A Leadless Intracardiac Transcatheter Pacing System

Study Questions:

What is the acute safety and 6-month efficacy of a leadless intracardiac transcatheter pacing system?

Methods:

The Micra Transcatheter Pacing Study was a prospective, single-arm study in which Medtronic’s Micra™ leadless pacemaker was implanted in patients needing ventricular pacing only. The primary safety endpoint was freedom from system- or procedure-related major complications. The primary efficacy endpoint was the percentage of patients with low and stable pacing capture thresholds at 6 months. The safety and efficacy endpoints were evaluated against performance goals based on historical data of 83% and 80%, respectively. The authors also compared the rates of major complications with 2,667 patients with transvenous pacemakers from six previously published studies.

Results:

The leadless pacemaker was successfully implanted in 719 of 725 patients (99.2%). The Kaplan-Meier estimate of the rate of the primary safety endpoint was 96%. There were 28 major complications in 25 patients. There were no dislodgements. Patients with transcatheter pacemakers had fewer major complications that the control patients (hazard ratio, 0.49; p = 0.0001).

Conclusions:

The Micra transcatheter pacemaker met the prespecified safety and efficacy goals.

Perspective:

This is the second study in the last 2 months describing the initial experience with a leadless pacemaker. The other study (NEJM 2015;373:1125-35) was a report on Nanostim™ (St. Jude Medical). By and large, the two products appear to have similar initial outcomes and complication rates. They both have the same limitation of providing single-chamber ventricular pacing, which will limit the usefulness of this technology in the near-term. Both have the advantage of transcatheter deployment directly into the right ventricle without the need for leads or a prepectoral device pocket. Further studies are needed to assess long-term efficacy, observed longevity, and ease of removal.


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