Assessment Of Left Ventricular Systolic Volume And Myocardial Mechanical Function With Left Bundle Branch Block Using Real-time Three-dimensional Echocardiography And Velocity Vector Imaging

Objective: To assess left ventricular (LV) volume and myocardialmechanical parameters in patients with complete left bundle branch block (CLBBB)using real-time three-dimensional echocardiography (RT3DE) and velocity vectorimaging (VVI), and to define the global and regional LV systolic function andmechanical motion features and establish the correlation of myocardial mechanics andthe cardiac volume function for providing more visual quantitative information ofpathophysiology for precise clinical diagnosis and treatment in patients with CLBBB.Methods:⑴Research subjects: Twenty-eight patients with CLBBB in test group,including15men and13women, age35～78years, average age59.67±15.03years;thirty-three normal subjects in normal control group, including17men and16women,age24～73years, average age54.36±12.15years.⑵Conventional two-dimensional(2D) echocardiography: After subjects resting and connecting ECG, measuredthickness of LV posterior wall (LVPW) and interventricular septum (IVS) and LVend-diastolic dimension (LVEDD) using SIEMENS ACUSON SC2000echocardiography system.⑶RT3DE: Based on the2D examination, acquired andstored dynamic three-dimensional (3D) images of apical four-chamber view. Selecteddynamic3D images with complete and clear LV endocardial edge, and ran LVAfunction on-line. The software automatically identified end-diastole and end-systole,and traced LV endocardial edge though the whole cardiac cycle. Subsequentlyadjusted the frame to make sketched lines to coincide with the endocardial edgemanually to obtain global and17segments of LV volume and ejection fraction (LVEF)and time-volume curve.⑷VVI: Based on the2D examination, acquired and stored dynamic2D gray-scale images of apical four-chamber view, two-chamber view andthree-chamber view. All of the stored2D dynamic images were imported to SyngoVVI workstation. Selected dynamic2D images with complete and clear LVendocardial edge, defined the left of the mitral annulus location as the starting point,and selected7to10points in clock-wise. By tracing LV endocardial edgeautomatically to obtain18segments of LV peak systolic strain (εsys) and peak systolicstrain rate (SRsys). All images were operated by the same operator. The correlationbetween segmental LVEF and segmental εsysor SRsyswas analysised separately.Results:⑴There was no statistically significant difference of age, sex, body massindex, blood pressure, heart rate, LVEDD, the thickness of LVPW and IVS betweenthe two groups(P>0.05).⑵Compared with the normal group, the patients withCLBBB had deteriorated volume function: EF values of global and17segmentsdecreased (P<0.05);17segmental stroke volvme (SV) reduced, especially atanterior(A), Basal antero-septal(AS), Basal infero-septal(IS) and Mid IS, Apicalinfero-lateral(IL)(P<0.05); LV end-systolic volume (LVESV) significantly increased(P=0.001), global SV significantly reduced (P<0.05).⑶Compared with the normalgroup, the group of CLBBB had a lower segmental peak εsysvalues and peak SRsysvalues: the segments of IS, antero-lateral (AL), inferior (I), A(Apical), IL(Apical),AS(Mid and Apical) had significantly lower peak εsysvalues (P<0.05); The segmentsof IS, AL(Basal and Mid), I, A(Basal and Mid), IL(Apical), AS(Mid and Apical) hadsignificantly lower peak SRsysvalues (P<0.05).⑷There was a positive correlationbetween the EF value and εsysvalue of the septal segments at middle antero-septal andinfero-septal segment separately (r=0.59and r=0.48, P=0.04and P=0.01).Conclusions:⑴Compared with the normal group, the global and17segments ofLVEF significantly reduced in group of CLBBB.⑵Compared with the normal group,peak εsysand SRsysvalues at each segments decreased in the patients of CLBBB.⑶ Systolic myocardial mechanics change might partly lead LV function reductionmainly at the middle septal segments of LV.