Implant, performance, and retrieval of an atrial leadless pacemaker in sheep.

Background: Medtronic is developing an atrial Micra Transcatheter Pacing System (Medtronic, Minneapolis, Minnesota) and associated retrieval system.

Objective: The purpose of this study was to evaluate chronic atrial Micra retrieval, reimplantation, and chronic pacing performance.

Methods: Sheep were implanted in 2 groups: group 1 (n = 6) for 6 months, a second device implanted, and first retrieved and studied for an additional 6 months; group 2 (n = 6) for 6 months, devices were retrieved, and a second device implanted and observed acutely.