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Objective: Pacemaker implantation remains the best therapeutic option that improves morbidity and mortality for patients with symptomatic bradycardia.Clinical studies have shown that pacing from the right ventricular apex(RVA) causes electrical-mechanical dyssynchrony, Left ventricular systolic dysfunction, Left ventricular enlargement and impaired ejection fraction.Effect of right ventricular pacing on right ventricular function has been clearly reported and effect of different pacing sites on right ventricular function remains unknown.Right cardiac chamber is an irregular geometry, inflow and outflow tract of right ventricle located in different planes on the spatial structure.In terms of numerous anatomical and physiological factors influencing right ventricular, it is difficult to assess right ventricular function using two-dimensional echocardiography.Real-time three-dimensional echocardiography (3D-RT) is a new reliable method to evaluate right ventricular function.The purpose of this study is to evaluate effect of right ventricular function on pacing sites of right ventricular septal and right ventricular apex by 3D-RT and Doppler tissue.Subjects: 30 patients aged 33-70 years old of both sexes were enrolled into this study between October 2011 and January 2013 at the Second Hospital of Hebei Medical University, including 15 patients with right ventricular apical pacing and 15 patients with right ventricular septal pacing.All patients should meet the following requirement: normal ventricular size, left ventricular ejection fraction ≥40% and right ventricular pacing ≥90% of total heart rate.Methods: All patients were examined using echocardiography before and 5 days after operation.Imaging was performed in all subjects using 3D-RT and Doppler tissue.All subjects were examined in left lateral position and connected with surface ECG, and apical four chamber view images were acquired.The attached software can automatically delineate dynamic 3D endocardial shape, display right ventricular ejection fraction, peak systolic velocity (Sm), tricuspid annular displacement distance (TAPSE) (in each cardiac cycle the greatest distance of tricuspid annulus from end-diastolic closing to the end-Systolic), Tei index, E/A ratio of Tricuspid inflow, the tricuspid annulus Em / Am ratio of Tricuspid inflow, deceleration time (DT), and isovolumic relaxation time (IVRT).Statistical analysis: The measurement data were represented as mean±SD.The count data were represented as a percentage.All the statistical examinations of measurement data were performed using either independent samples t-test or paired-samples t-test by SPSS 19.0 software.All the statistical examinations of count data were performed using chi-square test ,P<0.05 was considered statistically significant.