Abstract 15642: Relationship of Mechanical Dyssynchrony to QRS Morphology and CRT-D Efficacy in Patients with Heart Failure and Wide QRS: The MADIT-CRT Trial
Background: Cardiac resynchronization therapy (CRT) is effective for treating heart failure (HF) in patients (pts) with conduction delay and dyssynchronous contraction, although data from MADIT-CRT suggests that pts with LBBB derive considerably greater benefit than those with RBBB or IVCD. We assessed the relationship between mechanical dyssynchrony by 2D-speckle tracking imaging (2D-STI) and QRS morphology in MADIT-CRT.
Methods: We studied 1,069 pts with NYHA class I/II HF, EF <or= 30% and QRS >or= 130ms enrolled in MADIT-CRT with adequate image quality. Dyssynchrony was defined as the standard deviation of time to peak transverse strain out of 12 segments from the apical 4- and 2-chamber views. Time to peak transverse strain for basal-septal and basal-lateral wall was recorded. QRS morphology was defined as LBBB, RBBB, or IVCD. We assessed the treatment effect on the primary outcome of death or HF based on QRS morphology.
Results: Compared to the pts with RBBB (n = 126) or IVCD (n = 179), pts with LBBB (n=764) were more frequently female, were more likely to have non-ischemic etiology, had wider QRS duration and slightly lower ejection. No significant difference was noted in global longitudinal strain. Pts with LBBB had significantly higher transverse dyssynchrony than RBBB and IVCD pts. The greatest opposing wall delay was seen in pts with LBBB with an early basal-septal activation and late basal-lateral activation, compared with those with RBBB in which the reverse activation sequence was observed. Greatest benefit from CRT was observed in LBBB pts compared with RBBB or IVCD pts. (Table)
Conclusion: The magnitude of intraventricular dyssynchrony in HF pts with LBBB is significantly higher than those with RBBB. Considerable delayed lateral wall contraction is only seen in LBBB pts, suggesting a possible mechanism by which CRT therapy benefits pts with LBBB to a greater extent, and potentially questioning the strategy of LV resynchronization in RBBB and IVCD. .
- © 2010 by American Heart Association, Inc.