Pacing of the interventricular septum versus the right ventricular apex: A prospective, randomized study

Abstract

BackgroundLeft ventricular (LV) function may be impaired by right ventricular (RV) apical pacing. The interventricular septum is an alternative pacing site, but randomized data are limited. Our aim was to compare ejection fraction (EF) resulting from pacing the interventricular septum versus the RV apex. MethodsRV lead implantation was randomized to the apex or the mid-septum. LVEF and RVEF were determined at baseline and after 1 and 4years by radionuclide angiography. ResultsWe enrolled 59 patients, of whom 28 were randomized to the apical group and 31 to the septal group, with follow-up available in 47 patients at 1year and 33 patients at 4years. LVEF in the apical and in the septal groups was 55±8% vs. 46±15% (p=0.021) at 1year and 53±12% vs. 47±15% (p=0.20) at 4years. Echocardiography confirmed a mid-septal lead position in only 54% of patients in the septal group, with an anterior position in the remaining patients. In the septal group, LVEF decreased significantly in patients with an anterior RV lead (−10.0±7.7%, p=0.003 at 1year and −8.0±9.5%, p=0.035 at 4years), but not in patients who had a mid-septal lead. Left intraventricular dyssynchrony was significantly increased in case of an anterior RV lead. RVEF was not significantly impaired by RV pacing, regardless of RV lead position. ConclusionsPacing at the RV septum confers no advantage in terms of ventricular function compared to the apex. Furthermore, inadvertent placement of the RV lead in an anterior position instead of the mid-septum results in reduced LV function.