Preclinical safety and electrical performance of novel atrial leadless pacemaker with dual-helix fixation

Background: Complications associated with transvenous pacemakers, specifically those involving the lead or subcutaneous pocket, may be avoided with leadless pacemakers (LPs). The safety and efficacy of single-chamber right ventricular LPs have been demonstrated, but their right atrium (RA) use poses new design constraints. Objectives: The purpose of this study was to evaluate the implant success, electrical performance, and safety of a novel RA LP design in benchtop and preclinical studies. Methods: A new LP was designed with a dual-helix fixation mechanism specific to the RA anatomy. A 12-week preclinical ovine study was conducted to evaluate implant success, electrical performance, mechanical stability, and safety in vivo, with supporting benchtop measurements to quantify the mechanical forces needed for device retrieval and dislodgment. Results: LPs were successfully implanted in all 10 ovine subjects with no complications. The pacing capture threshold improved significantly over time from implant to week 12 (1.1 ± 0.7 V vs 0.4 ± 0.2 V, P =.008). Sensing amplitudes and pacing impedances were stable from implant to week 12 (4.8 ± 1.8 mV vs 6.0 ± 1.9 mV, P =.160; and 393 ± 77 Ω vs 398 ± 65 Ω, P =.922, respectively). Gross pathology and microscopic histology revealed no adverse interactions and no evidence of device dislodgment or clinically significant myocardial perforation. Benchtop ex vivo porcine atrial tissue measurements revealed greater pull forces required to dislodge the LP vs transvenous active fixation lead (0.42 ± 0.18 lbf vs 0.29 ± 0.08 lbf, P =.020), and greater rotational forces required for deliberate extraction (0.28 ± 0.04 lbf vs 0.14 ± 0.07 lbf, P <.001). Conclusion: The novel atrial LP demonstrated successful implantation, with acceptable electrical performance, mechanical stability, and safety in a 12-week preclinical study.