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Left bundle branch block (LBBB) is characterized by early septal radial inward thickening, followed by late posterior inward thickening. This results in a significant left ventricular (LV) dyssynchrony. LBBB, which is associated with increased mortality, may impair the mechanical functions of LV. In this study, we aimed to evaluate cardiac mechanics in patients with isolated LBBB using speckle tracking echocardiography (STE).
The study was composed of 45 patients who were admitted to cardiology clinic between October 2012 and April 2013. Patients with chronic obstructive lung disease, history of coronary artery disease, diabetes mellitus, primary pulmonary hypertension, constrictive pericarditis, moderate or severe mitral and/or aortic stenosis and regurgitation, and poor imaging quality were excluded. The patients with isolated complete LBBB (n=14) and incomplete LBBB (n=11) were included as group 1 and 2, respectively. The group 3 was composed of healthy individuals (n= 20). All patients provided written informed consent prior to transthoracic echocardiographic examination. In STE examination, the LVapical long, four- and two-chamber images and short-axis views at basal, mid-papillary and apical levels at frame rates between 40 and 80 frames/s were used for assessing 2D LV longitudinal, radial, circumferential strains and rotation. The LV twist was calculated as an absolute apex-to-base difference in LV rotation.
The mean age of the study population was 43±12 (F: 27, M:19). There were no significant differences between the groups in terms of age and gender. Group 1 and 2 had significantly lower 4C (17.6 ± 1.7 vs. 20 ± 1.3, p < 0.001 and 18.5±1.8 vs. 20±1.3, p:0.012, respectively), LAX (17.5 ± 1.3 vs. 19.8± 1.5, p<0.001 and 18.4±1.7 vs. 19.8±1.5, p: 0.023, respectively) and 2C (17.7± 1.4 vs. 20.1± 1.4, p<0.001 and 18.5±1.9 vs. 20.1±1.4, p:0.018, respectively) peak longitudinal strain values compared to group 3. No statistical difference was observed between Group 1 and group 2 regarding 4C (17.6 ± 1.7 vs 18.5±1.8 p:0.245), LAX (17.5 ± 1.3 vs 18.4±1.7, p:0.206) and 2C (17.7± 1.4 vs 18.5±1.9, p:0.236) peak longitudinal strain values. LV twist was not significantly different between group 2 and 3 (14.3±1.1 vs. 14.5±1.3, p:0.410), whereas group 1 had significantly reduced twist values (12.3±1.6 vs. 14.2±2.2 p:0.027 and 12.3±1.6 vs.14.7±1.4 p<0.001, respectively).
LV twist and peak longitudinal strain values are impaired in patients with isolated complete LBBB, in contrast to patients who had incomplete LBBB or non-LBBB electrocardiography.