Effect Of Left Ventricular Activation Sequence And Systolic Synchrony During Pacing At Variant Right Ventricular Sites On Cardiac Function

Objective:To compare left ventricular(LV) activation sequence and systolic synchrony and left ventricular systolic function associated with right ventricular outflow tract (RVOT) pacing and right ventricular apex (RVA) pacing by real-time three-dimensional echocardiography and CARTO system.Methods:In the acute tests of six anesthetized closed-chest beagle canines,the pacing leads were navigated and deplored at right ventricular outflow tract and right ventricular apex with pacing rate(138±33)beats perminute by X-ray,then the deflectable quadripolar open irrigated catheters were inserted into the left ventricle for mapping,and the LV real-time three-dimensional LAT maps were built by CARTO system.And then the change of QRS duration was measured.RT-3DE data was acquired with the SIEMENS ACUSON SC2000 system,then analyzed by the LVA software.The percentage of standard deviation and maximal difference of the time to minimal systolic volume in appointed segments(Tmsv)were standardized by cardiac cycle such Tmsv16-SD%,Tmsv12-SD%,Tmsv6-SD%,Tmsv16-Dif%,Tmsv12-Dif% and Tmsv6-Dif% as the index of left ventricular systolic synchronicity.The global end-systolic volume(gESV),global end-diastolic volume(gEDV),global Stroke volume(gSV),global left ventricular ejection fraction(gEF),regional end-systolic volume(rESV),regional end-diastolic volume(rEDV),regional stroke volume(rSV),regional left ventricular ejection fraction(rEF)were also obtained. And we evaluated LV activation sequence by analyzing Tmsv.Results:①LV electrical activation sequence and time were similar between RVOT pacing group and SR group.During RVA pacing,there was a big difference in LV electrical activation sequence compared with SR group,and it needed more time to complete the whole LV electrical activation(P<0.05).In comparing to normal sinus rhythm ,the QRS duration was lengthened significantly when pacing at RVOT and RVA(P=0.000).The QRS duration of RVA pacing was longer as compared with that of RVOT.②LV contraction sequence was similar in RVOT pacing group and SR group,but it changed during RVA pacing.The contraction of the whole LV delayed in RVA pacing group compared with SR group and the RVOT pacing group,most segments showed significant differences(P<0.05).Compared with SR group and the RVOT pacing group,Tmsv16-SD%,Tmsv12-SD%,Tmsv6-SD%,Tmsv16-Dif%,Tmsv12-Dif% and Tmsv6-Dif% were significantly higher and the global left ventricular systolic function was lower in RVA pacing group(P<0.05),but the regional left ventricular systolic function was no significant decline. No significant difference was found between RVOT pacing group and SR group.Conclusion:Comparing with RVA pacing,RVOT pacing remains relatively normal ventricular activation sequence and systolic synchrony and it is associated with more favorable myocardial function.