The Evaluation Of Different Right Ventricular Pacing Sites On Right Ventricular Function

Objective: Pacemaker implantation remains the best therapeutic optionthat improves morbidity and mortality for patients with symptomaticbradycardia. Clinical studies have shown that pacing from the right ventricularapex(RVA) causes electrical–mechanical dyssynchrony, Left ventricularsystolic dysfunction, Left ventricular enlargement and impaired ejectionfraction. Effect of right ventricular pacing on right ventricular function hasbeen clearly reported and effect of different pacing sites on right ventricularfunction remains unknown. Right cardiac chamber is an irregular geometry,inflow and outflow tract of right ventricle located in different planes on thespatial structure. In terms of numerous anatomical and physiological factorsinfluencing right ventricular, it is difficult to assess right ventricular functionusing two-dimensional echocardiography. Real-time three-dimensionalechocardiography (3D-RT) is a new reliable method to evaluate rightventricular function. The purpose of this study is to evaluate effect of rightventricular function on pacing sites of right ventricular septal and rightventricular apex by3D-RT and Doppler tissue.Subjects:30patients aged33-70years old of both sexes were enrolledinto this study between October2011and January2013at the Second Hospitalof Hebei Medical University, including15patients with right ventricularapical pacing and15patients with right ventricular septal pacing. All patientsshould meet the following requirement: normal ventricular size, leftventricular ejection fraction≥40%and right ventricular pacing≥90%of totalheart rate.Methods: All patients were examined using echocardiography beforeand5days after operation. Imaging was performed in all subjects using3D-RT and Doppler tissue. All subjects were examined in left lateral position and connected with surface ECG，and apical four chamber view images wereacquired. The attached software can automatically delineate dynamic3Dendocardial shape, display right ventricular ejection fraction, peak systolicvelocity (Sm), tricuspid annular displacement distance (TAPSE)(in eachcardiac cycle the greatest distance of tricuspid annulus from end-diastolicclosing to the end-Systolic), Tei index, E/A ratio of Tricuspid inflow, thetricuspid annulus Em/Am ratio of Tricuspid inflow, deceleration time (DT),and isovolumic relaxation time (IVRT).Statistical analysis: The measurement data were represented asmean±SD. The count data were represented as a percentage. All the statisticalexaminations of measurement data were performed using either independentsamples t-test or paired-samples t-test by SPSS19.0software. All thestatistical examinations of count data were performed using chi-square test,P＜0.05was considered statistically significant.Results:1QRS duration were significantly longer in post-operation than inpre-operation. QRS duration with the RVA pacing was significantly narrowerthan the RVS pacing (P＜0.05).2Indexes assessing the right ventricular function of pre-operation andpost-operation2.1There is no significant difference in BNP,RVEF%, Sm, TAPSE, IVRT,DT and Tei in RVA group between pre-operation and post-operation (P＞0.05). Em/Am and E/A in RVA group were significantly lower inpost-operation than in pre-operation (P＜0.05).2.2There is no significant difference in RVEF%, Sm, TAPSE, IVRT, DT andBNP in RVS group between pre-operation and post-operation (P＞0.05).Em/Am, E/A and Tei in RVS group were significantly lower in post-operationthan in pre-operation (P＜0.05).3There is no significant difference in the different value of RVEF%, Sm,TAPSE, IVRT, DT,Em/Am and E/A of RVS group compared with that of RVA group (P＞0.05). Compared with RVA group, the different value of Teiof RVS group were significant (P＜0.05).Conclusion:1QRS duration with the RVA pacing was significantly narrower than theRVS pacing. Compared with right ventricular apical pacing,right ventricularseptal pacing is closer to the physiological pacing.2Tei in RVS group were significantly lower in post-operation than inpre-operation. Compared with RVA pacing, RVS pacing may be a promisingpacing site.