BACKGROUND: Cardiac pacemakers have complications related to long pacemaker leads, subcutaneous pockets, and endovascular hardware. OBJECTIVE: We report on the development of a leadless micropacemaker for percutaneous implantation into the pericardial space. METHODS: Percutaneous implantations of a micropacemaker system were performed in 15 pigs through subxiphoid access to the pericardial space. In our concept phase, 10 implants were performed with iterative changes to the design and implantation techniques until a design was reached for a viable device. In the study phase, a viable device was implanted in 5 pigs and observed during 8 weeks. RESULTS: At the completion of the concept phase, a prototype micropacemaker device was fabricated that met 3 mandatory system requirements: can be safely and reproducibly implanted percutaneously into the pericardial space
does not migrate after implantation
and successfully captures the myocardium at implantation and during long-term follow-up (up to 8 weeks). The prototype device was successfully and safely implanted into all 5 pigs in the study phase. These 5 animals survived to the 8-week end point without complications. Ventricular capture threshold calculations at implantation were a median 0.43 V at 0.4 ms (range, 0.05-0.75 V at 0.4 ms). At 8 weeks of follow-up, median capture thresholds were 2.8 V at 0.4 ms (total range, 2.2-7.1 V). CONCLUSION: A novel pericardial micropacemaker system allows minimally invasive implantation of a leadless cardiac pacemaker without entering the vascular space. We provide proof of concept of this design with encouraging follow-up data.