The pacing threshold improvement of leadless pacemaker is better when mid or high right ventricular septal (RVS) approach than lower RVS approach after follow-up of 3 months

Abstract

Abstract Introduction Leadless pacemaker procedures are rapidly increasing in last decade. Compared to conventional trans-venous pacemaker, pacing threshold of leadless pacemaker is important parameter for longevity (reference 1.). For the safety, right ventricular septum (RVS) is recommended as the pacing location. Recent study (reference 2.) showed that pacing thresholds in most leadless pacemaker implantation patients with elevated thresholds decrease after implant. Therefore, leadless pacemaker repositioning may not be necessary if the pacing threshold is ≤2 V. However, according to pacing location with mid-or above septum versus low or apical septum, pacing threshold stability and improvement during follow-up period after implantation is not clear. Method 68 cases of leadless pacemaker implantation in 2 hospitals with 3 physicians was analysed. According to pacing location, we divided 2 groups with mid or above RVS and lower RVS. Patients with pacing location on mid or above RVS was 27 (Group A). Other patients with pacing location on lower RVS was 41 (Group B). During follow-up (mean 6 months), we analysed pacing threshold and QRS duration on electrocardiography (ECG) after implantation. Results Table 1. shows baseline characteristics including age, sex, and comorbidity were not different significantly between 2 groups. Only HF is lower in group A (14.8% versus 36.6%, p=0.044). Table 2. shows the comparison of 2 groups. Initial threshold of lower RV septal approach (Group B, 0.39±0.14V/0.24ms) showed better than mid or high septal approach (Group A, 0.70±0.33V/0.24ms), p <0.001. However, 3 months later, pacing threshold decreased lower in Group A (mid or above RVS, 0.49±0.17V/0.50ms) than Group B (lower RVS, 0.67±0.50V/0.24ms), p <0.001. Therefore, the change of pacing threshold is improved in Group A (mid or above RVS, -0.20±0.24V/0.24ms) than Group B (lower RVS, 0.28±0.51V/0.24ms), p <0.001. However, other parameters including QRS duration and LVEF after implantation was not different between 2 groups. Conclusion The improvement of pacing threshold in mid or high RVS approach demonstrates that pacing threshold stability is more dominant than lower RVS approach. Our data shows that, after follow-up of 3 months, pacing threshold improvement of leadless pacemaker after implantation is better when mid or high RVS approach than lower RVS approach.Figure 1.Table 1. and 2.