Objective:To explore the influence of cardiac pacing at different sites on left atrial structure and function . Methods:A total of 62 patients ,who needed cardiac pacing therapy because of bradycardia in our hospital from Jan 2012 to Jan 2014 ,were selected .According to the implanted sites of pacing electrode ,patients were equally divided into right ventricular cardiac apex group (RVA group) and right ventricular outflow tract group (RVOT group) . Left atrial volume before atrial contraction (LAVp) ,minimum left atrial volume (LAVmin) ,maximum left atrial volume (LAVmax) ,left atrial active emptying fraction (LAAEF) and left atrial passive emptying fraction (LA-PEF) etc .were compared between two groups before and after cardiac pacing therapy .Results:There were no sig-nificant difference in all indexes between two groups before treatment ,P>0.05 all .Compared with RVA group af-ter six-month pacing treatment ,there were significant reductions in LAVp [ (29.5 ± 3.2) ml vs .(27.1 ± 3.5) ml] , LAVmin [ (18.6 ± 2.0) ml vs . (17.2 ± 2.7) ml] ,LAVmax [ (48.9 ± 4.8) ml vs .(46.1 ± 5.1) ml] and LAAEF [(47.2 ± 4.5)% vs .(43.5 ± 4.2)% ] ,and significant rise in LAPEF [(40.9 ± 5.3)% vs .(43.6 ± 3.9)% ] in RVOT group ,P<0.05 or <0.01. Conclusion:Effect of right ventricular outflow tract pacing is more than that of right ventricular cardiac apex pacing and may be used as a replacement of right ventricular cardiac apex .