Systolic improvement and mechanical resynchronization does not require electrical synchrony in the dilated failing heart with left bundle-branch block.
BACKGROUND
Biventricular (BiV) and left ventricular (LV) pacing similarly augment systolic function in left bundle-branch block (LBBB)-failing hearts despite different electrical activation. We tested whether electrical synchrony is required to achieve mechanical synchronization and functional benefit from pacing.


RESULTS
Epicardial mapping, tagged MRI, and hemodynamics were obtained in dogs with LBBB-failing hearts during right atrial, LV, and BiV stimulation. BiV and LV both significantly improved chamber hemodynamics (eg, 25% increase in dP/dt(max) and aortic pulse pressure) compared with atrial pacing-LBBB, and this improvement correlated with mechanical resynchronization. Electrical dispersion, however, decreased 13% with BiV but increased 23% with LV pacing (P<0.01).


CONCLUSIONS
Improved mechanical synchrony and function do not require electrical synchrony. Mechanical coordination plays the dominant role in global systolic improvement with either pacing approach.
D000818:Animals; D002037:Bundle-Branch Block / Q000150:complications / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000379:methods; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D004195:Disease Models, Animal; D004285:Dogs; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods; D019786:Gadolinium DTPA; D006329:Heart Conduction System / Q000503:physiopathology; D006334:Heart Function Tests; D006439:Hemodynamics; D008279:Magnetic Resonance Imaging; D013599:Systole
D019786:Gadolinium DTPA