The Comparative Study Of Interventricular Electrical And Mechanical Synchrony On Different Cardiac Pacing Sites

Background: With the development of pacemaker implantation technique and the expanse of cardiac electrophysiology study, cardiac pacing has been no longer confined to raise heart rate, and physiological activation order and interventricular synchronization is increasingly emphasized. Since the introduction of permanent pacing,the preferred site for ventricular stimulation has been almost exclusively the right ventricular apex(RVA).However,RVA pacing altered ventricular depolarization vector and increased ventricular asynchronous contraction,which resulted in deterioration of left ventricular function finally. Pacing from the right ventricular outflow tract(RVOT) might provide better performance of the heart because it had a almost normal ventricular activation and conduction sequence. However, previous studies had not obtained consistent results about RVOT pacing . The possible reasons for this might be difference in patient selection and exactly pacing position in RVOT and evaluation criteria.For a long time DDD pacing has been considered as physiological pacing mode as AAI.However, different clinical trial results were far different, even some studies indicated DDD pacing was apt to increase rates of death and heart failure . For patients without atrial ventricular block, which pacing mode is most physiological? For patients of dependent on ventricular pacing, which pacing site is closer to physiology,more interventricular electrical and mechanical synchrony? It is necessary to have further study.Objective: This study is aimed to appraise the feasibility for utilizing value of conductive time interval between left ventricular posterior lateral wall and right ventricular anterior lateral wall (LVPLW-RVALW) to reflect interventricular activation synchrony.To compare interventricular electrical and mechanical synchrony among no pacing (NP) and high right atrial (HRA) pacing and RVA pacing and right ventricular septum (RVS) pacing is aimed to obtain optimal pacing site and mode and to guide the introduction of permanent pacing.Methods: Thiry patients aged 15-69 years (mean age 41.10±14.24years) without structural heart disease were studied.They were executed for radiofrequency catheter ablation. ECG of postoperation is without the left and right bundle branch block and intraventricular conduction block.According to the random order stimulated different pacing sites. QRS duration and LVPLW - RVALW and APEI - PPEI value were recorded. They were respectively compared between HRA group and NP group, between RVA group and RVS group, between HRA group and RVS group.Relevance was analyzed between LVPLW-RVALW and QRS and APEI-PPEI.Results: There were no differences in QRS duration and LVPLW-RVALW and PPEI-APEI between HRA and NP group (P> 0.05), but there were significant differences between HRA and RVS group(P <0.001). Compared with the RVA pacing group,QRS duration was relatively shorter and values of LVPLW-RVALW and PPEI-APEI were smaller in RVS pacing group.There were significant differences between RVA and RVS group (P <0.001). Correlation analysis showed that both absolute value of APEI-PPEI and the enlargement of QRS duration had a positive relationship with the change of LVPLW-RVALW(r = 0.978, p <0.001;r = 0.993, p <0.001).Conclusions: Atrial pacing is a better interventricular electrical and mechanical synchrony than ventricular pacing,a more physiological pacing mode. Patients without atrial ventricular block select AAI pacing as far as possible. Compared with RVA pacing, RVS pacing is closer to the physiological way.It's proper to choose RVS pacing for patients of dependent on ventricular pacing. LVPLW-RVALW value can be utilized for indicators estimating interventricular activation synchrony.