Left ventricular remodeling during dyssynchrony acts as an adaptive process to equilibrate regional myocardial work distribution, which closely correlates with regional glucose metabolism.
Does inhomogeneous LV work distribution due to pacing-induced dyssynchrony affect regional metabolism and remodeling?
Regionally different LV remodeling during dyssynchrony is an adaptive process that equilibrates work distribution, and its correction triggers reverse remodeling.
Background: The interaction between regional left ventricular (LV) myocardial work and metabolism in remodeled hearts has not yet been well established. Our aim was to investigate the effect of inhomogeneous LV work distribution on regional metabolism and remodeling in our animal model with reversible dyssynchrony due to pacing. Methods: In 12 sheep, 8 weeks of right atrial and right ventricular free wall (DDD) pacing lead to LV dilatation, a thinned septum, and thickened lateral wall. Left bundle branch block–like dyssynchrony caused by DDD pacing could be acutely reverted by right atrial pacing (AAI) only. Invasive hemodynamics and echocardiography were used to assess regional work by stress-strain loop area and compared with regional glucose metabolism measured by 18 F-fluorodeoxyglucose positron emission tomography with and without improved spatial resolution by motion and anatomy correction on gated reconstructions. Results: Glucose metabolism by positron emission tomography with anatomic correction on gated positron emission tomography reconstruction showed a different regional distribution than with clinical reconstructions and correlated best and significantly with regional myocardial work. At baseline, work was homogeneously distributed with normal conduction (AAI pacing), whereas during dyssynchrony (DDD pacing), the lateral wall was more loaded, and the septum was unloaded. After 8 weeks of remodeling under DDD pacing, however, an almost homogeneous work distribution was found with DDD pacing, whereas with AAI pacing, the thin septum showed exaggerated loading and the lateral walls a low load. Our experimental observations were confirmed in 5 patient responders to cardiac resynchronization therapy. Conclusions: Regional LV glucose metabolism closely correlates with regional work. Our data indicate that regionally different LV remodeling after exposure to inhomogeneous loading conditions, such as during LV dyssynchrony, is an adaptive process that helps to equilibrate work distribution. Correction of the inhomogeneous loading conditions, such as during cardiac resynchronization therapy, then triggers a reverse LV remodeling through the same mechanism.
Duchenne et al. (Fri,) conducted a other in Left ventricular remodeling and dyssynchrony (n=17). DDD pacing (dyssynchrony) vs. AAI pacing (normal conduction) was evaluated on Regional myocardial work and glucose metabolism. Left ventricular remodeling during dyssynchrony acts as an adaptive process to equilibrate regional myocardial work distribution, which closely correlates with regional glucose metabolism.