Leadless pacemakers at 5-year follow-up: the Micra transcatheter pacing system post-approval registry

Abstract

Background and aims: Prior reports have demonstrated a favourable safety and efficacy profile of the Micra leadless pacemaker over mid-term follow-up; however, long-term outcomes in real-world clinical practice remain unknown. Updated performance of the Micra VR leadless pacemaker through five years from the worldwide post-approval registry (PAR) was assessed.

Methods: All Micra PAR patients undergoing implant attempts were included. Endpoints included system- or procedure-related major complications and system revision rate for any cause through 60 months post-implant. Rates were compared through 36 months post-implant to a reference dataset of 2667 transvenous pacemaker patients using Fine-Gray competing risk models.

Results: 1809 patients were enrolled between July 2015 and March 2018 and underwent implant attempts from 179 centres in 23 countries with a median follow-up period of 51.1 months (IQR: 21.6-64.2). The major complication rate at 60 months was 4.5% [95% confidence interval (CI): 3.6%-5.5%] and was 4.1% at 36 months, which was significantly lower than the 8.5% rate observed for transvenous systems (HR: .47, 95% CI: .36-.61; P < .001). The all-cause system revision rate at 60 months was 4.9% (95% CI: 3.9%-6.1%). System revisions among Micra patients were mostly for device upgrades (41.2%) or elevated thresholds (30.6%). There were no Micra removals due to infection noted over the duration of follow-up. At 36 months, the system revision rate was significantly lower with Micra vs. transvenous systems (3.2% vs. 6.6%, P < .001).

Conclusions: Long-term outcomes with the Micra leadless pacemaker continue to demonstrate low rates of major complications and system revisions and an extremely low incidence of infection.

Keywords: Bradycardia; Clinical trial; Leadless pacing; Long-term outcomes; Pacemaker.

Structured Graphical Abstract

Five-year outcomes of patients implanted with a Micra VR leadless pacemaker. The flowchart on the left depicts the disposition of system revisions. The figure on the right shows a comparison of system revision rates for Micra VR and a historical transvenous pacemaker cohort. CI, confidence interval; CRT, cardiac resynchronization therapy; HR, hazard ratio.

Figure 1

System revisions in Micra patients. Diagram depicting number of system revisions, action taken, and reason for revision

Figure 2

Summary of device electrical values and ventricular pacing. Average pacing capture threshold at .24 ms over time (A), average pacing impedance over time (B), average R-wave sensing amplitude over time (C), and distribution of ventricular pacing percentage at last device interrogation (D). Error bars represent ± standard deviation

Figure 3

System or procedure-related major complication rates through 60 months post-implant for the Micra VR PAR and historical TV-PPM cohort. Sub-distributional hazard ratio based on data through 36-months post-implant as indicated by the dashed vertical line

Figure 4

System revision rates for any cause through 60 months post-implant for the Micra VR PAR and historical TV-PPM cohort. Sub-distributional hazard ratio based on data through 36-months post-implant as indicated by the dashed vertical line. The impact of leadless pacing on the risk for system revisions was more pronounced within the first month following implant (HR: .28, 95% CI: .13–.61) compared to after 1 month (HR: .64, 95% CI: .44–.92)