of the left ventricle?

Résumé fourni par la source

Background: The left ventricle (LV) converts metabolic energy into external mechanical work. The amount of metabolic energy needed to perform a certain mechanical work can be considered as efficiency. Little how is known, how LV efficiency is affected by mechanical dyssynchrony. Study plan: We therefore compared invasively measured LV external mechanical work and myocardial glucose metabolism by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in an animal model of LV dilatation with and without pacing-induced left bundle branch block (LBBB)-like dyssynchrony. Methods: Twelve sheep were subjected to 8 weeks of rapid (180 bpm) pacing on the right atrium and right ventricular free wall, causing LV dilatation with LBBB-like dyssynchrony. All animals underwent invasive haemodynamic pressure-volume analysis and FDG-PET scans at week 8. High-resolution PET images were acquired with ECG- and respiratory gating, and resolution remodelling. Global LV glucose metabolism was assessed by the FDG activity, measured as standardised uptake ratio (SUR) of the entire LV myocardium and corrected for glycaemia level. External mechanical work was calculated from pressure-volume-loop areas, acquired with a conductance and pressure tip catheter. Volumes were calibrated by magnetic resonance imaging. The ratio of LV external mechanical work and FDG activity was considered to represent LV the mechanical efficiency ratio (MER). All data was acquired at 110 bpm, during normal contraction (AAI pacing) and LBBB-like dyssynchrony (DDD pacing).

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