Objective:To investigate the influence of different cardiac pacemaker implantation site on plasma interleukin-6(IL-6),atrial natriuretic peptide(ANP) and left ventricular systolic function. Methods:Forty-two patients with DDD pacing were randomly divided into two groups:right ventricular apex pacing group (RVA,n = 20) and middle right ventricular septum pacing group (mid-RVS,n = 22). The plasma IL-6,ANP level,LAD,LVEDD,LVEF and QRS complex duration of pre-operation and post-operation were tested. Results:There was no statistical significance of IL-6,ANP level and LAD,LVEDD,LVEF between two groups before implantation and three months after implantation. The plasma leves of IL-6,ANP and LAD,LVEDD in RVA pacing group were higher than those in mid-RVS pacing group six months after implantation(P < 0.01). The plasma leves of IL-6,ANP and LAD,LVEDD in RVA pacing group six months after implantation were higher than those pre-implantation and three months after implantation(P < 0.01). The pacing QRS complexs duration was shorter in mid-RVS pacing group than that in RVA pacing group. Conclusion:Compared with the RVA pacing,mid-RVS pacing can avoid the elevation of IL-6,ANP level,left artial and ventricular dilation and the impairment of left ventricular systolic function.