Retrospective cross-sectional analysis of MicraTM leadless pacemaker implantation: UK tertiary single centre experience from 2022-2025

Abstract Introduction Leadless pacemakers (LPM), such as the Micra™ transcatheter pacing system, have emerged as an alternative to conventional transvenous pacemakers. This study aims to contribute to the growing body of evidence supporting the use of LPMs with real-world outcomes. Methods We conducted a retrospective cross-sectional analysis of all patients who underwent Micra™ implantation at a single UK tertiary referral centre. Results Among 56 patients, the mean (SD) age was 69 ± 14.1 years, with a slight male predominance (68%), and a high prevalence of multi-comorbidities. The most common indication for leadless pacemaker implantation was complete heart block (66%), followed by second degree atrioventricular block (16%) and sinus node dysfunction (16%). Forty-four patients (78.5%) received the MicraTM AV and 12 patients (21.5%) received the MicraTM VR transcatheter pacing system implanted via femoral venous approach. Seven patients (12.5%) had previous transvenous pacemakers that were complicated by issues such as lead infection (57.3%), pocket erosion (14.2%), and venous occlusion (28.6%), necessitating the use of a LPM as a rescue intervention, while 49 patients (87.5%) were receiving LPM as a denovo implantation. Procedures were predominantly performed under local anesthesia (93%), with mean (SD) fluoroscopy time was 6.4 ± 3.7 minutes while the mean procedural time was 53.3 ± 18.5 minutes. Procedural success was achieved in 100 % of cases, with twelve cases (21.4%) requiring more than one time repositioned due to initial deployment failure. During implantation, the mean (SD) sensing amplitude was 10.5 ± 4.7 mV, and the impedance measured 751.6 ± 185.2 Ω, with pacing thresholds averaging 0.75 ± 0.55 V at 0.24 ms. Over the mean follow-up period of 9 months, device performance remained stable with mean pacing thresholds of 0.67 ± 0.45 V at 0.24 ms, sensing amplitudes of 11.5 ± 4.8 mV and impedance of 601 ± 128 Ω. Two cases (0.36%) demonstrated high threshold above 2 V at 0.24 ms during implantation. One of them showed improvement in right ventricular pacing threshold from 2.5 V to 0.75 V at 0.24 ms, while the other case showed a gradual improvement in pacing threshold from 3.25 V at 0.24 ms, but remains at high pacing threshold at 2.38 V at 0.24 ms at a six-week follow-up. The overall complication rate was 8.9% (5 patients), consisting mainly of minor complications (7.2%) in dialysis patients, including two cases of groin haematoma (3.6%) and two cases of pericardial effusion (3.6%) which were managed conservatively. One major complication (1.8%) case of large pericardial effusion required pericardiocentesis. Conclusion This retrospective analysis at a UK tertiary single centre demonstrates that leadless pacemaker implantation is feasible and effective. The high procedural success rate, combined with low complication rates, supports the use of LPMs as an alternative to traditional transvenous pacemakers.