Horizontal Axis Affects Paced QRS Duration More Than Vertical Axis at Leadless Pacemaker Implantation Site

Background Leadless pacemaker (LP) implantation at the apical septum has been linked to pacing‐induced cardiomyopathy (PICM). This study aimed to examine the precise position for LP implantation in the RV septum using the three‐dimensional rotational angiography (3D‐RA) system. The accurate implantation sites were visualized through the fluoroscopic image, and the relationship to the measured QRS duration during pacing (p‐QRS duration) was investigated to evaluate their potential association with cardiomyopathy. Methods Fifty‐four patients underwent LP implantation with 3D‐RA guidance. Implantation sites were assessed using the horizontal axis from the apex to the center of the tricuspid valve and the vertical axis from the inferior border of the apex to the outflow tract transition. The p‐QRS durations were measured intraoperatively using electrocardiograms. Echocardiography was performed 12 months later to assess PCIM progression. Results All 54 LPs were successfully implanted in the septum. Mean horizontal and vertical positions within the RV were 69.7 ± 10.5% and 66.5 ± 13.1%, respectively. Mean p‐QRS duration was 148 ± 11 ms. The horizontal position was correlated with QRS duration ( R = 0.59), while the vertical position showed no correlation ( R = 0.03). The native QRS (n‐QRS) duration was also an independent predictor of prolonged p‐QRS duration ( p = 0.018). No patients developed cardiomyopathy progression on follow‐up, and no association with p‐QRS duration was observed. Conclusion In LP implantation, the horizontal position within the RV septum correlates more strongly with p‐QRS duration than vertical position. Prolonged n‐QRS duration also prolonged p‐QRS duration; however, further research is needed to evaluate the relationship between the implanted position and the occurrence of PICM.