Background: Permanent pacing is the treatment for chronotropically incompetent hearts. However, the right ventricular (RV) apical pacing-induced asynchrony, even maintaining the atrioventricular (AV) sequential activation, has depressed left ventricular contractility. Whether RV septal pacing would less compromise the electromechanical performance of the left ventricle and the chronotropic effect on myocardial contractility, is unknown.
Methods: We prospectively studied 42 patients without structural heart diseases and with symptomatic bradycardia. There were 10 patients receiving atrial pacing (AAI) pacemakers, 18 patients having AV sequential pacing at RV apex (DDDapx) and 14 patients being AV sequentially paced at septum (DDDspt). Echocardiography was performed before and within 72 h after the pacemaker implantation. The ventricular mechanical performance and asynchrony was compared in conditions of programmed rates of 60, 80 and 100/min.
Results: Myocardial performance index was significantly better in DDDspt than in DDDapx patients (p=0.003). With faster programmed rate, the QRS/RR increased (p<0.05) in DDDapx patients with more inter- and intraventricular asynchrony, implicating the disadvantage of prolonged depolarization time. The DDDspt group demonstrated comparable parameters of diastolic function to AAI patients and preserved mechanical performance during accelerated pacing.
Conclusions: RV septal pacing showed the advantages of shorter depolarization time, less ventricular contractile asynchrony, better mechanical performance and preserved chronotropic response on myocardial contractility in comparison with apical pacing.