Abstract: AIM:To compare the effects on left ventricular systolic function by long-term permanent pacing in right ventricular apex(RVA) and right ventricular outflow tract septal(RVOT-S) and to investigate the optimal right ventricular site for permanent pacing.METHODS:Thirty-six patients diagnosed as having complete atrial-ventricular block(CAVB) and normal left ventricular systolic function and who were hospitalized during the period of August 2007 to December 2009 male/female=20/16,mean age:(51.3±22.2) years were randomly assigned to RVA pacing group and RVOT-S pacing group.Twelve months after implantation of permanent pacemakers,left ventricular ejection fraction(LVEF),left ventricular end-systolic volume(LVESV),aortic velocity time integral(VTI),activation delay between aortic and pulmonary artery valve(QAO-QP),atrial fibrillation burden(AFb),automatic mode switch(AMS),serum NT-Pro-BNP(NT-proBNP) and width of QRS were analyzed and compared between groups.RESULTS:After 12 months pacing,LVEF and VTI in RVOT-S group were significant higher than those in RVA group(P<0.05).LVESV,QAO-QP,AFb,AMS,N-BNP and QRS width in RVOT-S group were statistically lower than those in RVA group(P<0.05).CONCLUSION:Long-term RVA pacing could induce inter-and intraventricular desynchrony and left ventricular remodeling,which would impair the left ventricular systolic function.RVOT-S could be the optimal site for permanent ventricular pacing.