Objective:To investigate the effects of right ventricular apex pacing(RVAP) or right ventricular outflow tract septal pacing(RVSP) on left ventricular systolic synchronicity and cardiac function in VVI mode after 1-year of implantation. Methods:Sixty patients who were dependent on pacemaker and can only received VVI single-chamber pacemaker implantation were devided into two groups: the right ventricular apex pacing group(RVAP group, n=30) and the right ventricular outflow tract septal pacing group(RVSP group, n=30). The left ventricular ejection fraction(LVEF) was measured before and one year after operation. The time-volume curves were also recorded by real time three dimensional echocardiography (RT-3DE) to evaluate left ventricular systolic synchronicity. Results: There were no differences on left ventricular systolic synchronicity and LVEF between the two groups before operation. After one year’ follow-up, LVEF in RVSP group increased, but no difference compared with that in RVAP group(P > 0.05). However, the parameters of left ventricular systolic synchronieity(Tmsv 16-SD%and Tmsv 12-SD%) significantly decreased in RVSP group(P < 0.05). Conclusion: The RVSP pacemaker keeps better left ventricular synchronous contraction and has less negative effects on the cardiac function than RVAP pacemaker. Therefore RVSP pacemaker is in accordance with physiological pacing.