Impact of Left Bundle Branch Block on Left Atrial Dyssynchrony and Its Relationship to Left Ventricular Diastolic Function in Patients with Heart Failure and Dilated Cardiomyopathy

The impact of left bundle branch block (LBBB) on left atrial (LA) dyssynchrony in heart failure (HF) patients with non-ischemic dilated cardiomyopathy (DCM) has not been clearly elucidated. Methods: Eighty consecutive symptomatic HF patients with non-ischemic DCM (left ventricular ejection fraction, LVEF<35%) were included. LBBB was defined on electrocardiography. Left ventricular (LV) systolic and diastolic dyssynchrony index and LA dyssynchrony index were obtained by color-coded tissue Doppler imaging. Results: There was no significant difference in LV size, LVEF, LV global longitudinal strain, peak atrial longitudinal strain and LA volume between patients with LBBB (n=38) and no LBBB (n=42). There was a significant difference in LV systolic dyssynchrony index (p=0.014) and there was a mild difference in LV diastolic synchronicity index (p=0.045) between patients with LBBB and no LBBB. However, there was no difference in LA dyssynchrony index between the 2 groups (p=0.60). LA dyssynchrony index was not related to LV systolic and diastolic dyssynchrony indexes, but it was related to the deceleration time of mitral early diastolic velocity (E), the ratio of E to mitral annular early diastolic velocity (E/e) and LA volume. E/e was most related to LA dyssynchrony index (r 2 =0.325, p=0.002). Conclusions: LBBB influences both LV systolic and diastolic dyssynchrony, but not LA dyssynchrony. LA dyssynchrony was related to LV diastolic function regardless of the presence of LBBB in in patients with non-ischemic DCM.