Evaluation Of Left Ventricular Systolic Synchrony Undergoing Pacemaker Implantation Through Real-time 3-dimensional Echocardiography

Background:As proved by more and more clinical and experimental researches, right ventricular pacing for long time inducing LBBB may cause hemodynamic disorder and systolic dys-synchrony of LV,which drives people to find new alternative pacing site-right ventricular outflow tract pacing.RVOT pacing over RVA still remains controversial owning to lack of clinical evidence.Real-time three-dimensional echocardiography,a novel technique focusing on volume measurements without geometrical modeling,can assess systolic synchrony by volume-time curves of all 17 segments of LV.Objective:to evaluate systolic synchrony of left ventricular by real-time 3-dimensional echocardiography undergoing right ventricular pacing and right ventricular outflow tract pacing.Methods:Consecutively enrolled 15 samples in total,diagnosed with 6 peopleⅢAVB,3 peopleⅡAVB,6 people sinus bradycardia;12 of them undergoing RVA pacing,6 of them undergoing RVOT pacing,another 11 normal people as control. Collect the full-volume echo images before and 3 months after the implantation using Philips IE33 echo-machine.Analysis these images with 3DQ advanced software quantitatively.This software automatically measure left ventricular end diastolic volume(LVEDV),left ventricular end systolic volume(LVEDV),ejection fraction (EF) and also shows the volume-time curves of LV and all its 17 segments.It measures time to minimum systolic volume(Tmsv) of each segment,then calculates standard deviation and difference of Tmsv(Tmsv-SD,Tmsv-Dif),applying to 16 segments(Tmsv-16),12 segments(Tmsv-12),6 segments(Tmsv-6) and Tmsv-SD%, Tmsv-Dif%to eliminate the influence of different heart rate.Results:Analyze 3-dimensional echo images of 10 patients undergoing right ventricular apex pacing and 5 patients undergoing right ventricular outflow tract pacing,normal 11 people as control.1.After RVOT pacing,ESV enlarged(pre vs post,31.56ml±18.15 vs 47.90ml±26.39,P=0.017) and EF decreased(prevs post,68.72%±12.51 vs 55.00%±11.04, P=0.030).No statistic difference exists before and after RVA pacing,in EDV/ESV/SV/EF.2.No statistic difference exists within the groups before and after the operation,in LV excursion Avg/Sd/Max/Min and also excursion of all the 16 segments.Excursions are smaller in basal anteroseptal/mid anterolateral/apical inferior segments,compared with normal control,undergoing right apex pacing.While excursions are smaller in basal inferior/basal inferolateral/mid inferoseptal/mid inferior/apical inferior segments, compared with normal control,undergoing right ventricular outflow tract pacing..3.After RVA or RVOT pacing,Tmsv16-dif/Tmsv16-dif%/Tmsv16-sd/Tmsv16-sd% are worsen than normal control,while with no difference before and after the implantation.No difference exists in all parameters assessing LV synchrony of 12 segments or 6 segments.4.No statistic difference exists between the groups of RVA pacing and RVOT pacing, in all the parameters.Conclusions:After 3 months of right ventricular apex pacing or right ventricular outflow tract pacing,the excursion of LV remains the same while that of certain segments may decrease.Systolic synchrony of LV does not deteriorate,with no difference between RVA pacing and RVOT pacing.