الفهرس 
The Left Bundle Branch Block (LBBBOnly 14 pages are availabe for public view
 |  | from | 149 |  |  |
| | | from | 149 | | |
Abstract
Left bundle branch block (LBBB) is related to abnormal cardiac conduction and mechanical dyssynchrony and is associated with hypertension and coronary artery disease. Ventricular dyssynchrony exhibits negative effects on left ventricular performance (Cleland et al., 2005). The increasing number of patients with left bundle branch block and poor ejection fraction mandated the development of new imaging modalities for better assessment of electromechanical dyssynchrony, as up to 30% of these patients do not improve after CRT when selected by current recommended criteria (Cazeau et al., 1996). To improve patient selection, many studies have quantified the magnitude of intraventricular mechanical dyssynchrony indexes by tissue Doppler imaging (Bleeker et al., 2005). Systolic velocity timing derived from tissue Doppler imaging has been used most frequently, with other several indexes have been reported to predict positive responses to CRT (Jansen et al., 2006). Others showed that dyssynchrony indexes based on time to peak strain predict a favorable effect of CRT (Suffoletto et al., 2006). Moreover, whether the various cutoff values of echocardiographic dyssynchrony indexes associated with left ventricular reverse remodeling after CRT are specific for the patients with decreased left ventricular systolic function and/or conduction delay is not well known (Mele et al.,2006).
The study included 30 patients with complete LBBB excluding those with acute myocardial infarction, those with atrial fibrillation and decompensated heart failure. The study also included 10 age matched controls.
A 12-lead surface ECG was done to all patients to calculate QRS duration. All patients underwent conventional echocardiographic using GE Vivid 5 and 7 software (General Electric, Horten, Norway), to get left ventricular dimensions and ejection fraction. Color-coded tissue Doppler imaging was acquired from 2 apical views (the apical four and two-chamber views) of three consecutive cardiac cycles in digital format of echo pac to measure tissue Doppler velocities, time to peak systolic velocity and strain and strain rate were measured.
We found that, the mean age of the study group was 55.8years with male predominance. The medial- lateral delay time was 55 msec with mean systolic strain was 6.7±1.8 with mean strain rate 0.54±0.2. The group with poor ejection fraction had a significant basal medio-lateral time delay to peak systolic velocity than those with good ejection fraction (47.2±11.9). There was no significant correlation, between the QRS duration and basal medio-lateral time delay.
So we concluded from the present study that, left bundle branch block significantly altered the electromechanical synchronization, by prolonging the time delay to peak systolic velocity. Left bundle branch block was associated with markedly lower strain as recorded from the basal septal segment as compared to the reported age matched healthy people.