This study aimed to explore if the right ventricular outflow tract (RVOT) pacing is superior to right ventricular apical (RVA) pacing on the overall left ventricular (LV) function and regional wall motion.Methods and results
Sixty patients with atrio-ventricular (AV) block and normal ejection fraction undergoing dual-chamber pacemaker implantation were randomized to permanent ventricular stimulation either in the RVOT or the RVA. Left ventricular volume, ejection fraction, and LV regional wall motion were assessed by echocardiography. Right ventricular apical pacing had prolonged QRS duration, compared with RVOT pacing (154.1 ± 26.5 vs. 120.9 ± 22.3, P< 0.05). There were also significant differences in LV pre-ejection interval and interventricular mechanical delay (IVMD) at 12-month follow-up between the two groups, but none in the LV volume, left ventricular ejection fraction, and index of systolic synchrony (Ts-SD). During RVA pacing, the average peak systolic velocity (Sm) of 12 LV segments [3.5, 95% confidence interval (CI) 3.2–3.8 cm/s] had a trend of being lower compared with RVOT pacing (3.9, 95% CI 3.5–4.1 cm/s) (P= 0.09). Further analysis showed that the Sm at the inferior wall and posterior-septum wall was significantly decreased during RVA pacing compared with RVOT pacing. There were no significant differences for other LV segments.Conclusion
The RVOT pacing in AV block patients over 1 year may be superior to RVA pacing in terms of regional LV performance, LV global electromechanical delay, and IVMD, although intraventricular dyssynchrony and LV volumes do not differ. Larger trials with clinical endpoints are warranted to conclusively define the advantages of RVOT or RV septal pacing.