A Leadless Intracardiac Transcatheter Pacing System
What is the acute safety and 6-month efficacy of a leadless intracardiac transcatheter pacing system?
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.
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).
The Micra transcatheter pacemaker met the prespecified safety and efficacy goals.
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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