Echocardiographic evaluation of ventricular dyssynchrony in patients with left bundle branch block.

OBJECTIVE: To test whether patients with left bundle branch block (LBBB) and low ejection fraction (EF) have greater dyssynchrony than those with LBBB and normal LV systolic function.

METHODS: From a group of patients with LBBB, 38 patients with low EF (<50%) and 31 with normal LV systolic function (EF > or = 50%), all comparable in age and sex underwent standard Doppler echo, ECG and tissue Doppler imaging (TDI). The precontraction time (PCTm) was calculated as an index of myocardial systolic activation in 5 different basal myocardial segments (LV anterior, inferior, septal, lateral walls and RV lateral wall). Intraventricular systolic dyssynchrony was analyzed by difference of PCTm in different LV myocardial segments. Interventricular activation delay was calculated by the difference of PCTm between the most delayed LV segment and RV lateral wall.

RESULTS: Patients with low LV EF showed increased QRS duration, intraventricular delay (p = 0.03) and interventricular dyssynchrony (p = 0.006). Patients with normal EF also had evidence of some dyssynchrony. The LV basal lateral segment was significantly delayed when compared to all other segments in the low EF group. The PCTm was greater for those with low EF when compared to the normal EF group.

CONCLUSIONS: All patients with LBBB on baseline ECG had some degree of cardiac dyssynchrony; those with lower EF had more dyssynchrony. TDI is an effective non-invasive technique for assessing the severity of regional delay in activation of ventricular walls in patients with LBBB.