Evaluating Left Ventricular Asynchrony In Patients Of Pacing-induced Versus Left Bundle Branch Block With And Without Left Ventricular Dysfunction By Strain Rate Imaging

Objective To demonstrate the systolic asynchrony and diastolic asynchronyin patients of left bundle branch block (LBBB) with and without left ventriculardysfunction and right ventricular pacing with normal left ventricular ejectionfraction (LVEF) by using strain rate imaging (SRI), as well as their relationship.Methods 17 patients with LBBB, 11 patients with right ventricular pacingand normal left ventricular ejection fraction (LVEF) were enrolled in this study and20 healthy volunteers were used as the control group. Echocardiography wasperformed to obtain the left ventricular internal dimension at end diastole (LVIDd),interventricular septal thickness at end diastole (IVSd) and left ventricular posteriorwall thickness at end diastole (LVWPd) in the parasternal long axis view. LVEFwas measured by using the biplane Simpson's method. Patients with LBBB werefurther divided into those with LVEF＞50％(n=7), and LVEF＜35％(n=11). M-modeechocardiography of the aortic and mitral valves was performed to assess the exacttiming of aortic and mitral valve opening. Pulse Doppler tracings of transmitraldiastolic flow was used to calculate the diastolic filling time. From the apical4-and 2-chamber views, the basical segment and middle segment of interventricularseptal, left ventricular lateral wall, anterior wall and inferior wall were obtained byStrain rate imaging for the long-axis motion. The time intervals from the beginningof the QRS complex to both peak systolic and early diastolic relaxation velocitieswere measured in 4 different LV segments. The coefficient of variation (SD/mean)of 4 different systolic and diastolic time intervals were calculated and use as theindex of systolic asynchrony index (SAI) and diastolic asynchrony index (DAI).Result There were no significant deference in gender, heart rate, IVSd andLVWPd between LBBB, right ventricular pacing and controls. Patients with right ventricular pacing and LBBB had significant longer QRS duration (162±20 vs93±7ms, P＜0.01) and longer systolic(15.2±3.2％vs 4.2±1.8％, P＜0.01) anddiastolic(3.6±1.9％vs 1.4±0.4％P＜0.01) asynchrony than controls. Those withLBBB and low LVEF had significamly longer diastolic asynchrony (5.4±2.0％) thanthose with right vemricular pacing (3.0±1.0％) and those with LBBB and normalLVEF(2.1±0.6％). Although systolic and diastolic asynchrony all showed asignificant negative correlation with LVEF, diastolic asynchrony was the onlyindependent factor that correlated with LVEF (r=-0.71, P＜0.01) by stepwise linearregression analysis.Conclusion The systolic and diastolic asynchrony shows a positive correlationwith QRS duration in LBBB patients. LBBB with left ventricular dysfunction ischaracterized not only by systolic but also by diastolic asynchrony, and the diastolicasynchrony was the only independent factor correlated with LVEF.