Optimal Right Ventricular Pacing Site from the Perspective of QRS Duration, Heart Function and the Configuration of 12-lead Electrocardiogram

Introduction: It has become clear that the onset of heart failure is closely linked to right apex pacing, which lengthens the QRS duration and evokes discoordinate contraction of the left ventricle (LV). Currently, it is thought that the site inducing the shortest QRS duration is optimal for pacing. Objectives: The purpose of this study was to ascertain the pacing site inducing the shortest QRS duration and to examine the configuration of the 12-lead electrocardiogram and heart function while pacing at this site. Methods: Nine patients with normal heart function were enrolled. Pacing at right ventricular outflow, mid-interventricular septum (MS), and right ventricular apex was performed. QRS duration was measured and the configuration of the 12-lead electrocardiogram changed by pacing was studied. Output and LV dp/dt were calculated at each pacing site. Results: QRS duration became shorter with MS pacing and the pacing lead situated at the periphery of the coronary sinus and turned in a posterior direction. The configuration of the 12-lead electrocardiogram showed an Rs or rS pattern with II, III, and aVF leads. Output and LV dp/dt showed a tendency to increase with MS pacing. Conclusion: It is thought that mid-interventricular septum pacing shortens the QRS duration.